Hepatocellular carcinoma: response to TACE assessed with semiautomated volumetric and functional analysis of diffusion-weighted and contrast-enhanced MR imaging data.

PURPOSE: To determine the association of early changes in posttreatment apparent diffusion coefficient (ADC) and venous enhancement (VE) with tumor size change after transarterial chemoembolization (TACE) by using an investigational semiautomated software. MATERIALS AND METHODS: This retrospective HIPAA-compliant study was approved by the institutional review board, with waiver of informed consent. Patients underwent magnetic resonance (MR) imaging at 1.5 T before TACE, as well as 1 and 6 months after TACE. Volumetric analysis of change in ADC and VE 1 month after TACE compared with pretreatment values was performed in 48 patients with 71 hepatocellular carcinoma (HCC) lesions. Diagnostic accuracy was evaluated with receiver operating characteristic (ROC) analysis, using tumor response at 6 months according to Response Evaluation Criteria in Solid Tumors (RECIST) and modified RECIST as end points. RESULTS: According to RECIST criteria, 6 months after TACE, 30 HCC lesions showed partial response (PR), 35 showed stable disease (SD), and six showed progressive disease (PD). Increase in ADC and decrease in VE 1 month after TACE were significantly different between PR, SD, and PD. At area under the ROC curve (AUC) analysis of the ADC increase, there was an AUC of 0.78 for distinguishing PR from SD and PD and an AUC of 0.89 for distinguishing PR and SD from PD. The AUC for decrease in VE was 0.73 for discrimination of PR from SD and PD and 0.90 for discrimination of PR and SD from PD. CONCLUSION: Volumetric analysis of increase in ADC and decrease in VE 1 month after TACE can provide an early assessment of response to treatment. Volumetric analysis of multiparametric MR imaging data may have potential as a prognostic biomarker for patients undergoing local-regional treatment of liver cancer.

Mediastinal Masses in Nuclear Medicine Studies: A Diagnostic Algorithm.

There are multiple reasons for an anterior mediastinal mass. In this case, we discuss possible etiologies and offer an algorithm to narrow the differential diagnosis. When the mass cannot be diagnosed radiographically, the next step in imaging is a physiologic assessment with radionuclide modalities.

The Evaluation of Cardiac Sarcoidosis with 18F-FDG PET.

Cardiac involvement in sarcoidosis is associated with poor prognosis. (18)F-FDG PET can detect the presence of cardiac sarcoidosis, assess disease activity, and serve as a means to monitor treatment response in patients with cardiac sarcoidosis.

Optimizing 18F-FDG Uptake Time Before Imaging Improves the Accuracy of PET/CT in Liver Lesions.

UNLABELLED: (18)F-FDG PET/CT has emerged as one of the fastest-growing imaging modalities. A shorter protocol results in a lower target-to-background ratio, which can increase the challenge of identifying mildly (18)F-FDG-avid lesions and differentiating inflammatory or physiologic activity from malignant activity. The purpose of this study was to determine the delay between radiotracer injection and imaging that optimizes target-to-background ratio while maintaining counts high enough to ensure scan sensitivity. METHODS: The study included 140 patients (66 male and 74 female; age range, 42-95 y) with suspected hepatic lesions as seen on an (18)F-FDG PET scan. SUV was determined as region-of-interest activity/(dose/total body weight). RESULTS: The mean injected dose was 610 ± 66.6 MBq (16.5 ±1.8 mCi), with a mean glucose level of 107 ± 26.6 mg/dL (standardized to 90 mg/dL). The uptake time before imaging ranged from 61 to 158 min, with a mean of 108.8 ± 24.8 min. The P values for the correlation of SUV to time were 0.004, 0.003, and 0.0001 for malignant lesions, benign lesions, and background hepatic tissue, respectively. CONCLUSION: An approximately 90-min time window from (18)F-FDG injection to PET imaging would significantly improve target-to-background ratio and, thus, quantitation and visual interpretation. This benefit outweighs the minimal loss in patient throughput.

Use of SPECT/CT with 99mTc-MDP Bone Scintigraphy to Diagnose Symptomatic Os Acromiale.

Os acromiale is an anatomic variant that in rare cases can cause pain. (99m)Tc-methylene diphosphonate bone scintigraphy with SPECT/CT can play an important role in diagnosing this clinical entity. We present a male football player with shoulder pain secondary to a symptomatic os acromiale, and we demonstrate the findings on bone scanning with limited SPECT/CT that diagnosed this important clinical abnormality.

Implications of unexpected diffuse lung uptake on a 99mTc-sestimibi parathyroid scan.

Diffuse (99m)Tc-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.

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.

Painful knee arthroplasty.

A triple-tracer nuclear medicine study that incorporates (99m)Tc-sulfur colloid, (111)In-labeled leukocytes, and (99m)Tc-methylene diphosphonate can be useful for the diagnosis of aseptic loosening in a patient after total-knee arthroplasty, as demonstrated in this case study. The triple-tracer technique takes less time and is more accurate than a bone scan alone.

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 patient's seizures. Neurocysticercosis is a neurologic infection caused by Taenia solium. It is rare in the United States and difficult to diagnose.

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

On (18)F-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 (18)F-FDG PET.

Complementary role of 18F-FDG PET and 123I-ioflupane SPECT in the diagnosis of Lewy body disease.

We present a case demonstrating how correlative imaging with (123)I-ioflupane SPECT and (18)F-FDG PET can be used to help make the diagnosis of Lewy body disease more specific.

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-((18)F)-fluoro-D-glucose ((18)FDG) positron emission tomography (PET) and to establish a method for glucose correction. PATIENTS AND METHODS: Eighty-six patients with hepatic lesions identified on (18)FDG 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 (18)FDG 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 (18)F-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.

Time sensitivity-corrected retention index: an enhanced metabolic index from 18F-FDG PET to differentiate between benign and malignant pulmonary nodules.

The aim of the study was to evaluate pulmonary nodules (PNs) by incorporating time sensitivity (S) factor in the retention index (RI) and compare with the traditional fixed interval method. After obtaining approval from the Human Investigations Committee, 97 PNs from 81 patients (age=70±11) referred for dual-time fluorine-18 fluorodeoxyglucose PET (16.1±1.9 mCi) with definite pathological diagnosis or 1-year computed tomography follow-up were retrospectively studied. S=d{ln[SUV]]/d{ln[T]} was obtained by logarithmic regression using scan times, T (0, 1, 2), and standard uptake value (SUV) (0, 1, 2). This time-corrected RI, RIs=[(T2/T1)-1]×100%, was compared with traditional fixed time interval RI, RIx=[(SUV2/SUV1)-1]×100%, by means of receiver operating characteristic curve analysis. The mean±SD of T1 and T2 (72.3±14.0 and 134.9±17.6 min, respectively) skewed markedly from the intended time of PET scans (skewness=2.076 and 1.356, respectively). There were 27 benign tumors, 37 cases of non-small-cell lung cancer, 15 other types of cancer, and 18 stable lesions by 1-year computed tomography follow-up. There were significant differences between the nonmalignant group (NM, n=45) and the cancer group (CA, n=52) in time sensitivity (0.186±0.161 vs. 0.483±0.180, P<0.0005) and RIs (12.7±12.5 vs. 37.4±17.5%, P<0.0005). The RIx showed wider variation than RIs, although the difference between NM and CA was also significant (18.0±28.8 vs. 37.8±32.0%, P=0.002). The RIs and RIx were only weakly correlated (r=0.257, P=0.011). Receiver operating characteristic curve analysis performed for the CA or NM groups revealed a significant improvement in the diagnostic accuracy for malignancy by RIs (area under the curve=0.880±0.035, P<0.0005) compared with RIx (area under the curve=0.694±0.054, P=0.001). Incorporating the time sensitivity factor improves the diagnostic performance of RI for malignant PNs by using additional biologic information from the variation in fluorine-18 fluorodeoxyglucose uptake times and rates.

Semantic Dementia Diagnosed by F-18 FDG PET/MRI: Co-registered Images.

We report a case of a 61-year-old male who presented with a sudden change in mental status. From a psychiatric standpoint, his symptoms were consistent with a bipolar disorder. A neurology consult raised suspicion for vascular dementia, given the sudden onset of symptoms; however, the magnetic resonance angiography (MRA) was unremarkable. The magnetic resonance imaging (MRI) had findings that were suggestive of both vascular and frontotemporal lobe dementia based on parenchymal atrophy and a lacunar infarct near the thalamus. However, by co-registering the magnetic resonance images with a subsequent fluorine-18 Fluorodeoxyglucose positron emission tomography (F-18 FDG PET), and combining the functional data with the anatomic appearance, the diagnosis was narrowed to semantic dementia, which is one of the lesser known subtypes of frontotemporal lobe dementia (FTD).

Application of heat-damaged Tc-99m RBCs in a patient with suspected hepatic metastasis.

We present a patient with a remote history of splenectomy and recent hemicolectomy for colon adenocarcinoma. On routine surveillance chest/abdomen/pelvis CT, a lesion suspicious for hepatic metastasis was identified. Followup MRI was inconclusive. For more specific tissue characterization, imaging with Tc-99m heat-damaged RBCs was obtained to guide further patient management. Tc-99m-labeled, heat-damaged RBC scintigraphy is an underused modality that is highly specific for detecting ectopic or accessory splenic tissue. There have been many reported cases of patients undergoing unnecessary biopsies or laparotomies to remove suspicious masses that were subsequently found to be ectopic splenic tissue.

The role of scintigraphy in confirmation of suspected brain death.

We present a case illustrating how cerebral perfusion scintigraphy can be used to assist in crucial medical decision making in the intensive care setting for patients who are maintained on life support but are clinically suspected to have brain death. Cerebral perfusion scintigraphy can confirm brain death but cannot be used to diagnose it. (99m)Tc-HMPAO and (99m)Tc-ethylcysteinate dimer are the preferred imaging agents since they cross the blood-brain barrier.

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 (18)F-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 (18)F-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 (18)F-FDG PET/CT findings were then re-stratified using the ratio of the SUV(max) of the liver lesion to the SUV(avg) of liver background (SUV(TLR)). 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 SUV(TLR) 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 (PET(VA)), (18)F-FDG PET/CT had an accuracy of 74.6% with a high sensitivity (95.5%), but limited specificity (33.3%). Using the SUV(TLR) 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 PET(VA) and SUV(TLR). 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 SUV(TLR) to objectively evaluate for potential hepatic metastases on (18)F-FDG PET results in a significant improvement in diagnostic accuracy over subjective visual analysis alone. In this limited study, use of SUV(TLR) more accurately characterized hepatic lesions than the original CT or MRI interpretations.

Radiographically Occult Latent Radiogenic Osteosarcoma Uncovered on Tc-99m Methylene-diphosphonate Bone Scintigraphy.

We present a case of a 70-year-old male who was referred for a technetium-99m methylene-diphosphonate bone scan for mild left hip pain and an elevated alkaline phosphatase level of 770 units/L. No additional information was provided and the patient's history was limited due to a language barrier. We were able to ascertain that the patient had a remote history of prostate cancer, which had been treated with radiation. Originally, we felt the bone scan was compatible with Paget's disease; however, further work-up revealed the presence of osteosarcoma, which was potentially radiation-induced.