Yttrium-90-labeled microsphere tracking during liver selective internal radiotherapy by bremsstrahlung pinhole SPECT: feasibility study and evaluation in an abdominal phantom (original) (raw)
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arXiv: Medical Physics, 2015
The quality of SPECT Bremsstrahlung images of patients treated with Y-90 is poor, mainly because of scattered radiation and collimator septa penetration. To minimize the latter effect, High Energy (HE) or Medium Energy (ME) collimators can be used. Scatter correction is not possible through the methods commonly used for the diagnostic radionuclides (Tc-99m, etc.) because the Bremsstrahlung radiation does not have distinct photopeaks, but a broad spectrum of energies ranging from zero to the maximum one detectable by the gamma-camera crystal is registered. Scatter radiation and collimator septa penetration affect the Contrast and the Contrast Recovery Coefficient (CRC) : our research focused on finding the best energy position for the acquisition window in order to maximize these parameters. To be guided in this finding, we first made a Monte Carlo (MC) simulation of a SPECT acquisition of a Y-90 cylindrical phantom and then we measured at different energies the Line Spread Function ...
2015
The Selective Internal Radiation Therapy (SIRT) is used to treat unresectable hepatic tumors by injecting microspheres labelled with 90 Y into the hepatic artery. In clinical practice, two conventional methods, the Body Surface Area (BSA) method and the Partition Model, are used to determine the activity to administer to the patient. Whether based on an empirical approach or on the MIRD formalism, both techniques suppose a uniform repartition of the microspheres. However, the 90 Y-microspheres distribution is heterogeneous. Methods: In collaboration with the HEGP, a predictive and personalized 3D-dosimetry, which takes into account the distribution heterogeneity, has been developed and applied to a 70 years-old woman with hepatic metastases. Patient's anatomy and tumor were segmented using CT images to create a patient-specific voxel phantom. Activity distribution was defined using SPECT images acquired after the injection of 99m Tc albumin aggregated (99m Tc-MAA). Dose calculations were performed at the voxel scale with the MCNPX transport code associated to OEDIPE, French acronym for "tool for personalised internal dose assessment", developed at IRSN. For a given injected activity, tumor and healthy liver mean absorbed doses were compared to those predicted by conventional methods, lungs' mean absorbed doses were estimated and isodose curves superimposed on anatomical images were obtained. Finally, dose volume histograms (DVHs) were analysed to determine the activity which is optimum for treatment efficiency and patient's radiation protection. Results: The Partition Model overestimates tumor and healthy liver absorbed doses by 36% and 45% respectively, and underestimates lungs absorbed dose by 34%. Whereas the BSA method and the Partition Model recommend respectively the injection of 1.42 GBq and 0.74 GBq, the analysis of healthy liver's DVH leads to an optimum activity of 1.33 GBq. Conclusion: In the context of SIRT, a predictive dosimetry has been performed and used for treatment optimization.
Advances in SPECT for Optimizing the Liver Tumors Radioembolization Using Yttrium-90 Microspheres
World Journal of Nuclear Medicine, 2015
Radioembolization (RE) with Yttrium-90 ( 90 Y) microspheres is an effective treatment for unresectable liver tumors. The activity of the microspheres to be administered should be calculated based on the type of microspheres. Technetium-99m macroaggregated albumin ( 99m Tc-MAA) single photon emission computed tomography/computed tomography (SPECT/CT) is a reliable assessment before RE to ensure the safe delivery of microspheres into the target. 90 Y bremsstrahlung SPECT imaging as a posttherapeutic assessment approach enables the reliable determination of absorbed dose, which is indispensable for the verification of treatment efficacy. This article intends to provide a review of the methods of optimizing 90 Y bremsstrahlung SPECT imaging to improve the treatment efficacy of liver tumor RE using 90 Y microspheres.
2010
Selective internal radiation therapy (SIRT), a catheter-based liver-directed modality for treating primary and metastatic liver cancer, requires appropriate planning to maximize its therapeutic response and minimize its side effects. 99m Tc-macroaggregated albumin (MAA) scanning should precede the therapy to detect any extrahepatic shunting to the lung or gastrointestinal tract. Our aim was to compare the ability of SPECT/CT with that of planar imaging and SPECT in the detection and localization of extrahepatic 99m Tc-MAA accumulation and to evaluate the impact of SPECT/CT on SIRT treatment planning and its added value to angiography in this setting. Methods: Ninety diagnostic hepatic angiograms with 99m Tc-MAA were obtained for 76 patients with different types of cancer. All images were reviewed retrospectively for extrahepatic MAA deposition in the following order: planar, non-attenuation-corrected SPECT, and SPECT/CT. Review of angiograms and follow-up of patients with abdominal shunting served as reference standards. Results: Extrahepatic accumulation was detected by planar imaging, SPECT, and SPECT/CT in 12%, 17%, and 42% of examinations, respectively. The sensitivity for detecting extrahepatic shunting with planar imaging, SPECT, and SPECT/CT was 32%, 41%, and 100%, respectively; specificity was 98%, 98%, and 93%, respectively. The respective positive predictive values were 92%, 93%, and 89%, and the respective negative predictive values were 71%, 73%, and 100%. The therapy plan was changed according to the results of planar imaging, SPECT, and SPECT/CT in 7.8%, 8.9%, and 29% of patients, respectively. Conclusion: In pre-SIRT planning, 99m Tc-MAA SPECT/CT is valuable for identifying extrahepatic visceral sites at risk for postradioembolization complications.
Physics in Medicine and Biology, 2011
The aim of this study is to determine the feasibility of achieving quantitative measurement in 90 Y-microspheres liver selective internal radiotherapy (SIRT) by imaging 90 Y with a conventional non-time of flight (TOF) PET device. Instead of the bremsstrahlung x-rays of the β-decay, the low branch of e − -e + pair production in the 90 Y-decay was used. The activity distribution in a phantom-simulated liver SIRT was obtained by direct 90 Y-PET imaging. We tested a LYSO TOF PET and two GSO and BGO non-TOF PET scanners using a 3.6-l cylindrical phantom filled with the 90 Y solution containing two sets of hot and cold spheres. The best hot contrast was obtained with the LYSO TOF. It was close to the expected value and remained constant, even for short acquisition times. The LYSO non-TOF was about 10% lower. The GSO performed similarly but degraded for shorter times whilst the BGO was the worst with 40% loss. For the cold spheres, the LYSO TOF and the GSO provided the best results, while the LYSO non-TOF and the BGO were the worst. 90 Y PET imaging in liver SIRT is achievable with LYSO TOF. Conventional LYSO and GSO show a loss of contrast and require longer acquisition times. BGO imaging is not feasible for dosimetry calculation. 90 Y imaging by TOF and non-TOF PET in a phantom of liver SIRT
EJNMMI Research, 2021
Background 99mTc-macroaggregated albumin (99mTc-MAA) scintigraphy is utilized in treatment planning for Yttrium-90 (90Y) Selective Internal Radiation Therapy (SIRT) of liver tumors to evaluate hepatopulmonary shunting by calculating the lung shunt fraction (LSF). The purpose of this study was to evaluate if LSF calculation using SPECT/CT instead of planar gamma camera imaging is more accurate and if this can potentially lead to more effective treatment planning of hepatic lesions while avoiding excessive pulmonary irradiation. Results LSF calculation was obtained using two different methodologies in 85 cases from consecutive patients intended to receive 90Y SIRT. The first method was based on planar gamma camera imaging in the anterior and posterior views with geometric mean calculation of the LSF from regions of interest of the liver and lungs. The second method was based on segmentation of the liver and lungs from SPECT/CT images of the thorax and abdomen. The differences in plana...
Radiotherapy and Oncology, 2020
To investigate the potential benefit of multileaf collimator (MLC) tracking guided by kilovoltage intrafraction monitoring (KIM) during stereotactic body radiotherapy (SBRT) in the liver, and to understand trends of target overdose with MLC tracking. Methods: Six liver SBRT patients with 2-3 implanted gold markers received SBRT delivered with volumetric modulated arc therapy (VMAT) in three fractions using daily cone-beam CT setup. The CTV-to-PTV margins were 5 mm in the axial plane and 10 mm in the cranio-caudal directions, and the plans were designed to give minimum target doses of 95% (CTV) and 67% (PTV). The three-dimensional marker trajectory estimated by post-treatment analysis of kV fluoroscopy images acquired throughout treatment delivery was assumed to represent the tumor motion. MLC tracking guided by real-time KIM was simulated. The reduction in CTV D95 (minimum dose to 95% of the clinical target volume) relative to the planned D95 (DD95) was compared between actual non-tracking and simulated MLC tracking treatments. Results: MLC tracking maintained a high CTV dose coverage for all 18 fractions with DD95 (mean: 0.2 percentage points (pp), range: À1.7 to 1.9 pp) being significantly lower than for the actual nontracking treatments (mean: 6.3 pp range: 0.6-16.0 pp) (p = 0.002). MLC tracking of large target motion perpendicular to the MLC leaves created dose artifacts with regions of overdose in the CTV. As a result, the mean dose in spherical volumes centered in the middle of the CTV was on average 2.4 pp (5 mm radius sphere) and 1.3 pp (15 mm radius sphere) higher than planned (p = 0.002). Conclusions: Intrafraction tumor motion can deteriorate the CTV dose of liver SBRT. The planned CTV dose coverage may be restored with KIM-guided MLC tracking. However, MLC tracking may have a tendency to create hotspots in the CTV.
2020
Purpose A multidisciplinary expert panel convened to formulate state-of-the-art recommendations for optimisation of selective internal radiation therapy (SIRT) with yttrium-90 (90 Y)-resin microspheres. Methods A steering committee of 23 international experts representing all participating specialties formulated recommendations for SIRT with 90 Y-resin microspheres activity prescription and post-treatment dosimetry, based on literature searches and the responses to a 61-question survey that was completed by 43 leading experts (including the steering committee members). The survey was validated by the steering committee and completed anonymously. In a face-to-face meeting, the results of the survey were presented and discussed. Recommendations were derived and level of agreement defined (strong agreement ≥ 80%, moderate agreement 50%-79%, no agreement ≤ 49%). Results Forty-seven recommendations were established, including guidance such as a multidisciplinary team should define treatment strategy and therapeutic intent (strong agreement); 3D imaging with CT and an angiography with cone-beam-CT, if available, and 99m Tc-MAA SPECT/CT are recommended for extrahepatic/intrahepatic deposition assessment, treatment field definition and calculation of the 90 Y-resin microspheres activity needed (moderate/strong agreement). A personalised approach, using dosimetry (partition model and/or voxel-based) is recommended for activity prescription, when either whole liver or selective, non-ablative or ablative SIRT is planned (strong agreement). A mean absorbed dose to non-tumoural liver of 40 Gy or less is considered safe (strong agreement). A minimum mean targetabsorbed dose to tumour of 100-120 Gy is recommended for hepatocellular carcinoma, liver metastatic colorectal cancer and cholangiocarcinoma (moderate/strong agreement). Post-SIRT imaging for treatment verification with 90 Y-PET/CT is recommended (strong agreement). Post-SIRT dosimetry is also recommended (strong agreement). Conclusion Practitioners are encouraged to work towards adoption of these recommendations.
EJNMMI Physics, 2020
Introduction Strong correlation has been demonstrated between tumor dose and response and between healthy liver dose and side effects. Individualized dosimetry is increasingly recommended in the current clinical routine. However, hepatic and tumor segmentations could be complex in some cases. The aim of this study is to assess the reproducibility of the tumoral and non-tumoral liver dosimetry in selective internal radiation therapy (SIRT). Material and methods Twenty-three patients with hepatocellular carcinoma (HCC) who underwent SIRT with glass microspheres were retrospectively included in the study. Tumor (TV) and total liver volumes (TLV), and mean absorbed doses in tumoral liver (TD) and non-tumoral liver (THLD) were determined on the 90Y PET/CT studies using Simplicit90YTM software, by three independent observers. Dosimetry datasets were obtained by a medical physicist helped by a nuclear medicine (NM) physician with 10 years of experience (A), by a NM physician with 4-year ex...