Patent Application
20080004500
In the drawings, which are not necessarily drawn to scale, like numerals describe substantially similar components throughout the several views. Like numerals having different letter suffixes represent different instances of substantially similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.
The following detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments, which are also referred to herein as “examples,” are described in enough detail to enable those skilled in the art to practice the invention. The embodiments may be combined, other embodiments may be utilized, or structural, logical and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.
In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one. In this document, the term “or” is used to refer to a nonexclusive or, unless otherwise indicated. Furthermore, all publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.
In some examples, the IMD 102 is adapted to store patient data and use the data to provide tailored therapy. For example, using historical physiological data, an IMD 102 may be able to discriminate between lethal and non-lethal heart rhythms and deliver an appropriate therapy. However, it is often desirable to establish a proper baseline of historical data by collecting a sufficient amount of data in the IMD 102. In some examples, a “learning period” of some time (e.g., thirty days) is used to establish the baseline for one or more physiological signals. An IMD 102 may, in an example, store a moving window of data of operation, such as a time period equal to the learning period, and use the information as a baseline indication of the patient's biorhythms or biological events.
When an IMD 102 malfunctions or reaches the end of its lifecycle, a new IMD (not shown) may be implanted in place of the retired IMD 102. In some examples, the replacement IMD is a newer or different model than the unit being replaced. In other examples, the replacement IMD is substantially the same as the explanted IMD. The replacement IMD, however, generally does not have the benefit of the historical patient data, and thus, the patient 100 must endure another learning period as the new IMD builds its baseline. In addition, any patient-specific device settings stored on the explanted IMD 102 are typically not automatically transferred to the replacement device. The current inventor has recognized that providing historical patient data to a replacement IMD advantageously bypasses any necessary learning period. Additionally, the current inventor has recognized that automatically transferring device settings to a replacement IMD may be more efficient and less prone to human error.
Data 202 may include stored physiological data, calculated summary data, event data or device data. For example, an implantable medical device may sense and collect raw physiological data, temporarily store the physiological data, use the data to calculate summary data, such as trend data, and store the trend data while discarding the temporarily stored raw physiological data. By only storing summary data, such as trend data, a more efficient use of the device's internal memory may be achieved. As another example, when an implanted medical device senses an event, such as a tachyarrhythmia episode, the IMD may store event markers or other details about the event (e.g., time of event, severity, length of event). Historical event data can be used for predictively determining similar future events and adapting treatment accordingly.
In an example, the external transfer device 204 can temporarily store the data 202 and process the stored data 202. For example, if the first patient device 200 is an IMD that is being explanted to be replaced with another IMD 206, the external transfer device 204 may condition the data 202 to be compatible with the replacement IMD 206. The conditioning may, in some examples, not involve any data transformation, such as when the first patient device 200 and the IMD 206 are substantially the same device. In other examples, the data conditioning may involve complex de-filtering and re-filtering of data, such as when the replacement IMD 206 is a different model or has different capabilities than the first patient device 200. In another example, the conditioning may only partially transform the data, such as to an un-processed or raw, sensed form, and provide the data to the target device (e.g., the replacement IMD 206), which can treat it as sensed data and perform its own signal processing. In addition, data conditioning may involve a translation of device settings, such as from one device model to another model with more or fewer settings, or with settings that may be a combination or subcombination of the other device's settings.
As another example, the external transfer device 204 may also provide data 202, either processed or unprocessed, to another destination, such as a research laboratory 208 or a centralized patient management system 210. Users at a research laboratory 208 may be interested in the data 202 for several reasons including offline analysis or simulation. In addition, providing data 202 to a centralized patient management system 210 may allow for other health care practitioners to access the data for research, statistical population use, patient monitoring, or for data recovery purposes. In other examples, the external transfer device 204 may also provide data 202, either processed or unprocessed, to an external patient monitor (not shown) or a data storage device (not shown).
At 308, the data is processed. In an example, at 308 the data is processed to a format compatible with the target device before being transferred (block 306). In another example, the data is processed to a substantially unprocessed (e.g., sensed) format at 308. Then the substantially unprocessed data is transferred to the target device (block 306) where the data is processed by the target device, such that it is substantially similar to the target device's native format. At 310, the method 300 determines if the data is to be transferred to another device. If so, then the method 300 proceeds to decision block 304 to continue processing.
At 502, the method 308 determines if the data was processed by the source device. In an example, a lookup table is used to record and track which signals are modified or processed on which devices in which modes. Also, an indication of how the signals were modified or processed is recorded in the lookup table for later reference when determining how to invert or revert such processing. For example, the source device may collect raw signal data and then process it, such as with a signal processing function, and only store the processed signal data. Signal processing functions may include a frequency-selective function, an upsampling function, a downsampling function, a re-sampling function, a filtering function, an amplifying function, an attenuating function, an averaging function, a function to calculate the median, mode, standard deviation or quartiles, a function to build a histogram, a function to estimate a probability distribution function or cumulative distribution function or a compressing function in various examples. Alternatively, the source device may store the raw or lesser-processed sensed signal data either alone or in combination with more-processed data. In an example, if both a lesser-processed signal data set and a more-processed signal data set are available, the method 308 can attempt to de-process the lesser-processed signal data first. This may advantageously avoid introducing artifacts when trying to reverse the additional processing undergone by the more-processed signal data set.
At 504, if the signal data was initially processed by the source device, then the data is at least partially de-processed, such as to substantially revert to the original signal data format. For example, a source IMD may sense electrocardiogram data and use a first filter function H1 to filter the incoming signal to remove noise and provide a cleaner signal to analyze. In order to de-process or substantially revert the data toward the original signal form, the method 308 may apply an inverse filter function H−1′1, where “′” indicates that H−1′1 is an estimate of an inverse function of H1, as an exact inverse function may not be possible due to mathematical limitations or limitations of physics. In some examples, the first filter function H1 is a linear determined 1:1 process and thus, an actual inverse filter function H−11 can be realized and implemented such that H−1′1=H−11 and the resulting signal has no distortion. In examples, the inverse filter function H−1′1 is applied in a time domain or a frequency domain. In a further example, the inverse filter function H−1′1 includes an amplitude-modification function. For example, a first IMD may provide 8-bit data storage whereas a second IMD may provide 12-bit data storage. To properly transform binary data from the first IMD's format to the second IMD's format, a left shift of 4 bits is used, which will appropriately scale the binary data to the second IMD's native format. As another example, if an input signal was subjected to automatic gain control or intentional gain compression (e.g., non-linear gain) at a first IMD, to compensate, one or more functions may be used to reverse the first IMD's transfer function to produce substantially unprocessed data.
In a further example, either the actual inverse filter function H−11 or the estimated inverse filter function H−1′1 may be determined based on population data of patients with the same or similar devices, or with devices that implement the same acquisition filter function H1. In such an example, the inverse filter function (e.g., H−11, H−1′1) can be approximated using methods such as adaptive filtering or using a neural network, which seek to minimize signal distortion until, for example, the distortion meets a “minimum distortion” criteria or threshold. In general, a population-based derivation method may be helpful in the cases where it is difficult or computationally expensive to directly derive H−11 from H1 or when a derivation results in unacceptable distortion.
In an example, the inverse filter function H−1′1 designed such that a comparison between the reconstructed signal and the original raw signal indicate minimal distortion. For example, the inverse filter function H−1′1 is designed to minimize one or more of a mean squared error, a minimum phase shift, a minimum dominant frequency component deterioration, a reserved signal-to-noise ratio, or a high cross-correlation between the raw and the reconstructed signal data.
Similarly, if multiple signal processing functions were used during data acquisition, then one or more other signal processing functions can be reversed by applying one or more other corresponding inverse or reverse signal processing functions.
Using either an analytical or a data-driven (e.g., population-based) method a maximum error or distortion in signal magnitude or phase introduced by H−1′1 can be determined. The maximum error may be used to indicate quantitatively how good the estimate H−1′1 is. Using the quantitative value as an “error bound” of the reconstructed signal, the rate of false detection (due to magnitude distortion) and/or the timing error of the detected event (due to phase distortion) may be determined and used to adjust discrimination processes when detecting an event.
At 506, a target device is determined. The target device may include a second (replacement) IMD, a workstation in a research computer system or a database in a centralized patient management system. In addition, the target device may be an offline storage device or a simulation or analysis machine.
At 508, the physiological data is transformed to the target device's format. For example, the target may be an IMD that uses its own signal processing function H2. In order to transform the physiological data obtained from the source IMD to simulate data captured on the target IMD, an associated function H′2 can be used. Again, the “′” indicates that H′2 is an estimate of H2, as it may not be possible to recreate H2 exactly due to mathematical limitations or limitations of physics. In some examples, H2=H′2, such that the function used to transform or make the data compatible with the target device is the same as that used by the target device during its own data acquisition process. In other examples, a different function or group of functions may be used to prepare the data for the target device.
At 604, if the signal data was initially processed by the source device, then the data is at least partially de-processed, such as to substantially revert to the original signal data format. For example, a source IMD may sense electrocardiogram data and use a first filter function H1 to filter the incoming signal to remove noise and provide a cleaner signal to analyze. In order to de-process or substantially revert the data toward the original signal form, the method 308 may apply an inverse filter function H−1′1, where “′” indicates that H−1′1 is an estimate of an inverse function of H1, as an exact inverse function may not be possible due to mathematical limitations or limitations of physics. As described above with reference to
At 606, a target device is determined. The target device may include a second (replacement) IMD, a workstation in a research computer system or a database in a centralized patient management system. In addition, the target device may be an offline storage device or a simulation or analysis machine. In an example, the reverted (e.g., substantially unprocessed) data is provided to the determined target device, which may use its native signal processing functions to process the data.
At 702, the method 308 determines if the physiological data was modified during acquisition by a first signal processing function. In some examples, as the physiological data is acquired at a source device, the first signal processing function includes a first filter to clean and prepare the data for analysis. If the physiological data was modified by signal processing by the source device, then the method 308 determines the function that was used.
In an example, more than one function may be used to process acquired data at the source device. In some examples, the functions may be applied serially. For example, the source device may sample, buffer, amplify, filter, upsample, downsample, or perform analog-to-digital conversion on an intrinsic cardiac signal. In other examples, one or more functions may be applied at different times during signal acquisition.
Referring to
At 706, an inverse signal processing function H−1′1 is determined. As discussed above, H−1′1 may be an actual inverse function or an estimated inverse function conforming to a minimum threshold level of distortion. In some examples, the inverse function may be a multi-step process, such as involving multiple sequential functions to substantially reverse the processing effects of the source device's acquisition process. In an example, when multiple sequential functions were used during the data acquisition, a reverse sequence of corresponding inverse functions is determined.
At 708, the inverse function H−1′1 is applied to the physiological data. In an example, more than one inverse function is needed to revert the data to its raw form. For example, if the source device applied three filter functions in series to the raw sensed data, the temporary device would use one or more corresponding inverse filter functions to undo the processing. Similarly, if the source device's acquisition processing involved first filtering and then down-sampling, then the temporary device's recovery processing may involve first up-sampling and then inverse-filtering.
At 710, a target device and an associated signal processing function H′2 are determined. For example, if the target device is a replacement IMD, a function H′2 is determined such that the function will transform the reverted physiological data to a form that is substantially similar to that of the target device's signal-processed format. As described above, in order to transform the physiological data obtained from the source IMD to simulate data captured on the target IMD, an associated function H′2 can be used. The “′” indicates that H′2 is an estimate of H2, as it may not be possible to recreate H2 exactly due to mathematical limitations or limitations of physics. In some examples, H2=H′2, such that the function used to transform or make the data compatible with the target device is the same as that used by the target device during its own data acquisition process. In other examples, a different function or set of functions may be used to prepare the data for the target device.
At 712, the transformation function H′2 is applied to the reverted physiological data. In an example, more than one filter function is used to transform the data to a compatible form.
De-processed data can also be provided to one or more intermediate processing devices 1018. The intermediate processing devices 1018 can then transform the physiological data to be compatible with a second target device 1020. The intermediate processing devices 1018 may process the de-processed data serially or in parallel. After fully transforming the data, the re-processed physiological data is transferred to the second target device 1020.
In some cases, de-processing is a multi-step process and the external transfer device 1000 can perform one or more steps and transfer the partially de-processed data to a secondary processing device 1022, which can complete the de-processing. In other examples, two or more secondary processing devices (not shown) can be used, either serially or in parallel, to further process the partially de-processed data received from the external transfer device 1000. Fully de-processed data can then be transferred to one or more tertiary processing devices 1024. The tertiary processing devices 1024 can re-process the physiological data such that it is compatible with a third target device 1026. Alternatively, the third target device 1026 can receive the de-processed physiological data from the secondary processing device 1024 to process internally, such as with the same or similar signal processing function used during data acquisition.
It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.
For the purposes of this specification, the term “machine-readable medium” or “computer-readable medium” shall be taken to include any medium which is capable of storing or encoding a sequence of instructions for execution by the machine and that cause the machine to perform any one of the methodologies of the inventive subject matter. The terms “machine-readable medium” or “computer-readable medium” shall accordingly be taken to include, but not be limited to, solid-state memories, optical and magnetic disks, and carrier wave signals. Further, it will be appreciated that the software could be distributed across multiple machines or storage media, which may include the machine-readable medium.
Method embodiments described herein may be computer-implemented. Some embodiments may include computer-readable media encoded with a computer program (e.g., software), which includes instructions operable to cause an electronic device to perform methods of various embodiments. A software implementation (or computer-implemented method) may include microcode, assembly language code, or a higher-level language code, which further may include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, the code may be tangibly stored on one or more volatile or non-volatile computer-readable media during execution or at other times. These computer-readable media may include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.
The foregoing description of specific embodiments reveals the general nature of the inventive subject matter sufficiently that others can, by applying current knowledge, readily modify and/or adapt it for various applications without departing from the generic concept. Therefore, such adaptations and modifications are within the meaning and range of equivalents of the disclosed embodiments. The phraseology or terminology employed herein is for the purpose of description and not of limitation. Accordingly, the inventive subject matter embraces all such alternatives, modifications, equivalents and variations as fall within the spirit and broad scope of the appended claims.
The Abstract is provided to comply with 37 C.F.R. §1.72(b), which requires that it allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.
