Purpose To compare the diagnostic and prognostic value of 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 vs. 32.8 mos if SUVmax > 6.10 vs. ≤ 6.10, p=0.002) and BSI (14.7 vs. 28.2 mos if BSI >1.27 vs. < 1.27; p=0.004). Only SUV was an independent factor in multivariate analysis. In castrate resistant patients combining a nomogram for progressive prostate cancer with SUV dichotomized patients into a high vs. low risk group (median survival 14.4 vs. 34.6 mos, p=.015) more prognostic than either nomogram or SUV alone. Conclusion The current 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.

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The aim of this study was to develop a clinically applicable noninvasive method to quantify changes in androgen receptor (AR) levels based on 18 F-16b-fluoro-5a-dihydrotestosterone ( 18 F-FDHT) PET in prostate cancer patients undergoing therapy. Methods: Thirteen patients underwent dynamic 18 F-FDHT PET over a selected tumor. Concurrent venous blood samples were acquired for blood metabolite analysis. A second cohort of 25 patients injected with 18 F-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 18 F-FDHT in blood was between 6 and 7 min. As a consequence, the uptake of 18 F-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 18 F-FDHT PET to estimate free AR concentration. This process involved the estimation of a net uptake parameter such as the k trap 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 k trap estimates, which we surmise may be proportional to AR expression. Validation studies to test this hypothesis are underway.

Collagen vascular diseases are a diverse group of immunologically mediated systemic disorders that often lead to thoracic changes. The collagen vascular diseases that most commonly involve the lung are rheumatoid arthritis, progressive systemic sclerosis, systemic lupus erythematosus, polymyositis and dermatomyositis, mixed connective tissue disease, and Sjögren syndrome. Interstitial lung disease and pulmonary arterial hypertension are the main causes of mortality and morbidity among patients with collagen vascular diseases. Given the broad spectrum of possible thoracic manifestations and the varying frequency with which different interstitial lung diseases occur, the interpretation of thoracic images obtained in patients with collagen vascular diseases can be challenging. The task may be more difficult in the presence of treatment-related complications such as drug toxicity and infections, which are common in this group of patients. Although chest radiography is most often used for screening and monitoring of thoracic alterations, high-resolution computed tomography can provide additional information about lung involvement in collagen vascular diseases and may be especially helpful for differentiating specific disease patterns in the lung. General knowledge about the manifestations of thoracic involvement in collagen vascular diseases allows radiologists to provide better guidance for treatment and follow-up of these patients.

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 18 F-FDG uptake. BH PET/CT had the advantage of reducing misregistration and permitted a better localization of sites with 18 F-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.

Lymphadenopathy is a common radiological finding in many thoracic diseases and may be caused by a variety of infectious, inflammatory, and neoplastic conditions. This review aims to describe the patterns of mediastinal and hilar lymphadenopathy found in benign diseases in immunocompetent patients. Computed tomography is the method of choice for the evaluation of lymphadenopathy, as it is able to demonstrate increased size of individual nodes, abnormalities of the interface between the mediastinum and lung, invasion of surrounding fat, coalescence of adjacent nodes, obliteration of the mediastinal fat, and hypo- and hyperdensity in lymph nodes. Intravenous contrast enhancement may be needed to help distinguish nodes from vessels. The most frequent infections resulting in this finding are tuberculosis and fungal disease (particularly histoplasmosis and coccidioidomycosis). Sarcoidosis is a relatively frequent cause of lymphadenopathy in young adults, and can be distinguished from other diseases - especially when enlarged lymph nodes are found to be multiple and symmetrical. Other conditions discussed in this review are silicosis, drug reactions, amyloidosis, heart failure, Castleman's disease, viral infections, and chronic obstructive pulmonary disease.

Coronavirus disease 2019 (COVID-19), which is caused by a new coronavirus-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-is a pandemic with major impacts on the health care sector, and a broad view of the disease is of fundamental importance for any radiologist. The purpose of this review is to address the main clinical and imaging aspects of COVID-19, as well as guidelines for requesting and using imaging methods; measures to protect patients and health care professionals; systems for quantifying pulmonary findings and preparing integrated reports; and the main innovations that have emerged during this pandemic.

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