Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-12-15
2003-09-02
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S443000, C600S437000
Reexamination Certificate
active
06612988
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to medical systems and, more particularly, to non-invasive application of focused ultrasound energy to subjects such as humans, and in particular to the brain of a human subject.
BACKGROUND OF THE INVENTION
Treatment of tissues lying at specific locations within the skull may be limited to removal or ablation. While these treatments have proven effective for certain localized disorders, such as tumors, they involve delicate, time-consuming procedures that may result in destruction of otherwise healthy tissues. These treatments are generally not appropriate for disorders in which diseased tissue is integrated into healthy tissue, except in instances where destruction of the healthy tissue will not unduly effect neurologic function.
The noninvasive nature of ultrasound surgery has special appeal in the brain where it is often desirable to destroy or treat deep tissue volumes without disturbing healthy tissues. Focused ultrasound beams have been used for noninvasive surgery in many other parts of the body. Ultrasound penetrates well through soft tissues and, due to the short wavelengths (1.5 mm at 1 MHz), it can be focused to spots with dimensions of a few millimeters. By heating, e.g., using ultrasound, tumorous or cancerous tissue in the abdomen, for example, it is possible to ablate the diseased portions without significant damage to surrounding healthy tissue.
SUMMARY OF THE INVENTION
In general, in one aspect, the invention provides a method of delivering ultrasound signals. The method includes providing an image of at least a portion of a subject intended to receive ultrasound signals between sources of the ultrasound signals and a desired region of the subject for receiving focused ultrasound signals, identifying, from the image, physical characteristics of different layers of material between the sources and the desired region, and determining at least one of phase corrections and amplitude corrections for the sources depending on respective thicknesses of portions of each of the layers disposed between each source and the desired region.
Implementations of the invention may include one or more of the following features. The physical characteristics are associated with material type and at least one of material density and material structure, the identifying further comprising identifying thicknesses of the layers. The phase corrections are determined in accordance with propagation characteristics of each of the layers. The propagation characteristics are determined based upon the material type and at least one of the material density and the material structure of each of the respective layers. The layers are identified using values associated with portions of the image. The values are intensities of the portions of the image. The phase corrections are determined using a three-layer model of a skull of the subject. Two of the three layers are assumed to have approximately identical speeds of sound, c
i
, therein, with the other layer having a speed of sound c
ii
therein, wherein the phase corrections are determined using a phase shift determined according to:
φ
=
360
f
∑
n
=
1
3
D
n
(
1
c
0
-
1
c
n
)
where c
n
is a speed of sound in the n
th
layer, and D
n
is a thickness of the n
th
layer, and wherein the speeds of sound in the layers are determined according to:
c
i
(
ρ
)
=
(
d
1
+
d
3
)
[
d
1
+
d
2
+
d
3
c
0
-
d
2
c
ii
-
φ
(
ρ
)
360
fD
]
-
1
where d
1
, d
2
, d
3
, are thicknesses of the three layers, &phgr;(&rgr;) is a measured phase shift as a function of density, and &rgr; is density.
Further, implementations of the invention may include one or more of the following features. The physical characteristics are associated with x-ray attenuation coefficients, &mgr;. The material between the sources and the desired region is bone. The phase corrections are related to the attenuation coefficient by a phase function including parameters derived at least partially experimentally. Each phase correction equals M+B&Sgr;(1/&mgr;(x))+C&Sgr;(1/&mgr;(x))
2
, where &mgr;(x) is the attenuation coefficient as a function of distance x along a line of propagation between each source and the desired region, and where M, B, and C are derived at least partially experimentally. The amplitude corrections are related to the attenuation coefficient by an amplitude function including parameters derived at least partially experimentally. Each amplitude correction is related to N+F&Sgr;&mgr;(x)+G&Sgr;(&mgr;(x))
2
, where &mgr;(x) is the attenuation coefficient as a function of distance x along a line of propagation between each source and the desired region, and where N, F, and G are derived at least partially experimentally.
Further, implementations of the invention may include one or more of the following features. The layers are identified according to both material density and material structure. Providing the image includes producing the image using magnetic resonance imaging. Providing the image includes producing the image using computer tomography. The sources are piezoelectric transducer elements. Both phase and amplitude corrections are determined.
In general, in another aspect, the invention provides a system for delivering ultrasound signals. The system includes an apparatus configured to analyze an image of at least a portion of a subject intended to receive ultrasound signals between sources of the ultrasound signals and a desired region of the subject for receiving focused ultrasound signals, the apparatus configured to determine, from the image, information about different layers of the at least a portion of the subject, and an array of sources of ultrasound signals having at least one of their relative phases and their amplitudes set in accordance with the information about each layer of the at least a portion of the subject provided by the apparatus.
Implementations of the invention may include one or more of the following features. The phases are set in accordance with propagation characteristics of each layer of the at least a portion of the subject. The propagation characteristics are dependent upon the material type and at least one of the material density and the material structure of each layer of the at least a portion of the subject. The apparatus is configured to identify the layers using values associated with portions of the image. The values are intensities of the portions of the image. The apparatus is configured to determine the information about different layers of bone. The apparatus is configured to determine the phase corrections using a three-layer model of a skull of the subject. The information is associated with an x-ray attenuation coefficient, &mgr;. The phase corrections are related to the attenuation coefficient by a phase function including parameters derived at least partially experimentally. The amplitude corrections are related to the attenuation coefficient by an amplitude function including parameters derived at least partially experimentally.
Further, implementations of the invention may include one or more of the following features. The system further includes a magnetic resonance imager coupled to the apparatus and configured to produce the image. The system further includes a computer tomography imager coupled to the apparatus and configured to produce the image. The sources are piezoelectric transducer elements.
In general, in another aspect, the invention provides a computer program product residing on a computer readable medium and comprising instructions for causing a computer to analyze an image of at least a portion of a subject to receive ultrasound signals between sources of the ultrasound signals and a desired region of the subject for receiving focused ultrasound signals to identify, from the image, physical characteristics of layers of material between the sources and the desired region, and to determine at least one of phase corrections and amplitude corrections for the sources depending o
Grinfeld Javier
Hynynen Kullervo
Maor Dov
Brigham and Women's Hospital, Inc.
Elrifi, Esq. Ivor R.
Hunter, Esq. Shane H.
Jaworski Francis J.
Mintz Levin Cohn Ferris Glovsky and Popeo P.C.
LandOfFree
Ultrasound therapy does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ultrasound therapy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ultrasound therapy will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3041097