The feasibility of 11C-methionine-PET in diagnosis of solitary lung nodules/masses when compared with 18F-FDG-PET.

OBJECTIVE: To differentiate between benign and malignant lesions of the lung, 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) has limitations such as a lower specificity in cases of non-specific inflammation. The positive predictive value is unsatisfactory in countries where inflammatory lung disorders are prevalent. We present the preliminary results of the usefulness of combining 11C-methionine-PET and 18F-FDG-PET in this context. METHODS: Fifteen patients with indeterminate solitary pulmonary nodules/masses (10 men, 5 women; average age 64.7 +/- 14.0 years, ranging from 25 to 87 years) were studied using 11C-methionine- and 18F-FDG-PET. Interpretations were primarily made on visual analysis with five-point scale and a consensus of two nuclear medicine physicians, using standardized uptake value as an accessory reference. Foci of abnormal radiotracer uptake were subsequently correlated with clinical follow-up, imaging modalities such as chest radiography, chest computed tomography (CT), serial PET studies, and pathology results from bronchoscopic biopsy and/or surgical specimen. RESULTS: Diagnoses were established in 14 patients. The 11C-methionine-PET and 18F-FDG-PET studies were both true positive in two cases of adenocarcinoma and true negative in two cases of clinical benign nodules. In one case of lymphoid hyperplasia both 11C-methionine-PET and 18F-FDG-PET showed false-positive findings. Discordant results were obtained in nine cases. In spite of the false-positive results of 18F-FDG-PET, 11C-methionine-PET was true negative in four cases with chronic inflammatory nodules and three cases of pulmonary tuberculosis. Furthermore, (11)C-methionine-PET was true positive in one case of lung metastasis of thyroid cancer, and in another with recurrence of gastric cancer, respectively, for which 18F-FDG-PET imaging was false negative. CONCLUSIONS: Our experience indicates that 11C-methionine-PET seems more specific and sensitive when compared with 18F-FDG-PET for the purpose of differentiating benign and malignant thoracic nodules/masses. The possibility of an FDG-avid lesion being malignant is decreased if it shows a negative result by 11C-methionine-PET.

Unilateral thalamic hypometabolism in patients with temporal lobe epilepsy.

BACKGROUND/PURPOSE: Interictal brain 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is useful for localizing the focus of a seizure, and thalamic hypometabolism has been observed in temporal lobe epilepsy (TLE). In this study, we aimed to investigate the prevalence of thalamic hypometabolism and to assess the usefulness of this supplementary finding for lateralizing epileptic foci on FDGPET scans in patients with TLE. METHODS: This was a retrospective study of 47 patients who underwent anterior temporal lobectomy to treat medically intractable TLE. Other inclusion criteria were age older than 18 years, preoperative interictal FDG-PET, no structural abnormality (except for mesial temporal sclerosis) on preoperative magnetic resonance imaging, and seizure-free status (Engel class I) for at least 2 years after the operation. The presence and location of hypometabolism on FDG-PET scans were recorded. RESULTS: Of the 47 patients examined, 12 were subsequently excluded. Concomitant hypometabolism in both the temporal lobe and the ipsilateral thalamus was observed on FDG-PET scans in seven (20%) of the remaining 35 patients. One patient had thalamic hypometabolism contralateral to the hypometabolic temporal lobe. CONCLUSION: Ipsilateral thalamic hypometabolism is a supplementary finding on FDG-PET scans in patients with TLE and can aid in lateralizing epileptic foci during FDG-PET. However, in rare cases, hypometabolism of the contralateral thalamus can occur and cause false lateralization.

A practical background correction method for an immediately repeated first-pass radionuclide angiography.

BACKGROUND: A satisfactory bolus injection is essential for a successful first-pass radionuclide angiography (FPRNA). Rescheduling the FPRNA study is usually needed due to high background interference caused by an unsatisfactory bolus injection. We developed a protocol to correct the pre-existing background activity subsequent to immediately repeating the study. METHODS: Seventy-four consecutive patients who had their bone scan and FPRNA scheduled on the same day were included for analysis. The initial 51 cases constituted the "validation-only" group. In the other 23 cases, the "validation plus clearance constants" group, a 5-min dynamic acquisition was performed during the 5-min equilibrium to obtain the background clearance curve and the clearance constants. For all included 74 cases ejection fraction (EF) analysis was proceeded using the images from the first injection, second injection, and second injection with the corrected background to yield EF1, EF2, and EF2', respectively. EF2 and EF2' were then compared to the ejection fraction without background interference, the EF1. RESULTS: For the LV, the mean difference between the EF1 and the uncorrected EF2 (|LVEF1-LVEF2| in mean ± SD) was 3.1 ± 2.0% and the difference between the EF1 and the corrected EF2' (|LVEF1-LVEF2'|) was 1.6 ± 2.1%, while the mean differences for RV are 2.2 ± 1.9% and 1.8 ± 1.8%, respectively. A significant difference (p < 0.05) was observed between the uncorrected and the corrected data for both the LV and RV. CONCLUSION: In FPRNA, when a bolus injection is immediately readministered, both LVEF and RVEF can be underestimated. With our correction method, the results are superior to those without correction.

Unusual Presentation of Postradiation Sarcoma With Subsequent Intestinal Metastasis Revealed by 18F-FDG PET/CT.

Radiation-related sarcoma is a rare but serious complication for patients after receiving radiation therapy initially for their primary malignancy. However, it usually takes several years and needs enough in-field radiation dose to develop this sarcoma. We describe a 60-year-old man with right axillary sarcoma revealed by whole-body F-FDG PET/CT 1 year after chemoradiotherapy, which presented ultrashort latency period and did not match the consensus definition of radiation-related sarcoma. Besides, metastatic sarcoma to small intestine was accidentally noted in the F-FDG PET/CT image.

Demonstration of large bladder diverticulum on bone scan.

A 74-year-old man underwent low anterior resection for rectal cancer. Technetium-99m methylene diphosphonate (MDP) bone scanning was performed as part of the patient's postoperative follow-up study. Scans revealed an area of increased tracer uptake in the left hemipelvis. Coronal single-photon emission computed tomography and caudal images clearly separated the lesion from the skeletal structures. Transverse magnetic resonance images showed a large diverticulum originating from the left lateral wall of the bladder. The pelvic findings on the bone scan were the result of tracer retained within this diverticulum.

Added Value of Dual-Time-Point 18F-FDG PET/CT With Delayed Imaging for Detecting Aortic Graft Infection: An Observational Study.

F-FDG PET/CT is a promising tool in detecting aortic graft infection. Present study investigated the value of dual-time-point F-FDG PET/CT imaging (DTPI) with delayed imaging in assessing aortic graft infection.Twenty-nine patients with suspected aortic graft infection were prospectively enrolled in this DTPI study. Two nuclear medicine physicians read all the images and achieved consensus about the measurement of maximal standardized uptake value (SUVmax) and grading of image quality. The percentages of SUVmax change between initial and delayed images were recorded as retention index (RI); sensitivity, specificity, and accuracy were calculated based on reference standard.All the 5 infected aortic grafts had positive RIs, which were generally higher than that of noninfected grafts. Those noninfected grafts had variable RIs. Seven patients had improved image quality in delayed imaging. DTPI with delayed image detected all the infected grafts with improved specificity (88%) and accuracy (90%), providing conspicuous delineation of the infected graft extent.In conclusion, noninfected aortic grafts had more variable RIs than infected ones. DTPI might be useful for detecting aortic graft infection, improving image quality, and enhancing delineation of the infected aortic grafts.

Supernumerary breast masquerading as metastasis on serial 67Ga scan.

We report the incidental discovery of supernumerary breast changes on sequential 67Ga scans in a woman with dermatofibrosarcoma protuberans excised 5 years before. The appearance of the accessory breast fluctuated with physiological 67Ga uptake of the breast tissue was evident. Awareness of the concomitant changes in accessory breast with breast tissue could help narrow the differential diagnosis.

Gorham's disease: the disappearing bone.

Gorham's disease is a rare disorder characterized by proliferation of vascular channels. The clinical presentation of Gorham's disease is variable and depends on the site of involvement. A high index of clinical suspicion is needed for accurate diagnosis, and recognition of distinctive radiologic and histopathologic features can help facilitate and expedite diagnosis. The subsequent images were obtained from a 31-year-old male patient. Nuclear scintigraphy and computed tomography identified active bone destruction in the lower thoracic and upper lumbar spine in addition to the absence of the left lower rib cage. Gorham's disease was subsequently confirmed by biopsy.

F-18 FDG PET/CT in evaluation of pulmonary sclerosing hemangioma.

PURPOSE: Pulmonary sclerosing hemangioma (PSH), or the alternative name of "sclerosing pneumocytoma," is a rare benign neoplasm. PSH is often asymptomatic and presents as a solitary pulmonary nodule on radiologic imaging studies. Few articles have been reported to describe the FDG PET findings about PSH. We reported FDG PET findings of 6 cases of PSH and reviewed the literatures. MATERIALS AND METHODS: FDG PET and PET/CT imaging studies of 6 patients with proven PSH were reviewed. The relation between the degree of FDG uptake and tumor size was analyzed. RESULTS: All 6 tumors were detected by FDG PET or PET/CT. Mean diameter of these tumors was 2.9 cm. Mean standard uptake value was 2.45 (range, 1.8-3.93). The maximal standard uptake value of FDG uptake was positively correlated with the tumor size (R = 0.9694, P < 0.05). CONCLUSIONS: PSH demonstrates low to moderate uptake on FDG PET imaging. The larger PSH has higher uptake and might be misrecognized as a malignancy. The possibility of false-positive result caused by PSH should be considered while interpreting FDG PET images of solitary pulmonary nodules.

Incidental finding of autosomal dominant polycystic kidney disease with liver involvement on Tc-99m sestamibi scintigraphy.

Autosomal dominant polycystic kidney disease is a systemic hereditary disease characterized by renal cysts and sometimes involvement of the liver. We present a 65-year-old woman with autosomal dominant polycystic kidney disease on regularly hemodialysis who recently experienced intermittent right upper quadrant abdominal pain and elevated intact parathyroid hormone for more than a year. She was referred for double-phase Tc-99m sestamibi scintigraphy, under the impression of hyperparathyroidism. Apart form increased uptake in the right thyroid bed, the images showed a large photon-deficient area in the upper portion of the abdomen corresponding to the liver.

Locally advanced oncocytic carcinoma of the nasal cavity treated with surgery and intensity-modulated radiotherapy.

Oncocytic carcinomas of the nasal cavity are extremely rare. We report 1 patient whose primary tumor and neck lymphadenopathies were under control nearly 2 years after combined surgery and radiotherapy. An 80-year-old man with a history of nasal oncocytoma had received excision twice previously. Computed tomography demonstrated locally advanced recurrent tumor invading the paranasal sinuses and orbit with lymphadenopathies in the right neck. Skull base surgery was performed. Pathological examination revealed oncocytic carcinoma. Positron emission tomography showed hypermetabolic lesions in the surgical bed and right neck. The patient subsequently received intensity-modulated radiotherapy to the primary site and the whole neck. Follow-up computed tomography 4 months later showed marked shrinkage of the neck lymphadenopathies. There was no progression after nearly 2 years. Although these tumors have historically been regarded as radioresistant, the combined treatment of surgery followed by radiotherapy may offer the best chance for control of locally advanced disease.

Bone scan flare phenomenon in non-small-cell lung cancer patients treated with gefitinib.

PURPOSE: The bone scan flare phenomenon has been evaluated in various cancers in the presence of positive response to therapy. The aim of this study was to determine whether flare phenomenon occurs in non-small-cell lung cancer patients, especially adenocarcinoma in East-Asians, who respond dramatically and promptly to gefitinib. METHODS: We retrospectively evaluated the radiographic and scintigraphic images of 125 lung cancer patients who had previous gefitinib treatment between July 2003 and October 2005. Those patients who had the first post-treatment scan done within 3 months and the second scan performed after 3 months after starting the therapy were included. New lesions or increased intensity observed on the first follow-up bone scan with improvement on the second one during gefitinib treatment was defined as positive for flare phenomenon. The results were correlated with clinical disease status. RESULTS: Thirty-three non-small-cell lung cancer patients were included. Seven (21.2%) of them showed bone scan flare phenomenon. Of these seven, 5 had adenocarcinoma and 2 had unclassified non-small-cell lung cancer. Partial response was achieved after treatment in all these cases, and flare phenomena were detected between 29 and 77 days (median: 34 days) after treatment. CONCLUSION: The findings show that the flare is common during the first 3 months of gefitinib initiation; hence, a repeat bone scan should be reserved for later in the treatment course.

PET imaging of brain astrocytoma with 1-11C-acetate.

PURPOSE: The purpose of this study was to assess the use of 1-(11)C-acetate (ACE) as a metabolic tracer for the detection and characterisation of astrocytomas. METHODS: Positron emission tomography (PET) studies with ACE and 2-(18)F-fluoro-2-deoxy-D-glucose (FDG) were performed sequentially in 26 patients with primary astrocytomas. Images were analysed by visual interpretation and determination of the tumour to cortex ratio (T/C ratio) and standardised uptake value (SUV). The tumour uptake was visually scored into three grades as compared with the contralateral cortex: clearly lower (-), almost equal (+) and clearly higher (++). RESULTS: There were 85% of astrocytomas with ++ ACE uptake, 15% with + ACE uptake and none with - ACE uptake. Only 19% of astrocytomas had ++ FDG uptake. Thirty-seven percent of high-grade astrocytomas had + FDG uptake and 37% had - FDG uptake. The sensitivity and specificity of the FDG T/C ratio in discriminating high-grade from low-grade astrocytomas were 79% and 100%, respectively, at the cutoff value of 0.75. Using 2.33 as the cutoff value of the ACE T/C ratio, the sensitivity and specificity were 42% and 86%, respectively. FDG was better than ACE in discriminating high-grade from low-grade astrocytomas. T/C ratios and SUVs of FDG uptake of tumours correlated with the histological grades, but those of ACE uptake did not. CONCLUSION: ACE appears to be a promising tracer for use in the detection of primary astrocytomas, but is of limited value in the differentiation of high- and low-grade astrocytomas. ACE is complementary to FDG for the diagnosis and characterisation of astrocytoma.

Decreased salivary gland function in patients with autoimmune thyroiditis.

BACKGROUND/AIMS: It has been speculated that impaired salivary flow contributes to autoimmune thyroiditis (chronic thyroiditis, Hashimoto's thyroiditis). To test this hypothesis, salivary function was measured by quantitative salivary scintigraphy in autoimmune thyroiditis patients, as well as in age- and gender-matched controls for comparison. METHODOLOGY: One hundred and twenty patients with an autoimmune thyroiditis history of more than 10 years each and 36 healthy controls were enrolled in the study. All the 120 autoimmune thyroiditis patients had good blood sugar control. None had autonomic neuropathy. These 120 autoimmune thyroiditis patients were separated into two subgroups: group 1, 60 patients with xerostomia; and group 2, 60 patients without xerostomia. After intravenous injection of 5 mCi Tc-99m pertechnetate, sequential images at 1 min/frame were acquired for 30 min. The first- and 15th-minute uptake ratios (UR) were calculated from the tracer uptakes in the four major salivary glands over the background regions of interest (ROIs). Saliva excretion was stimulated by 1 tablet of 200 mg ascorbic acid given orally 15 min after injection of the tracer. Then, the maximal excretion ratios (ER) of the four major salivary glands after sialagogue stimulation were calculated. RESULTS: Impaired salivary function, represented by significantly decreased UR and ER values, in autoimmune thyroiditis patients with xerostomia was demonstrated in this study. In addition, there was a significantly higher prevalence of salivary gland dysfunction in group 1 patients than in group 2 patients. CONCLUSIONS: Significantly poorer salivary function was found in autoimmune thyroiditis patients with xerostomia compared with autoimmune thyroiditis patients without xerostomia and healthy controls by means of objective and quantitative salivary scintigraphy.