Disseminated Nocardia farcinica Infection and Treatment Response on F-18 Fludeoxyglucose Positron Emission Tomography Computed Tomography.

We report a rare case of nocardiosis with increased F-18 Fludeoxyglucose (F-18 FDG) uptake in widespread abscess foci of Nocardia farcinica infection in an immunocompromised patient on positron emission tomography computed tomography (PET/CT) imaging. A relatively infrequent cause of nocardiosis, N. farcinica is an opportunistic infection that may present with clinically aggressive disseminated disease. Whole-body F-18 FDG-PET/CT allows identifying the extent of disease, as well as monitoring response to therapy in patients with nocardiosis especially the disseminated form.

Evaluation of Colonoscopic Results of Patients with Incidental Colonic FDG Uptake in PET/CT Imaging.

BACKGROUND: Colorectal cancer is a significant global health concern, ranking as the second most deadly and third most common cancer worldwide. Early detection and removal of precancerous lesions play a crucial role in preventing cancer development and reducing mortality. Since FDG uptake is not specific for malignancy, incidental increased FDG uptake in the gastrointestinal tract may be challenging to interpret and may require further colonoscopic examination. This study aimed to investigate the features associated with malignant and premalignant pathology in patients with incidental colonic FDG uptake and determine the necessity of colonoscopy for each FDG uptake. METHODS: Retrospective analysis was performed on data from patients who underwent colonoscopies between January 2016 and December 2021. Patients with FDG uptake in known colorectal malignancy regions were excluded. The study included 56 patients with incidental colonic FDG uptake. PET/CT images were visually and quantitatively analyzed, and the corresponding colonoscopy and histopathological results were recorded. Statistical analyses were conducted to evaluate the relationship between FDG uptake patterns, SUVmax values, and histopathological diagnoses. Colonoscopic findings were categorized as malignancy, polyps, and non-neoplastic lesions. RESULTS: Among the 56 patients with incidental colonic FDG uptake, 36 lesions were identified, and histopathology revealed malignancy in 10 (17.9%) patients and premalignant polyps in the 26 (46.4%) cases. Focal FDG uptake with corresponding wall thickening or soft tissue density on CT was associated with a higher likelihood of premalignant or malignant lesions. The SUVmax values demonstrated a significant difference between negative findings and polyps/malignancies. However, no significant difference was observed between malignant and premalignant lesions. A ROC curve analysis was made and assesed a cut-off value of 11.1 SUVmax (sensitivity: 83.3% and specificity: 90%) to distinguish premalignant or malignant lesions from non-malignant lesions. CONCLUSION: Incidental colonic FDG uptake with a focal pattern and corresponding CT findings were more likely to indicate premalignant or malignant lesions. SUVmax values were helpful in predicting the presence of pathological findings, but histopathological verification remains necessary for a definitive diagnosis. These findings contribute to our understanding of the clinical implications of incidental colonic FDG uptake and highlight the importance of follow-up colonoscopy for further evaluation.

Lhermitte-Duclos Disease Related With Cowden Syndrome Mimicking Metastatic Lung Cancer on FDG PET/CT.

ABSTRACT: Cowden syndrome is characterized by multiple hamartomatous and neoplastic lesions including Lhermitte-Duclos disease, which is the main criterion for the diagnosis. Herein, we presented a patient with suspected metastatic disease referred to PET/CT, which showed mildly hypermetabolic multinodular thyroid goiter, multiple hamartomatous pulmonary, and breast nodules. Also, intense hypermetabolism was noted on the cerebellar tumor lesion. Lhermitte-Duclos disease was diagnosed based on the characteristic MRI findings, and she was followed up with a diagnosis of Cowden syndrome. Our case indicates that Cowden syndrome should be included as a differential diagnosis of abnormal FDG uptake in the multiple systemic hamartomatous tumors.

Nocardia Infection With Adrenal Gland Abscess Mimicking Metastatic Lung Cancer on FDG PET/CT.

ABSTRACT: We present FDG PET/CT findings of a human immunodeficiency virus-positive patient suspicious for lung cancer with a solitary metastasis to the adrenal gland. Wedge resection of the pulmonary nodules revealed Nocardia infection and a repeat FDG PET/CT imaging after the antibiotic treatment demonstrated complete metabolic response of the adrenal lesion and pulmonary nodules. It should be kept in mind that nocardiosis may present with FDG-avid lesions masquerading as malignancies in immunocompromised patients.

Nasolacrimal Duct Obstruction on 131I SPECT/CT: Atypical False-positive Paranasal Radioiodine Uptake as a Complication of Single-dose RAI Treatment.

Nasolacrimal duct obstruction (NLDO) is a rare complication after radioiodine therapy and may cause false positive 131I uptake at the point of obstruction in 131I whole body scan. Here, we report a 59-year-old female patient with papillary thyroid cancer treated with total thyroidectomy followed by 131I therapy. 131I whole body scan revealed focal uptake in the head. Single photon emission computed tomography/computed tomography (CT) showed focal uptake at the right proximal nasolacrimal duct. The ophthalmologic examination and the diagnostic maxillofacial CT confirmed the diagnosis of NLDO.

68Ga-PSMA Uptake in Brain Metastasis of Gastric Carcinoma.

ABSTRACT: A 69-year-old man with a known history of gastric and prostate adenocarcinoma was referred to 68Ga-prostate-specific membrane antigen (PSMA) PET/CT for restaging due to biochemical recurrence of prostate cancer. 68Ga-PSMA PET/CT revealed tracer accumulation in the primary prostatic lesion, lymph node, bone metastases, and brain lesion, which was later confirmed on biopsy to be metastasis of gastric carcinoma. This case reminds us of the variable spectrum of 68Ga-PSMA uptake in prostatic and nonprostatic metastatic lesions, the potential pitfalls on PET/CT images in the workup of patients with concomitant malignancies.

FDG PET/CT Features of Polysaccharide-Based Hemostatic Agent: Chronic Inflammatory Changes Can Mimic Metastatic Lesions.

PURPOSE: To prevent hemorrhagic complications, hemostatic agents (HAs) have been widely used in recent years. The use of HAs can lead to false-positive results on postoperative imaging. There exists only 1 study in the literature evaluating these applications during surgical procedures. Therefore, we aimed to evaluate the postoperative imaging features of polysaccharide-based HAs in thoracic surgery patients who have had 18F-FDG PET/CT scans. PATIENTS AND METHODS: Two hundred nine consecutive patients who underwent thoracic surgery were enrolled in this study. A topical polysaccharide-based HA was applied to the surgical bed for all of the patients. The patients diagnosed with cancer were followed up with subsequent thoracic CT scans, and 42 of these patients were also imaged with 18F-FDG PET/CT, which then comprised the main study group. Due to suspicion of metastasis, 19/42 patients were reoperated or rebiopsied. The latest histopathological findings were accepted as criterion standard, and previous FDG PET/CT images were retrospectively reevaluated. RESULTS: Polysaccharide-based HAs that appear as amorphous basophilic material were identified in histopathological samples of 11/19 patients. Lymphocytes, plasma cells, and histiocytes, which formed foreign body reaction and/or foreign body granuloma, indicating the presence of chronic inflammation, were seen in all of the samples. 18F-FDG PET/CT showed increased FDG uptake in all of these lesions. CONCLUSIONS: Despite the inconsistency of the literature, polysaccharide-based HAs can be demonstrated in human surgical specimens as amorphous basophilic materials even after a long time from the initial surgical procedure. These agents almost always cause chronic inflammatory changes. In addition, these agents may mimic "false-positive" findings on postoperative FDG PET/CT scans.

Detection of Chyle Leakage Site With Lymphoscintigraphy SPECT/CT in a Patient With Chylothorax Secondary to T-Cell Lymphoblastic Leukemia.

ABSTRACT: We present a pediatric case with T-cell lymphoblastic leukemia and persistent chylothorax who was referred to lymphoscintigraphy to identify the site of leakage. Planar lymphoscintigraphy with SPECT/CT revealed hot spots at the left jugulovenous angle and the confluens of the vena brachiocephalica to vena cava, which were compatible with the sites of leakage. Hybrid imaging with SPECT/CT technique have great impact on accurate detection of the defects in the lymphatic system in patients with chylothorax.

Distinguishing Meningioma From Metastasis of Prostate Cancer on 68Ga-PSMA PET/CT.

ABSTRACT: Meningiomas are typically benign and the most common primary brain tumors. They are usually diagnosed based on their characteristic appearance on both MRI and CT. Meningiomas can easily be misdiagnosed as metastasis of prostate cancer due to their high 68Ga-PSMA uptake on 68Ga-PSMA PET/CT. We present a case of a metastatic prostate adenocarcinoma with PSMA-avid lesion in the right frontal lobe on 68Ga-PSMA PET/CT. Later, MRI confirmed the brain lesion as meningioma.

Primary Adenosquamous Carcinoma of the Liver on FDG PET/CT.

ABSTRACT: Primary adenosquamous carcinoma (ASC) of the liver is a rare subtype of intrahepatic cholangiocarcinoma. Hepatic ASC consists of both adenocarcinoma and squamous cell carcinoma components. Because hepatic ASC is extremely rare, only a few cases describing the imaging findings of hepatic ASC were reported before. Herein, we present FDG PET/CT findings of hepatic ASC in a 78-year-old woman who was admitted to hospital with a 4-week history of right upper quadrant pain.

Correlation Between Perfusion Abnormalities Extent in Ventilation/Perfusion SPECT/CT with Hemodynamic Parameters in Patients with Chronic Thromboembolic Pulmonary Hypertension

Objectives: Chronic thromboembolic pulmonary hypertension (CTEPH) is a type of pulmonary hypertension with persistent pulmonary vascular obstruction and exercise intolerance, which may benefit from pulmonary endarterectomy (PEA). Ventilation/perfusion (V/Q) scan is the preferred screening test of CTEPH, which can be used to assess the anatomical extent of the disease. This study aimed to analyze the correlation between the extent of mismatched Q defects in V/Q single photon emission computed tomography/computed tomography (SPECT/CT) with preoperative clinical and hemodynamic parameters in patients with CTEPH. Methods: A total of 102 patients with CTEPH prior to PEA having V/Q SPECT/CT scans were retrospectively reviewed. Age, gender, New York Heart Association classification, intraoperative right-sided heart catheterization (mPAP and PVR), and 6-minute walk test (6MWT) findings were obtained from clinical records of patients. Results: Linear regression analysis showed a significant but weak correlation between the preoperative mPAP and PVR with the extent of mismatched Q defects in V/Q SPECT/CT (rs=0.09474 with p=0.0016 and rs=0.045 with p=0.045, respectively). No significant correlation was found between 6MWT and extent of mismatched Q defects in V/Q SPECT/CT (p>0.05). Conclusion: A quantitative assessment of Q defects on V/Q SPECT/CT might provide information about hemodynamic parameters in patients with CTEPH.

Physiological Biodistribution of 68Ga-DOTA-TATE in Normal Subjects

Objectives: Somatostatin is an endocrine peptide hormone that regulates neurotransmission and cell proliferation by interacting with G protein-coupled somatostatin receptors (SSTRs). SSTRs are specific molecular targets of several radiotracers for neuroendocrine tumor (NET) imaging. Gallium-68 (68Ga)-DOTA-TATE is widely used for positron emission tomography/computed tomography (PET/CT) imaging of SSTRs and has shown a higher affinity for SSTR2, the most common SSTR subtype found in NETs. We aimed to analyze the distribution pattern of 68Ga-DOTA-TATE in normal subjects. Methods: A total of 617 consecutive 68Ga-DOTA-TATE PET/CT whole-body scans performed in our department from May 2015 through April 2020 with known or suspected neuroendocrine malignancies, mostly to evaluate adrenal adenomas, were retrospectively analyzed by 2 nuclear medicine physicians. One hundred eighteen subjects without a diagnosis of NET, with no tracer avid lesion of NET on 68Ga-DOTA-TATE PET/CT, and followed up for at least 6 months (average 2-3 years) without any biochemical, clinical, or imaging findings suggestive of NET were included in this study. Results: The highest uptake of 68Ga-DOTA-TATE was noted in the spleen followed by the kidneys, adrenal glands, liver, stomach, small intestine, prostate gland, pancreas head, pancreas body, thyroid gland, and uterus, in descending order. Minimal to mild uptake was detected in the submandibular glands, parotid glands, thymus, muscles, bones, breast, lungs, and mediastinum. Conclusion: Our study shows the biodistribution pattern of 68Ga-DOTA-TATE in normal subjects and the ranges of the maximum standard uptake value (SUVmax) and SUVmean values of 68Ga-DOTA-TATE obtained in several tissues for reliably identifying malignancy in 68Ga-DOTA-TATE PET/CT studies.

Incidental 68Ga-Prostate-Specific Membrane Antigen Uptake in Compression Fracture of a Vertebral Body.

ABSTRACT: Prostate-specific membrane antigen (PSMA) is a membrane glycoprotein, which is overexpressed in prostate cancer cells. With its wide use, there is a growing number of case reports describing non-prostate cancer-related benign and malignant lesions showing increased 68Ga-PSMA uptake. We herein present the case of an 89-year-old man with prostate cancer who was referred for 68Ga-PSMA PET/CT for restaging, which revealed incidental 68Ga-PSMA uptake in compression fracture of a vertebral body. This case demonstrates that PSMA expression may occur in acute compression fractures, and it can be a potential pitfall when reporting 68Ga-PSMA PET/CT images.

Porta Hepatic Schwannoma on FDG PET/CT.

ABSTRACT: Schwannomas are benign tumors that arise from Schwann cells of neural sheath. They can occur in any part of the body. However, the most common locations are the head, neck, spinal cord, and extremities. Schwannoma in the porta hepatis is extremely rare. Herein, we describe a case of porta hepatic schwannoma in a 36-year-old woman who presented with abdominal pain for a month.

Endotracheal metastasis of colon cancer on FDG PET/CT.

Although tracheal involvement of lung cancer is frequently seen, endotracheal metastasis of colon cancer is a rare entity. Since endotracheal lesion gives no symptom until tracheal lumen nearly occluded, the diagnosis of endotracheal metastasis could be challenging. F-18 fluorodeoxyglucose positron emission tomography/computed tomography may be crucial to detect this unusal distant metastasis of colon cancer. Herein, we report FDG avid endotracheal lesion that was confirmed as metastasis from colon cancer in 56-year-old female patient.

FDG-Avid Lung Nodule Formation by the Use of Hemostatic Powder: A Potential Cause of False-Positive FDG PET/CT.

ABSTRACT: FDG PET/CT is used in the diagnosis and follow-up of various malignant tumors and changes patient management in routine clinical practice. However, inflammatory, infectious, physiological, and technical causes and benign pathological conditions may lead to false-positive FDG uptake. We report a case of a 59-year-old man who was considered having a false-positive FDG-PET pulmonary nodular lesion in favor of metastasis, which was formed by the use of hemostatic powder.