Biochemical recurrence (BCR) of prostate cancer (PCa) occurs in about 25% of patients treated with radical prostatectomy (RP) and up to 45% in patients who receive external beam radiotherapy (RT). Early diagnosis of PCa recurrence is of high importance for successful salvage therapy. The aim of the present study is to analyze the efficacy of ⁶⁸ Ga-PSMA PET/CT in detecting the presence of local and/or systemic disease in patients with a history of PCa who have BCR. A total of 52 PCa patients with BCR referred for ⁶⁸ Ga-PSMA PET/CT were recruited from the American University of Beirut Medical Center between November 2017 and December 2019. We compared the performance of PSMA PET/CT to the results and clinical factors based on follow up: PSA, PSA kinetics, primary treatment, and Gleason score. The relationship between the PET/CT findings and clinical indicators of disease were assessed by univariate and multivariate logistic regression. From a total of 52 patients, 34 (65.4%) had positive PSMA-PET/CT scans. Among those, 8/34 (23.5%) received primary RT. For all patients with a positive PSMA-PET: the detection rate was 2/4 (50%) for PSA < 0.2, 5/10 (50%) for PSA 0.2–0.49, 3/6 (50%) for PSA 0.5–0.99, 6/12 (50%) for PSA 1–1.99, 8/9 (88.9%) for PSA 2–3.99, and 10/11 (90.9%) for PSA 4–10.PSMA-PET/CT positivity was significantly associated with PSA level at time of PET scan, PSA doubling time, Gleason score and TNM staging. However, it did not show a significant correlation with radiotherapy as primary treatment, ongoing androgen deprivation therapy (ADT), time to relapse, and initial PSA before therapy. In our single center prospective trial, ⁶⁸ Ga-PSMA PET/CT successfully detected the recurrence of PCa in patients with BCR. Scan positivity was significantly associated with PSA level at time of PET scan, PSA doubling time, Gleason score, and TNM staging. PSMA- PET/CT is a highly promising modality in the work up of patients with PCa in the setting of BCR for earlier detection of disease recurrence.

Incidental gastrointestinal tract (GIT) [18F]-Fluorodeoxyglucose (FDG) uptake in positron emission technology/computed tomography (PET/CT) is an unexpected and often complicated finding for clinicians. This retrospective study reviewed 8991 charts of patients who underwent PET/CT: 440 patients had incidental GIT uptake, of which 80 underwent endoscopy. Patient characteristics, imaging parameters, and endoscopic findings were studied. Of the 80 patients, 31 had cancer/pre-cancer lesions (16 carcinomas; 15 pre-malignant polyps). Compared to patients with benign/absent lesions, patients with cancer/pre-cancer lesions were significantly older (p = 0.01), underwent PET/CT for primary evaluation/staging of cancer (p = 0.03), had focal GIT uptake (p = 0.04), and had lower GIT uptake (p = 0.004). Among patients with focal uptake, an SUVmax of 9.2 had the highest sensitivity (0.76) and specificity (0.885) in detecting cancer/pre-cancerous lesions. Lower GIT uptake was most common in the sigmoid colon, and upper GIT uptake was most frequent in the stomach. In a bivariate analysis, predictors of cancer/pre-cancer were older age, PET/CT indicated for primary evaluation, focal uptake, uptake in the lower GIT, and higher SUVmax. Further endoscopic investigation is warranted for patients with incidental GIT uptake, especially in the elderly or those presenting for primary evaluation with PET/CT, with the following findings on imaging: lower GIT uptake, focal uptake, or high SUVmax.

Supine [18F]Fluorodeoxyglucose (FDG) positron emission technology/computed tomography (PET/CT) is a commonly used modality for the initial staging of breast cancer, and several previous studies have shown superior sensitivity and specificity of prone FDG PET/CT in comparison to its supine counterpart. This retrospective study included 25 females with breast cancer referred for staging. They underwent supine FDG PET/CT followed by prone FDG PET/CT. The outcomes were: number of primary breast lesions, anatomical site of FDG-avid lymph nodes (LNs), and number and type of bone lesions, with SUVmax of all corresponding parameters. Performance was superior in prone acquisition compared to supine acquisition, with the respective results: 29 vs. 22 breast tumor lesions detected, 62 vs. 27 FDG-avid axillary LNs detected, sensitivity of 68% vs. 57%, specificity of 64% vs. 53%. The detection rate of axillary LNs in the prone position was significantly higher (p = 0.001). SUVmax for breast tumor lesions (p = 0.000) and number of detected axillary LNs (p = 0.002) were significantly higher in prone acquisition. Five patients were upstaged after experts read the prone acquisition. Prone FDG PET/CT acquisition is a promising technique in detecting primary breast lesions and metastatic LNs possibly missed in supine acquisition, which may lead to change in patient staging and management.

PSMA-targeted radioligand therapy (RLT) is effective in metastatic castration-resistant prostate cancer, but interpretation is challenging when PSA rises despite apparent response on post-therapy ¹⁷⁷ Lu-PSMA SPECT/CT. We present 2 patients with this PSA-PSMA discordance after 2 cycles: ¹⁷⁷ Lu-PSMA post-therapy SPECT/CT showed a significant reduction in PSMA-derived tumor volume, yet PSA levels progressed. ¹⁸ F-FDG PET/CT performed after 2 cycles clarified disease status by revealing new hypermetabolic skeletal and visceral lesions, consistent with progression. PSMA-targeted RLT was discontinued early in both cases. ¹⁸ F-FDG PET/CT may resolve discordant PSA and PSMA findings and help prevent futile continuation of ineffective PSMA‑targeted RLT.

Caroli disease is a rare congenital disorder of segmental cystic dilatations of the intrahepatic biliary ducts that maintain communication with the rest of the biliary tree. Its typical clinical presentation is recurrent episodes of cholangitis. The diagnosis is usually made using abdominal imaging modalities. We present a patient with Caroli disease showing atypical presentation of acute cholangitis with ambiguous labs and initial negative imaging findings, which was later diagnosed by [18F]-fluorodeoxyglucose positron emission tomography/computed tomography and confirmed by magnetic resonance imaging and tissue pathology. The use of such imaging modalities in moments of doubt or clinical suspicion provide the patient with accurate diagnosis, proper management, and better clinical outcome, thus obviating the need for further invasive investigations.

Pattern recognition remains a cornerstone of radiologic interpretation, as it facilitates a confident and comprehensive differential diagnosis. Certain pathologies present with specific and highly recognizable patterns on imaging modalities. These patterns can resemble familiar real-life phenomena, including cosmic bodies that surround us. We present in this article a compilation of radiologic signs across various modalities that take inspiration from cosmic phenomena. For each sign, we summarize its defining imaging appearance, typical clinical context, and common pitfalls; where available, we note diagnostic performance (e.g., sensitivity/specificity) to guide appropriate weighting in practice. By coupling memorable imagery with succinct clinical guidance, this pictorial review aims to support a faster, more accurate pattern recognition that is applicable in both low-resource and tertiary care settings, while recognizing that these signs function as educational aids rather than validated diagnostic tests. In familiarizing themselves with these classic signs, training radiologists can benefit from an engaging and memorable way of recognizing various pathological conditions.