Thomas Olsavsky

Bio: Thomas Olsavsky is an academic researcher. The author has contributed to research in topics: Positron emission tomography & Prostate. The author has an hindex of 2, co-authored 3 publications receiving 14 citations.

"The Great Masquerader": Sonographic Pictorial Review of Testicular Tuberculosis and its Mimics

Abstract: Testicular tuberculosis (TB) is an uncommon presentation of extrapulmonary TB. Although rare in incidence, it is a great masquerader and should be kept in consideration while assessing focal abnormalities involving the testis. Ultrasound findings alone may be non-specific and mimic other diagnoses including infection, inflammation, tumor, infarct, and trauma. The main objective of this sonographic pictorial review is to discuss the imaging findings, specific differentiating features against each differential and use of ancillary imaging findings whenever available. Concurrent involvement of epididymis, septated hydrocele, scrotal wall edema, and calcification of tunica vaginalis provides strong evidence in an appropriate setting. Available extratesticular ancillary imaging findings must be correlated for correct diagnosis due to non-specific imaging and clinical presentation. Misdiagnosis of scrotal TB may lead to otherwise avoidable epididymo-orchiectomy.

Axumin Positron Emission Tomography: Novel Agent for Prostate Cancer Biochemical Recurrence

Abstract: Prostate cancer remains one of the top common cancers in terms of incidence and cancer-related deaths. Approximately 1/3rd cases develop biochemical recurrence during surveillance post-definite therapy. Multiple imaging modalities, including computed tomography (CT), magnetic resonance imaging (MRI) (including multiparametric prostate MRI), bone scan, and positron emission tomography (PET) using different tracers are being used for the characterization of the prostate cancer recurrence. CT and MRI do not provide physiological information, thus have lower sensitivity in detecting the metastasis. A bone scan has low sensitivity (depending on the prostate-specific antigen level) with low specificity as well. Among different PET tracers, Axumin PET appears to be the most promising tool. Axumin PET is Food and Drug Administration approved for the evaluation of prostate cancer biochemical recurrence. Several studies have shown that Axumin PET findings played a key role in treatment modification by finding otherwise undetected lesions. We briefly discuss the salient characteristics, imaging protocol and image interpretation criteria for Axumin PET in the workup of prostate cancer biochemical recurrence.

18F-fluciclovine (Axumin) PET/CT detecting occult bone metastasis

Abstract: 18F-fluciclovine (Axumin) positron emission tomography (PET) is a novel agent for detection of biochemical recurrence of the prostate cancer. In this article, we present an interesting case of prostate cancer recurrence with bone metastasis not visualized with conventional CT, but detected with Axumin PET/CT. This case report will help reader to understand shortcomings of conventional modalities (CT/MRI/bone scan) in evaluation of biochemical recurrence of prostate cancer. We report a case of 73-year-old male previously diagnosed with adenocarcinoma of prostate, status post-radiation treatment with excellent response to therapy. He presented with progressively increasing right groin pain and rising PSA level indicating biochemical recurrence. A bony metastasis to right inferior pubic ramus was diagnosed with Axumin PET/CT, not detected with conventional CT. He underwent local radiation treatment with excellent response to therapy. 18F-fluciclovine (Axumin) PET/CT is the most sensitive tool in detection of biochemical recurrence of prostate cancer. CT and MRI may not detect early cases of tumor recurrence which affects disease prognosis and patient management.

NRG Oncology Updated International Consensus Atlas on Pelvic Lymph Node Volumes for Intact and Postoperative Prostate Cancer.

Abstract: Purpose In 2009, the Radiation Therapy Oncology Group (RTOG) genitourinary members published a consensus atlas for contouring prostate pelvic nodal clinical target volumes (CTVs). Data have emerged further informing nodal recurrence patterns. The objective of this study is to provide an updated prostate pelvic nodal consensus atlas. Methods and Materials A literature review was performed abstracting data on nodal recurrence patterns. Data were presented to a panel of international experts, including radiation oncologists, radiologists, and urologists. After data review, participants contoured nodal CTVs on 3 cases: postoperative, intact node positive, and intact node negative. Radiation oncologist contours were analyzed qualitatively using count maps, which provided a visual assessment of controversial regions, and quantitatively analyzed using Sorensen-Dice similarity coefficients and Hausdorff distances compared with the 2009 RTOG atlas. Diagnostic radiologists generated a reference table outlining considerations for determining clinical node positivity. Results Eighteen radiation oncologists’ contours (54 CTVs) were included. Two urologists’ volumes were examined in a separate analysis. The mean CTV for the postoperative case was 302 cm3, intact node positive case was 409 cm3, and intact node negative case was 342 cm3. Compared with the original RTOG consensus, the mean Sorensen-Dice similarity coefficient for the postoperative case was 0.63 (standard deviation [SD] 0.13), the intact node positive case was 0.68 (SD 0.13), and the intact node negative case was 0.66 (SD 0.18). The mean Hausdorff distance (in cm) for the postoperative case was 0.24 (SD 0.13), the intact node positive case was 0.23 (SD 0.09), and intact node negative case was 0.33 (SD 0.24). Four regions of CTV controversy were identified, and consensus for each of these areas was reached. Conclusions Discordance with the 2009 RTOG consensus atlas was seen in a group of experienced NRG Oncology and international genitourinary radiation oncologists. To address areas of variability and account for new data, an updated NRG Oncology consensus contour atlas was developed.

Radiopharmaceuticals for PET and SPECT Imaging: A Literature Review over the Last Decade

Abstract: Positron emission tomography (PET) uses radioactive tracers and enables the functional imaging of several metabolic processes, blood flow measurements, regional chemical composition, and/or chemical absorption. Depending on the targeted processes within the living organism, different tracers are used for various medical conditions, such as cancer, particular brain pathologies, cardiac events, and bone lesions, where the most commonly used tracers are radiolabeled with 18F (e.g., [18F]-FDG and NA [18F]). Oxygen-15 isotope is mostly involved in blood flow measurements, whereas a wide array of 11C-based compounds have also been developed for neuronal disorders according to the affected neuroreceptors, prostate cancer, and lung carcinomas. In contrast, the single-photon emission computed tomography (SPECT) technique uses gamma-emitting radioisotopes and can be used to diagnose strokes, seizures, bone illnesses, and infections by gauging the blood flow and radio distribution within tissues and organs. The radioisotopes typically used in SPECT imaging are iodine-123, technetium-99m, xenon-133, thallium-201, and indium-111. This systematic review article aims to clarify and disseminate the available scientific literature focused on PET/SPECT radiotracers and to provide an overview of the conducted research within the past decade, with an additional focus on the novel radiopharmaceuticals developed for medical imaging.

PET Molecular Imaging in Drug Development: The Imaging and Chemistry Perspective

Abstract: Positron emission tomography with selective radioligands advances the drug discovery and development process by revealing information about target engagement, proof of mechanism, pharmacokinetic and pharmacodynamic profiles. Positron emission tomography (PET) is an essential and highly significant tool to study therapeutic drug development, dose regimen, and the drug plasma concentrations of new drug candidates. Selective radioligands bring up target-specific information in several disease states including cancer, cardiovascular, and neurological conditions by quantifying various rates of biological processes with PET, which are associated with its physiological changes in living subjects, thus it reveals disease progression and also advances the clinical investigation. This study explores the major roles, applications, and advances of PET molecular imaging in drug discovery and development process with a wide range of radiochemistry as well as clinical outcomes of positron-emitting carbon-11 and fluorine-18 radiotracers.

Male genital tract tuberculosis: A comprehensive review of imaging findings and differential diagnosis

Abstract: Urogenital tuberculosis is the most common form of extrapulmonary tuberculosis. Genital organ involvement occurs as a continuum of urinary tract tuberculosis and often presents a diagnostic challenge due to the non-specific nature of the symptoms. Delay in diagnosis may lead to complications such as infertility and perineoscrotal sinuses. Imaging plays an important role in raising timely suspicion of tuberculosis. In this article, we describe the imaging findings of male genital tuberculosis and the differential diagnosis. High-resolution ultrasonography (HRUS) is the best modality for assessing the epididymis, testis, scrotum and vas deferens, whereas MRI is optimal for evaluating the prostate, seminal vesicles and ejaculatory ducts. Epididymis is the most common site of genital tuberculosis, and presents as a nodular lesion limited to the tail or as diffuse enlargement. The proximal vas deferens is also frequently involved due to anatomical contiguity and shows diffuse or nodular thickening. Advanced cases may show pyocele formation and scrotal wall sinuses. Testicular involvement is almost always secondary to epididymal tuberculosis and presents as single or multiple nodules, diffuse enlargement, or the 'miliary' pattern. Isolated testicular involvement should raise suspicion of malignancy. Tuberculosis of the prostate is often asymptomatic. The most common imaging manifestations are nodules and the diffuse forms, which may later evolve into abscesses. Fibrosis and calcification occur with healing. Seminal vesicle and ejaculatory duct involvement with fibrosis may cause infertility. Awareness of the imaging findings would enable the radiologist to raise timely suspicion, so that prompt treatment is initiated and complications are prevented.

Use of 55 PET radiotracers under approval of a Radioactive Drug Research Committee (RDRC)

Abstract: In the US, EU and elsewhere, basic clinical research studies with positron emission tomography (PET) radiotracers that are generally recognized as safe and effective (GRASE) can often be conducted under institutional approval. For example, in the United States, such research is conducted under the oversight of a Radioactive Drug Research Committee (RDRC) as long as certain requirements are met. Firstly, the research must be for basic science and cannot be intended for immediate therapeutic or diagnostic purposes, or to determine the safety and effectiveness of the PET radiotracer. Secondly, the PET radiotracer must be generally recognized as safe and effective. Specifically, the mass dose to be administered must not cause any clinically detectable pharmacological effect in humans, and the radiation dose to be administered must be the smallest dose practical to perform the study and not exceed regulatory dose limits within a 1-year period. In our experience, the main barrier to using a PET radiotracer under RDRC approval is accessing the required information about mass and radioactive dosing. The University of Michigan (UM) has a long history of using PET radiotracers in clinical research studies. Herein we provide dosing information for 55 radiotracers that will enable other PET Centers to use them under the approval of their own RDRC committees. The data provided herein will streamline future RDRC approval, and facilitate further basic science investigation of 55 PET radiotracers that target functionally relevant biomarkers in high impact disease states.