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A 54-year-old man with hepatocellular carcinoma from alcohol-induced cirrhosis presented with hepatic encephalopathy and refractory ascites related to decompensated liver disease. MRI confirmed disease progression adjacent the site of prior radiofrequency ablation, performed 2 years prior, with associated right hepatic vein tumor thrombus. 99mTc-labeled macroaggregated albumin lung shunt imaging performed before 90Y radioembolization identified a left lower lobe wedge-shaped defect, confirmed as pulmonary embolism on CT pulmonary angiography and MRI.

Rationale We evaluated K-means clustering to classify amyloid brain PETs as positive or negative. Patients and methods Sixty-six participants (31 men, 35 women; age range, 52-81 years) were recruited through a multicenter observational study: 19 cognitively normal, 25 mild cognitive impairment, and 22 dementia (11 Alzheimer disease, 3 subcortical vascular cognitive impairment, and 8 Parkinson-Lewy Body spectrum disorder). As part of the neurocognitive and imaging evaluation, each participant had an 18F-flutemetamol (Vizamyl, GE Healthcare) brain PET. All studies were processed using Cortex ID software (General Electric Company, Boston, MA) to calculate SUV ratios in 19 regions of interest and clinically interpreted by 2 dual-certified radiologists/nuclear medicine physicians, using MIM software (MIM Software Inc, Cleveland, OH), blinded to the quantitative analysis, with final interpretation based on consensus. K-means clustering was retrospectively used to classify the studies from the quantitative data. Results Based on clinical interpretation, 46 brain PETs were negative and 20 were positive for amyloid deposition. Of 19 cognitively normal participants, 1 (5%) had a positive 18F-flutemetamol brain PET. Of 25 participants with mild cognitive impairment, 9 (36%) had a positive 18F-flutemetamol brain PET. Of 22 participants with dementia, 10 (45%) had a positive 18F-flutemetamol brain PET; 7 of 11 participants with Alzheimer disease (64%), 1 of 3 participants with vascular cognitive impairment (33%), and 2 of 8 participants with Parkinson-Lewy Body spectrum disorder (25%) had a positive 18F-flutemetamol brain PET. Using clinical interpretation as the criterion standard, K-means clustering (K = 2) gave sensitivity of 95%, specificity of 98%, and accuracy of 97%. Conclusions K-means clustering may be a powerful algorithm for classifying amyloid brain PET.

Dopamine transporter SPECT with I-N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropane (I-ioflupane) aids in the diagnosis of parkinsonian syndrome by demonstrating loss of striatal dopamine transporters, proportional to nigrostriatal dopaminergic neuronal loss. Quantitative software analysis (QSA) is a helpful adjunct to visual interpretation. An atlas of pearls and pitfalls of QSA is presented. Examples include correction for head tilt/orientation, scaling artifacts, and detection of balanced loss of activity. Additional examples are provided where QSA can potentially fail such as patient variation and vascular disease.

A 74-year-old woman with primary hyperparathyroidism diagnosed from routine laboratory tests described symptoms of fatigue and difficulty with concentration. During surgical consultation, the cervical and thoracic spine MRI scans from the preceding 10-year period, performed for relapsing-remitting multiple sclerosis, were reviewed. In this clinical context, the slowly enlarging left upper paraesophageal lesion, reported as a lateral proximal esophageal (Killian-Jamieson) diverticulum, was reevaluated for a potential parathyroid adenoma. 99mTc-sestamibi SPECT/CT demonstrated focal uptake in the paraesophageal lesion with surgical resection, confirming it to be a large parathyroid adenoma.

To evaluate random forests (RFs) as a supervised machine learning algorithm to classify amyloid brain PET as positive or negative for amyloid deposition and identify key regions of interest for stratification.The data set included 57 baseline F-florbetapir (Amyvid; Lilly, Indianapolis, IN) brain PET scans in participants with severe white matter disease, presenting with either transient ischemic attack/lacunar stroke or mild cognitive impairment from early Alzheimer disease, enrolled in a multicenter prospective observational trial. Scans were processed using the MINC toolkit to generate SUV ratios, normalized to cerebellar gray matter, and clinically read by 2 nuclear medicine physicians with interpretation based on consensus (35 negative, 22 positive). SUV ratio data and clinical reads were used for supervised training of an RF classifier programmed in MATLAB.A 10,000-tree RF, each tree using 15 randomly selected cases and 20 randomly selected features (SUV ratio per region of interest), with 37 cases for training and 20 cases for testing, had sensitivity = 86% (95% confidence interval [CI], 42%-100%), specificity = 92% (CI, 64%-100%), and classification accuracy = 90% (CI, 68%-99%). The most common features at the root node (key regions for stratification) were (1) left posterior cingulate (1039 trees), (2) left middle frontal gyrus (1038 trees), (3) left precuneus (857 trees), (4) right anterior cingulate gyrus (655 trees), and (5) right posterior cingulate (588 trees).Random forests can classify brain PET as positive or negative for amyloid deposition and suggest key clinically relevant, regional features for classification.

Osteosarcoma (OS) is a malignant bone tumor which is found primarily in adolescents, with the distal femur as the most common location. OS with a jaw primary is present in only about 10% of cases and the risk of recurrence is considered to be decreased in the jaw versus other primary locations. We present a unique case of a patient with localized OS of the jaw with an isolated recurrence in her bone marrow almost 5 years after completion of initial treatment.

An 85-year-old man with stage IIIA Merkel cell carcinoma of the left arm was initially treated with local excision and axillary node dissection followed by radiation therapy. Eight months after surgery, whole-body FDG PET/CT demonstrated intensely hypermetabolic hepatic metastases and abdominal lymphadenopathy. Given his age and comorbidities, he was considered a poor candidate for chemotherapy, and therefore the novel programmed cell death ligand 1 inhibitor avelumab was initiated. FDG PET/CT after 4 cycles showed complete resolution of hepatic and nodal metastases. Whole-body FDG PET/CT can be used for monitoring response of multisystem metastases from Merkel cell carcinoma to active immunotherapy.

A 61-year-old woman with lung adenocarcinoma failed first-line treatment and was placed on immunotherapy with nivolumab. FDG-PET/CT before immunotherapy showed metastases to thoracic nodes, liver, adrenal gland, and skeleton. Seven weeks after starting nivolumab, FDG-PET/CT showed mild residual activity in thoracic nodes and otherwise complete response. After 15 weeks, enlarged and FDG-avid axillary lymphadenopathy and worsening supraclavicular lymphadenopathy developed. After 20 weeks, FDG-PET/CT demonstrated marked improvement of axillary and supraclavicular lymphadenopathy. This case demonstrates that later progression of disease can still respond to continuing immunotherapy, hypothetically because of dynamic adaptations in the tug-of-war between the immunotherapy-augmented immune system and tumor.

PET using FDG is a critical tool for evaluation of dementias, with characteristic patterns of hypometabolism suggesting specific diagnoses. Hypometabolism in the occipital region is recognized as an important finding associated with dementia with Lewy bodies and posterior cortical atrophy. We describe here the novel "occipital tunnel" sign, which results from relative sparing of FDG uptake in the medial occipital (primary visual) cortex compared with more severe loss in the surrounding lateral occipital (visual association) cortex. This sign is useful for recognizing the occipital findings of dementia with Lewy bodies and posterior cortical atrophy, especially when viewing sagittal projections.

OBJECTIVE Nuclear imaging can confirm pleuroperitoneal shunt as the cause of pleural effusion. No society guidelines exist for scintigraphic pleuroperitoneal shunt detection. Our institutional protocol was evaluated to determine optimal imaging time points for shunt detection. METHODS Pleuroperitoneal shunt studies over 4 years were blindly reviewed by 2 nuclear radiologists. Data from blinded review included presence or absence of pleuroperitoneal shunt, laterality of shunt and time points for shunt detection. RESULTS Chart review yielded 30 studies. Three cases were excluded because of improper injection. Imaging was positive for pleuroperitoneal shunt in 81% (22/27) of cases. In positive cases, activity was identified in the right hemithorax in 82% (18/22), left hemithorax in 9% (2/22), and bilaterally in 9% (2/22). One-hour imaging demonstrated 91% (20/22) of positive cases. The remaining 2 positive cases were negative at 1 hour but positive after 4 hours. No study was negative at 1 and 4 hours and positive at 24 hours. All negative cases (5/27) were confirmed on 24-hour imaging. CONCLUSIONS The majority of positive pleuroperitoneal shunt examinations will demonstrate activity in the right hemithorax on 1-hour imaging. Although no case was negative at 1 and 4 hours and positive at 24 hours, imaging at 24 hours may still be necessary to confirm absence of shunt. Therefore, optimal imaging time points consist of early 1-hour and delayed 24-hour images if the 1-hour time point was negative. The 4-hour time point may be considered optional, thereby potentially optimizing patient safety and resource utilization.

A patient with systemic mastocytosis underwent a FDG-PET/CT scan. CT demonstrated loss of corticomedullary differentiation in the axial skeleton and thickening of cortical bone in the appendicular skeleton consistent with myelofibrosis and osteosclerosis. Remarkably, the bones of the lower

Intense FDG uptake by bone marrow following recent chemotherapy limits evaluation for osseous metastases. The impact of marrow rebound on accuracy of (18)F-fluoride PET/CT is unclear. A 73-year-old woman with breast cancer presented for restaging FDG PET/CT, which showed intense activity throughout almost the entire axial skeleton and no osseous metastases. An (18)F-fluoride PET/CT performed 7 days later identified multiple osseous metastases in the spine, ribs, and pelvis. This case demonstrates that (18)F-fluoride PET/CT should be considered for the evaluation of osseous metastases in patients with rebound marrow uptake on FDG PET/CT.

A 64-year-old male with a history of allogeneic bone marrow transplantation for lymphoma 10 months earlier presented for evaluation of bacteremia. The white blood cell count was 4,400 cells/microliter with 76% neutrophils. A tagged white blood cell scan was performed to localize the infection. Images obtained 4 hours postinjection of radiolabeled leukocytes displayed no focus of infection, but delayed 24-hour images demonstrated the interval development of markedly increased activity in the left shoulder. Arthrocentesis yielded purulent fluid. We hypothesize that delayed leukocyte migration in this immunosuppressed patient might have accounted for the significant disparity between the standard and delayed scans.