Sparing the Hippocampus in Prophylactic Cranial Irradiation Using Three Different Linear Accelerators: A Comparative Study.

Hippocampus protection, as an organ at risk in brain radiotherapy, might protect patients' quality of life. Prophylactic cranial irradiation (PCI) has been used traditionally in small cell lung cancer (SCLC) patients as it increases survival. This study aimed to discover the contributing parameters for a successful PCI with simultaneous protection of the hippocampus by using three different treatment machines. For this purpose, treatment plans were generated for 45 SCLC patients using three half-arcs in three linear accelerators (LINACs; Elekta Infinity, Synergy, and Axesse; Elekta Ltd, Stockholm, Sweden) with different radiation field sizes and multileaf collimator (MLC) leaf thickness characteristics. The prescribed dose was 25 Gy in 10 fractions. Thresholds for the hippocampus were calculated based on the Radiation Therapy Oncology Group 0933 dose constraints. The planning and treatment system templates were common to all three LINACs. Plan evaluation was based on the dosimetric target coverage by the 95% isodose, the maximum dose of the plan, the conformity index (CI), the degree of plan modulation (MOD), and the patient-specific quality assurance (QA) pass rate. The mean target coverage was highest for Infinity (97.3%), followed by Axesse (96.6%) and Synergy (95.5%). The mean maximum dose was higher for Synergy (27.5 Gy), followed by Infinity (27.0 Gy) and Axesse (26.9 Gy). Axesse plans had the highest CI (0.93), followed by Infinity (0.91) and Synergy (0.88). Plan MOD was lower for Synergy (2.88) compared with Infinity (3.07) and Axesse (3.69). Finally, patient-specific QA was successful in all Infinity plans, in all but one Synergy plan, and in 17/45 Axesse plans, as was expected from the field size in that treatment unit. Based on overall performance, the most favorable combination of target coverage, hippocampus sparing, and plan deliverability was obtained with the LINAC, which has the largest field opening and thinnest MLC leaves.

Towards improved diagnosis: radiomics and quantitative biomarkers in 18 F-PSMA-1007 and 18 F-fluorocholine PET/CT for prostate cancer recurrence.

OBJECTIVE: This study compared the radiomic features and quantitative biomarkers of 18 F-PSMA-1007 [prostate-specific membrane antigen (PSMA)] and 18 F-fluorocholine (FCH) PET/computed tomography (CT) in prostate cancer patients with biochemical recurrence (BCR) enrolled in the phase 3, prospective, multicenter BIO-CT-001 trial. METHODS: A total of 106 patients with BCR, who had undergone primary definitive treatment for prostate cancer, were recruited to this prospective study. All patients underwent one PSMA and one FCH PET/CT examination in randomized order within 10 days. They were followed up for a minimum of 6 months. Pathology, prostate-specific antigen (PSA), PSA doubling time, PSA velocity, and previous or ongoing treatment were analyzed. Using LifeX software, standardized uptake value (SUV) maximum, SUV mean , PSMA and choline total volume (PSMA-TV/FCH-TV), and total lesion PSMA and choline (TL-PSMA/TL-FCH) of all identified metastatic lesions in both tracers were calculated. RESULTS: Of the 286 lesions identified, the majority 140 (49%) were lymph node metastases, 118 (41.2%) were bone metastases and 28 lesions (9.8%) were locoregional recurrences of prostate cancer. The median SUV max value was significantly higher for 18 F-PSMA compared with FCH for all 286 lesions (8.26 vs. 4.99, respectively, P  < 0.001). There were statistically significant differences in median SUV mean , TL-PSMA/FCH, and PSMA/FCH-TV between the two radiotracers (4.29 vs. 2.92, 1.97 vs. 1.53, and 7.31 vs. 4.37, respectively, P  < 0.001). The correlation between SUV mean /SUV max and PSA level was moderate, both for 18 F-PSMA ( r  = 0.44, P  < 0.001; r  = 0.44, P  < 0.001) and FCH ( r  = 0.35, P  < 0.001; r  = 0.41, P  < 0.001). TL-PSMA/FCH demonstrated statistically significant positive correlations with both PSA level and PSA velocity for both 18 F-PSMA ( r  = 0.56, P  < 0.001; r  = 0.57, P  < 0.001) and FCH ( r  = 0.49, P  < 0.001; r  = 0.51, P  < 0.001). While patients who received hormone therapy showed higher median SUV max values for both radiotracers compared with those who did not, the difference was statistically significant only for 18 F-PSMA ( P  < 0.05). CONCLUSION: Our analysis using both radiomic features and quantitative biomarkers demonstrated the improved performance of 18 F-PSMA-1007 compared with FCH in identifying metastatic lesions in prostate cancer patients with BCR.

Dose optimization of 2D X-ray image acquisition protocols in image-guided radiotherapy.

PURPOSE: In contemporary radiotherapy, patient positioning accuracy relies on kV imaging. This study aims at optimizing planar kV image acquisition protocols regarding patient dose without degrading image quality. MATERIALS AND METHODS: An image quality test-object was placed in-between PMMA plates, suitably arranged to model head or pelvis. Constructed phantoms were imaged using default protocols, the resultant image quality was assessed and the corresponding radiation dose was measured. The process was repeated using numerous kV/mAs combinations to identify those acquisition settings providing images at lower dose than the default protocols but without deterioration in image quality. Default and dose-optimized protocols were then tested on an anthropomorphic phantom and on 51 patients during two successive treatment sessions. Image quality was independently assessed by two readers. Organ and effective doses were estimated using a Monte Carlo simulation software. RESULTS: Low-contrast detectability exhibited a stronger dependence on kV/mAs settings, compared to high-contrast resolution. Dose-optimized protocols resulted in significant dose reductions (anteroposterior-head 48.0 %, lateral-head 30.0 %, anteroposterior-pelvis 28.4 %, lateral-pelvis 27.0 %) compared to the default ones, without compromising image quality. Optimized protocols decreased effective doses by 54 % and 29.6 % in head and pelvic acquisitions, respectively. Regarding image quality, anthropomorphic and patient images acquired using the dose-optimized protocols were subjectively evaluated equivalent to those obtained with the corresponding default settings, indicating that the proposed protocols may be routinely used. CONCLUSIONS: Given the potentially large number of radiotherapy fractions and the pertinent image acquisitions, dose-optimized protocols could significantly reduce patient dose associated with planar imaging without compromising positioning accuracy.

Spleen visualization in both TTR and AL amyloidosis during 99mTc-DPD scintigraphy. Do we have to deal with a different than the myocardial uptake mechanism?

Technetium-99m- diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) is currently used in Europe for the diagnosis of cardiac amyloidosis, being able to distinguish light chain (AL) from transthyretin (TTR) type. We are reporting obvious spleen visualization in two patients suffering the first from proven TTR and the second from AL type of cardiac amyloidosis, with myocardial uptake-as anticipated-only in the first one. We raise the hypothesis that a common uptake mechanism exists for the spleen amyloid regardless of the type of the disease (AL or TTR), and is possibly different than the cardiac uptake mechanism.

Differentiated thyroid cancer: Case report of false positive 131I uptake on whole body scintigraphy in a patient with bilateral femur osteonecrosis.

OBJECTIVE: Differentiated thyroid cancer (DTC) is one of the fastest growing cancers worldwide. Despite the generally good prognosis of thyroid carcinoma, about 5% of patients will develop metastatic disease, exhibiting a more aggressive behavior. Radioiodine whole-body scintigraphy (WBS) has been used in the detection of DTC. Radioiodine is a sensitive marker for detection of thyroid cancer; however, radioiodine uptake is not specific for thyroid tissue. It can also be seen in healthy tissue as well as in inflammation, or in a variety of benign and malignant non-thyroidal entities. SUBJECT AND METHODS: The subject of the present case report is a 52 years old man with brain metastatic DTC who received radioiodine therapy and corticosteroids as palliative therapy. Whole-body scintigraphy revealed bilateral iodine uptake of the femur. Corticosteroid therapy is among the most widely recognized risk factor for osteonecrosis, which at the present case had to be recognized as a false positive (iodine-131) 131I uptake in order to avoid diagnostic error. RESULTS: Post therapeutic whole body scintigraphy revealed no uptake in the thyroid bed as well as pathologic uptake of radioiodine in both femurs. The magnetic resonance imaging (MRI) of the femurs combined with the history of long term exposition on high doses of corticosteroids evidenced diagnosis of steroid-induced osteonecrosis of the femurs. CONCLUSION: Radioiodine WBS plays an important role in clinical decision making for the evaluation and the management of patients with DTC. Despite its high range of sensitivity and specificity, a variety of reports of false positive whole body scans has demonstrated a diversity of causes. Comprehension of the physiology of iodine uptake and of the pathophysiology of clinical entities which end up giving false positives scans, provides clinicians a useful tool in order to avoid diagnostic and therapeutic errors as far as DTC is concerned.

Unusually seen pattern of 99mTc-DPD soft tissue uptake in a patient with AL amyloidosis. Is it an amyloid type indicator in specific cases?

Technetium-99m (99mTc)-labeled pyrophosphate (PYP) and 3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) are currently the most established imaging agents for the diagnosis of cardiac amyloidosis, being able to distinguish light chain (AL) from transthyretin (TTR) type of the disease. We present a pattern of increased uptake in all soft tissues, sparing the organs that are usually most affected.

Could the Majority of the Greek and Cypriot Population Be Vitamin D Deficient?

OBJECTIVE: Hypovitaminosis D is prevalent in epidemic proportions in many developed countries. The aim of this study is to investigate the prevalence of adequate 25-hydroxyvitamin D [25(OH)D] levels in two Mediterranean countries, Greece and Cyprus. METHODS: Data such as 25(OH)D, the month of blood sample collection, and demographic information were blindly collected from 8780 Greek and 2594 Cypriot individuals over 5 years. Comorbidities were also recorded for 839 Greek subjects. Univariate and multivariate analyses were used to examine the relationship between these variables and 25(OH)D levels. RESULTS: In the samples studied, 72.7% of the Greek and 69.3% of the Cypriot population sample had inadequate levels of 25(OH)D. The mean level for the Greek subjects was 25.1 ng/mL and for Cypriots 25.8 ng/mL. For both samples, only month and gender were significantly associated with 25(OH)D levels, and the highest mean levels were recorded in September. For the recorded diseases, the lowest levels were recorded in sickle cell anaemia 13.6 ± 10.2 ng/mL, autoimmune diseases 13.0 ± 8.4 ng/mL, and cancer 22.6 ± 9.5 ng/mL. CONCLUSIONS: The prevalence of vitamin D deficiency is paradoxically high in both Mediterranean countries.

A novel quantitative method for assessing the therapeutic response to Tafamidis therapy in patients with cardiac TTR amyloidosis. A preliminary report.

OBJECTIVE: Cardiomyopathy is a common manifestation of transthyretin amyloidosis (ATTR), leading to heart failure, associated with high morbidity and mortality. The aim of this study was to investigate the effect of Tafamidis treatment by means of cardiac radiotracer uptake on myocardial scintigraphy. SUBJECTS AND METHODS: Five male patients, mean age 76.2 years, with wild-type ATTR were included in the protocol. Total body scanning using technetium-99m-3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) (in four patients) and technetium-99m-hydroxymethylene diphosphonate (99mTc-HMDP) (in one) was performed pre- and one year post-Tafamidis therapy. A novel quantitation method for assessing radiotracer cardiac uptake was employed. The geometric mean was computed for both cardiac and thigh region of interest (ROI) and the heart-to-thigh (HtT) ratio was assessed by dividing the corresponding geometric mean counts. RESULTS: Heart-to-thigh ratio was improved (decreased) in four of the patients receiving Tafamidis, in keeping with lower uptake to the cardiac region. These patients also demonstrated a relatively favorable clinical response to Tafamidis. The patient evaluated by 99mTc-HMDP exhibited minimal HtT ratio reduction and stable clinical and echocardiographic characteristics. CONCLUSION: Sequential HtT ratio measurements could potentially identify patients with a favorable response to Tafamidis treatment at earlier stages, compared to other imaging modalities or serological biomarkers.

Institutional Diagnostic Reference Levels and Peak Skin Doses in selected diagnostic and therapeutic interventional radiology procedures.

PURPOSE: Institutional (local) Diagnostic Reference Levels for Cerebral Angiography (CA), Percutaneous Transhepatic Cholangiography (PTC), Transarterial Chemoembolization (TACE) and Percutaneous Transhepatic Biliary Drainage (PTBD) are reported in this study. MATERIALS AND METHODS: Data for air kerma-area product (PKA), air kerma at the patient entrance reference point (Ka,r), fluoroscopy time (FT) and number of images (NI) as well as estimates of Peak Skin Dose (PSD) were collected for 142 patients. Therapeutic procedure complexity was also evaluated, in an attempt to incorporate it into the DRL analysis. RESULTS: Local PKA DRL values were 70, 34, 189 and 54 Gy.cm2 for CA, PTC, TACE and PTBD respectively. The corresponding DRL values for Ka,r were 494, 194, 1186 and 400 mGy, for FT they were 9.2, 14.2, 27.5 and 22.9 min, for the NI they were 844, 32, 602 and 13 and for PSD they were 254, 256, 1598 and 540 mGy respectively. PKA for medium complexity PTBD procedures was 2.5 times higher than for simple procedures. For TACE, the corresponding ratio was 1.6. PSD was estimated to be roughly 50% of recorded Ka,r for procedures in the head/neck region and 10% higher than recorded Ka,r for procedures in the body region. In only 5 cases the 2 Gy dose alarm threshold for skin deterministic effects was exceeded. CONCLUSION: Procedure complexity can differentiate DRLs in Interventional Radiology procedures. PSD could be deduced with reasonable accuracy from values of Ka,r that are reported in every angiography system.