Gustavo S.P. Meirelles

Prognostic Value of Baseline [18F] Fluorodeoxyglucose Positron Emission Tomography and 99mTc-MDP Bone Scan in Progressing Metastatic Prostate Cancer

Purpose: To compare the diagnostic and prognostic value of [18F] fluorodeoxyglucose positron emission tomography (FDG-PET) and bone scans (BS) in the assessment of osseous lesions in patients with progressing prostate cancer. Experimental Design: In a prospective imaging trial, 43 patients underwent FDG-PET and BS prior to experimental therapies. Bone scan index (BSI) and standardized uptake value (SUV) on FDG-PET were recorded. Patients were followed until death (n = 36) or at least 5 years (n = 7). Imaging findings were correlated with survival. Results: Osseous lesions were detected in 39 patients on BS and 32 on FDG-PET (P = 0.01). Follow-up was available for 105 FDG-positive lesions, and 84 (80%) became positive on subsequent BS. Prognosis correlated inversely with SUV (median survival 14.4 versus 32.8 months if SUVmax > 6.10 versus ≤ 6.10; P = 0.002) and BSI (14.7 versus 28.2 months if BSI > 1.27 versus < 1.27; P = 0.004). Only SUV was an independent factor in multivariate analysis. Conclusion: This study of progressive prostate cancer confirms earlier work that BSI is a strong prognostic factor. Most FDG-only lesions at baseline become detectable on follow-up BS, suggesting their strong clinical relevance. FDG SUV is an independent prognostic factor and provides complementary prognostic information. Clin Cancer Res; 16(24); 6093–99. ©2010 AACR.

Deep-Inspiration Breath-Hold PET/CT: Clinical Findings with a New Technique for Detection and Characterization of Thoracic Lesions

Respiratory motion during PET/CT acquisition can cause misregistration and inaccuracies in calculation of standardized uptake values (SUVs). Our aim was to compare the detection and characterization of thoracic lesions on PET/CT with and without a deep-inspiration protocol. Methods: We studied 15 patients with suspected pulmonary lesions who underwent clinical PET/CT, followed by deep-inspiration breath-hold (BH) PET/CT. In BH CT, the whole chest of the patient was scanned in 15 s at the end of deep inspiration. For BH PET, patients were asked to hold their breath 9 times for 20-s intervals. One radiologist reviewed images, aiming to detect and characterize pulmonary, nodal, and skeletal abnormalities. Clinical CT and BH CT were compared for number, size, and location of lesions. Lesion SUVs were compared between clinical PET and BH PET. Images were also visually assessed for accuracy of fusion and registration. Results: All patients had lesions on clinical CT and BH CT. Pulmonary BH CT detected more lesions than clinical CT in 13 of 15 patients (86.7%). The total number of lung lesions detected increased from 53 with clinical CT to 82 with BH CT (P < 0.001). Eleven patients showed a total of 31 lesions with abnormal 18F-FDG uptake. BH PET/CT had the advantage of reducing misregistration and permitted a better localization of sites with 18F-FDG uptake. A higher SUV was noted in 22 of 31 lesions on BH PET compared with clinical PET, with an average increase in SUV of 14%. Conclusion: BH PET/CT enabled an increased detection and better characterization of thoracic lesions compared with a standard PET/CT protocol, in addition to more precise localization and quantification of the findings. The technique is easy to implement in clinical practice and requires only a minor increase in the examination time.

Pharmacokinetic Assessment of the Uptake of 16β-18F-Fluoro-5α-Dihydrotestosterone (FDHT) in Prostate Tumors as Measured by PET

The aim of this study was to develop a clinically applicable noninvasive method to quantify changes in androgen receptor (AR) levels based on 18F-16β-fluoro-5α-dihydrotestosterone (18F-FDHT) PET in prostate cancer patients undergoing therapy. Methods: Thirteen patients underwent dynamic 18F-FDHT PET over a selected tumor. Concurrent venous blood samples were acquired for blood metabolite analysis. A second cohort of 25 patients injected with 18F-FDHT underwent dynamic PET of the heart. These data were used to generate a population-based input function, essential for pharmacokinetic modeling. Linear compartmental pharmacokinetic models of increasing complexity were tested on the tumor tissue data. Four suitable models were applied and compared using the Bayesian information criterion (BIC). Model 1 consisted of an instantaneously equilibrating space, followed by a unidirectional trap. Models 2a and 2b contained a reversible space between the instantaneously equilibrating space and the trap, into which metabolites were excluded (2a) or allowed (2b). Model 3 built on model 2b with the addition of a second reversible space preceding the unidirectional trap and from which metabolites were excluded. Results: The half-life of the 18F-FDHT in blood was between 6 and 7 min. As a consequence, the uptake of 18F-FDHT in prostate cancer lesions reached a plateau within 20 min as the blood-borne activity was consumed. Radiolabeled metabolites were shown not to bind to ARs in in vitro studies with CWR22 cells. Model 1 produced reasonable and robust fits for all datasets and was judged best by the BIC for 16 of 26 tumor scans. Models 2a, 2b, and 3 were judged best in 7, 2, and 1 cases, respectively. Conclusion: Our study explores the clinical potential of using 18F-FDHT PET to estimate free AR concentration. This process involved the estimation of a net uptake parameter such as the ktrap of model 1 that could serve as a surrogate measure of AR expression in metastatic prostate cancer. Our initial studies suggest that a simple body mass–normalized standardized uptake value correlates reasonably well to model-based ktrap estimates, which we surmise may be proportional to AR expression. Validation studies to test this hypothesis are underway.

18F-FDG uptake and calcifications in the thoracic aorta on positron emission tomography/computed tomography examinations: frequency and stability on serial scans.

Purpose Vascular 18F-2-fluoro-2-deoxy-D-glucose (18F-FDG) uptake has been suggested as a means of identifying metabolically active atheroma, whereas vascular calcification is accepted as an indicator of atherosclerosis. This investigation describes the frequency and stability of 18F-FDG uptake and vascular calcification in the thoracic aorta on serial 18F-FDG positron emission tomography/computed tomography (PET/CT) studies and correlates the findings with clinical data and risk factors for cardiovascular disease (CVD). Materials and Methods Serial 18F-FDG-PET/CT scans of 100 cancer patients who had at least 2 PET/CT studies were reviewed. Sites of aortic 18F-FDG uptake and calcifications were identified. Results were compared to assess the frequency and stability of the vascular findings and their correlation with clinical data. Results 18F-FDG aortic uptake was seen in 70% of the patients on the initial scan and changed on the second scan in 55% of the patients. Calcifications were often seen in patients with 18F-FDG uptake, but calcification and 18F-FDG uptake were present at the same site in only 2 cases. Both calcification and 18F-FDG uptake correlated with age. Patients with diabetes, hypertension, hyperlipidemia, or a history of CVD had significantly more calcifications. No correlation was seen between 18F-FDG uptake and calcification stability and the interval between scans, age, risk factors, or history of CVD. Conclusions 18F-FDG vascular uptake was common on PET/CT and correlated with vascular calcifications, although the specific sites rarely overlapped. Calcifications were stable over time, but 18F-FDG uptake changed in more than half of the patients, supporting the postulate that inflammation in atheroma is a waxing and waning inflammatory process.

F-18 FDG uptake in subcutaneous panniculitis-like T-cell lymphoma.

A 41-year-old male presented to an outside institution complaining of a lump under the skin of his right abdomen. CT scan reported ill-defined densities with streaky inflammatory changes in the anterior abdominal wall. Excisional biopsy of the subcutaneous adipose tissues of the right anterior abdominal wall was consistent with subcutaneous panniculitis-like T-cell lymphoma. Flow cytometry demonstrated CD3+ and CD8+ population. On immunohistochemistry, most lymphoid cells were positive for CD3, CD45RO, CD5, and CD8 and negative for CD10, CD43, CD4, CD20, and CD56. The MIB-1 proliferative index was 30%. Bone marrow biopsy revealed no evidence of lymphomatous involvement.

Imagem nas doenças ocupacionais pulmonares

This chapter consists of a review of the literature regarding radiographic and tomographic characteristics of the principal occupational respiratory diseases (silicosis and asbestosis). Special attention is given to the practical relevance of high-resolution computed tomography, which is the most sensitive and specific method of identifying and quantifying the extent of pleural and parenchymal lesions related to such diseases.