Proton therapy in combination with PET as monitor: a feasibility study

Paans, Amj; Schippers, J.M.

doi:10.1109/23.256709

Cited by 53 publications

(41 citation statements)

References 5 publications

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“…8,9 Extensive in-beam phantom experiments with proton beams in the same facility supported a similar potential for proton therapy, showing that for the same dose delivery the higher proton induced activation can provide sufficient accuracy for range verification in spite of its limitation to target ͑no projectile͒ fragmentation. 10,11 In addition to preliminary phantom experiments of several groups, [12][13][14][15] two recent but only qualitative clinical acquisitions 16,17 have also suggested the applicability and usefulness of off-line ͑i.e., after the irradiation͒ PET monitoring for proton therapy. Although this approach is limited to the detection of long-lived isotopes ͑mostly 11 C, half-life T 1/2 = 20.39 min͒, it allows for the direct use of existent commercial detector systems without the effort to develop customized solutions.…”

Section: Introductionmentioning

confidence: 99%

PET/CT imaging for treatment verification after proton therapy: A study with plastic phantoms and metallic implants

et al. 2007

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The feasibility of off-line positron emission tomography/computed tomography (PET/CT) for routine three dimensional in-vivo treatment verification of proton radiation therapy is currently under investigation at Massachusetts General Hospital in Boston. In preparation for clinical trials, phantom experiments were carried out to investigate the sensitivity and accuracy of the method depending on irradiation and imaging parameters. Furthermore, they addressed the feasibility of PET/CT as a robust verification tool in the presence of metallic implants. These produce x-ray CT artifacts and fluence perturbations which may compromise the accuracy of treatment planning algorithms. Spread-out Bragg peak proton fields were delivered to different phantoms consisting of polymethylmethacrylate (PMMA), PMMA stacked with lung and bone equivalent materials, and PMMA with titanium rods to mimic implants in patients. PET data were acquired in list mode starting within 20 min after irradiation at a commercial luthetium-oxyorthosilicate (LSO)-based PET/CT scanner. The amount and spatial distribution of the measured activity could be well reproduced by calculations based on the GEANT4 and FLUKA Monte Carlo codes. This phantom study supports the potential of millimeter accuracy for range monitoring and lateral field position verification even after low therapeutic dose exposures of 2 Gy, despite the delay between irradiation and imaging. It also indicates the value of PET for treatment verification in the presence of metallic implants, demonstrating a higher sensitivity to fluence perturbations in comparison to a commercial analytical treatment planning system. Finally, it addresses the suitability of LSO-based PET detectors for hadron therapy monitoring. This unconventional application of PET involves countrates which are orders of magnitude lower than in diagnostic tracer imaging, i.e., the signal of interest is comparable to the noise originating from the intrinsic radioactivity of the detector itself. In addition to PET alone, PET/CT imaging provides accurate information on the position of the imaged object and may assess possible anatomical changes during fractionated radiotherapy in clinical applications. a) Present address: Heidelberg

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Section: Introductionmentioning

confidence: 99%

PET/CT imaging for treatment verification after proton therapy: A study with plastic phantoms and metallic implants

et al. 2007

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“…This induced activity has been studied as a source of patient dose, 11,20,21 as a means of determining elemental tissue composition, 10,11,13 and for determining dose distributions. 14,15,17,[22][23][24][25][26][27][28][29][30][31] In vivo dose localization by imaging positron-emitting nuclei is considered essential for light-ion, and radioactive-ion beam therapy. 30 Investigations of PET as a monitor for proton radiotherapy beams generally indicate that it is capable of measuring useful dosimetric, compositional, and range information.…”

Section: Introductionmentioning

confidence: 99%

“…30 Investigations of PET as a monitor for proton radiotherapy beams generally indicate that it is capable of measuring useful dosimetric, compositional, and range information. 11,12,22,[25][26][27][28][29]31 However, many of these experiments were conducted off-line by detection systems in the vicinity of the treatment beam requiring that the phantoms or subjects under study be moved. The resulting images predominantly show activity from radioisotopes whose half-life is comparable to or longer than the transportation and setup time.…”

Section: Introductionmentioning

confidence: 99%

On‐line monitoring of radiotherapy beams: Experimental results with proton beams

et al. 1999

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Proton radiotherapy is a powerful tool in the local control of cancer. The advantages of proton radiotherapy over gamma-ray therapy arise from the phenomenon known as the Bragg peak. This phenomenon enables large doses to be delivered to well-defined volumes while sparing surrounding healthy tissue. To fully realize the potential of this technique the location of the high-dose volume must be controlled very accurately. An imaging system was designed and tested to monitor the positron-emitting activity created by the beam as a means of verifying the beam's range, monitoring dose, and determining tissue composition. The prototype imaging system consists of 12 pairs of cylindrical BGO detectors shielded in lead. Each crystal was 1.9 cm in diameter, 5.0 cm long, and separated by 0.5 cm from other detectors in the row. These are arranged in two rows, 60 cm apart, with the proton beam and tissue phantoms half-way between and parallel to the detector rows. Experiments were conducted with 150 MeV continuous and macro-pulsed proton beams which had beam currents ranging from 0.14 nA to 1.75 nA. The production and decay of short-lived isotopes, 15O and 14O, was studied using 1 min irradiations with a continuous beam. These isotopes provide a significant signal on short time scales, making on-line imaging possible. Macro-pulsed beams, having a period of 10 s, were used to study on-line imaging and the production and decay of long-lived isotopes, 13N, 11C, and 18F. Decay data were acquired and on-line images were obtained between beam pulses and indicate that range verification is possible, for a 150 MeV beam, after one beam pulse, to within the 1.2 cm resolution limit of the imaging system. The dose delivered to the patient may also be monitored by observing the increase in the number of coincidence events detected between successive beam pulses. Over 80% of the initial positron-emitting activity is from 15O while the remainder is primarily 11C, 13N, 14O with traces of 18F, and 10C. Radioisotopic imaging may also be performed along the beam path by fitting decay data collected after the treatment is complete. Using this technique, it is shown that variations in elemental composition in inhomogenous treatment volumes may be identified and used to locate anatomic landmarks. Radioisotopic imaging also reveals that 14O is created well beyond the Bragg peak, apparently by secondary neutrons.

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“…Several methods have been proposed for this purpose, and one of them uses positron emitters generated through fragmentation reactions of target nuclei induced by incident protons. [1][2][3][4][5][6][7][8][9][10][11] While the positron emitters are generated through either target or projectile fragmentation reactions in heavy ion therapy, [12][13][14][15][16][17] only target fragmentation reactions occur in proton therapy. When incident protons travel through a patient's body, a small fraction of the protons generates positron emitters such as 11 C, 13 N, and 15 O along their penetration paths.…”

Section: Introductionmentioning

confidence: 99%

Maximum likelihood estimation of proton irradiated field and deposited dose distribution

et al. 2007

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In proton therapy, it is important to evaluate the field irradiated with protons and the deposited dose distribution in a patient's body. Positron emitters generated through fragmentation reactions of target nuclei can be used for this purpose. By detecting the annihilation gamma rays from the positron emitters, the annihilation gamma ray distribution can be obtained which has information about the quantities essential to proton therapy. In this study, we performed irradiation experiments with mono-energetic proton beams of 160 MeV and the spread-out Bragg peak beams to three kinds of targets. The annihilation events were detected with a positron camera for 500 s after the irradiation and the annihilation gamma ray distributions were obtained. In order to evaluate the range and the position of distal and proximal edges of the SOBP, the maximum likelihood estimation (MLE) method was applied to the detected distributions. The evaluated values with the MLE method were compared with those estimated from the measured dose distributions. As a result, the ranges were determined with the difference between the MLE range and the experimental range less than 1.0 mm for all targets. For the SOBP beams, the positions of distal edges were determined with the difference less than 1.0 mm. On the other hand, the difference amounted to 7.9 mm for proximal edges.

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Proton therapy in combination with PET as monitor: a feasibility study

Cited by 53 publications

References 5 publications

PET/CT imaging for treatment verification after proton therapy: A study with plastic phantoms and metallic implants

PET/CT imaging for treatment verification after proton therapy: A study with plastic phantoms and metallic implants

On‐line monitoring of radiotherapy beams: Experimental results with proton beams

Maximum likelihood estimation of proton irradiated field and deposited dose distribution

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