Patent Application
20060095100
Photodynamic therapy (PDT) is a clinical treatment in which a photoreactive agent is typically injected or applied at a patient treatment site (e.g., a tumor), and then activated by light emitted from a light source. In some cases, the light source may be a light bar on which a plurality of solid-state light emitters (e.g., light emitting diodes (LEDs)) are mounted. When activated by the light, the photoreactive agent may help to cure a problem at the treatment site. For example, the photoreactive agent may target and destroy unhealthy cells such as cancer cells. If the agent is primarily isolated at the treatment site, or if the light is primarily directed toward the treatment site, damage to healthy tissue surrounding the treatment site may be limited.
In some cases, photodynamic therapy may be administered without a photoreactive agent. That is, certain wavelengths of light, administered alone, may also help to cure a problem at the treatment site.
One exemplary light source that may be used in photodynamic therapies is the LitX™ platform offered by Light Sciences Corporation (having its principal place of business in Snoqualmie, Wash., USA).
In one embodiment, apparatus for regulating light administered at a patient treatment site comprises at least one solid-state light emitter, at least one fiber optic light guide, at least one photosensor and a control system. The light emitter(s) are provided to be positioned adjacent the treatment site. The light guide(s) each have a first end to receive light emitted by the solid-state light emitter(s). The photosensor(s) are each positioned to receive light emitted from a second end of one of the light guides. The control system is operably associated with the solid-state light emitter(s) and the photosensor(s), to regulate the light output of the light emitter(s) in accordance with measurements received from the photosensor(s).
In another embodiment, apparatus comprises at least one solid-state light emitter, at least one fiber optic light guide, at least one photosensor and a control system. The light guide(s) each have a first end that is independently positionable with respect to the solid-state light emitter(s), to receive light that is emitted by the solid-state light emitter(s). The photosensor(s) are each positioned to receive light emitted from a second end of one of the light guides. The control system is operably associated with the solid-state light emitter(s) and the photosensor(s), to regulate the light output of the light emitter(s) in accordance with measurements received from the photosensor(s).
In yet another embodiment, a method comprises positioning at least one solid-state light emitter adjacent a patient treatment site. A first end of at least one fiber optic light guide is then positioned to receive light emitted by the solid-state light emitter(s). Via a control system, the solid-state light emitter(s) are activated; at least one photosensor is activated to measure light emitted from a second end of one of the fiber optic light guides; and the light emitted from the solid-state light emitter(s) is regulated in accordance with the measurements taken by the photosensor(s).
In an additional embodiment, a method for activating a photoreactive agent at a patient treatment site comprises applying a photoreactive agent to the treatment site (with the photoreactive agent being activated by one or more wavelengths of light). At least one solid-state light emitter, capable of emitting the one or more wavelengths of light, is then positioned adjacent the treatment site; and a first end of at least one fiber optic light guide is positioned to receive light emitted the solid-state light emitter(s). The control system is then activated to, in turn, 1) activate the solid-state light emitter(s), 2) activate at least one photosensor to measure light emitted from a second end of one of the fiber optic light guides, and 3) tune the light emitted from the solid-state light emitter(s) to the one or more wavelengths, in accordance with the measurements taken by the photosensor(s).
Other embodiments are also disclosed.
Illustrative and presently preferred embodiments of the invention are illustrated in the drawings, in which:
Solid-state light emitters (e.g., LEDs) are particularly useful in PDT systems because they are inexpensive to manufacture, do not contain glass or other highly fragile materials, are widely available, and do not generate a lot of heat. However, the physical and electrical characteristics of solid-state light emitters (e.g., turn-on voltage) can vary from batch to batch, leading to nominally identical LEDs having different optical properties. Furthermore, the optical properties of LEDs can change or deteriorate with factors such as changes in temperature and age. As a result, in PDT systems where the integrity of light emitted by a light source needs to be maintained, it would be useful to have some sort of means for regulating the light source's light.
The method 100 continues with the positioning 104 of a first end 210 of at least one fiber optic light guide 212 to receive light emitted by the solid-state light emitter(s) 202, 204. The first end(s) 210 of the light guide(s) 212 may be positioned adjacent the light emitter(s) 202, 204, the treatment site 300 or both.
After positioning 102, 104 the light emitter(s) 202, 204 and light guide(s) 212, a control system 214 may be used 106 to activate 108 the light emitter(s) 202, 204. The control system 214 may also 1) activate 110 at least one photosensor 216, 218, 220 to measure light emitted from a second 222 end of one of the light guides 212, and 2) regulate 112 the light emitted from the light emitter(s) 202, 204 in accordance with the measurements taken by the photosensor(s) 216-220. By way of example, the photosensor(s) 216-220 may comprise one or more photodiodes or phototransistors that measure the intensity of one or more wavelengths of light.
In one embodiment, the control system 214 may regulate the intensity of light emitted from the light emitter(s) 202, 204, in accordance with a light intensity measurement obtained from a single photosensor. For example, the control system 214 may compare a light intensity obtained from the photosensor with a desired intensity, and then adjust the drive signal(s) of the light emitter(s) if the measured intensity is out of range. This method of regulation is especially useful if the light emitter(s) all emit the same wavelength of light (e.g., if all of the light emitters are red LEDs).
In another embodiment, the control system 214 may regulate the color of light emitted from the light emitter(s) 202, 204, in accordance with light intensity measurements obtained from plural photosensors 216-220 (e.g., red, green and blue photosensors), or in accordance with a single photosensor that is serially filtered to detect different wavelengths of light (e.g., a photosensor behind a color wheel). For example, the control system 214 may compare each of the light intensity measurements obtained from the photosensors 216-220 with a plurality of intensities corresponding to a desired color and, if a measured intensity is out of range, the control system 214 may adjust the drive signal(s) of a corresponding color of light emitter 202. This latter method of regulation is especially useful if the different light emitters 202, 204 emit two or more different wavelengths of light.
As partially introduced above,
The light emitters 202, 204 may variously comprise LEDs, laser diodes, or other solid-state devices. As shown in
The light bar 208 may be surrounded by a lens, light mixer sheath 400 or other element to encapsulate the light emitters and 1) provide a protective barrier between the circuitry of the light bar 208 and a patient 302, and 2) mix the light emitted by different-colored light emitters. In some cases, a light mixer sheath may comprise a diffusant or coating (e.g., a titanium oxide or silicon oxide coating) that serves to diffuse light. In other cases, a paper, gel or encapsulant-type diffuser could be provided between the light bar 208 and the sheath 400.
The apparatus 200 also comprises at least one fiber optic light guide 212, at least one photosensor 216-220, and a control system 214. For each fiber optic light guide 212, a first end 210 of the light guide is positioned to receive light (A) emitted by the light emitter(s) 202, 204. In addition to receiving the light emitted by the light emitter(s) 202, 204, the fiber optic light guide(s) 212 may serve to mix and/or filter light. If a plurality of light guides are provided, they could be enclosed in a common sheath.
Each photosensor 216-220 may be positioned to receive light emitted from a second end 222 of one of the light guides 212. In one embodiment, the apparatus 200 comprises only a single fiber optic light guide 212, with one or more photosensors 216-220 being positioned to receive light from the single fiber optic light guide 212. To disperse the light emitted from the light guide 212 to multiple photosensors 216-220, a diffuser 224 or one or more lenses may be positioned between the light guide 212 and the photosensors 216-220. Alternately, only a single photosensor could be used to sense the light emitted from the light guide. In this latter case, the single photosensor could sense different wavelengths of light by replacing the diffuser 224 with a color wheel (or some other element to differently and serially filter the light emitted from the light guide). Alternately, different photosensors may be positioned to receive light from different light guides. Mounting the photosensor(s) 216-220 to receive light from the end(s) 222 of light guide(s) 212 opposite the end(s) 210 positioned near a treatment site 300 can be advantageous in that the photosensor(s) 216-220 and their associated electronics do not block the light (λ) being administered at the treatment site 300.
In one embodiment, the photosensors 216-220 comprise two or more photosensors, each having a differently filtered input to measure a different wavelength (or range of wavelengths) of light. For example, different photosensors could respectively measure red, green and blue wavelengths of light.
The fiber optic light guide(s) 212 may be naturally flexible. Likewise, the light emitter(s) 202, 204 may be coupled to an elongate flexible member 226. The light emitter(s) 202, 204 and light guide(s) 212 are preferably independently positionable with respect to one another. In this manner, a physician is provided with more versatility in positioning the light emitter(s) 202, 204 and light guide(s) 212, possibly allowing the physician to position the light guide(s) 212 closer to the treatment site 300 than is possible to maneuver a light bar 208 or the like. This, in turn, enables the light guide(s) 212 to sense light as it is actually being administered to the treatment site 300. Alternately, the light emitter(s) 202, 204 and light guide(s) 212 may be fixed with respect to one another (e.g., via a bracket, or by attaching the light guide(s) 212 to the light bar 208). In one embodiment, the light guide(s) 212 and wiring for the light bar 208 may be enclosed within a common sheath, and the light guide(s) may be attached to the substrate 206 of the light bar 208.
As shown in
In one exemplary embodiment, the control system 214 may comprise driver circuitry 230, a color management system 232, and a microcontroller 234. The physical boundaries between these functional components 230-234 are somewhat arbitrary, and the functionality of the components 230-234 could be merged or divided into a fewer or greater number of components. In use, the color management system 232 receives desired color and/or intensity settings from the microcontroller 234, and converts the color setting (if provided) to a plurality of intensity settings for different colored light emitters. The color management system 232 also receives intensity measurements from the photosensor(s) 216-220. The color management system 232 then compares corresponding intensity measurements and, if a measurement is out of range, it adjusts the light output of a corresponding light emitter 202 by, for example, modulating its drive current via the driver circuitry 230.
By raising or lowering the drive currents of all light emitters 202, 204 in unison, the color management system 232 can control the intensity of a light source 208. By adjusting the ratios of drive currents supplied to different-colored light emitters 202, 204, the color management system 232 can control the color of the light source 208.
The apparatus 200 shown in
As shown in
