Patent Application
20160155364
The present disclosure relates to models of the mammalian head and brain. More particularly, the present disclosure relates to models or phantoms of the mammalian head and brain for training and/or simulation of medical procedures, such as training with different types of imaging modalities and training for invasive surgical procedures to mention just a few.
In the field of medicine, imaging and image guidance are a significant component of clinical care. From diagnosis and monitoring of disease, to planning of the surgical approach, to guidance during procedures and follow-up after the procedure is complete, imaging and image guidance provides effective and multifaceted treatment approaches, for a variety of procedures, including surgery and radiation therapy. Targeted stem cell delivery, adaptive chemotherapy regimes, and radiation therapy are only a few examples of procedures utilizing imaging guidance in the medical field.
Advanced imaging modalities such as Magnetic Resonance Imaging (“MRI”) have led to improved rates and accuracy of detection, diagnosis and staging in several fields of medicine including neurology, where imaging of diseases such as brain cancer, stroke, Intra-Cerebral Hemorrhage (“ICH”), and neurodegenerative diseases, such as Parkinson's and Alzheimer's, are performed. As an imaging modality, MRI enables three-dimensional visualization of tissue with high contrast in soft tissue without the use of ionizing radiation. This modality is often used in conjunction with other modalities such as Ultrasound (“US”), Positron Emission Tomography (“PET”) and Computed X-ray Tomography (“CT”), by examining the same tissue using the different physical principals available with each modality. CT is often used to visualize boney structures, and blood vessels when used in conjunction with an intra-venous agent such as an iodinated contrast agent. MRI may also be performed using a similar contrast agent, such as an intra-venous gadolinium based contrast agent which has pharmaco-kinetic properties that enable visualization of tumors, and break-down of the blood brain barrier. These multi-modality solutions can provide varying degrees of contrast between different tissue types, tissue function, and disease states. Imaging modalities can be used in isolation, or in combination to better differentiate and diagnose disease.
In neurosurgery, for example, brain tumors are typically excised through an open craniotomy approach guided by imaging. The data collected in these solutions typically consists of CT scans with an associated contrast agent, such as iodinated contrast agent, as well as MRI scans with an associated contrast agent, such as gadolinium contrast agent. Also, optical imaging is often used in the form of a microscope to differentiate the boundaries of the tumor from healthy tissue, known as the peripheral zone. Tracking of instruments relative to the patient and the associated imaging data is also often achieved by way of external hardware systems such as mechanical arms, or radiofrequency or optical tracking devices. As a set, these devices are commonly referred to as surgical navigation systems.
Since image-guided surgical procedures are complex in nature and the risk associated with use of such procedures in the brain is very high, the surgical staff must often resort to performing a simulated rehearsal of the entire procedure. Unfortunately, the tools and models that are currently available for such simulated rehearsal and training exercises typically fail to provide a sufficiently accurate simulation of the procedure.
An embodiment provides a complimentary head phantom kit, comprising: complimentary head phantom kit, comprising:
a) a first imaging head phantom including mammalian brain anatomical mimics constructed of materials selected on the basis of being imageable with one or more imaging technique;
b) at least a second biomechanical head phantom including mammalian brain anatomical mimics constructed of one or more materials selected on the basis that said one or more materials mimic one or more biomechanical properties of a mammalian head; and
c) said first imaging head phantom and said at least a second biomechanical head phantom being registered together, wherein one or more acquired images taken of said first imaging head phantom using said at least one imaging technique are registered with said at least a second biomechanical phantom, by ensuring that features in the one or more acquired images from the imaging phantom are geometrically correlated to corresponding features in the biomechanical head phantom, for providing navigation of said second biomechanical head phantom during surgical training procedures.
There is also provided a method of producing a brain phantom including deep sulci, comprising:
acquiring an image of a human brain;
using said image to 3D-print an anatomically accurate model of the brain with deep sulci emulating the human brain;
applying a flexible mold material to an outer surface of the model of the brain and after the mold material has set to form a brain mold, releasing the brain mold from the model of the brain;
placing the brain mold into a rigid outer shell and filing the mold with a liquid precursor of a brain material mimic, optionally embedding in the liquid precursor one or more mimics for one or more structural brain features;
inducing the liquid precursor to set to form an anatomically correct brain phantom in one piece with deep sulci; and
releasing the brain phantom from the brain mold.
There is also provided a mammalian brain phantom, comprising:
a simulated mammalian brain including sulci topographical structure on an outer surface thereof, said a simulated mammalian brain having a composition which,
Embodiments will now be described, by way of example only, with reference to the drawings, in which:
Various embodiments and aspects of the disclosure will be described with reference to details discussed below. The following description and drawings are illustrative of the disclosure and are not to be construed as limiting the disclosure. Numerous specific details are described to provide a thorough understanding of various embodiments of the present disclosure. However, in certain instances, well-known or conventional details are not described in order to provide a concise discussion of embodiments of the present disclosure.
As used herein, the terms “comprises” and “comprising” are to be construed as being inclusive and open ended, and not exclusive. Specifically, when used in the specification and claims, the terms “comprises” and “comprising” and variations thereof mean the specified features, steps or components are included. These terms are not to be interpreted to exclude the presence of other features, steps or components.
As used herein, the term “exemplary” means “serving as an example, instance, or illustration,” and should not be construed as preferred or advantageous over other configurations disclosed herein.
As used herein, the terms “about” and “approximately” are meant to cover variations that may exist in the upper and lower limits of the ranges of values, such as variations in properties, parameters, and dimensions. In one non-limiting example, the terms “about” and “approximately” mean plus or minus 10 percent or less.
When performing surgical and/or diagnostic procedures that involve the brain, neurosurgical techniques such as a craniotomy, or a minimally invasive procedure such as an endo-nasal surgery or a port based surgical method, may be performed to provide access to the brain. In such procedures, as indicated, the medical procedure is invasive of the mammalian head. For example, in the port-based surgical method illustrated in
According to embodiments provided herein, the simulation of such procedures may be achieved by providing a brain model that is suitable for simulating the surgical procedure through one or more layers of the head. Such a procedure may involve perforating, drilling, boring, punching, piercing, or any other suitable methods, as necessary for an endo-nasal, port-based, or traditional craniotomy approach. For example, some embodiments of the present disclosure provide brain models comprising an artificial skull layer that is suitable for simulating the process of penetrating a mammalian skull. As described in further detail below, once the skull layer is penetrated, the medical procedure to be simulated using the training model may include further steps in the diagnosis and/or treatment of various medical conditions. Such conditions may involve normally occurring structures, aberrant or anomalous structures, and/or anatomical features underlying the skull and possibly embedded within the brain material.
In some example embodiments, the brain model is suitable for simulating a medical procedure involving a brain tumor that has been selected for resection. In such an example embodiment, the brain model is comprised of a brain material having a simulated brain tumor provided therein. This brain material simulates, mimics, or imitates at least a portion of the brain at which the medical procedure is directed or focused.
The simulation of the above described medical procedure is achieved through simulation of both the surgical procedure and the associated imaging steps that are performed prior to surgery (pre-operative imaging) and during surgery (intra-operative imaging). Pre-operative imaging simulation is used to train surgical teams on co-registration of images obtained through more than one imaging methodology such as MR, CT and PET. Appropriate co-registration geometrically aligns images from different modalities and, hence, aids in surgical planning step where affected regions in the human body are identified and suitable route to access the affected region is selected.
Another use of pre-operative imaging is to train the surgical team and radiologists on optimizing the imaging parameters so that clinically relevant images are acquired prior to the surgical procedure. For example, pre-operative MR images need to be acquired in a specific manner to ensure that the acquired data can be used to generate tractography information, such as Diffusion Tensor Imaging (DTI), which shows the location and direction of the brain tracks which are not visually observable by the surgeon. Intra-operative imaging is used to guide the surgeon through accurate surgical intervention while avoiding damaging the brain tracks if possible. Surgical intervention includes accessing a previously identified affected region in the human body and subsequent resection of affected tissue.
Referring to
Referring now to
Referring to
The base component may have any size, shape and configuration capable of maintaining the training component, mounted within the training component receptacle, in a position suitable for performing the medical procedure to be trained. This base component comprises features that enable registration, such as fiducials, touchpoint locations, and facial contours for 3D surface scanning, MR, CT, OCT, US, PET, optical registration or facial registration. Furthermore, the base component is adapted or configured to maintain the training component in a relatively stable or fixed position throughout the performance of the medical procedure to be simulated during the training procedure. The base component provides both mechanical support during the training procedure and aids in the proper orientation of the training components to mimic actual positioning of a patient's head during the surgical procedure.
Referring to
The head component (210) is sized, configured or otherwise adapted to be compatible with, or complementary to the tray component (200) and the training component. The head component (210) is adapted or configured to maintain the training component (230) (located under skull component 300) in a relatively stable or fixed position throughout the performance of the medical procedure to be simulated. This head component (210) is adapted or configured to enable anatomically correct surgical positioning. This may include affixing the head component (210) with a surgical skull clamp or headrest, for example a Mayfield skull clamp. This head component (210) is also adapted or configured to enable anatomically correct imaging positioning for any contemplated imaging modality including, but not limited to, MR, CT, OCT, US, PET, optical registration or facial registration. For example the head component (210) may be positioned in a supine position within an MRI apparatus to enable anatomically accurate coronal image acquisition.
In some embodiments, the head component (210) is shaped or configured to simulate a complete or full skull. In other words, the training component comprises bowl section (210) and skull section (220), while the bowl section (210) comprises a further portion of a complete skull and head. In some embodiments, as shown in
In addition, the base and training components of the training model (100), and particularly the head component, may also include one or more external anatomic landmarks or fiducial locations 400, as shown in
In this regard, navigation to establish the location of the hole or passage through the skull of the patient during the craniotomy procedure is often critical for the success of the medical procedure. Accordingly, external anatomic landmarks and/or touchpoints are provided by the simulated head in order to provide training on the correct registration of the training model with the acquired images. These anatomic landmarks and touchpoints may be utilized for attaching registration hardware, for example a facial registration mask or fiducial landmark. Thus, the training model, and particularly the simulated head, are sized, configured and shaped to approximate and closely resemble the size, configuration and shape of the head of a patient on which the medical procedure is to be performed. In other words, the head component may be both ‘life-like’ and ‘life-sized’.
The base component may be comprised of any composition or material suitable for providing the training component receptacle, and may be suitable for being cast, molded or otherwise configured to provide or support the simulated head when assembled with the training component. For instance, the base component may be comprised of any suitable casting compound, casting composition or plaster. The base component may be comprised of a material that is rigid, non-reflective, non-ferrous, non-porous, cleanable, and lightweight, for example a urethane or acrylonitrile butadiene styrene (ABS). In addition, the bowl (210) and skull (220) components of the base component may be comprised of a material that is visible by the imaging procedure of interest to enable registration. The material for the bowl (210) and skull (220) components of the base may therefore be selected to be visible by MR, CT, and/or PET. Suitable properties for mimicking the skull component (220) for various imaging modalities are illustrated in Tables 1, 2 and 3.
In another embodiment, the base component may be manufactured from a material that is not visible in MR, CT and PET. This is particularly of value when the scope of training does not include facial registration and craniotomy. For example, it is widely known that Teflon™ may be chosen when the base component needs to be transparent in MRI. This further eliminates subsequent software processing steps where the skull structure of the head needs to be removed prior to visualizing the brain structure. This step is commonly known as skull stripping and it can be computationally costly.
The three simulation steps described previously (namely, pre-operative imaging simulation, surgical simulation and intra-operative imaging simulation) can be realized using models or phantoms that share some properties in common. Properties of tissue mimicking materials that are suitable for imaging using various modalities are presented next.
PET imaging requires the injection of radioactive contrast agent prior to the imaging step. The half-life of the contrast agents will limit the shelf-life of the training phantom. This can be overcome by manufacturing the phantom with micro-capillaries so that contrast agents can be introduced via the capillaries just prior to PET imaging. Alternatively, contrast agents may be injected to selected regions of the brain component.
Densities for Brain Mimicking for Imaging in CT and US
Physical properties of the brain that are preferred for CT and US imaging are illustrated in Table 1 (Barber, Ted W., Judith A. Brockway, and Lawrence S. Higgins. “The Density Of Tissues In And About The Head.” Acta Neurologica Scandinavica 46.1 (1970): 85-92. Web.).
Optical Properties for Brain mimicking for imaging using OCT are presented in Table 2 (Cheong, W. f., S. a. Prahl, and A. j. Welch. “A Review of the Optical Properties of Biological Tissues.” IEEE Journal of Quantum Electronics 26.12 (1990): 2166-185. Web.).
Alternately, the properties of materials suitable for mimicking intra-operative ultrasound (i-US) may be established using operating frequency of typical ultrasound transducers.
(reference: http://www.bkmed.com/Intraoperative_US_en.htm).
For intra-operative US, frequency range is from 4 to 10 MHz. This is based on such instruments as BK medical transducers, intraoperative 8815, T-shaped intraoperative 8816, Intraoperative biplane 8814, Hockey Stick 8809, and the, Intraoperative biplane 8824. At 5 Mhz the average propagation speed through mixed tissue is 1565m/s. Another property of the tissue that is preferred for ultrasound imaging is attenuation coefficient. This is illustrated in Table 3.
Parameters of the brain tissue that are essential for mimicking MR images are T1, T2, and Spin Densities. This is illustrated in Table 4 for various components of the brain.
Finally, PS-OCT is used to visualize birefringence property of living tissue. Birefringence is directionality dependent and would therefore vary quantitatively depending on the particular brain being imaged; however, the visually invisible brain tracts could be reproduced and optimized using a particular material that may be organized in such a way to give the desired brain tract orientation.
As shown in
In some embodiments, in order to permit the replacement or substitution of the training component (230), the training component is detachably or releasably mounted in the base component (210). Any detachable or releasable fastener or fastening mechanism may be used which is capable of securing the training component (230) in the receptacle, while also permitting the training component (230) to be readily detached, released or removed as desired or required. In one embodiment, the training component (230) is releasably or detachably mounted within the base component (210), specifically the training component is held within the base component (210) to emulate the mechanical fixation of the brain in the skull.
Thus, in the present example embodiment, the training component (230) may be removed from the base component (210) and replaced with an alternate, replacement or substitute training component as desired or required by the user of the training model. For instance, a replacement training component (230) may be required where the previous training component (230) is damaged or modified during the training of the procedure. An alternate training component (230) may be adapted or designed for use in the training of the performance of a specific medical procedure or condition of the patient, allowing for the reuse of the base component (210).
Alternatively, as indicated, the training model (100) may not include the base component (210). In this instance, the other components comprising the training model (100), such as the training component (230) in isolation, may be supported directly by a supporting structure or a support mechanism (not shown) that does not look like a mammalian head. Specifically, the supporting structure may securely maintain the training component (230), without the other components of the training model, in the desired orientation. In such an embodiment, the training component (230) may be releasably attached or fastened with the supporting structure such that the training component (230) may be removed from the supporting structure and replaced with an alternate, replacement or substitute training component (230) as desired or required by the user of the training model.
Referring to
In one embodiment, the skull layer (220) is included as an element of the training component (230). The skull layer (220) is formed from osseous type material as described herein. This skull layer (220) is constructed of a skull material which simulates osseous tissue when penetrated. Hence, this layer (220) is intended to simulate surgical resection. Thus, the skull material of the skull section (220) mimics or imitates osseous tissue when penetrated, pierced or passed into or through. In an embodiment described herein, the medical procedure is comprised of drilling into or through a portion of the skull, which is simulated by the skull section (600). In order for the skull section (220) of the present phantom to mimic or imitate osseous tissue, properties illustrated in Table 5 need to be met by the material simulating skull section (220).
Thus, in such embodiments, the skull material particularly simulates, mimics or imitates the “feel” and resistance of osseous tissue when it is being penetrated by drilling. For example, the osseous tissue mimic may be formed from an acrylonitrile butadiene styrene (ABS) material texturized and patterned to resemble skull tissue. ABS is a terpolymer of acrylonitrile, butadiene and styrene and typical or usual compositions are about half styrene with the balance divided between butadiene and acrylonitrile. An advantage of using ABS material is that considerable compositional variation is possible, resulting in many different grades of acrylonitrile butadiene styrene with a range of properties so if material tuning is required to achieve the properties noted in Table 5 there are considerable options. In addition, many blends with other materials such as polyvinylchloride, polycarbonates and polysulfones may be used. Acrylonitrile butadiene styrene materials can be processed by any of the standard thermoplastic processing methods.
In addition, in order to more closely simulate the skull, the skull layer (220) may have a thickness which approximates that of the mammalian skull. In one embodiment, the skull layer (220) has a thickness which particularly approximates that of the portion or area of the neurocranium typically penetrated in performance of the medical procedure to be trained. Thus, the skull section of the training model, may have a total thickness in a range of about 5 to about 10 millimeters.
However, depending upon the medical procedure to be trained, the training model need not include the skull layer (220). Specifically, in some medical procedures, the medical procedure is directed at structures underlying the dural layer (610). In these instances, the emulation of the skull layer (220) is not critical. Thus the skull section (600) will not be required in the training model for that procedure. Further, as shown in
Thus, the dural material of the dura section (610) also mimics or imitates dural tissue visually, or when imaged with MR, CT, OCT, US, and/or PET, or when penetrated, pierced, stitched, or passed into or through. Thus, in the embodiments, as indicated above, the dural material particularly simulates, mimics or imitates the “feel” and resistance of dural tissue when it is being cut by a scalpel or surgical scissors. In some embodiments, the dural layer (610) also simulates the non-absorbent and liquid tightness exemplified by dural tissue. Thus creating a water-tight enclosure for the liquid surrounding the brain and preventing absorption of the CSF-type liquid used in the training model (230).
For instance, in some embodiments, the dural layer (610) material may be comprised of urethane or silicone brushed fibers. Although any suitable silicone or urethane may be used for the purpose of mimicking biomechanical properties of the dural layer (610), it may be beneficial to select a silicone or urethane that is opaque in nature, in order to obscure the view of the brain and its sulci below. Furthermore, it may be beneficial to select a silicon or urethane that forms or takes on the shape of the underlying sulci.
In addition, the biomechanical property of the dural layer (610) may be mimicked using a layer that may have a thickness which approximates that of the dura matter underlying the skull. In some embodiments, the dural layer (610) has a thickness which particularly approximates that of the dura mater underlying the inner portion or area of the neurocranium typically penetrated in performance of the medical procedure to be trained. In an embodiment, the dural layer (610) has a thickness of less than approximately 1 mm, for example, between about 0.5 to about 0.8 mm which is typical of the human dura.
Furthermore, as shown in
In addition, the vessel layer (630) may have a tubular shape with a diameter which approximates that of the vessels within the skull. In some embodiments, the vessel layer (630) is hollow to allow for the routing of fluids within, for example, a blood-like liquid mimic. In an embodiment, the vessel layer (630) has a thickness of between about 0.2 mm and 3 mm, and more preferably has a thickness of about 1 mm, a typical range for the human brain. Further, as shown in
The CSF liquid in the CSF layer (620) may be comprised of any liquid or substance capable of simulating CSF as described when passing through or imaging the training component. Thus, the CSF liquid mimics or imitates CSF visually and when imaged, for example with MR, CT, OCT, US, and/or PET, or when passed into or through. Thus, in the embodiments, as indicated above, the CSF material in CSF layer (620) particularly simulates, mimics or imitates the “feel” and viscosity of CSF liquid when it is being passed through by surgical instruments. For instance, in some embodiments, the CSF liquid mimic may be comprised of a mineral oil or saline solution. The above stated CSF liquid mimicking material primarily simulates biomechanical property of the brain. In an embodiment, this liquid may be used to hydrate the fibrous structures included within the brain layer including grey matter layer (640), white matter layer (650).
In addition, the dural layer (610) may enclose a volume which approximates that of the CSF in the mammalian brain. In an embodiment, the CSF section (620) has a volume of between about 100 ml and 200 ml, such as, approximately 150 ml.
Further, as shown in
In some embodiments, the brain layer is constructed of brain layer material which simulates or mimics brain tissue, including grey matter layer (640) and white matter layer (650), when physically penetrated and/or when imaged, for example with MR, CT, OCT, US, and/or PET. As noted above, this brain layer may be divided into grey (640) and white matter (650) so that the brain layer material may be configured to mimic or imitate grey and white matter tissue when penetrated, pierced, or passed into or through and/or when imaged. For example, following the cutting or incising of the dura mater, the medical procedure may comprise penetration of the brain layer by inserting or passing surgical instruments, for example, a trocar, catheter, drain, port, obturator, Myriad™, into or through a portion of the brain. In such a case, the brain layer material mimic may have a composition that responds to these instruments in a manner that mimics that of real brain tissue, for example, the brain tissue will not clog up the Myriad™.
Thus, the brain layer material may particularly simulate, mimic and/or imitate the “feel” and resistance of brain tissue when it is being penetrated in this manner. However, the specific nature and composition of the grey and white matter (640) and (650) being penetrated may vary depending upon the particular medical condition of the patient and the procedure to be trained for. Accordingly, the grey and white matter material mimic (640) and (650) may be specifically selected to simulate, mimic or imitate the “feel” resistance, and imaging properties of the brain tissue likely to be encountered in the context of the patient's medical condition and the performance of the medical procedure being trained.
Accordingly, the brain layer mimic material may be comprised of any material or substance capable of simulating brain tissue as described. For instance, in some embodiments, the brain layer mimic material may be comprised of a polyurethane MCG-1 or PVA-C material. In an embodiment, the brain layer mimic material is comprised of a polyurethane material mixed with an additive such as glass bubbles or mineral oil to achieve the desired consistency of brain material.
In one example implementation, the brain layer material is comprised of a mixture of the polyurethane and glass bubbles. The glass bubbles may be incorporated so that they do not exceed 5% of the total volume, to mimic the tear strength and tensile properties of brain tissue. In another embodiment, the brain layer material mimic is comprised of 6% PVA-C mixed with water and one freeze-thaw cycle.
In some embodiments, the brain layer mimic material may have a thickness, dimensions, and anatomically accurate sulci and ventricles, which approximates the brain tissue likely to be encountered in the performance of the medical procedure to be trained. As indicated, in some medical procedures, the medical procedure is directed at the brain or structures lying within the brain. Thus the thickness of the brain layer mimic material will be selected to simulate the location within the brain, or the location of a structure within the brain, at which the medical procedure is directed.
Furthermore, as shown in
In addition, the diffusion fibers (660) may have a tubular shape with a diameter which approximates that of the white matter tracts within the brain section. In some embodiments, the diffusion fibers (660) are threaded through the brain matter mimic and protrude from the brain matter where they are exposed and hydrated by the surrounding CSF fluid mimic layer (620). This CSF fluid layer (620) provides the hydration which diffuses through the tubes and is visible in the acquired images. These diffusion fiber mimics (660) provide an enhanced training experience for the surgeon as during the training procedure they are encouraged to avoid tearing or harming the diffusion fibers during the operation.
Furthermore, as shown in
In general terms, the target is intended to simulate, mimic or imitate a specific structure embedded within the brain layer material which is the focus of the medical procedure to be trained or at which the medical procedure is directed. The specific structure or focus of the medical procedure may be normal or aberrant anatomical structure, clot, lesion, structure resulting from a pathological condition or other structure desired to be acted upon by the medical practitioner.
In one embodiment, the specific structure to be acted upon, or at which the medical procedure is directed, is a target tumor (670). This target tumor (670) may be comprised of any material or substance capable of simulating tumor tissue as described when applying surgical instruments or when imaged.
Thus, the target tumor (670) material mimics or imitates tumor tissue visually, when imaged, for example with MR, CT, OCT, US, and/or PET, or when penetrated, pierced, resected, or passed into or through. Thus, in the embodiments, as indicated above, the target tumor (670) material particularly simulates, mimics or imitates the “feel” and resistance of tumor tissue when it is being cut by a scalpel or MyriadTM. For instance, in some embodiments, the target tumor (670) material may be comprised of a hydrocolloid material, a rubber-glass mixture, or a PVA-C mixture. These materials may be doped with contrast agents to simulate the imaging characteristics of tumor tissue. Exemplary, non limiting examples of contrast agents include any one of a fluoride, a chloride, or sulfate. Non-limiting examples include chromium fluoride, gadolinium chloride, copper sulfate, barium sulfate, manganese chloride. In addition, agarose may be used as well.
Hence, the simulated tumor (670) is suitable for mimicking biomechanical properties and for generating images that resemble tumor regions in living tissue. In an embodiment, pigmentation may be applied to the target tumor (670) material to represent a lifelike tumor coloring.
Referring to
The imaging and biomechanical brain phantoms may be constructed to have specific dedicated sites, anywhere under the skull layer (220), sized to receive specifically sized target tumors (670) which match known types of tumors. The various parts of the brain phantom may have a modular construction, for example the skull (220), dura (610), CSF (620), vessels (630), brain section including grey matter (640), white matter (650), and diffusion fibers (660), may be constructed in a lego style so that sections can be readily removed to allow insertion of the target tumor (670) in pre-selected locations in the head below skull layer (220). The brain phantom kit disclosed herein may come with a plurality of different sized and shaped tumor targets (670) in order to be able to reconfigure the brain phantoms to allow training to be conducted for multiple types of tumors and multiple locations within the skull as well as for differently sized head phantoms emulating or mimicking differently aged patients.
In addition, one or both of the imaging and biomechanical phantoms may be constructed to include strategically placed sensors within the different anatomical mimics for the purpose of, but not limited to, assisting in navigation. The sensors may be coded for pre-selected locations in the brain phantom.
As noted elsewhere, to produce a lifelike brain phantom with biomechanical properties to allow a practitioner to train on various brain invasive surgical procedures, using the port based method involving insertion of the surgical port into the brain via the sulci, requires the model to be life size and with the deep sulci morphology.
An exemplary, non-limiting method of producing a one piece brain phantom including deep sulci includes acquiring an image of a human brain using MRI, using this image to 3D-print an anatomically accurate one piece model of the brain with deep sulci emulating the human brain. Once the model is produced, applying a flexible mold material to an outer surface of the model of the brain and after the mold material has set to form a brain mold, releasing the brain mold from the model of the brain. The brain mold is placed into a rigid outer shell to prevent swelling. The mold is filed with a liquid precursor of a brain material mimic. Depending on the ultimate purpose of the particular phantom being produced, there may be embedded in the liquid precursor one or more mimics for one or more structural brain features, such as a dural layer, blood vessel layer, and brain matter tracks to mention a few. The liquid precursor is then induced to set to form an anatomically correct brain phantom in one piece with deep sulci and after the liquid precursor has set, the set brain mold is released from the brain mold.
The gyri and sulci may be produced to exhibit any one or combination of elastic modulus, shear modulus, tensile strength and nonlinear elastic properties comparable to a mammalian sulci.
It is noted that the MR image used to make the model may be that of the patient to be operated on, so that the outer sulci morphology closely resembles that of the patient. Non patient specific, or generic brain phantoms may be produced for general training procedures, but the advantage of using the patient's brain phantom allows the practitioner to practise on a brain phantom closely matching that of the patient in question.
An example shape for the brain component of the training component is illustrated in
The CT image of the same training model is illustrated in
The tumor target may have any shape, configuration and dimensions, capable of and suitable for simulating, mimicking or imitating the specific structure underlying the skull of a patient which is the focus of the medical procedure to be trained on or at which the medical procedure is directed. An example size range may be from 1 mm to 3 cm, and the consistency may range from gelatinous to rigid. In one embodiment a tumor is made with a size of 1 cm of hydrocolloid material with a concentration of 0.2% copper sulfate as contrast agent. In another embodiment, rubber glass may be used as a tumor target with a rubber glass to slacker ratio of up to 1:4 or only composed of rubber glass, see:
http://www.smooth-on.com/tb/files/Slacker_Tactile_Mutator.pdf
In an embodiment, the training model or phantom may be provided with a simulated skin. Specifically, a skin layer may be provided for overlying at least the outer-most surface of the skull section. In other words, the skin layer overlies the skull section (230). In addition to overlying the skull section (230), which comprises the outer surface of the training component in some embodiments, a skin layer may also be provided for overlying all or a portion of the outer surface of the head component. Thus, for instance, the head component may include the skin layer in order to provide a more realistic simulation of the medical procedure.
The skin layer is constructed of a skin layer mimic material which simulates skin tissue when penetrated. Thus, the skin layer material mimics or imitates skin tissue when penetrated, pierced or passed into or through.
In an embodiment described herein, prior to penetrating the skull, the medical procedure may further require the penetration of the skin in order to provide access to the skull for the subsequent procedure. In this instance, the skin is typically cut or incised. Thus, in such embodiments, the skin layer material particularly simulates, mimics or imitates the “feel” and resistance of skin tissue being penetrated by cutting or incising.
The skin layer mimic material may be comprised of any material or substance capable of simulating skin tissue as described. For instance, in some embodiments, the skin layer mimic material is comprised of a silicone rubber or a flexible silicone elastomer. This material is intended to simulate biomechanical and imaging properties of living skin layer. Further, the skin layer material may provide a surface enabling image registration and/or facial registration, for example with MR, CT, US, and/or PET. In an embodiment, the skin layer material is comprised of a platinum cure silicone rubber which may be tinted with flesh colored dye or pigment, and which is commercially available under the name Dragon Skin, Dragon Skin is a trade-mark of Smooth-On Inc. This is suitable for mimicking the biomechanical and visual properties of the skin.
In addition, the skin layer may have a thickness which approximates that of the skin of the human head. In some embodiments, the skin layer has a thickness which particularly approximates that of the skin covering the portion or area of the neurocranium typically penetrated in performance of the medical procedure to be trained. In an embodiment, the skin layer has a thickness of about 2 millimeters.
In one embodiment of this training model, the imaging phantom and the biomechanical phantom are constructed independently however are identical in form and reference each other identically In other words, the imaging and biomechanical phantoms are anatomical analogues of each other or they are anatomically correlated. Therefore, the imaging phantom can be used for imaging purposes, for example with MR, CT, OCT, US, and/or PET. These images can be registered with the biomechanical phantom and used for navigation for the surgical procedure to be trained. In other words the imaging phantom and the biomechanical phantom both embody the characteristics of the training model, however the imaging phantom targets the imaging characteristics specifically and is directly correlated with the biomechanical phantom. While the biomechanical phantom embodies the biomechanical and physical characteristics of the phantom, for instance mimicking the tactile and tensile properties associated with the various layers within the training component.
The above described independent construction of two phantoms that are identical in form and reference each other may be extended to more than two phantoms where third and subsequent phantoms may be constructed to be optimal for third and different imaging modalities. In one such embodiment, a quality assurance/control phantom is constructed which may be a deformable or non-deformable phantom that generates known and consistent Diffusion Tensor Images (DTI), so that these images are obtained with a phantom containing diffusion bundles (660) as shown in
Provided along with the DTI are all the imaging parameters that were used to obtain the DTI so that the practitioner may reproduce these imaging parameters when they are practicing on the phantom. The quality control phantom will include known truths to be tested, such as being imaged with optimal pulse sequences that may be recorded and included with the phantom. For example, an optimal DTI scan may be used to image the diffusion fiber mimics whereupon at the practitioner's scanner, they can tune their diffusion sequence to optimize the pulse sequence for the practitioners scanner in order to recreate the quality control DTI sequence, knowing the reference level that they can and should achieve.
A software package containing appropriate algorithms may be used by the practitioner to run the analysis. For example, the practitioner scans the phantom and runs the analysis with the software analyzing the acquired image for quality and comparing it with the factory produced reference image. The software package is programmed with instructions to provide appropriate feedback to the practitioner, for example with respect to the resolution used by the practitioner, the feedback may be “your resolution is too low thus resulting in a noisy image, please try increasing your slice thickness to x”. Alternatively, if it is a research site they can use the quality control phantom to develop new pulse sequences knowing what they should achieve based on the quality control DTI sequence.
The software package may also contain appropriate algorithms programmed to analyze patient images for quality. For example, once an operator or technician performs a scan, the software may be programmed with algorithms to detect movement causing a reduction the quality of the image and then prompt the technician to repeat the scan given the artifact. If the artifact does not disappear, the operator/technician has the opportunity to scan the quality control phantom to try and troubleshoot the problem.
It is noted that pulse sequences are continually evolving, so that the software can be updated to reflect these new pulse sequences. For example due to continual improvements in MRI hardware, an optimal DTI scan today will unlikely be what is optimal is a year's time.
The development of optimal imaging parameters by the practitioner training on the phantom such as optimal MR pulse sequences may be further guided through the development of a scoring system (1230) that may be implemented as software or dedicated hardware. The scoring system (1230) will compare the MR image (1220) generated by the practitioner training on the phantom against the reference image (1210) generated at the time just after manufacturing the phantom where the latter image is considered to be the golden standard to the truth. Parameters for score may include aspects of the image that are relevant to development of optimal DTI output. Such parameters may include, but not are not limited to, resolution, scan time, contrast, signal-to-noise ratio, correct representation of direction of fiber bundles via DTI, raw dimensions of the acquired image etc. Hence, the imaging phantom teaches capture of optimal MR images with clinically useful DTI information that are of value for safely approaching and resecting tumor targets from the biomechanical phantom.
It will be understood that above described DTI phantom for qualification and optimization of data acquisition parameters need not be anatomically identical to a human organ such as brain or heart. Instead, it could be a fixed geometrical shape such as a sphere or a cylinder. Hence, total set or kit of training phantoms may include a brain-like biomechanical phantom, a brain-like imaging phantom and a third rigid phantom of fixed geometric shape for optimizing MR data acquisition parameters. Some of the hardware features of the phantom used to optimize MRI acquisition are illustrated in Table 6. These features may be compared with optimal values established a priori. Hence, the latter phantom can be used qualify acquisition protocols and used to perform root-cause analysis when failure of the MR equipment is suspected.
Some of the parameters analyzed using the latter phantom and their role are presented in Table 7. These parameters are intended to reduce the need for repeat scans for patients due to lack of insufficient data or quality in pre-operative scans, diagnostic scans, post-operative scans and functional MRI scans. The analysis result can be used to automatically deduce faults in the data acquisition process and suggest ways of improving the scans.
It will be understood that mammalian (human or animal) brain and head models disclosed herein may be employed for a wide variety of applications, for example, involving simulation, training, demonstration, education, research, and/or calibration of instruments and systems. In some example applications, embodiments provided herein may be employed for the simulation of medical procedures including brain tumor resection, deployment of deep brain stimulation devices, clot removal, craniotomy and installation of shunts. Furthermore, the procedures may be image guided where imaging modalities may include MR, DWI, CT, OCT, PET and ultrasound.
The above discussion has listed various materials that may be used for head and brain phantoms. The following give examples of imaging and biomechanical phantoms.
Example Imaging Phantom and Method of Making
An image obtained through MRI was used to 3D-print an anatomically accurate shape of the brain with deep sulci emulating the human brain. While MRI was used in this example, it will be appreciated that images obtained using other modalities may also be used, including, but not limited to, MRI, CT, and PET. This brain was then used to form a mold by painting it with a flexible mold material such as a silicon plastic, rubbers, or latex. This mold was then released from the printed brain by scoring a large X on the underside of the brain, allowing the underside of the mold to be folded back to release the printed brain within. The flexible mold may then be used to mold an anatomically correct brain in one piece with deep sulci that may be released from the mold via the crosshairs on the underside. The brain material to be molded may by a firm or soft material, such as agar, gelatin, polyurethane, soybean gel, or a PVA formulation between 1 and 15% with between 1 and 8 freeze/thaw cycles. During the molding process, the brain mold is situated within a tough outer shell that prevents the mold from expanding during the process. A PVA hydrogel was constructed by emulsifying 4% PVA and 0.1% biocide in water. This formulation was poured into the mold and processed with 2 freeze/thaw cycles to achieve the appropriate biomechanical properties of the brain.
As discussed previously, this brain phantom may contain targets for resection, such as for example tumor targets, blood clots, abnormal anatomical features and the like. These targets are designed to emulate the biomechanical and imaging (MRI, CT, US) properties of the particular target(s). For example, in the case of brain tumors, ICH/Abscess, Metastatic/Cavernoma, High grade glioma, or low grade glioma mimics are provided. These targets are shaped by forming a mold with a size approximating a lesion, from 0.1 cm to 5 cm. This mold may be spherical in nature or erratically shaped as brain lesions may be. These molds may also contain leads which serve to tether the tumor within the brain. For example, one target may model a 3 cm metastatic tumor in the frontal-left portion of the brain, 2-4 cm from the surface of the sulci. These tumors are formed from between 1-15% PVA concentration dissolved in water and sent through between 1 and 8 freeze/thaw cycles to achieve the desired biomechanical and imaging properties. The targets may be situated within the brain phantom using a series of intersecting wires for support. These wires serve to position and suspend the targets in desired and repeatable locations. The tumor target(s) are positioned on the wires prior to pouring the brain formulation precursor within. Once the mold has set, the wires are pulled out from the mold and the targets remain within.
The imaging phantom will be composed of the same PVA-C concentration as the resection phantom, although enclosed in a skull for preservation as this imaging phantom is non-disposable. This imaging phantom may contain other brain features that are not present within the resection (biomechanical) phantom and do not disrupt the relationship between the two phantoms. For example, a target within the imaging brain phantom will correspond directly to the target within the resection or biomechanical phantom. Although, it will be understood that the imaging phantom may be produced to differentiate white matter from gray matter, contain a cerebellum, ventricles, CSF, and diffusion fibers. The gray matter layer may be over-molded on the white matter layer and both may be comprised of a PVA-C hydrogel mixture of between 2% and 8% with one or more freeze/thaw cycles and doped with appropriate concentrations of a suitable contrast agent to achieve the T1, T2, and T2* properties of the human brain. This will be achieve by mixing the appropriate chemical into the PVA formulation a suitable material. As noted above, these contrast agents may be any one of a fluoride, a chloride, or sulfate. Non-limiting examples include chromium fluoride, gadolinium chloride, copper sulfate, barium sulfate, manganese chloride. In addition, agarose may be used as well.
Diffusion fibers or fiber bundle mimics may be constructed by arranging and immersing strands of wicking material such as thread, twine, cloth, or rope within a hydrogel. The phantoms maybe produced replicating various fractional anisotropy (FA) and apparent diffusion coefficient (ADC) characteristics. Fractional anisotropy (FA) is a scalar constant with a value between zero and one that indicates the strength of directionality, where zero is isotropic and one indicates strong diffusion in only one direction. The apparent diffusion coefficient (ADC), indicates how diffusive the fiber is, where a large value indicates lots of diffusion and a low value indicates very little.
Within the diffusion phantom, these ADC and FA values are achieved by varying fiber parameters, such as the material of the fibers, diameter of the fibers (0.001mm-5 mm), and the amount of fibers within a bunch or rope formation. Fiber organization may include individual threads or tube like structures, these may be braided or bunched. Sample fiber materials include wire, organic, and/or synthetic fibers, for instance nylon, cotton, polyester, polyethylene, animal hair, wool, silk, teflon, bamboo, rayon, fiberglass, silica and microfibers. These fibers may be coated in a material such as wax which will also determine the FA and ADC properties of the diffusion.
These strands may be individual or formed together in a bundle. The individual strand or bundle may be less than 5 mm in diameter or be thinner to approximate the diameter of fiber tracts within the human brain. These fibers may be constructed from material such as wood, bamboo, silk, polypropylene, or nylon. The hydrogel serves to hydrate while the wicking and fibrous nature of the strand provides direction. These fibers may be arranged to emulate the pattern of diffusion fibers or tracks within the brain. Alternatively, these fibers may be arranged within a quality assurance or quality control phantom to develop diffusion pulse sequences, or alternatively to assess the quality of imaging. A diffusion tensor image phantom was constructed from a 4 mm diameter nylon kernmantle rope that has been suspended in a grid formation within a plastic container. This container was then filled with a hydrogel formed from 8% PVA that was processed with two freeze-thaw cycles. A diffusion weighted image (DWI) was acquired with this phantom and is included in
Alternatively, diffusion fibers or fiber bundle mimics may be constructed by immersing strands of the wicking material within a tube filled with water and sealed. For example, a nylon kernmantle rope with a diameter of 4 mm is threaded through a Teflon tube with a 6 mm diameter, filled with water and then sealed with a heat sealing plastic. These fibers, when immersed within an imaging liquid, such as a PVA hydrogel, can be used to replicate the diffusion fibers or diffusion tracks within the brain or alternatively to calibrate or qualify diffusion weighted imaging scans with MRI.
While the preceding disclosure relates to a brain phantom exhibiting both imaging properties and biomechanical properties (either in a single phantom or in a pair of phantoms in which one is specifically optimized for use as an imaging phantom and the other is optimized for use as a biomechanical phantom), it will be appreciated that the same principles above may be applied to produce phantoms of other anatomical parts, organs, joints, spine, etc. Mimic materials are chosen to give imaging properties and biomechanical properties which closely mimic the actual anatomical parts based on the same principles as disclosed above for the brain phantom or brain simulator.
The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.
This application claims priority to U.S. Provisional Application No. 61/845,256, titled “SURGICAL TRAINING AND IMAGING BRAIN PHANTOM” and filed on Jul. 11, 2013, the entire contents of which are incorporated herein by reference. This application claims priority to U.S. Provisional Application No. 61/900,122, titled “SURGICAL TRAINING AND IMAGING BRAIN PHANTOM” and filed on Nov. 5, 2013, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2014/050659 | 7/10/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61845256 | Jul 2013 | US | |
| 61900122 | Nov 2013 | US |
