Positron camera for range verification of heavy-ion radiotherapy

Iseki, Y.; Mizuno, Hideyuki; Futami, Yasuyuki; Tomitani, Takehiro; Kanai, Tatsuaki; Kanazawa, M.; Kitagawa, A.; Murakami, Takeshi; Nishio, Teiji; Suda, M.; Urakabe, E.; Yunoki, Akira; Sakai, Hirotaka

doi:10.1016/j.nima.2003.07.005

Cited by 98 publications

(71 citation statements)

References 8 publications

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“…At the carbon ion facility at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany a partial ring in-beam PET scanner was developed for in-situ monitoring of delivered dose (Enghardt et al, 1999) during beam delivery and has been operational for many years. New experimental planar positron cameras suitable for in-situ imaging have also been developed at HIMAC (Iseki et al, 2003), Kashiwa (Nishio et al, 2006, Nishio et al, 2010), and in Pisa (Attanasi et al, 2008). All these in-situ PET scanners operate with a fixed ring diameter.…”

Section: Introductionmentioning

confidence: 99%

Design study of anin situPET scanner for use in proton beam therapy

et al. 2011

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Proton beam therapy can deliver high radiation dose to a tumor without significant damage to surrounding healthy tissue or organs. One way of verifying the delivered dose distribution is to image the short-lived positron emitters produced by the proton beam as it travels through the patient. A potential solution to the limitations of PET imaging in proton beam therapy is the development of a high sensitivity, in-situ PET scanner that starts PET imaging almost immediately after patient irradiation while the patient is still lying on the treatment bed. A partial ring PET design is needed for this application in order to avoid interference between the PET detectors and the proton beam, as well restrictions on patient positioning on the couch. A partial ring also allows us to optimize the detector separation (and hence the sensitivity) for different patient sizes. Our goal in this investigation is to evaluate an in-situ PET scanner design for use in proton therapy that provides tomographic imaging in a partial ring scanner design using time-of-flight (TOF) information and an iterative reconstruction algorithm. A GEANT4 simulation of an incident proton beam was used to produce a positron emitter distribution, which was parameterized and then used as the source distribution inside a water-filled cylinder for EGS4 simulations of a PET system. Design optimization studies were performed as a function of crystal type and size, system timing resolution, scanner angular coverage, and number of positron emitter decays. Data analysis was performed to measure the accuracy of the reconstructed positron emitter distribution as well as the range of the positron emitter distribution. We simulated scanners with varying crystal size (2 to 4 mm) and type (LYSO and LaBr3) and our results indicate that 4-mm wide LYSO or LaBr3 crystals (resulting in 4-5-mm spatial resolution) are adequate; for a full-ring, non-TOF scanner we predict a low bias (< 0.6-mm) and a good precision (< 1-mm) in the estimated range relative to the simulated positron distribution. We then varied the angular acceptance of the scanner ranging from 1/2 to 2/3 of 2π; with a partial ring TOF imaging with good timing resolution (≤ 600ps) is necessary to produce accurate tomographic images. A two-third ring scanner with 300ps timing resolution leads to a bias of 1.0-mm and a precision of 1.4-mm in the range estimate. With a timing resolution of 600ps, the bias increases to 2.0-mm while the precision in the range estimate is similar. For a half ring scanner design, more distortions are present in the image, which is characterized by the increased error in the profile difference estimate. We varied the number of positron decays imaged by the PET scanner by an order of magnitude and we observe some decrease in the precision of the range estimate for lower number of decays, but all partial ring scanner designs studied have a precision ≤ 1.5-mm. The largest number tested, 150M total positron decays, is considered realistic for a clinical fraction of delivered dose, while the...

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Section: Introductionmentioning

confidence: 99%

Design study of anin situPET scanner for use in proton beam therapy

et al. 2011

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“…A detector arrangement that does not interfere with the beam paths is required for the in-beam PET. Therefore, dual-head PET cameras have been developed and studied [7][8][9][10], although the resolution along an axis perpendicular to the detector surfaces is very poor. Recently published results of an ''offbeam'' PET study with clinical PET/CT scanners placed outside the treatment room [11] are encouraging for the development of a 3D PET scanner dedicated to in-beam PET.…”

Section: Discussionmentioning

confidence: 99%

Imaging simulations of an “OpenPET” geometry with shifting detector rings

Yamaya¹,

Inaniwa²,

Mori³

et al. 2009

Radiol Phys Technol

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We have proposed a new "OpenPET" geometry consisting of two detector rings of axial length W each separated by a gap G. For obtaining an axially continuous field of view (FOV) of 2W + G, the maximum limit for G must be W. However, two valleys of sensitivity appear on both sides of the gap. Setting a more limited range for the gap as G < W, which is desirable for filling in the sensitivity valleys, results in not only a shortened gap, but also a shortened axial FOV. In this paper, we propose an alternative method for improving the uniformity of sensitivity by shifting two detector rings axially closer or further apart at the same velocity to each other. In addition, image reconstruction of the OpenPET is an incomplete problem, and low-frequency components are missing in the gap. Therefore, the proposed method is also expected to improve the conditions for the inverse problem. We simulated an OpenPET scanner which measures events simultaneously by shifting the detector rings. The results showed that the right and left peaks of the sensitivity approach each other upon shifting of the detector rings, and these valleys of sensitivity are effectively recovered. The results also showed that distortion, which is observed for objects containing low-frequency components, is reduced. Larger detector shifts allow a more uniform axial distribution of sensitivity and a higher image quality, but at the cost of a smaller minimum gap. Therefore, an appropriate detector-shifting pattern should be determined based on the desired scanner application.

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“…In-beam PET detectors inside the treatment room have been installed at two sites for carbon beam therapy (Pawelke et al , 1997; Iseki et al , 2003), with a third for proton therapy (Nishio et al , 2010). In-beam detectors allow the real-time PET acquisition in the treatment position during the pauses of pulsed beam delivery and immediately after irradiation, therefore short-lived radionuclides such as 15 O can be detected.…”

Section: Introductionmentioning

confidence: 99%

Monitoring proton radiation therapy with in-room PET imaging

et al. 2011

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Purpose We used a mobile PET scanner positioned within the proton therapy treatment room to study the feasibility of proton range verification with an in-room, stand-alone PET system, and compared with off-line equivalent studies. Methods and materials Two subjects with adenoid cystic carcinoma were enrolled into a pilot study in which in-room PET scans were acquired in list-mode after a routine fractionated treatment session. The list-mode PET data were reconstructed with different time schemes to generate in-room short, in-room long and off-line equivalent (by skipping coincidences from the first 15 minutes during the list-mode reconstruction) PET images for comparison in activity distribution patterns. A phantom study was followed to evaluate the accuracy of range verification for different reconstruction time schemes quantitatively. Results The in-room PET has a higher sensitivity compared to the off-line modality so that the PET acquisition time can be greatly reduced from 30 min to <5 min. Features in deep-site, soft-tissue regions were better retained with in-room short PET acquisitions because of the collection of 15O component and lower biological washout. For soft tissue-equivalent material, the distal fall-off edge of an in-room short acquisition is deeper compared to an off-line equivalent scan, indicating a better coverage of the high-dose end of the beam. Conclusions In-room PET is a promising low cost, high sensitivity modality for the in vivo verification of proton therapy. Better accuracy in Monte Carlo predictions, especially for biological decay modeling, is necessary.

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Positron camera for range verification of heavy-ion radiotherapy

Cited by 98 publications

References 8 publications

Design study of anin situPET scanner for use in proton beam therapy

Design study of anin situPET scanner for use in proton beam therapy

Imaging simulations of an “OpenPET” geometry with shifting detector rings

Monitoring proton radiation therapy with in-room PET imaging

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