An extended bore length solid-state digital-BGO PET/CT system: design, preliminary experience, and performance characteristics.

PURPOSE: A solid-state PET/CT system uses bismuth germanium oxide (BGO) scintillating crystals coupled to silicon photomultipliers over an extended 32 cm axial field-of-view (FOV) to provide high spatial resolution and very high sensitivity. Performance characteristics were determined for this digital-BGO system, including NEMA and EARL standards. METHODS: Spatial resolution, scatter fraction (SF), noise equivalent count rate (NECR), sensitivity, count rate accuracy, and image quality (IQ) were evaluated for the digital-BGO system as per NEMA NU 2-2018, at 2 sites of first clinical install. System energy resolution was measured. Bayesian penalized-likelihood reconstruction (BPL) was used for IQ. EARL Standards 2 studies were reconstructed by BPL combined with a contrast-enhancing deep learning algorithm. An Esser PET phantom was evaluated. Three patient examples were obtained with low-dose radiotracer activity: 2 MBq/kg of [18F]FDG ([18F]-2-fluoro-2-deoxy-D-glucose), 2.3 MBq/kg [68Ga]Ga-DOTA-TATE ([dodecane tetra-acetic acid,Tyr3]-octreotate), and 14.5 MBq/kg [82Rb]RbCl ([82Rb]-rubidium-chloride). Total scan times were ≤ 8 min. RESULTS: NEMA sensitivity was 47.6 cps/kBq at the axial center. Spatial resolution at 1 cm from the center axis was ≤4.5 mm (filtered back projection) and ≤3.8 mm (ordered subset expectation maximization). SF was 35.6%, count rate accuracy was 2.16%, and peak NECR was 485.2 kcps at 16.9 kBq/mL. Contrast for IQ was 61.1 to 90.7% (smallest to largest sphere) with background variations from 7.6 to 2.1%, and a "lung" error of 4.7%. The average detector energy resolution was 9.67%. Image quality for patient scans was good. EARL Standards 2 criteria were robustly met and Esser phantom features ≥4.8 mm were resolved at 2 min per bed position. CONCLUSION: A solid-state 32 cm axial FOV digital-BGO PET/CT system provides good spatial and energy resolution, high count rates, and superior NEMA sensitivity in its class, enabling fast clinical acquisitions with low-dose radiotracer activity.

The role of single positron emission computed tomography imaging in the diagnosis of brain death whenever Trans-cranial Doppler fails to support it: A retrospective cohort study.

OBJECTIVE: Although there is widespread acceptance of the concept of brain death/death by neurologic criteria (BD/DNC), there is marked variability in the use of ancillary tests worldwide. Transcranial Doppler (TCD) is a useful ancillary test for brain death confirmation because it is safe, noninvasive, and done at the bedside. However, it is considered less sensitive than Single Photon Emission Computed Tomography (SPECT) Tc-HMPAO (99 m). This study aims to test the yield of brain perfusion SPECT testing after a TCD has demonstrated some level of intracranial blood flow among patients fulfilling clinical criteria for BD/DNC. METHODS: This was a single-center retrospective cohort study of all the patients fulfilling clinical criteria for BD/DNC who underwent brain perfusion SPECT after an intracerebral circulatory arrest was not confirmed by TCD between July 2016 and January 2022. RESULTS: TCD was an initial ancillary test performed in 252 patients (99.6%) fulfilling clinical criteria for BD/DNC. A complete circulatory arrest was demonstrated in 228 (90.5%) patients. Brain perfusion SPECT was performed in the remaining 24 patients. The absence of cerebral perfusion consistent with BD/DNC was found in 21 cases (87.5%). BD/DN could not be confirmed in three patients (12.5%). CONCLUSIONS: SPECT testing has a high diagnostic yield when TCD fails to confirm a suspected diagnosis of BD/DNC. Combining these two modalities may be an optimal strategy for BD/DNC diagnosis when this is required by local regulations or when confounding factors interfere with the performance of a complete clinical assessment.

FDG PET in Evaluation of Patients With Fever of Unknown Origin: AJR Expert Panel Narrative Review.

Fever of unknown origin (FUO) is a diagnostic challenge, with its cause remaining undiagnosed in approximately half of patients. Nuclear medicine tests typically are performed after a negative or inconclusive initial workup. Gallium-67 citrate and labeled leukocytes were previous mainstays of radionuclide imaging for FUO, although they had limited diagnostic performance. FDG PET/CT has subsequently emerged as the nuclear medicine imaging test of choice, supported by a growing volume of evidence. A positive FDG PET/CT result contributes useful information by identifying potential causes of fever, localizing sites for further evaluation, and guiding further management; a negative result contributes useful information by excluding focal disease as the cause of fever and predicts a favorable prognosis. In 2021, CMS rescinded a prior national noncoverage determination for FDG PET for infection and inflammation, leading to increasing national utilization of FDG PET/CT for FUO workup. This article reviews the current status of the role of FDG PET/CT in the evaluation of patients with FUO. The literature reporting the diagnostic performance and yield of FDG PET/CT in FUO workup is summarized, with comparison with historically used nuclear medicine tests included. Attention is also given to the test's clinical impact; protocol, cost, and radiation considerations; and application in children.

Integration of FDG-PET/CT in the Diagnostic Workup for Staphylococcus aureus Bacteremia: A Prospective Interventional Matched-cohort Study.

BACKGROUND: Staphylococcus aureus bacteremia (SAB) is uniquely characterized by focal pyogenic complications that might not be apparent clinically. We investigated the benefit of adding fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) in the workup of patients with SAB. METHODS: In a matched-cohort study patients with SAB (intervention group) were prospectively recruited to undergo FDG-PET/CT 7-14 days after diagnosis. Treatment was directed by FDG-PET/CT findings. Clinical outcomes were compared with a control group of patients with SAB who had not undergone FDG-PET/CT, matched by age, Charlson score, methicillin susceptibility, and survival duration to FDG-PET/CT. The primary outcome was 90-day mortality. Residual confounding was controlled through regression analyses. RESULTS: During the study period 149 patients with 151 separate episodes of SAB underwent FDG-PET/CT and were compared with 150 matched patients with 151 SAB episodes. Patients in the intervention group acquired infections more frequently in the community and had less frequently solid malignancies and more frequently high-risk SAB. Ninety-day mortality in the intervention group was significantly lower than in the control group (21/151 [13.9%] vs 43/151 [28.5%], P = .002). The difference remained significant in a subgroup analysis of patients with community-onset infections without malignancy and among patients with low-risk SAB. Controlling for other risk factors for mortality, FDG-PET/CT performance among all patients was independently associated with lower mortality (OR, .39; 95% CI, .18-.84). Patients in the intervention group had longer duration of treatment and more focus control procedures performed compared with the control group. CONCLUSIONS: FDG-PET/CT in patients with SAB seems to improve survival through guidance of treatment duration and co-interventions.

Complete Pathologic Response Prediction by Radiomics Wavelets Features of Unenhanced CT Simulation Images in Locally Advanced Rectal Cancer Patients after Neoadjuvant Chemoradiation.

BACKGROUND: For locally advanced rectal cancer patients a watch-and-wait strategy is an acceptable treatment option in cases of complete tumor response. Clinicians need robust methods of patient selection after neoadjuvant chemoradiation. OBJECTIVES: To predict pathologic complete response (pCR) using computer vision. To analyze radiomic wavelet transform to predict pCR. METHODS: Neoadjuvant chemoradiation for patients with locally advanced rectal adenocarcinoma who passed computed tomography (CT)-based simulation procedures were examined. Gross tumor volume was examind on the set of CT simulation images. The volume has been analyzed using radiomics software package with wavelets feature extraction module. Statistical analysis using descriptive statistics and logistic regression was performed was used. For prediction evaluation a multilayer perceptron algorithm and Random Forest model were used. RESULTS: In the study 140 patients with II-III stage cancer were included. After a long course of chemoradiation and further surgery the pathology examination showed pCR in 38 (27.1%) of the patients. CT-simulation images of tumor volume were extracted with 850 parameters (119,000 total features). Logistic regression showed high value of wavelet contribution to model. A multilayer perceptron model showed high predictive importance of wavelet. We applied random forest analysis for classifying the texture and predominant features of wavelet parameters. Importance was assigned to wavelets. CONCLUSIONS: We evaluated the feasibility of using non-diagnostic CT images as a data source for texture analysis combined with wavelets feature analysis for predicting pCR in locally advanced rectal cancer patients. The model performance showed the importance of including wavelets features in radiomics analysis.

[NUCLEAR MEDICINE IN ISRAEL: PAST, PRESENT AND ESPECIALLY THE FUTURE].

INTRODUCTION: The current issue is dedicated to nuclear medicine in Israel. It contains articles concerning various fields in nuclear medicine including imaging and treatment. These articles provide a glimpse into the vast scope of nuclear medicine. Over the years, the nuclear medicine profession has undergone many changes and developed extensively. Currently, it is not just part of the imaging domain, but rather, it is an independent entity, that continues to grow and develop. This profession has had a great influence on patient health because of advanced imaging technologies, the possibility of treating with unique radioactive materials, and theranostics (imaging the therapeutic material) that enables the combination of diagnostic imaging and targeted treatment personally tailored for the patient. Today, nuclear medicine is considered one of the most dynamic and advanced professions. Research in nuclear medicine points to a future with ultrafast imaging technology. This includes a seemingly limitless number of new radiopharmaceuticals for diagnosis and treatment and collaborations with other scientific fields.

[18F-FDG-PET/CT AS A TOOL FOR DIAGNOSIS AND FOLLOW-UP OF INFLAMMATORY DISEASES OF LARGE BLOOD VESSELS].

INTRODUCTION: Fluorodeoxyglucose (FDG)-Positron Emission Tomography (PET) / Computed Tomography (FDG-PET/CT) is a well-established functional-anatomical imaging technique mostly used in oncology. In addition, it was found to have an important role in the diagnosis and follow-up of large vessel vasculitis mainly when combined with computed tomography angiography. Large vessel vasculitis is a disease mainly affecting large blood vessels and has two major groups: Takayasu arteritis (TA) and Giant cell arteritis (GCA). GCA is usually accompanied by polymyalgia rheumatica (PMR).

Strategies for Minimizing Occupational Radiation Exposure in Cardiac Imaging.

PURPOSE OF REVIEW: Radiation safety has been at the center of interest of both researchers and healthcare institutions. This review will summarize and shed light on the various techniques adapted to reduce staff exposure to ionizing radiation (IR) in the field of cardiac imaging. RECENT FINDINGS: In the last years, with the advance of awareness and the development of new technologies, there have been several tools and techniques adapted. The breakthrough of several technologies to lower radiation dose and shorten the duration of diagnostic tests associated with IR, the use of protection devices by staff members, and mostly the awareness of exposure to IR are the hallmark of these advances. Using all these measures has led to a significant decrease in staff exposure to IR. Reducing staff exposure to meet the "As Low As Reasonably Achievable" principle is feasible. This review introduces the most important strategies applied in cardiac imaging.

Low-risk Non-ST-Elevation Acute Coronary Syndrome and Normal Troponin: Do We Need Further Evaluation?

BACKGROUND: With the recent introduction of high-sensitivity troponin (hsTn), the incremental benefit of stress myocardial perfusion imaging (MPI) in the evaluation of patients who present to the emergency department (ED) with acute coronary syndrome (ACS) is unclear. OBJECTIVES: To assess the added value of stress MPI in low-risk ACS patients with normal range hsTnI. METHODS: We analyzed all patients who were hospitalized at our medical center from February 2016 to November 2017, who presented with low-risk ACS and underwent stress MPI, and in whom hsTnI was in the normal range after the introduction of hsTnI. RESULTS: During the study period, 161 patients were admitted with a diagnosis of unstable angina (i.e., ACS with normal range hsTnI) and underwent stress MPI during index admission. The study population included 52/161 patients (31.7%) with low-risk ACS who had no indication for initial invasive strategy. No patients had positive MPI. One patient underwent coronary angiography due to suggestive history; however, he did not have a significant coronary artery disease and had no indication for percutaneous coronary intervention. CONCLUSIONS: In patients with low-risk ACS and normal range hsTnI without additional high-risk features, stress MPI has little additional value for the correct diagnosis and management. Prospective studies are warranted to confirm whether resting hsTnI could serve as a powerful triage tool in chest pain patients in the ED before diagnostic testing and thus, improve patient management.

[111 INDIUM LABELED LEUKOCYTE SCINTIGRAPHY IS A LOW SENSITIVITY TEST FOR DIAGNOSING PROSTHETIC JOINT INFECTION IN EQUIVOCAL CASES].

INTRODUCTION: Nuclear medicine techniques are suggested to be used in equivocal cases only. Nuclear medicine procedures, specifically labeled leucocytes however, are widely used in the diagnosis of joint infection across Europe. The aim of our study was to determine if Indium 111 labeled leukocyte scintigraphy has a role in the diagnosis of infected prosthetic joints. METHODS: In this retrospective cohort study, the records of a total of 146 prosthetic hip or knee revision surgeries, in 116 patients, performed in our Institute between the years 2013-2016 were reviewed. A total of 34 patients with labeled leukocyte scans were analyzed. Ten patients had more than one scan (two to four times). The scintigraphy result reports were correlated with the outcome with respect to intra-/post-operative diagnosis of prosthetic joint infection. RESULTS: The findings of 42 of 44 scintigraphy tests were negative. One study in a patient who had three prior negative labeled white blood cells (WBC) scintigraphies was equivocal. One study was positive, but a later test in the same patient was negative. Of these 34 patients, nine were demonstrated intra- or post operatively as positive for infected prosthetic joint, including the two positive cases above. The remaining 25 patients went through revision surgery with no evidence of infection; 30 of 38 bone scans were positive. Of these 30 patients, seven were demonstrated intra- or post-operatively as positive for infected prosthetic joint. CONCLUSIONS: In our study population indium labeled leukocyte scintigraphy was found to be a non-sensitive test for the diagnosis of a prosthetic joint infection and had a poor negative predictive value. It is expected that following the guidelines more strictly and choosing the appropriate modality for assessing prosthetic joint infection will improve the diagnostic accuracy of these techniques.

Fortuitous administration of denosumab in breast carcinoma with osteoclastic giant cells.

Breast carcinoma with osteoclastic giant cells (OGCs) is a rare entity characterized by an admixture of giant cells and malignant epithelial cells within an inflammatory and vascular stroma. Denosumab is a monoclonal antibody that targets the pathway for osteoclast formation and activation, indicated for the prevention of skeletal-related events in patients with bone metastases, as well as for the treatment of giant cell tumor of bone. We report a patient who presented with aggressive bone recurrence of breast cancer 12 years after her original diagnosis, showing a transformed histology that included multinucleated OGCs, and that was refractory to traditional therapy. Misdiagnosed with a tumor-to-tumor metastasis of breast cancer to a giant cell tumor of bone, she was treated with denosumab for her presumed primary bone disease and had a remarkable clinical and radiological response. To the best of our knowledge, this is the first report of breast cancer with OGCs occurring initially in a metastasis while absent in the original tumor and the first description of its successful treatment with denosumab. This case sheds light on the development of giant cells in the tumor microenvironment and suggests the potential use of denosumab in the management of cancers with giant cell elements.

Diagnostic performance of the quantification of myocardium at risk from MPI SPECT/CTA 2G fusion for detecting obstructive coronary disease: A multicenter trial.

BACKGROUND: The effective non-invasive identification of coronary artery disease (CAD) and its proper referral for invasive treatment are still unresolved issues. We evaluated our quantification of myocardium at risk (MAR) from our second generation 3D MPI/CTA fusion framework for the detection and localization of obstructive coronary disease. METHODS: Studies from 48 patients who had rest/stress MPI, CTA, and ICA were analyzed from 3 different institutions. From the CTA, a 3D biventricular surface of the myocardium with superimposed coronaries was extracted and fused to the perfusion distribution. Significant lesions were identified from CTA readings and positioned on the fused display. Three estimates of MAR were computed on the 3D LV surface on the basis of the MPI alone (MARp), the CTA alone (MARa), and the fused information (MARf). The extents of areas at risk were used to generate ROC curves using ICA anatomical findings as reference standard. RESULTS: Areas under the ROC curve (AUC) for CAD detection using MARf was 0.88 (CI = 0.75-0.95) and for MARp and MARa were, respectively 0.82 (CI = 0.69-0.92) and 0.75 (CI = 0.60-0.86) using the ≥70% stenosis criterion. AUCs for CAD localization (all vessels) using MARf showed significantly higher performance than either MARa or MARp or both. CONCLUSIONS: Using ICA as the reference standard, MAR as the quantitative parameter, and AUC to measure diagnostic performance, MPI-CTA fusion imaging provided incremental diagnostic information compared to MPI or CTA alone for the diagnosis and localization of CAD.

Conduction abnormalities during dipyridamole stress testing.

Pharmacological stress tests using dipyridamole are considered to be safe. However, cases of atrioventricular (AV) block have been reported. We retrospectively analyzed ECG at baseline and during dipyridamole stress tests of 2010 consecutive patients (patients with second or third degree AV block were excluded). At baseline, 350 (17.4%) patients had conduction abnormalities. Following dipyridamole infusion 16 patients (0.8%) developed a transient change in AV conduction (15 patients) and or sinus arrest (1 patient). Compared to patients without baseline conduction abnormalities, patients with any conduction abnormalities at baseline were at a higher risk for the development of AV block after dipyridamole infusion [0.3% vs 3.14%, respectively; P < .0001].

Pazopanib for metastatic pulmonary epithelioid hemangioendothelioma-a suitable treatment option: case report and review of anti-angiogenic treatment options.

BACKGROUND: Epithelioid hemangioendothelioma is a rare vascular tumor of borderline or low-grade malignancy. The lungs and liver are the two common primary organs affected. Metastatic disease was reported in more than 100 cases in the literature. However, no firm conclusions can be determined for recommended treatment options. CASE PRESENTATION: The current case presents a patient with metastatic pulmonary epithelioid hemangioendothelioma to the cervical and mediastinal lymph nodes, lungs and liver that has been treated with pazopanib for more than two years with PET avid complete metabolic response in the mediastinum and lungs, and long-lasting stable disease. Target therapies that block VEGFR have a logical base in this rare malignancy. CONCLUSIONS: The current case is the first to report objective, long-lasting response to pazopanib.

[THE ROLE OF PET/CT IMAGING IN THE ASSESSMENT OF INFECTION].

Diagnosis (essentially early detection of infection) and also management decision-making pose clinical challenges. Many resources are invested in developing precise, non- invasive diagnostic tests and efficient therapies for infectious processes. Nuclear medicine procedures are part of the evaluation armamentarium of patients with suspected or confirmed infection. Their strength relies on the fact that they are non-invasive tests that provide both functional as well as metabolic information early during the course of disease. The most frequent nuclear medicine procedures used in the assessment of infection are bone, Gallium and labeled white blood cells scans. PET/CT, using mainly labeled glucose (FDG), is redefining the diagnostic work-up and is currently leading to changes in the management of patients with suspected or known infections. Current evidence supports the use of FDG imaging as a first-line diagnostic tool in patients with suspected or known infectious processes, with convincing data available mainly for indications such as fever of unknown origin (FUO), vertebral osteomyelitis, vasculitis and vascular graft infection. Whether FDG-PET/CT or hybrid imaging with new, more infectious-specific tracers will replace standard nuclear medicine procedures or stand-alone conventional imaging modalities, is still debatable. The future looks promising and the role of molecular hybrid imaging techniques in the assessment of inflammatory and infectious processes is undoubtedly on the rise.

SPECT/CT and tumour imaging.

Scintigraphic techniques are sensitive imaging modalities in the diagnosis and follow-up of cancer patients providing the functional and metabolic activity characteristics of the tumour. Hybrid SPECT/CT improves the diagnostic accuracy of these well-established imaging techniques by precise anatomical localization and characterization of morphological findings, differentiation between foci of physiological and pathological tracer uptake, resulting in a significant impact on patient management and more definitive interpretations. The use of SPECT/CT has been studied in a variety of applications in tumour imaging which are reviewed in this article. By combining functional and anatomical information in a single imaging session, SPECT/CT has become a one-stop cancer imaging modality.

Prostate Cancer Radioligand Therapy: Beta-labeled Radiopharmaceuticals.

Prostate cancer is the most common malignancy in men worldwide, with an estimated 174,650 new cases per year in the United States, and the second cancer-related cause of death, after lung cancer, with 31,620 deaths per year. While the 5 year survival rate for prostate cancer in patients without metastatic spread is nearly 100%, those with distant metastases have 5 year survival rates of approximately 30%. Initial diagnosis and assessment are based on PSA levels, Gleason score (derived from prostate biopsy), and advanced imaging modalities, including prostate MR imaging and PSMA-PET/computed tomography in patients with high-risk features.