Multi-parametric whole-body MRI evaluation discerns vital from non-vital multiple myeloma lesions as validated by 18F-FDG and 11C-methionine PET/CT.

PURPOSE: We tested a novel multi-parametric (mp) whole body (WB)-MRI evaluation algorithm for medullary lesions in comparison to positron emission tomography (PET) radiotracers 18F-fluorodeoxyglucose (18F-FDG) and 11C-methionine (11C-MET). METHODS AND MATERIALS: This retrospective single-center study included 44 MM patients, who received both 18F-FDG-PET and WB-MRI within ten days. MRI classified focal lesions as vital when showing 1) significant diffusion-restriction, 2) a fat fraction (FF) less than 20 % and 3) homogenous hypointensity on T2-weighted images. On a lesion-by-lesion level the findings were compared to 18F-FDG PET by using a 5-point scoring system (analogous to the Deauville score [DS]). In 24/44 (55 %) patients additional comparison to 11C-MET PET was available. RESULTS: Among two radiologists, an excellent inter-observer reliability for mpWB-MRI in a total of 84 medullary lesions was observed (ICC = 1, k = 1, p <.01). 16/17 (94.1 %) MRI-classified vital lesions had a DS of 4 or 5 on either 18F-FDG-PET or 11C-MET-PET. MRI-rated non-vital lesions correlated with PET-based DS ≤ 3. When results of mpWB-MRI were compared to 18F-FDG, a fair inter-observer agreement was recorded (ICC = 0.52, k = 0.53, p <.01), while for 11C-MET, an excellent concordance rate was achieved (ICC = 0.81, k = 0.79, p <.01). CONCLUSION: The proposed mpWB-MRI interpretation algorithm allowed to assess tumor activity of myeloma lesions with high inter-observer reproducibility. We observed a substantial concordance between the mpWB-MRI classification of lesions and PET assessment based on a semi-automatically calculated 5-point scoring system analogous to the Deauville scores.

Adrenal wash-out CT: moderate diagnostic value in distinguishing benign from malignant adrenal masses.

OBJECTIVE: Reliable results of wash-out CT in the diagnostic workup of adrenal incidentalomas are scarce. Thus, we evaluated the diagnostic accuracy of delayed wash-out CT and determined thresholds to accurately differentiate adrenal masses. DESIGN: Retrospective, single-center cohort study including 216 patients with 252 adrenal lesions who underwent delayed wash-out CT. Definitive diagnoses based on histopathology (n = 92) or comprehensive follow-up. METHODS: Size, average attenuation values of the adrenal lesions in all CT scan phases, and absolute and relative percentage wash-out (APW/RPW) were determined by an expert radiologist blinded for clinical data. Adrenal lesions with unenhanced attenuation values >10 Hounsfield units (HU) built a subgroup (n = 142). Diagnostic accuracy was calculated. RESULTS: The study group consisted of 171 adenomas, 32 other benign tumors, 11 pheochromocytomas, 9 adrenocortical carcinomas, and 29 other malignant tumors. All (potentially) malignant and 46% of benign lesions showed unenhanced attenuation values >10 HU. In this most relevant subgroup, the established thresholds of 60% for APW and 40% for RPW misclassified 35.9 and 35.2% of the masses, respectively. When we applied optimized cutoffs (APW >83%; RPW >58%) and excluded pheochromocytomas, we missed only one malignant tumor by APW and none by RPW. However, only 11 and 15% of the benign tumors were correctly identified. CONCLUSIONS: Wash-out CT with the established thresholds for APW and RPW is insufficient to reliably diagnose adrenal masses. Using the proposed cutoff of 58% for RPW, malignant tumors will be correctly identified, but the added value is limited, namely 15% of patients with benign tumors can be prevented from additional imaging or even unnecessary surgery.

DNA Damage in Peripheral Blood Lymphocytes of Thyroid Cancer Patients After Radioiodine Therapy.

UNLABELLED: The aim of the study was to investigate DNA double-strand break (DSB) formation and its correlation to the absorbed dose to the blood in patients with surgically treated differentiated thyroid cancer undergoing their first radioiodine therapy for remnant ablation. METHODS: Twenty patients were included in this study. At least 7 peripheral blood samples were obtained before and between 0.5 and 120 h after administration of radioiodine. From the time-activity curves of the blood and the whole body, residence times for the blood self-irradiation and the irradiation from the whole body were determined. Peripheral blood lymphocytes were isolated, ethanol-fixed, and subjected to immunofluorescence staining for colocalizing γ-H2AX/53BP1 DSB-marking foci. The average number of DSB foci per cell per patient sample was analyzed as a function of the absorbed dose to the blood and compared with an in vitro calibration curve for (131)I and (177)Lu established previously in our institution. RESULTS: The average number of radiation-induced foci (RIF) per cell increased over the first 3 h after radionuclide administration and decreased thereafter. A linear fit from 0 to 2 h as a function of the absorbed dose to the blood agreed with our in vitro calibration curve. At later time points, RIF numbers diminished, along with dropping dose rates, indicating progression of DNA repair. Individual patient data were characterized by a linear dose-dependent increase and a biexponential response function describing a fast and a slow repair component. CONCLUSION: With the experimental results and model calculations presented in this work, a dose-response relationship is demonstrated, and an analytic function describing the time course of the in vivo damage response after internal irradiation of patients with (131)I is established.

DNA damage in blood lymphocytes in patients after (177)Lu peptide receptor radionuclide therapy.

PURPOSE: The aim of the study was to investigate DNA double strand break (DSB) formation and its correlation with the absorbed dose to the blood lymphocytes of patients undergoing their first peptide receptor radionuclide therapy (PRRT) with (177)Lu-labelled DOTATATE/DOTATOC. METHODS: The study group comprised 16 patients receiving their first PRRT. At least six peripheral blood samples were obtained before, and between 0.5 h and 48 h after radionuclide administration. From the time-activity curves of the blood and the whole body, residence times for blood self-irradiation and whole-body irradiation were determined. Peripheral blood lymphocytes were isolated, fixed with ethanol and subjected to immunofluorescence staining for colocalizing γ-H2AX/53BP1 DSB-marking foci. The average number of DSB foci per cell per patient sample was determined as a function of the absorbed dose to the blood and compared with an in vitro calibration curve established in our laboratory with (131)I and (177)Lu. RESULTS: The average number of radiation-induced foci (RIF) per cell increased over the first 5 h after radionuclide administration and decreased thereafter. A linear fit from 0 to 5 h as a function of the absorbed dose to the blood agreed with our in vitro calibration curve. At later time-points the number of RIF decreased, indicating progression of DNA repair. CONCLUSION: Measurements of RIF and the absorbed dose to the blood after systemic administration of (177)Lu may be used to obtain data on the individual dose-response relationships in vivo. Individual patient data were characterized by a linear dose-dependent increase and an exponential decay function describing repair.

Impact of nonhybrid 99mTc-MDP-SPECT/CT image fusion in diagnostic and treatment of oromaxillofacial malignancies.

PURPOSE: The aim of this study was to prospectively investigate the clinical impact of image fusion of computed tomography (CT) and single photon emission computed tomography (SPECT) diagnostics in head and neck cancer adjacent or fixed to bony maxillofacial structures. PROCEDURES: Computer-based manual image fusion has been applied in 74 patients with suspected malignancies in the oromaxillofacial region following CT and SPECT. Afterward, image fusion was compared to separate evaluation of CT and SPECT and visual coregistration with histopathological results serving as control. RESULTS: In nine out of 74 patients, image fusion achieved more precise anatomical findings regarding tumor dimension than simultaneous evaluation of CT and SPECT, but there was no improvement of identification of bone infiltration. CONCLUSION: Manual image fusion of CT and SPECT does not improve identification of bone infiltration compared to simultaneous evaluation. Though particularly in complex anatomical regions, a fixed preoperative diagnostic algorithm in image registration lead to a more precise evaluation and treatment of head and neck malignancies.

Use of integrated FDG-PET/CT in sarcoidosis.

We studied five patients with mediastinal lymph node enlargement suggestive of malignant lymphoma, lung cancer, or sarcoidosis. Integrated [(18)F]fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) was performed on all patients. Sarcoidosis can be a pitfall in PET/CT imaging, which may lead to false-positive results of malignancy. Increased FDG uptake in mediastinal lymph nodes is often comparable with malignant lymphoma or lymph node metastases. Histological confirmation of the lesions should be mandatory, except for patients in whom sarcoidosis can be accurately confirmed by other diagnostic methods.