PET system with a positron lifetime measurement function and positron lifetime measurement method in a PET system

Patent metadata

Field	Value
Publication number	US-11143766-B2
Application number	US-201816612624-A
Country	US
Kind code	B2
Filing date	May 7, 2018
Priority date	May 11, 2017
Publication date	Oct 12, 2021
Grant date	Oct 12, 2021

Abstract

A PET system with a positron lifetime measurement function includes: a first gamma ray detector configured to receive, from an imaging target containing a nuclide that goes into an excited state of a daughter nucleus by undergoing beta decay and that then, subsequently to emission of a positron resulting from the beta decay, emits a deexcitation gamma ray when transiting into a ground state of the daughter nucleus, three annihilation gamma rays resulting from the positron annihilating with an electron, the first gamma ray detector thereby detecting the three annihilation gamma rays; a second gamma ray detector configured to detect the deexcitation gamma ray; and a processor configured to derive, in three dimensions, a distribution state of the nuclide in the imaging target and to determine information on a positron lifetime in association with a derived distribution position.

First claim

The invention claimed is:

1. A PET system with a positron lifetime measurement function, comprising:
a first gamma ray detector configured to receive, from an imaging target containing a nuclide that goes into an excited state of a daughter nucleus by undergoing beta decay and that then, subsequently to emission of a positron resulting from the beta decay, emits a deexcitation gamma ray when transiting into a ground state of the daughter nucleus, three annihilation gamma rays resulting from the positron annihilating with an electron, the first gamma ray detector thereby detecting the three annihilation gamma rays;
a second gamma ray detector provided separately from the first gamma ray detector and configured to detect the deexcitation gamma ray; and
a processor configured
to derive, in three dimensions, a distribution state of the nuclide in the imaging target and
to determine information on a positron lifetime in association with a derived distribution position
based on
a detected energy and a detection position of each of the annihilation gamma rays as detected by the first gamma ray detector and
a detection time point of the annihilation gamma rays as detected by the first gamma ray detector and a detection time point of the deexcitation gamma ray as detected by the second gamma ray detector, wherein

the first gamma ray detector outputs a detection signal of a gamma ray that is incident on the first gamma ray detector, and
in response to the second gamma ray detector detecting the deexcitation gamma ray, the processor acquires from the detection signal the detected energy and the detection position of each of the annihilation gamma rays and the detection time point of the annihilation gamma rays.

2. The PET system according to claim 1 , wherein
the processor is configured
to generate a three-dimensional distribution image of the nuclide in the imaging target and
to derive the information on the positron lifetime individually at each of a plurality of positions in the three-dimensional distribution image

based on
the detected energy and the detection position of each of the annihilation gamma rays and
the detection time point of the annihilation gamma rays and the detection time point of the deexcitation gamma ray.

3. The PET system according to claim 2 , wherein
the processor is configured, for each event in which the three annihilation gamma rays have been measured coincidentally within a predetermined time of the detection time point of the deexcitation gamma ray,
to estimate a positron annihilation position in the event and
to derive, as a positron lifetime in the event, a time difference from the detection time point of the deexcitation gamma ray to a detection time point at which the three annihilation gamma rays have been measured coincidentally
based on the detected energy and the detection position of each of the annihilation gamma rays, and

the processor is configured further
to generate the three-dimensional distribution image and
to derive the information on the positron lifetime individually at a plurality of positions in the three-dimensional distribution image
based on the positron annihilation position estimated and the positron lifetime derived for a plurality of events.

4. The PET system according to claim 1 , wherein
the processor is configured to generate a positron lifetime image that shows, in three dimensions,
distribution of the nuclide in the imaging target and
information on the positron lifetime at each distribution position of the nuclide in the imaging target

based on
the detected energy and the detection position of each of the annihilation gamma rays and
the detection time point of the annihilation gamma rays and the detection time point of the deexcitation gamma ray.

5. The PET system according to claim 4 , wherein
the processor is configured, for each event in which the three annihilation gamma rays have been measured coincidentally within a predetermined time of the detection time point of the deexcitation gamma ray,
to estimate a positron annihilation position in the event and
to derive, as a positron lifetime in the event, a time difference from the detection time point of the deexcitation gamma ray to a detection time point at which the three annihilation gamma rays have been measured coincidentally
based on the detected energy and the detection position of each of the annihilation gamma rays, and

the processor is configured further
to generate the positron lifetime image based on the positron annihilation position estimated and the positron lifetime derived for a plurality of events.

6. The PET system according to claim 1 , wherein
when the second gamma ray detector detects the deexcitation gamma ray, the processor judges that an event has occurred,
in response to occurrence of the event, the processor performs processing in which the processor checks whether or not the three annihilation gamma rays have been measured coincidentally within a predetermined time point of the deexcitation gamma ray, and
through the processing, the processor acquires the detected energy and the detection position of each of the annihilation gamma rays and the detection time point of the annihilation gamma rays.

7. A method of measuring a lifetime of a positron in a PET system including a first gamma ray detector configured to receive, from an imaging target containing a nuclide that goes into an excited state of a daughter nucleus by undergoing beta decay and that then, subsequently to emission of a positron resulting from the beta decay, emits a deexcitation gamma ray when transiting into a ground state of the daughter nucleus, three annihilation gamma rays resulting from the positron annihilating with an electron, thereby to detect the three annihilation gamma rays, and a second gamma ray detector configured to detect the deexcitation gamma ray, the method comprising:
deriving, in three dimensions, a distribution state of the nuclide in the imaging target and determining information on a positron lifetime in association with a derived distribution position, based on a detected energy and a detection position of each of the annihilation gamma rays as detected by the first gamma ray detector and a detection time point of the annihilation gamma rays as detected by the first gamma ray detector and a detection time point of the deexcitation gamma ray as detected by the second gamma ray detector;
outputting, by the first gamma ray detector, a detection signal of a gamma ray that is incident on the first gamma ray detector; and
acquiring from the detection signal the detected energy and the detection position of each of the annihilation gamma rays and the detection time point of the annihilation gamma rays in response to detection of the deexcitation gamma ray by the second gamma ray detector.

8. The method according to claim 7 , further comprising:
judging that an event has occurred in response to detection of the deexcitation gamma ray by the second gamma ray detector; and
performing in response to occurrence of the event, processing comprising:
checking whether or not the three annihilation gamma rays have been measured coincidentally within a predetermined time point of the deexcitation gamma ray; and
acquiring the detected energy and the detection position of each of the annihilation gamma rays and the detection time point of the annihilation gamma rays.

Assignees

• Riken

Inventors

• Fukuchi Tomonori

Classifications

• G01T1/2985 Primary

  In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis); (using external radiation sources A61B6/02) · CPC title

• G01T1/161

  Applications in the field of nuclear medicine, e.g. in vivo counting {(apparatus for radiation diagnosis A61B6/00)} · CPC title

• G01T1/29 Primary

  Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation · CPC title

• G01T7/02

  Collecting means for receiving or storing samples to be investigated {and possibly directly transporting the samples to the measuring arrangement; particularly for investigating radioactive fluids (sampling, preparing specimens for investigation in general G01N1/00, G01N1/02; shielded cells or rooms structurally combined with manipulatin devices G21F; measuring of chromatographically separated samples G01N30/00 - G01N30/96)} · CPC title

• A61B6/4258

  for detecting non x-ray radiation, e.g. gamma radiation (A61B6/037 takes precedence) · CPC title