Browsing by Subject "Dosimetry"

Now showing 1 - 6 of 6
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    [68Ga]Ga-P16-093 as a PSMA-Targeted PET Radiopharmaceutical for Detection of Cancer: Initial Evaluation and Comparison with [68Ga]Ga-PSMA-11 in Prostate Cancer Patients Presenting with Biochemical Recurrence
    (SpringerLink, 2020-06) Green, Mark A.; Hutchins, Gary D.; Bahler, Clinton D.; Tann, Mark; Mathias, Carla J.; Territo, Wendy; Sims, Justin; Polson, Heather; Alexoff, David; Eckelman, William C.; Kung, Hank F.; Fletcher, James W.; Radiology and Imaging Sciences, School of Medicine
    Purpose: This study was undertaken to evaluate radiation dosimetry for the prostate-specific membrane antigen targeted [68Ga]Ga-P16-093 radiopharmaceutical, and to initially assess agent performance in positron emission tomography (PET) detection of the site of disease in prostate cancer patients presenting with biochemical recurrence. Procedures: Under IND 133,222 and an IRB-approved research protocol, we evaluated the biodistribution and pharmacokinetics of [68Ga]Ga-P16-093 with serial PET imaging following intravenous administration to ten prostate cancer patients with biochemical recurrence. The recruited subjects were all patients in whom a recent [68Ga]Ga-PSMA-11 PET/X-ray computed tomography (CT) exam had been independently performed under IND 131,806 to assist in decision-making with regard to their clinical care. Voided urine was collected from each subject at ~ 60 min and ~ 140 min post-[68Ga]Ga-P16-093 injection and assayed for Ga-68 content. Following image segmentation to extract tissue time-activity curves and corresponding cumulated activity values, radiation dosimetry estimates were calculated using IDAC Dose 2.1. The prior [68Ga]Ga-PSMA-11 PET/CT exam (whole-body PET imaging at 60 min post-injection, performed with contrast-enhanced diagnostic CT) served as a reference scan for comparison to the [68Ga]Ga-P16-093 findings. Results: [68Ga]Ga-P16-093 PET images at 60 min post-injection provided diagnostic information that appeared equivalent to the subject's prior [68Ga]Ga-PSMA-11 scan. With both radiopharmaceuticals, sites of tumor recurrence were found in eight of the ten patients, identifying 16 lesions. The site of recurrence was not detected with either agent for the other two subjects. Bladder activity was consistently lower with [68Ga]Ga-P16-093 than [68Ga]Ga-PSMA-11. The kidneys, spleen, salivary glands, and liver receive the highest radiation exposure from [68Ga]Ga-P16-093, with estimated doses of 1.7 × 10-1, 6.7 × 10-2, 6.5 × 10-2, and 5.6 × 10-2 mGy/MBq, respectively. The corresponding effective dose from [68Ga]Ga-P16-093 is 2.3 × 10-2 mSv/MBq. Conclusions: [68Ga]Ga-P16-093 provided diagnostic information that appeared equivalent to [68Ga]Ga-PSMA-11 in this limited series of ten prostate cancer patients presenting with biochemical recurrence, with the kidneys found to be the critical organ. Diminished tracer appearance in the urine represents a potential advantage of [68Ga]Ga-P16-093 over [68Ga]Ga-PSMA-11 for detection of lesions in the pelvis.
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    A global evaluation of advanced dosimetry in transarterial radioembolization of hepatocellular carcinoma with Yttrium-90: the TARGET study
    (Springer, 2022) Lam, Marnix; Garin, Etienne; Maccauro, Marco; Kappadath, S. Cheenu; Sze, Daniel Y.; Turkmen, Cuneyt; Cantasdemir, Murat; Haste, Paul; Herrmann, Ken; Alsuhaibani, Hamad Saleh; Dreher, Matthew; Fowers, Kirk D.; Salem, Riad; Radiology and Imaging Sciences, School of Medicine
    Purpose: To investigate the relationships between tumor absorbed dose (TAD) or normal tissue absorbed dose (NTAD) and clinical outcomes in hepatocellular carcinoma (HCC) treated with yttrium-90 glass microspheres. Methods: TARGET was a retrospective investigation in 13 centers across eight countries. Key inclusion criteria: liver-dominant HCC with or without portal vein thrombosis, < 10 tumors per lobe (at least one ≥ 3 cm), Child-Pugh stage A/B7, BCLC stages A-C, and no prior intra-arterial treatment. Multi-compartment pre-treatment dosimetry was performed retrospectively. Primary endpoint was the relationship between ≥ grade 3 hyperbilirubinemia (such that > 15% of patients experienced an event) without disease progression and NTAD. Secondary endpoints included relationships between (1) objective response (OR) and TAD, (2) overall survival (OS) and TAD, and (3) alpha fetoprotein (AFP) and TAD. Results: No relationship was found between NTAD and ≥ grade 3 hyperbilirubinemia, which occurred in 4.8% of the 209 patients. The mRECIST OR rate over all lesions was 61.7%; for the target (largest) lesion, 70.8%. Responders and non-responders had geometric mean total perfused TADs of 225.5 Gy and 188.3 Gy (p = 0.048). Probability of OR was higher with increasing TAD (p = 0.044). Higher TAD was associated with longer OS (HR per 100 Gy increase = 0.83, 95% CI: 0.71-0.95; p = 0.009). Increased TAD was associated with higher probability of AFP response (p = 0.046 for baseline AFP ≥ 200 ng/mL). Conclusion: Real-world data confirmed a significant association between TAD and OR, TAD and OS, and TAD and AFP response. No association was found between ≥ grade 3 hyperbilirubinemia and NTAD.
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    Clinical, dosimetric, and reporting considerations for Y-90 glass microspheres in hepatocellular carcinoma: updated 2022 recommendations from an international multidisciplinary working group
    (Springer, 2023) Salem, Riad; Padia, Siddharth A.; Lam, Marnix; Chiesa, Carlo; Haste, Paul; Sangro, Bruno; Toskich, Beau; Fowers, Kirk; Herman, Joseph M.; Kappadath, S. Cheenu; Leung, Thomas; Sze, Daniel Y.; Kim, Edward; Garin, Etienne; Radiology and Imaging Sciences, School of Medicine
    Purpose: In light of recently published clinical reports and trials, the TheraSphere Global Dosimetry Steering Committee (DSC) reconvened to review new data and to update previously published clinical and dosimetric recommendations for the treatment of hepatocellular carcinoma (HCC). Methods: The TheraSphere Global DSC is comprised of health care providers across multiple disciplines involved in the treatment of HCC with yttrium-90 (Y-90) glass microsphere-based transarterial radioembolization (TARE). Literature published between January 2019 and September 2021 was reviewed, discussed, and adjudicated by the Delphi method. Recommendations included in this updated document incorporate both the results of the literature review and the expert opinion and experience of members of the committee. Results: Committee discussion and consensus led to the expansion of recommendations to apply to five common clinical scenarios in patients with HCC to support more individualized efficacious treatment with Y-90 glass microspheres. Existing clinical scenarios were updated to reflect recent developments in dosimetry approaches and broader treatment paradigms evolving for patients presenting with HCC. Conclusion: Updated consensus recommendations are provided to guide clinical and dosimetric approaches for the use of Y-90 glass microsphere TARE in HCC, accounting for disease presentation, tumor biology, and treatment intent.
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    Direct comparison and reproducibility of two segmentation methods for multicompartment dosimetry: round robin study on radioembolization treatment planning in hepatocellular carcinoma
    (Springer, 2023) Lam, Marnix; Garin, Etienne; Palard‑Novello, Xavier; Mahvash, Armeen; Kappadath, Cheenu; Haste, Paul; Tann, Mark; Herrmann, Ken; Barbato, Francesco; Geller, Brian; Schaefer, Niklaus; Denys, Alban; Dreher, Matthew; Fowers, Kirk D.; Gates, Vanessa; Salem, Riad; Radiology and Imaging Sciences, School of Medicine
    Purpose: Investigate reproducibility of two segmentation methods for multicompartment dosimetry, including normal tissue absorbed dose (NTAD) and tumour absorbed dose (TAD), in hepatocellular carcinoma patients treated with yttrium-90 (90Y) glass microspheres. Methods: TARGET was a retrospective investigation in 209 patients with < 10 tumours per lobe and at least one tumour ≥ 3 cm ± portal vein thrombosis. Dosimetry was compared using two distinct segmentation methods: anatomic (CT/MRI-based) and count threshold-based on pre-procedural 99mTc-MAA SPECT. In a round robin substudy in 20 patients with ≤ 5 unilobar tumours, the inter-observer reproducibility of eight reviewers was evaluated by computing reproducibility coefficient (RDC) of volume and absorbed dose for whole liver, whole liver normal tissue, perfused normal tissue, perfused liver, total perfused tumour, and target lesion. Intra-observer reproducibility was based on second assessments in 10 patients ≥ 2 weeks later. Results: 99mTc-MAA segmentation calculated higher absorbed doses compared to anatomic segmentation (n = 209), 43.9% higher for TAD (95% limits of agreement [LoA]: - 49.0%, 306.2%) and 21.3% for NTAD (95% LoA: - 67.6%, 354.0%). For the round robin substudy (n = 20), inter-observer reproducibility was better for anatomic (RDC range: 1.17 to 3.53) than 99mTc-MAA SPECT segmentation (1.29 to 7.00) and similar between anatomic imaging modalities (CT: 1.09 to 3.56; MRI: 1.24 to 3.50). Inter-observer reproducibility was better for larger volumes. Perfused normal tissue volume RDC was 1.95 by anatomic and 3.19 by 99mTc-MAA SPECT, with corresponding absorbed dose RDC 1.46 and 1.75. Total perfused tumour volume RDC was higher, 2.92 for anatomic and 7.0 by 99mTc-MAA SPECT with corresponding absorbed dose RDC of 1.84 and 2.78. Intra-observer variability was lower for perfused NTAD (range: 14.3 to 19.7 Gy) than total perfused TAD (range: 42.8 to 121.4 Gy). Conclusion: Anatomic segmentation-based dosimetry, versus 99mTc-MAA segmentation, results in lower absorbed doses with superior reproducibility. Higher volume compartments, such as normal tissue versus tumour, exhibit improved reproducibility.
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    Pediatric Phantom Dosimetry of the Portable Handheld Xray2Go
    (Aegis, 2021-04) Hwang, Jackie; Yepes, Juan. F; Vinson, LaQuia A.; Sanders, Brian J.; Jones, James E.; Ware, Tawana K.; Johnson, Brandon K.; Tang, Qing; Pediatric Dentistry, School of Dentistry
    Purpose: The purpose of our study was to quantify radiation dose from the XTG (Xray2Go) Handheld X-ray device for bitewing and anterior occlusal projections using a pediatric phantom. The aim was to evaluate thyroid shielding effects on effective dose (E), tissue equivalent doses (HT), and assess operator backscatter radiation. Methods: A pediatric phantom with 24 tissue site dosimeters was exposed to radiation from the Xray2Go. Projections included: Right and left bitewing (BW) without thyroid collar on phantom, BW with thyroid collar, maxillary anterior occlusal (AO) without thyroid collar, AO with thyroid collar. New dosimeters were used for each projection type, for 30 exposures. Operator wore dosimeters on forehead and right hand to quantify backscatter. Average values of HT and E were calculated. Results: Thyroid shielding produced a statistically significant difference for posterior bitewing projections at thyroid (P<.001), lymphatic nodes (P=.04), and muscle (P=.04). Operator dose from the XTG was indistinguishable from background radiation. Conclusions: Mean effective dose was less than 1 μSv for all projections. Thyroid shielding made a statistically significant difference for radiation dose with the Xray2Go for several tissue locations and for posterior bitewings effective dose. Radiation to the operator was low and indistinguishable from background radiation.
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    Quantifying Proton Fields for Midline Brain Tumors: A Benefit/Cost Analysis of Planning Objectives
    (The Particle Therapy Cooperative Group, 2016) Estabrook, Neil C.; Hoene, Ted A.; Carlin, Paul S.; McDonald, Mark W.; Radiation Oncology, School of Medicine
    Purpose: We sought to quantify the optimum number of beams by using a midline sagittal arrangement for midline brain tumors when considering the competing demands of a high degree of target conformation and maximizing reduction of nontarget brain dose. The volume of nontarget brain tissue receiving between 5 and 20 Gy (V5-V20) was selected to measure "low-dose bath" to normal brain. Materials and Methods: An exploratory model was developed with 6 midline brain targets created by using spheres of 1-, 3-, and 5-cm diameters located in superficial and deep locations. For each, five 3-dimensional proton treatment plans with uniform beam scanning were generated by using 1 to 5 fields. Dose-volume histograms were analyzed to calculate conformation number and V5-V20. A benefit/cost analysis was performed to determine the marginal gain in conformation number and the marginal cost of V5-V20 for the addition of each field and hypothesize the optimum number of treatment fields. We tested our hypothesis by re-planning 10 actual patient tumors with the same technique to compare the averages of these 50 plans to our model. Results: Our model and validation cohort demonstrated the largest marginal benefit in target conformation and the lowest marginal cost in normal brain V5-V20 with the addition of a second proton field. The addition of a third field resulted in a relative marginal benefit in target conformation of just 3.9% but a relative marginal cost in V5-V20 of 78.7%. Normal brain absolute V5-V20 increased in a nearly linear fashion with each additional field. Conclusions: When treating midline brain lesions with 3-dimensional proton therapy in an array of midline sagittal beams, our model suggests the most appropriate number of fields is 2. There was little marginal benefit in target conformation and increasing cost of normal brain dose when increasing the number of fields beyond this.