Charles Steiner

18F-fluorocholine PET-guided target volume delineation techniques for partial prostate re-irradiation in local recurrent prostate cancer.

BACKGROUND AND PURPOSE We evaluate the contribution of (18)F-choline PET/CT in the delineation of gross tumour volume (GTV) in local recurrent prostate cancer after initial irradiation using various PET image segmentation techniques. MATERIALS AND METHODS Seventeen patients with local-only recurrent prostate cancer (median=5.7 years) after initial irradiation were included in the study. Rebiopsies were performed in 10 patients that confirmed the local recurrence. Following injection of 300 MBq of (18)F-fluorocholine, dynamic PET frames (3 min each) were reconstructed from the list-mode acquisition. Five PET image segmentation techniques were used to delineate the (18)F-choline-based GTVs. These included manual delineation of contours (GTV(man)) by two teams consisting of a radiation oncologist and a nuclear medicine physician each, a fixed threshold of 40% and 50% of the maximum signal intensity (GTV(40%) and GTV(50%)), signal-to-background ratio-based adaptive thresholding (GTV(SBR)), and a region growing (GTV(RG)) algorithm. Geographic mismatches between the GTVs were also assessed using overlap analysis. RESULTS Inter-observer variability for manual delineation of GTVs was high but not statistically significant (p=0.459). In addition, the volumes and shapes of GTVs delineated using semi-automated techniques were significantly higher than those of GTVs defined manually. CONCLUSIONS Semi-automated segmentation techniques for (18)F-choline PET-guided GTV delineation resulted in substantially higher GTVs compared to manual delineation and might replace the latter for determination of recurrent prostate cancer for partial prostate re-irradiation. The selection of the most appropriate segmentation algorithm still needs to be determined.

F-18 fluorodeoxyglucose (FDG) PET in the diagnosis of malignant transformation of fibrous dysplasia in the pelvic bones.

Fibrous dysplasia (FD) is a benign dysplastic pathology of bone-forming mesenchymal cells, resulting in replacement of trabecular bone by abnormal fibrous and immature osseous tissue. FD can be either monostotic or polyostotic, is more often unilateral, and can be part of the McCune-Albright syndrome (MIM 174800). Sarcomatous degeneration in FD is rare, ranging from less than 1% in monostotic forms to 4% in the McCune-Albright syndrome. We report the case of a 59-year-old woman with monostotic FD of the left ischium, known for over 30 years, who developed sarcomatous transformation in a low-grade spindle-cell sarcoma. The value of F-18 fluorodeoxyglucose positron emission tomography in the early diagnosis of malignant transformation, the evaluation of distant metastasis, as well as monitoring the efficacy of chemotherapy are discussed.

Target volume definition in high-risk prostate cancer patients using sentinel node SPECT/CT and 18 F-choline PET/CT.

BackgroundTo assess the influence of sentinel lymph nodes (SNs) SPECT/CT and 18 F-choline (18 F-FCH) PET/CT in radiotherapy (RT) treatment planning for prostate cancer patients with a high-risk for lymph node (LN) involvement.MethodsTwenty high-risk prostate cancer patients underwent a pelvic SPECT acquisition following a transrectal ultrasound guided injection of 99mTc-Nanocoll into the prostate. In all patients but one an 18 F-FCH PET/CT for RT treatment planning was performed. SPECT studies were coregistered with the respective abdominal CTs. Pelvic SNs localized on SPECT/CT and LN metastases detected by 18 F-FCH PET/CT were compared to standard pelvic clinical target volumes (CTV).ResultsA total of 104 pelvic SNs were identified on SPECT/CT (mean 5.2 SNs/patient; range 1–10). Twenty-seven SNs were located outside the standard pelvic CTV, 17 in the proximal common iliac and retroperitoneal regions above S1, 9 in the pararectal fat and 1 in the inguinal region. SPECT/CT succeeded to optimize the definition of the CTV and treatment plans in 6/20 patients due to the presence of pararectal SNs located outside the standard treatment volume. 18 F-FCH PET/CT identified abnormal tracer uptake in the iliac LN region in 2/19 patients. These abnormal LNs were negative on SPECT/CT suggesting a potential blockade of lymphatic drainage by metastatic LNs with a high tumour burden.ConclusionsMultimodality imaging which combines SPECT/CT prostate lymphoscintigraphy and 18 F-FCH PET/CT identified SNs outside standard pelvic CTVs or highly suspicious pelvic LNs in 40% of high-risk prostate cancer patients, highlighting the potential impact of this approach in RT treatment planning.

Long-Term Post-Treatment MR and PET/CT Imaging in Prostate Cancer Patients in Complete Remission after Curative Radiotherapy with or without Androgen Deprivation: The Image of Cure

18 F- Fluorocholine, 11 C-acetate, MRI Abstract Purpose: To investigate the risk of false positive MRI and 18F-Fluorocholine (FCH) or 11Cacetate (AC) PET/ CT in prostate cancer patients with long term biochemical and clinical remission after curative radiation therapy (RT). Methods and Materials: Twenty patients underwent MRI studies including T2-weighted, diffusion weighted, dynamic contrast-enhanced, and spectroscopic imaging. Nine of these patients were selected to have FCH and 10 AC PET/CT studies.