Soon after reports of a novel coronavirus capable of causing severe pneumonia surfaced in late 2019, expeditious global spread of Severe Acute Respiratory Distress Syndrome Coronavirus 2 (SARS-CoV-2) forced the World Health Organization to declare an international state of emergency. Although best known for causing symptoms of upper respiratory tract infection in mild cases and fulminant pneumonia in severe disease, Coronavirus Disease 2019 (COVID-19) has also been associated with gastrointestinal, neurologic, cardiac, and hematologic presentations. Despite concerns over poor specificity and undue radiation exposure, chest imaging nonetheless remains central to the initial diagnosis and monitoring of COVID-19 progression, as well as to the evaluation of complications. Classic features on chest CT include ground-glass and reticular opacities with or without superimposed consolidations, frequently presenting in a bilateral, peripheral, and posterior distribution. More recently, studies conducted with MRI have shown excellent concordance with chest CT in visualizing typical features of COVID-19 pneumonia. For patients in whom exposure to ionizing radiation should be avoided, particularly pregnant women and children, pulmonary MRI may represent a suitable alternative to chest CT. Although PET imaging is not typically considered among first-line investigative modalities for the diagnosis of lower respiratory tract infections, numerous reports have noted incidental localization of radiotracer in parenchymal regions of COVID-19-associated pulmonary lesions. These findings are consistent with data from Middle East Respiratory Syndrome-CoV cohorts suggesting an ability for 18 F-FDG PET to detect subclinical infection and lymphadenitis in subjects without overt clinical signs of infection. Though highly sensitive, use of PET/CT for primary detection of COVID-19 is constrained by poor specificity, as well as considerations of cost, radiation burden, and prolonged exposure times for imaging staff. Even still, decontamination of scanner bays is a time-consuming process, and proper ventilation of scanner suites may additionally require up to an hour of downtime to allow for sufficient air exchange. Yet, in patients who require nuclear medicine investigations for other clinical indications, PET imaging may yield the earliest detection of nascent infection in otherwise asymptomatic individuals. Especially for patients with concomitant malignancies and other states of immunocompromise, prompt recognition of infection and early initiation of supportive care is crucial to maximizing outcomes and improving survivability.

PET imaging using novel radiotracers show promises for tumor grading and molecular characterization through visualizing molecular and functional properties of the tumors. Application of PET tracers in brain neoplasm depends on both type of the neoplasm and the research or clinical significance required to be addressed. In clinical neuro-oncology, 18 F-FDG is used mainly to differentiate tumor recurrence from radiation-induced necrosis, and novel PET agents show attractive imaging properties. Novel PET tracers can offer biologic information not visible via contrast-enhanced MRI or 18 F-FDG PET. This review aims to provide an update on the complementary role of PET imaging in neuro-oncology both in research and clinical settings along with presenting interesting cases in this context.

Objective: This study evaluates the feasibility of direct scatter and attenuation correction of whole-body 68 Ga-PSMA PET images in the image domain using deep learning. Methods: Whole-body 68 Ga-PSMA PET images of 399 subjects were used to train a residual deep learning model, taking PET non-attenuation-corrected images (PET-nonAC) as input and CT-based attenuation-corrected PET images (PET-CTAC) as target (reference). Forty-six whole-body 68 Ga-PSMA PET images were used as an independent validation dataset. For validation, synthetic deep learning-based attenuation-corrected PET images were assessed considering the corresponding PET-CTAC images as reference. The evaluation metrics included the mean absolute error (MAE) of the SUV, peak signal-to-noise ratio, and structural similarity index (SSIM) in the whole body, as well as in different regions of the body, namely, head and neck, chest, and abdomen and pelvis. Results: The deep learning-guided direct attenuation and scatter correction produced images of comparable visual quality to PET-CTAC images. It achieved an MAE, relative error (RE%), SSIM, and peak signal-to-noise ratio of 0.91 ± 0.29 (SUV), −2.46% ± 10.10%, 0.973 ± 0.034, and 48.171 ± 2.964, respectively, within whole-body images of the independent external validation dataset. The largest RE% was observed in the head and neck region (−5.62% ± 11.73%), although this region exhibited the highest value of SSIM metric (0.982 ± 0.024). The MAE (SUV) and RE% within the different regions of the body were less than 2.0% and 6%, respectively, indicating acceptable performance of the deep learning model. Conclusions: This work demonstrated the feasibility of direct attenuation and scatter correction of whole-body 68 Ga-PSMA PET images in the image domain using deep learning with clinically tolerable errors. The technique has the potential of performing attenuation correction on stand-alone PET or PET/MRI systems.

We present a 48-year-old woman with an olfactory neuroblastoma who was referred for accurate staging using PET/CT. The 68Ga-DOTATATE PET/CT showed a 51 × 32-mm mass with an SUVmax of 7.59 in the sphenoidal sinuses, whereas radiotracer uptake on 18F-FDG PET/CT was similar to that of brain tissue. 68Ga-DOTATATE PET/CT might be especially useful in regions with difficult tumor visualization resulting from high background, such as brain tissue. The results of this case may suggest that somatostatin receptor imaging in patients with esthesioneuroblastoma may facilitate the potential application of radiotheranostic agents for the treatment of this aggressive subtype of tumors.

In recent years, lutetium-177 (177Lu)-labeled prostate-specific membrane antigen (PSMA)-617 has become a promising new therapeutic agent in patients with metastatic castration-resistant prostate cancer (mCRPC). In this study, we report on an early experience of177Lu-PSMA therapy with an evaluation of its efficacy and safety in mCRPC patients. Twenty-one mCRPC patients with a mean age of 70.3 ± 9.6 (54–88)-year-old were treated with one to four therapy cycles (median two cycles) and administered activity of 3.7–29.6 GBq (mean of 15.4 GBq). A prostate-specific antigen (PSA) decline ≥ 50% was considered to be a biochemical response (BCR). To evaluate the clinical response, the Eastern Cooperative Oncology Group (ECOG) status was used. Within 2 weeks before and 1 and 2 months after each therapy cycle, hematology, renal function, liver status, alkaline phosphatase, and PSA were checked. The Common Terminology Criteria for Adverse Events was used for grading adverse events induced by 177Lu-PSMA. Furthermore, overall survival (OS) was calculated and analyzed. During the treatment, a BCR was seen in 62% of patients; 19% of patients showed progression and 19% of patients showed stable disease. ECOG status was improved after treatment, and OS was 62.7 weeks. After the treatment, two patients showed Grade II toxicity of white blood cells, Grade I thrombocytopenia was observed in two patients, one patient showed Grade II toxicity in serum creatinine and transient Grade I toxicity in creatinine was seen in two patients. In total, our initial experience demonstrates that 177Lu-PSMA therapy has the potential to positively affect the development and maturation of radioligand practices in selected mCRPC patients, even in resource limited, developing country environments. However, some challenges, such as practitioner training, poor initial acceptance by colleagues and financial concerns, particularly in developing nations, still exist.