Pei-Shan Wu

Dual-Phase 18F-FDG PET in the Diagnosis of Pulmonary Nodules with an Initial Standard Uptake Value Less Than 2.5

OBJECTIVE A cutoff standard uptake value (SUV) of 2.5 has been commonly adopted for (18)F-FDG PET to evaluate pulmonary lesions, but false results can occur. Studies have shown the usefulness of delayed PET for improving accuracy. This study was designed to examine the efficiency of delayed PET of pulmonary nodules with an initial mean SUV less than 2.5. MATERIALS AND METHODS Dual-phase FDG PET studies were conducted with imaging 1 and 2 hours after FDG injection, and pulmonary lesions with an initial mean SUV less than 2.5 were identified. Nodules with pathologic reports were included in the study. The differences in mean SUV, maximal SUV, and retention index between benign and malignant pulmonary lesions were analyzed. Receiver operating characteristic analysis was performed to evaluate the discriminating validity of the retention index. RESULTS A total of 31 lesions (15 benign, 16 malignant) were included in the study. Among the benign lesions, 12 were granulomatous inflammation, including 10 tuberculosis lesions and two cryptococcosis lesions, and three were focal fibrosis. A retention index greater than 0% was observed in 87% of the benign lesions; 60% of the benign lesions had a retention index greater than 10%. Among the malignant lesions, 75% had a retention index greater than 0%, and 62% had a retention index greater than 10%. We found no significant differences in mean SUV, maximal SUV, and retention index between benign and malignant lesions. The area under the receiver operating characteristic curve did not differ from 0.5. CONCLUSION Delayed FDG PET is not useful for differentiating benign and malignant pulmonary nodules with an initial mean SUV less than 2.5 in geographic regions with epidemic granulomatous disease such as tuberculosis or in patients at high risk of granulomatous inflammation.

A False Positive 18F-FDG PET/CT Scan Caused by Breast Silicone Injection

We present here the case of a 40-year-old woman with a greater than 10 year prior history of bilateral breast silicone injection and saline bag implantation. Bilateral palpable breast nodules were observed, but the ultrasound scan was suboptimal and the magnetic resonance imaging showed no gadolinium-enhanced tumor. The 18F-FDG PET/CT scan showed a hypermetabolic nodule in the left breast with a 30% increase of 18F-FDG uptake on the delayed imaging, and this mimicked breast cancer. She underwent a left partial mastectomy and the pathology demonstrated a siliconoma.

Peritoneal tuberculosis with elevated serum CA125 mimicking peritoneal carcinomatosis on F-18 FDG-PET/CT

Abstract18F-fluorodeoxyglucose positron emission tomography (F-18 FDG-PET) plays an important role in differentiating benign from malignant tumors. However, some false-positive findings, such as tuberculosis, may occur. We report a case referred for F-18 FDG whole-body PET computed tomography (PET/CT) scan owing to an elevated serum cancer antigen 125 (CA125). An FDG-PET/CT scan showed multiple hypermetabolic foci in the mesentery and peritoneum with further increase of FDG uptake on the delayed scan, mimicking peritoneal carcinomatosis. Subsequent laparoscopic biopsy showed granulomatous inflammation, and tuberculosis polymerase chain reaction showed a positive result. Serum CA125 returned to normal following treatment with anti-tuberculosis drugs. Peritoneal tuberculosis should be considered as a differential diagnosis in a tuberculosis endemic region.

Evolution of differential renal function after acute pyelonephritis

99mTc dimercaptosuccinic acid (DMSA) renal scans can provide accurate diagnosis of acute pyelonephritis, its sequelae (renal scars) and differential renal function (DRF). The purposes of this retrospective study were (1) to assess the relationship between DRF obtained during acute pyelonephritis and at follow-up, and (2) to elucidate the value of initial DRF in predicting subsequent renal scars. A total of 47 children were enrolled. All had both unilateral acute pyelonephritis diagnosed by initial DMSA renal scans, and follow-up DMSA renal scans. We found the correlation between initial and follow-up DRF poor (adjusted R2 = 0.396). Whether or not renal scars developed determined the follow-up DRF. Vesicoureteral reflux was significantly more common in children who developed renal scars. In addition, the higher the grade of vesicoureteral reflux, the lower the follow-up DRF and the improvement in DRF. When using a DRF of 46% as the cut-off value to predict subsequent renal scars, the sensitivity and specificity were 47.8% and 83.3%, respectively. Owing to the low sensitivity, initial DRF is not suitable for predicting the occurrence of renal scars.

The use of dual-phase 18F-FDG PET in characterizing thyroid incidentalomas.

AIM To examine the usefulness of dual-phase 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography (PET) for the evaluation of thyroid incidentalomas. MATERIALS AND METHODS In this retrospective study, cases with focal thyroid lesions seen incidentally at FDG PET in which the histopathological diagnosis was available and in which dual-phase FDG PET imaging was performed at 1 and 2 h after FDG injection were reviewed. In the included cases, the 1 and 2 h maximal standard uptake value (1-hour maximal SUV and 2-hour maximal SUV, respectively) and retention index (RI) were calculated, and the differences between benign and malignant thyroid incidentalomas were analysed. Receiver operating characteristic (ROC) analysis was performed to evaluate the ability of 1-hour maximal SUV, 2-hour maximal SUV, and RI to discriminate benign from malignant lesions. RESULTS A total of 39 patients (25 females, 14 males) with 45 lesions (17 malignant, 28 benign) were included. In malignant thyroid incidentalomas, the average 1-hour maximal SUV, 2-hour maximal SUV, and RI were 5.20, 5.72, and 7.67%, respectively, and in benign thyroid incidentalomas the values were 4.67, 4.97, and 7.38%, respectively. There were no significant differences in 1-hour maximal SUV, 2-hour maximal SUV, and RI between benign and malignant lesions. The area under the ROC curve did not differ from 0.5. CONCLUSION Dual-phase FDG PET is not useful for differentiating benign from malignant thyroid incidentalomas.

Peritoneal Scintigraphy for Diagnosing Periumbilical Leakage in a Patient on Continuous Ambulatory Peritoneal Dialysis

Continuous ambulatory peritoneal dialysis (CAPD) offers several advantages over hemodialysis for patients with end-stage renal disease; however, this technique also includes many documented complications. A case with clinical suspicion of dialysate leakage on CAPD was investigated by peritoneal scintigraphy using technetium-99m macroaggregated human albumin (99mTc-MAA). Peritoneal scintigraphy showed radiotracer accumulation over the periumbilical area at 2 hours 30 minutes after intraperitoneal infusion of 99mTc-MAA. Six hours of imaging revealed more apparent radioactivity at the same site. This study is to illustrate the simple diagnostic helpfulness of peritoneal scintigraphy in a patient with a CAPD-related structural defect.

Hypermetabolic New Foci Detected by 18F-FDG PET/CT in the Heart of a Patient with Cervical Carcinoma

The presence of cardiac metastasis from cervical carcinoma is extremely rare. The diagnosis is made almost exclusively postmortem. Only with a high index of suspicion it is possible to make a diagnosis antemortem. Here we presented a case of uterine cervical carcinoma after surgery and chemotherapy who presented with rising serum SCC and was arranged for 18F-FDG-PET/CT scan. The 18F-FDG-PET/CT scan showed an unexpected metastasis in the right ventricle of the heart. The following CT and MRI also showed a mass in the right ventricle.

Abnormally Increased F-18 FDG PET Uptake in the Post-Partial Glossectomy Tongue on Delayed Images

F-18 FDG PET is effective for determining recurrence or treatment response of the head and neck cancer, but also some false-positive appearances are reported. Here we presented a patient of left tongue squamous cell carcinoma after partial glossectomy without concurrent chemoradiotherapy. After more than two years follow-up, he received right neck dissection because of recurrence and lymph nodes metastases, and underwent a FDG PET scan for distant metastasis survey. Although no abnormality in the tongue on initial PET imaging, high uptake of FDG in the left part of the remaining tongue mimicking a recurrent tumor was noted on delayed imaging. No recurrent tongue cancer was observed in a continuous follow-up. High FDG uptake in the tongue was presumed the result of altered balance in lingual muscle activity after operation in this patient.

Bone and Gallium Scintigraphies in Rhabdomyolysis: A Case Report

We present the case of a 71-year-old man experiencing sudden onset of conscious disturbance at home. 67Gagallium citrate scintigraphy was performed to find infectious foci. It showed intense gallium uptake in the muscles of bilateral shoulders, arms, thighs, and the trunk, indicating rhabdomyolysis. The diagnosis was compatible with the laboratory data of a remarkable increase in serum creatine kinase. Five days later, a (superscript 99m)Tc-MDP bone scan also showed intense uptake in the same muscle groups. Two and a half months after the first gallium scan, an additional gallium scan obtained for the detection of fever of unknown origin revealed complete resolution of the previous muscle lesions. According to the case, bone and gallium scintigraphies are not only valuable for an early diagnosis with a thorough evaluation of muscle injury in the whole body but also useful in the follow-up of rhabdomyolysis.

Relationship of Formula Creatinine Clearance, Serum Creatinine and Blood Urea Nitrogen to 99mTc-MAG3 Clearance

Background: We conducted this study to explore the correlation of formula creatinine clearance (FCcr), serum creatinine, blood urea nitrogen (BUN) to 99mTc- MAG3 clearance (CMAG3). Methods: Forty-seven adult patients with a wide range of renal function were included in this study. To assess glomerular filtration rate, FCcr was calculated from serum creatinine concentration, age and weight. CMAG3 was determined by one blood sample method. Linear regression was utilized to analyze correlation between CMAG3 and FCcr, serum creatinine or BUN. By using results of CMAG3 as a marker of renal dysfunction, the sensitivity and specificity of FCcr, serum creatinine and BUN were also calculated. Results: A good correlation was found between FCcr and CMAG3 (FCcr = 0.3469×CMAG3 + 1.6257, correlation coefficient (R) = 0.877, standard error of the estimate(SEE) = 17.64 ml/min). The correlation between serum creatinine and CMAG3 (serum creatinine = -0.009×CMAG3+ 3.2319, R = 0.633, SEE = 1.01) was not good. The correlation between BUN and CMAG3 (BUN = -0.0947× CMAG3 + 38.163, R = 0.698, SEE = 9.0) was not good, either. The sensitivities of FCcr, serum creatinine and BUN as markers for renal dysfunction were 86.2%, 45.8% and 50.0%, and specificities were 72.2%, 95.7% and 87.0%, respectively. Conclusions: This study showed a good correlation between FCcr and CMAG3, and poor correlation between serum creatinine, BUN to CMAG3. For detecting renal dysfunction,the sensitivity of FCcr was better than serum creatinine and BUN, but the specificity of FCcr was not good enough. CMAG3 could not be replaced by these three measurements for evaluating renal function.