Comparing various AI approaches to traditional quantitative assessment of the myocardial perfusion in [82Rb] PET for MACE prediction.

Assessing the individual risk of Major Adverse Cardiac Events (MACE) is of major importance as cardiovascular diseases remain the leading cause of death worldwide. Quantitative Myocardial Perfusion Imaging (MPI) parameters such as stress Myocardial Blood Flow (sMBF) or Myocardial Flow Reserve (MFR) constitutes the gold standard for prognosis assessment. We propose a systematic investigation of the value of Artificial Intelligence (AI) to leverage [ 82 Rb] Silicon PhotoMultiplier (SiPM) PET MPI for MACE prediction. We establish a general pipeline for AI model validation to assess and compare the performance of global (i.e. average of the entire MPI signal), regional (17 segments), radiomics and Convolutional Neural Network (CNN) models leveraging various MPI signals on a dataset of 234 patients. Results showed that all regional AI models significantly outperformed the global model ( p < 0.001 ), where the best AUC of 73.9% (CI 72.5-75.3) was obtained with a CNN model. A regional AI model based on MBF averages from 17 segments fed to a Logistic Regression (LR) constituted an excellent trade-off between model simplicity and performance, achieving an AUC of 73.4% (CI 72.3-74.7). A radiomics model based on intensity features revealed that the global average was the least important feature when compared to other aggregations of the MPI signal over the myocardium. We conclude that AI models can allow better personalized prognosis assessment for MACE.

Lung CT stabilization with high-frequency non-invasive ventilation (HF-NIV) and breath-hold (BH) in lung nodule assessment by PET/CT.

PURPOSE: To evaluate the effect of lung stabilization using high-frequency non-invasive ventilation (HF-NIV) and breath-hold (BH) techniques on lung nodule detection and texture assessment in PET/CT compared to a free-breathing (FB) standard lung CT acquisition in PET/CT. MATERIALS AND METHODS: Six patients aged 65 ± 7 years, addressed for initial assessment of at least one suspicious lung nodule with 18F-FDG PET/CT, underwent three consecutive lung PET/CT acquisitions with FB, HF-NIV and BH. Lung nodules were assessed on all three CT acquisitions of the PET/CT and characterized for any size, volume and solid/sub-solid nature. RESULTS: BH detected a significantly higher number of nodules (n = 422) compared to HF-NIV (n = 368) and FB (n = 191) (p < 0.001). The mean nodule size (mm) was 2.4 ± 2.1, 2.6 ± 1.9 and 3.2 ± 2.4 in BH, HF-NIV and FB, respectively, for long axis and 1.5 ± 1.3, 1.6 ± 1.2 and 2.1 ± 1.7 in BH, HF-NIV and FB, respectively, for short axis. Long- and short-axis diameters were significantly different between BH and FB (p < 0.001) and between HF-NIV and FB (p < 0.001 and p = 0.008), but not between BH and HF-NIV. A trend for higher volume was shown in FB compared to BH (p = 0.055) and HF-NIV (p = 0.068) without significant difference between BH and HF-NIV (p = 1). We found a significant difference in detectability of sub-solid nodules between the three acquisitions, with BH showing a higher number of sub-solid nodules (n = 128) compared to HF-NIV (n = 72) and FB (n = 44) (p = 0.002). CONCLUSION: We observed a higher detection rate of pulmonary nodules on CT under BH or HF-NIV conditions applied to PET/CT than with FB. BH and HF-NIV demonstrated comparable texture assessment and performed better than FB in assessing size and volume. BH showed a better performance for detecting sub-solid nodules compared to HF-NIV and FB. The addition of BH or HF-NIV to PET/CT can help improve the detection and texture characterization of lung nodules by CT, therefore improving the accuracy of oncological lung disease assessment. The ease of use of BH and its added value should prompt its use in routine practice.

A novel approach for fibrous dysplasia assessment using combined planar and quantitative SPECT/CT analysis of Tc-99m-diphosphonate bone scan in correlation with biological bone turnover markers of disease activity.

Purpose: To investigate the emerging role of Tc-99m-labeled diphosphonate (Tc-99m-DPD) uptake quantification by SPECT/CT in fibrous dysplasia (FD) bone lesions and its correlation with biological bone turnover markers (BTMs) of disease activity. Materials and methods: Seven patients (49 ± 16 years) with a confirmed diagnosis of FD were included in this retrospective study. Bone scans with Tc-99m-DPD and quantitative SPECT/CT (xSPECT/CT) were performed. SUVmax (maximum standard unit value) and SUVmean (mean standard unit value) were measured in all FD bone lesions. The skeletal burden score (SBS) was assessed on planar scintigraphy and multiplied by mean SUV max and SUVmean to generate two new parameters, SBS_SUVmax and SBS_SUVmean, respectively. Planar and xSPECT/CT quantitative measures were correlated with biological BTMs of disease activity, including fibroblast growth factor 23 (FGF-23), alkaline phosphatase (ALP), procollagen 1 intact N-terminal propeptide (P1NP) and C-terminal telopeptide (CTX), as well as scoliosis angle measured on radiographs. Statistical significance was evaluated with Spearman's correlations. Results: A total of 76 FD bone lesions were analyzed, showing an average SUVmax and SUVmean (g/mL) of 13 ± 7.3 and 8 ± 4.5, respectively. SBS, SBS_SUVmax and SBS_SUVmean values were 30.8 ± 25.6, 358 ± 267 and 220.1 ± 164.5, respectively. Mean measured values of FGF-23 (pg/mL), ALP (U/L), P1NP (µg/L) and CTX (pg/mL) were 98.4 (22-175), 283.5 (46-735), 283.1 (31-1,161) and 494 (360-609), respectively. Mean scoliosis angle was 15.7 (7-22) degrees. We found a very strong positive correlation between planar-derived SBS and CTX (r = 0.96, p = 0.010), but no significant correlation between SUVmax or SUVmean and biological BTMs. SBS_SUVmax showed a strong to very strong positive correlation with CTX (ρ = 0.99, p = 0.002), FGF-23 (ρ = 0.91, p = 0.010), ALP (ρ = 0.82, p = 0.020), and P1NP (ρ = 0.78, p = 0.039), respectively. Conclusion: This study showed that biological BTMs are significantly correlated with diphosphonate uptake on bone scan, quantified by a new parameter combining information from both planar and quantitative SPECT/CT. Further analysis of bone scan quantitative SPECT/CT data in a larger patient population might help better characterize the skeletal disease burden in FD, and guide treatment and follow-up.

Monte Carlo 90Y PET/CT dosimetry of unexpected focal radiation-induced lung damage after hepatic radioembolisation.

Transarterial radioembolization (TARE) with 90Y-loaded microspheres is an established therapeutic option for inoperable hepatic tumors. Increasing knowledge regarding TARE hepatic dose-response and dose-toxicity correlation is available but few studies have investigated dose-toxicity correlation in extra-hepatic tissues. We investigated absorbed dose levels for the appearance of focal lung damage in a case of off-target deposition of 90Y microspheres and compared them with the corresponding thresholds recommended to avoiding radiation induced lung injury following TARE. A 64-year-old male patient received 1.6 GBq of 90Y-labelled glass microspheres for an inoperable left lobe hepatocellular carcinoma. A focal off-target accumulation of radiolabeled microspheres was detected in the left lung upper lobe at the post-treatment 90Y-PET/CT, corresponding to a radiation-induced inflammatory lung lesion at the 3-months 18F-FDG PET/CT follow-up. 90Y-PET/CT data were used as input for Monte-Carlo based absorbed dose estimations. Dose-volume-histograms were computed to characterize the heterogeneity of absorbed dose distribution. The dose level associated with the appearance of lung tissue damage was estimated as the median absorbed dose measured at the edge of the inflammatory nodule. To account for respiratory movements and possible inaccuracy of image co-registration, three different methods were evaluated to define the irradiated off-target volume. Monte Carlo-derived absorbed dose distribution showed a highly heterogeneous absorbed dose pattern at the site of incidental microsphere deposition (volume = 2.13 ml) with a maximum dose of 630 Gy. Absorbed dose levels ranging from 119 Gy to 133 Gy, were estimated at the edge of the inflammatory nodule, depending on the procedure used to define the target volume. This report describes an original Monte Carlo based patient-specific dosimetry methodology for the study of the radiation-induced damage in a focal lung lesion after TARE. In our patient, radiation-induced focal lung damage occurred at significantly higher absorbed doses than those considered for single administration or cumulative lung dose delivered during TARE.

Outpatient Yttrium-90 microsphere radioembolization: assessment of radiation safety and quantification of post-treatment adverse events causing hospitalization.

PURPOSE: Quantification of post-interventional adverse events of outpatient SIRT leading to hospitalization and quantification of radiation exposure. MATERIALS AND METHODS: In this single-center, retrospective cohort study, we reviewed 212 patients treated with SIRT (90Y-microspheres) for primary and secondary liver malignancies. We searched for adverse events (AEs) and serious adverse events (SAEs), defined as AE's causing hospitalization. Additionally, radiation exposure was measured in 36 patients. RESULTS: Seven patients had an SAE (3.3%), four patients had AE without readmission/hospitalization (1.9%) and 201 patients had no complications (94.8%). The mean ambient dose rate at 1 m distance from the source after administration of 90Y-microspheres was 1.88 µSv/h ± 0.74 (± SD) with a range from 4.3 to 0.2 µSv/h. CONCLUSION: Outpatient radioembolization with 90Y-microspheres is safe and requires hospitalization only in a very small number of patients. The mean dose rate was low and met the national conditions for outpatient treatment (< 5 µSv/h).

Histogram Analysis of CT Perfusion of Hepatocellular Carcinoma for Predicting Response to Transarterial Radioembolization: Value of Tumor Heterogeneity Assessment.

PURPOSE: To evaluate in patients with hepatocellular carcinoma (HCC), whether assessment of tumor heterogeneity by histogram analysis of computed tomography (CT) perfusion helps predicting response to transarterial radioembolization (TARE). MATERIALS AND METHODS: Sixteen patients (15 male; mean age 65 years; age range 47-80 years) with HCC underwent CT liver perfusion for treatment planning prior to TARE with Yttrium-90 microspheres. Arterial perfusion (AP) derived from CT perfusion was measured in the entire tumor volume, and heterogeneity was analyzed voxel-wise by histogram analysis. Response to TARE was evaluated on follow-up imaging (median follow-up, 129 days) based on modified Response Evaluation Criteria in Solid Tumors (mRECIST). Results of histogram analysis and mean AP values of the tumor were compared between responders and non-responders. Receiver operating characteristics were calculated to determine the parameters' ability to discriminate responders from non-responders. RESULTS: According to mRECIST, 8 patients (50%) were responders and 8 (50%) non-responders. Comparing responders and non-responders, the 50th and 75th percentile of AP derived from histogram analysis was significantly different [AP 43.8/54.3 vs. 27.6/34.3 mL min(-1) 100 mL(-1)); p < 0.05], while the mean AP of HCCs (43.5 vs. 27.9 mL min(-1) 100 mL(-1); p > 0.05) was not. Further heterogeneity parameters from histogram analysis (skewness, coefficient of variation, and 25th percentile) did not differ between responders and non-responders (p > 0.05). If the cut-off for the 75th percentile was set to an AP of 37.5 mL min(-1) 100 mL(-1), therapy response could be predicted with a sensitivity of 88% (7/8) and specificity of 75% (6/8). CONCLUSION: Voxel-wise histogram analysis of pretreatment CT perfusion indicating tumor heterogeneity of HCC improves the pretreatment prediction of response to TARE.

Radioimmunotherapy in non-Hodgkin lymphoma: opinions of nuclear medicine physicians and radiation oncologists.

UNLABELLED: Despite approval by the Food and Drug Administration and consistent reports of the efficacy and safety of (90)Y-ibritumomab tiuxetan and (131)I-tositumomab, these therapies are infrequently used. This study investigates the opinions and patterns of the use of radioimmunotherapy by nuclear physicians, affiliated researchers, nuclear medicine technologists, and radiation oncologists and aims to identify possible barriers to the use of this promising therapy. METHODS: An e-mail-based survey with 13 broad questions related to radioimmunotherapy was sent electronically to 13,221 Society of Nuclear Medicine members and radiation oncologists throughout the United States. RESULTS: Six hundred thirteen individuals (4.6%) responded to the electronic survey. Two hundred fifty-one responders (40.9%) had treated patients with non-Hodgkin lymphoma (NHL) with radioimmunotherapy in the last 24 mo. Of the responders, 29.5% used only (90)Y-ibritumomab tiuxetan, 7.6% used only (131)I-tositumomab, and 24.9% used both radiopharmaceuticals; 37.9% did not treat NHL with radioimmunotherapy. Most responders said their patients came from university hospitals (33.9%) or private offices (25.6%), and they mainly treated in a second-line (42.9%), third-line (35.6%), or consolidation (23.5%) setting. Major concerns were that referring oncologists and hematologists wanted to treat by themselves with nonradioactive compounds (mean ± SD, 3.418 ± 1.49) and that (90)Y-ibritumomab tiuxetan and (131)I-tositumomab were expensive (mean ± SD, 3.413 ± 1.35). Of the responders and involved physicians, 40.4% and 35.2%, respectively, did not know if their institution accepted Medicare patients for radioimmunotherapy. Almost 30% (29.6%) of the responders thought radioimmunotherapy would probably grow and 38.0% thought it would grow in importance in the future. Responders who did not administer radioimmunotherapy for NHL thought it took too much time to administer radioimmunotherapy (P < 0.01) and had concerns about the dosimetry procedure (P < 0.01) and radiation safety (P < 0.01). Individuals who perceived a negative future for radioimmunotherapy had significantly more concerns about the time-consuming administration process (P < 0.05) and the high cost of radioimmunotherapy (P < 0.05). Responders from academic centers had significantly fewer concerns about payment (P < 0.01), dosimetry (P < 0.01), and radiation safety (P < 0.01). CONCLUSION: Radioimmunotherapy was generally viewed positively by the surveyed population. However, limited referrals due to alternative nonradioactive therapies and logistic, educational, and economic concerns played an important role for subgroups in the perception of radioimmunotherapy for NHL.