Optimal theranostic SPECT imaging protocol for 223radium dichloride therapy.

223Radium dichloride image-based individual dosimetry requires an optimal acquisition and reconstruction protocol and proper image correction methods for theranostic applications. To assess this problem, radium-223 dichloride SPECT images were acquired from a Jaszczak simulator with a dual-headed gamma camera, LEHR collimator, 128 × 128 matrix, and total time of 32 minutes. A cylindrical PMMA phantom was used to calibrate the measurements performed with Jaszczak. The image quality parameters (noise coefficient, contrast, contrast-to-noise ratio and recovery coefficient) and septal penetration correction were calculated by MATLAB®. The best results for the investigated image quality parameters were obtained with an 89 keV energy window (24% wide) produced together with OSEM/MLEM reconstruction (8 subsets and 4 iterations) applying a Butterworth filter (order 10 and cutoff frequency of 0.48 cycles·cm-1). The successfully performed recovery coefficient parameter evaluation allows uptake correction for future patient dosimetry applications.

Radiologic Assessment of Groin Lymph Nodes in Pelvic Malignancies.

INTRODUCTION: Metastatic involvement of groin nodes can alter radiation therapy planning for pelvic tumors. 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) can identify nodal metastases; however, interpretation of PET/CT-positive nodes can be complicated by non-malignant processes. We evaluated quantitative metrics as methods to identify groin metastases in patients with pelvic tumors by comparison with standard subjective interpretive criteria, with pathology as the reference standard. METHODS: We retrospectively identified patients with vulvar, vaginal, or anal cancers who underwent 18F-FDG PET/CT before pathologic evaluation of groin nodes between 2007 and 2017. Because patho-radiologic correlation was not possible for every node, one index node identified on imaging was selected for each groin. For each index node, standardized uptake value measurements, total lesion glycolysis, metabolic tumor volume, CT-based volume, and short and long axes were measured. Multivariate logistic regression was used to identify metrics predictive for pathologically positive groins and generate a probabilistic model. Area under the receiver-operating characteristic curves (AUCs) for the model were compared with clinical interpretation from the diagnostic report via a Wald's χ2 test. RESULTS: Of 55 patients identified for analysis, 75 groins had pathologic evaluation resulting in 75 index groin nodes for analysis with 35 groins pathologically positive for malignancy. Logistic regression identified mean standardized-uptake-value (50% threshold) and short-axis length as the most predictive imaging metrics for metastatic nodal involvement. The probabilistic model performed better at predicting pathologic involvement compared with standard clinical interpretation on analysis (AUC 0.91, 95% CI 0.84 to 0.97 vs 0.80, 95% CI 0.71 to 0.89; p<0.01). DISCUSSION: Accuracy of 18F-FDG PET/CT for detecting groin nodal metastases in patients with pelvic tumors may be improved with the use of quantitative metrics. Improving prediction of nodal metastases can aid with appropriate selection of patients for pathologic node evaluation and guide radiation volumes and doses.

Spatial relationship of 2-deoxy-2-[18F]-fluoro-D-glucose positron emission tomography and magnetic resonance diffusion imaging metrics in cervical cancer.

BACKGROUND: This study investigated the spatial relationship of 2-deoxy-2-[18F]-fluoro-D-glucose positron emission tomography ([18F]FDG-PET) standardized uptake values (SUVs) and apparent diffusion coefficients (ADCs) derived from magnetic resonance (MR) diffusion imaging on a voxel level using simultaneously acquired PET/MR data. We performed an institutional retrospective analysis of patients with newly diagnosed cervical cancer who received a pre-treatment simultaneously acquired [18F]FDG-PET/MR. Voxel SUV and ADC values, and global tumor metrics including maximum SUV (SUVmax), mean ADC (ADCmean), and mean tumor-to-muscle ADC ratio (ADCT/M) were compared. The impacts of histology, grade, and tumor volume on the voxel SUV to ADC relationship were also evaluated. The potential prognostic value of the voxel SUV/ADC relationship was evaluated in an exploratory analysis using Kaplan-Meier/log-rank and univariate Cox analysis. RESULTS: Seventeen patients with PET/MR scans were identified. There was a significant inverse correlation between SUVmax and ADCmean, and SUVmax and ADCT/M. In the voxelwise analysis, squamous cell carcinomas (SCCAs) and poorly differentiated tumors showed a consistent significant inverse correlation between voxel SUV and ADC values; adenocarcinomas (AdenoCAs) and well/moderately differentiated tumors did not. The strength of the voxel SUV/ADC correlation varied with metabolic tumor volume (MTV). On log-rank analysis, the correlation between voxel SUV/ADC values was prognostic of disease-free survival (DFS). CONCLUSIONS: In this hypothesis-generating study, a consistent inverse correlation between voxel SUV and ADC values was seen in SCCAs and poorly differentiated tumors. On univariate statistical analysis, correlation between voxel SUV and ADC values was prognostic for DFS.

Clinical outcomes of low and intermediate risk differentiated thyroid cancer patients treated with 30mCi for ablation or without radioactive iodine therapy.

OBJECTIVE: To retrospectively evaluate the outcomes of patients with low and intermediate risk thyroid carcinoma treated with total thyroidectomy (TT) and who did not undergo radioiodine remnant ablation (RRA) and to compare them to patients receiving low dose of iodine (30 mCi). SUBJECTS AND METHODS: A total of 189 differentiated thyroid cancer (DTC) patients treated with TT followed by 30mCi for RRA or not, followed in two referral centers in Brazil were analyzed. RESULTS: From the 189 patients, 68.8% was ATA low-risk, 30.6% intermediate and 0.6% high risk. Eighty-seven patients underwent RRA and 102 did not. The RRA groups tended to be younger and had a higher frequency of extra-thyroidal extension (ETE). RRA did not have and impact on response to initial therapy neither in low (p = 0.24) nor in intermediate risk patients (p = 0.66). It also had no impact on final outcome and most patients had no evidence of disease (NED) at final follow-up. Recurrence/persistence of disease was found in 1.2% of RRA group and 2% in patients treated only with TT (p = 0.59). CONCLUSIONS: Our study shows that in low and intermediate-risk patients, RRA with 30 mCi seems to have no major advantage over patients who did not undergo RRA regarding response to initial therapy in each risk group and also in long term outcomes.

Clinical outcomes of low and intermediate risk differentiated thyroid cancer patients treated with 30mCi for ablation or without radioactive iodine therapy

ABSTRACT Objective To retrospectively evaluate the outcomes of patients with low and intermediate risk thyroid carcinoma treated with total thyroidectomy (TT) and who did not undergo radioiodine remnant ablation (RRA) and to compare them to patients receiving low dose of iodine (30 mCi). Subjects and methods A total of 189 differentiated thyroid cancer (DTC) patients treated with TT followed by 30mCi for RRA or not, followed in two referral centers in Brazil were analyzed. Results From the 189 patients, 68.8% was ATA low-risk, 30.6% intermediate and 0.6% high risk. Eighty-seven patients underwent RRA and 102 did not. The RRA groups tended to be younger and had a higher frequency of extra-thyroidal extension (ETE). RRA did not have and impact on response to initial therapy neither in low (p = 0.24) nor in intermediate risk patients (p = 0.66). It also had no impact on final outcome and most patients had no evidence of disease (NED) at final follow-up. Recurrence/persistence of disease was found in 1.2% of RRA group and 2% in patients treated only with TT (p = 0.59). Conclusions Our study shows that in low and intermediate-risk patients, RRA with 30 mCi seems to have no major advantage over patients who did not undergo RRA regarding response to initial therapy in each risk group and also in long term outcomes.

Extensive Metastatic Sarcomatoid Renal Cell Carcinoma Evaluated by 18F-FDG PET/CT: a Case Report and Review of Literature.

Sarcomatoid renal cell carcinoma (sRCC) is a highly aggressive form of dedifferentiated renal cell carcinoma. We report a 62-year-old man who presented with respiratory symptoms and a lung mass on chest computed tomography (CT). The patient underwent positron emission tomography/computed tomography (PET/CT) with 18F-fluorodeoxyglucose (18F-FDG) and was found to have extensive metastatic disease. Based on the history and imaging findings, there were possible primary malignancies, including bronchogenic carcinoma, melanoma, or an aggressive lymphoma. An excisional biopsy surprisingly revealed a high-grade sarcomatoid carcinoma with no evidence of differentiation, and immunohistochemical (IHC) studies showed that the tumor cells were positive for markers of genitourinary origin (PAX-8 and vimentin). The histologic and IHC results, along with multiple FDG-avid exophytic lesions in both kidneys, were considered diagnostic of sRCC. Here we have highlighted the potential role of 18F-FDG-PET-CT in patients with sRCC, discussed the diagnostic challenges, and presented a brief review.