Ching-Yee Oliver Wong

Improvement of hepatic lesion characterization by 18F-FDG PET/CT with the use of the lesion to background liver activity ratio.

Objective This study aimed to develop a reproducible method to improve 18F-FDG PET/CT’s diagnostic accuracy when characterizing hepatic lesions. Methods This was a retrospective study of 76 patients with various types of cancer who had 134 liver lesions described on diagnostic CT, MRI, or 18F-FDG PET/CT. All 134 lesions were imaged by PET/CT. For comparison, all 134 lesions were also imaged either by MRI (58 lesions) or by diagnostic CT (107), with some imaged by both. The original reader’s interpretation was used to determine the diagnostic validity of each modality. The 18F-FDG PET/CT findings were then re-stratified using the ratio of the SUVmax of the liver lesion to the SUVavg of liver background (SUVTLR). The standard of reference was histopathology and/or imaging follow-up. Eighty-nine out of the 134 lesions were positive for metastases. Two-tailed P values were calculated using a chi-square test. Results A SUVTLR greater than 2.0 strongly correlated with metastasis, while less than 2.0 strongly correlated with benign activity. Based on the original interpreter’s visual analysis (PETVA), 18F-FDG PET/CT had an accuracy of 74.6% with a high sensitivity (95.5%), but limited specificity (33.3%). Using the SUVTLR cutoff value of 2.0 to objectively re-stratify these cases, there was improvement in accuracy to 97.8%, sensitivity to 100%, and specificity to 93.3%. These values were statistically significant by chi-square analysis, with P = 0.0001 for both PETVA and SUVTLR. The 58 MRI lesions and 107 diagnostic CT lesions that were reviewed had accuracies of 70.7% (P = 0.008) and 73.8% (P = 0.0001), respectively. Conclusion Using a cutoff value of 2.0 for SUVTLR to objectively evaluate for potential hepatic metastases on 18F-FDG PET results in a significant improvement in diagnostic accuracy over subjective visual analysis alone. In this limited study, use of SUVTLR more accurately characterized hepatic lesions than the original CT or MRI interpretations.

Neurocysticercosis on 18F-FDG PET/MRI: co-registered Images.

This is a case of a 32-year-old female patient who presented with new onset partial complex seizures. MRI of the brain demonstrated a suspicious ring-enhancing lesion in the right temporal lobe. This finding was felt to be a primary brain malignancy or less likely an infectious process. (18)F-FDG PET of the brain was able to exclude malignancy and provided evidence to support neurocysticercosis in the mesial temporal lobe as the cause for the patients seizures. Neurocysticercosis is a neurologic infection caused by Taenia solium. It is rare in the United States and difficult to diagnose.

The Appearance of Congenitally Corrected Transposition of the Great Arteries on Myocardial Perfusion Imaging

We present a case of incidentally discovered congenitally corrected transposition of the great arteries (ccTGA), initially seen on stress–rest myocardial perfusion imaging (MPI). ccTGA has a characteristic appearance on MPI, which reflects the functional alterations associated with this condition.

Implications of Ambient Glucose Variation on the Target-to-Background Ratio of Hepatic Tumors By 18 FDG-PET Imaging

Objectives: To investigate the effects of ambient glucose on quantitative analysis of hepatic tumors on 2-deoxy-2-(18F)-fluoro-D-glucose (18FDG) positron emission tomography (PET) and to establish a method for glucose correction. Patients and Methods: Eighty-six patients with hepatic lesions identified on 18FDG PET/computed tomography (CT) were analyzed. The serum glucose level (Glc) was recorded prior to imaging, and the maximum standardized uptake value (SUV) in the hepatic tumors and the average SUV in normal liver were determined. The inverse relationship of SUV to glucose can be defined as d (SUV)/d (Glc) = g*SUV/(Glc), where g is the glucose sensitivity. Simulations using glucose level from 70 to 250 mg/dl were performed to evaluate the effects of Glc on the maximum SUV of malignant hepatic lesions and normal liver. Results: By logarithmic transformation and linear regression, g for metastasis was significantly higher than that for normal liver (−0.636 ± 0.144 vs. −0.0536 ± 0.0583; P = 0.00092). Simulation studies showed that the SUV in malignant lesions will decrease rapidly when Glc level is >120 mg/dl, while background liver remains relatively constant up to 250 mg/dl. Conclusion: The tumor FDG uptake is much more sensitive to ambient glucose level variation than the background liver. Therefore, correction by the glucose sensitivity factor will result in more accurate SUV measurements and make semi-quantitative analysis of 18FDG PET scans more reliable.

Radiation Therapy–Induced Phrenic Neuropathy Mimicking Metastasis to the Diaphragmatic Crus on 18F-FDG PET/CT

Benign unilateral uptake in the diaphragmatic crus is a relatively uncommon finding on 18F-FDG PET/CT that can mimic the appearance of malignancy in patients with known cancer, as illustrated in this patient with neuroendocrine carcinoma. It is important for the PET interpreter to recognize this finding and attribute it to benign uptake based on the patient’s history and symptoms at the time of the scan. Correlation with the findings of other available imaging modalities is also important to characterize focal uptake in unusual locations.

18F-FDG PET Assessment of Lewy Body Dementia with Cerebellar Diaschisis

Alzheimer disease and Lewy body dementia are the 2 most common causes of dementia. Each disease has distinctive regional metabolic reduction patterns on 18F-FDG PET. In this report, we present a rare case of an elderly man with dementia whereby 18F-FDG PET clearly showed Lewy body disease with crossed cerebellar diaschisis.

Implications of Unexpected Diffuse Lung Uptake on a 99mTc-Sestimibi Parathyroid Scan

Diffuse 99mTc-sestimibi uptake in the lungs is a sign of serious pathology and merits further work-up. We present a case in which diffuse lung uptake was incidentally found on a parathyroid scan.

Atypical Presentation of Sarcoidosis on 18F-FDG PET/CT

On 18F-FDG PET, inflammatory processes can be one of the most confounding factors for interpretation, particularly when the presentation of the process is atypical, as it was in the case of sarcoidosis reported here. Clinicians should be aware that sarcoidosis may mimic lung malignancies and lymphomas, regardless of typical or atypical appearance on 18F-FDG PET.

The Use of 99mTc-MDP Bone Scanning to Assess Facial Bone Growth

Bone scanning is an important technique to detect mandibular growth, and its quantitation aids in deciding the optimal timing for surgery. Here, we will discuss a case of abnormal mandibular growth and use of bone scanning to evaluate the facial bone growth.

Use of SPECT/CT with 99mTc-MDP Bone Scintigraphy to Diagnose Sacral Insufficiency Fracture

Bone SPECT/CT offers additional information on pelvic insufficiency fractures, especially when there is incomplete formation of the H-sign on planar bone scanning.