CANCER RISK ESTIMATION FOR PATIENTS UNDERGOING WHOLE-BODY PET/CT SCANS.

The objective of this paper was to compute the effective dose, as well as the lifetime attributable risk (LAR) of cancer related to whole-body positron emission tomography (PET)/computed tomography (CT) scan for 193 adult patients. The mean effective dose for all patients from a single PET/CT scan was 20.6 mSv. For males aged 40 y, a single PET/CT scan is associated with a LAR of cancer incidence of 0.169%. This risk increased to 0.85% if an annual surveillance protocol for 5 y was performed. For female patients aged 40 y, the LAR of cancer mortality increased from 0.126 to 0.63% if an annual surveillance protocol for 5 y was performed. Since PET/CT scans are associated with a high dose and a risk of developing cancer, it was important to balance the advantages and risks before conducting any scans. This is especially important for younger patients and those who are overweight.

ESTIMATION OF PATIENT ORGAN AND WHOLE-BODY DOSES IN [18F-FDG] PET/CT SCAN.

The object of this study was to estimate organ doses and whole-body effective doses from positron emission tomography/computed tomography (PET/CT) scan using [fluorine-18]-fluoro-2-deoxy-d-glucose (18F-FDG) in adult patients and to assess the CT component contribution to organ and whole-body doses. The [18F-FDG] PET/CT scan was conducted on 204 adult patients (90 females and 114 males). For all patients, females and males, the whole-body effective doses were 20.54, 23.89 and 17.89 mSv, respectively. For all patients, females and males, the CT component contribution to the whole-body effective dose was 66, 71 and 62%, respectively. Since CT is the primary contributor to the effective dose in the [18F-FDG] PET/CT scan protocol, the significance of improving CT protocols to minimize patient dose is underscored. All attempts must be made, using available mechanisms and techniques, to reduce the patient's dose of PET/CT scan, especially in obese patients.

Diagnostic compatibility of V/Q SPECT and CTPA, which are non-invasive diagnostic methods, for the detection of CTEPH, which is a treatable cause of pulmonary hypertension.

OBJECTIVE: To evaluate the compatibility between ventilation/perfusion (V/Q) single photon emission computed tomography (SPECT) scintigraphy and computed tomography pulmonary angiography (CTPA) in diagnosing chronic thromboembolic pulmonary hypertension (CTEPH). SUBJECT AND METHODS: Twenty cases of CTEPH, out of 98 patients with pre-diagnosis of pulmonary hypertension (PH), who was diagnosed with CTEPH with a multidisciplinary approach and a council decision, were included in the study retrospectively. The diagnostic performances of V/Q SPECT and CTPA, which are used as noninvasive methods in diagnosing CTEPH, and the compatibility between them were calculated statistically. RESULTS: Of 20 patients diagnosed with CTEPH, 12 were female, and 8 were male; the mean age was 59.1 (range: 36-79). The sensitivity of V/Q SPECT scintigraphy of imaging methods used to diagnose CTEPH was 90%, CTPA was 80%, specificities were 88% and 92%, respectively, and accuracy was 88% in both cases methods. According to the reference standard, the kappa value for V/Q scintigraphy was calculated as 0.765 and 0.678 for CTPA. These values were statistically significant (P<0.01), and there was a substantial concordance between them. CONCLUSION: There is significant compatibility between V/Q SPECT scintigraphy and CTPA in diagnosing CTEPH, whose differential diagnosis is essential because of its high cure potential due to PH causes.

Influence of single photon emission computed tomography (SPECT) reconstruction algorithm on diagnostic accuracy of parathyroid scintigraphy: Comparison of iterative reconstruction with filtered backprojection.

BACKGROUND & OBJECTIVES: Preoperative localization of parathyroid lesions is essential for improving the results in patients with primary hyperparathyroidism. The purpose of this study was to evaluate retrospectively the value of technetium-99m (Tc-99m) methoxyisobutylisonitrile (MIBI) single photon emission computed tomography (SPECT) and to compare the diagnostic accuracy of iterative reconstruction (IR) and filtered backprojection (FBP) reconstruction algorithms about localization of parathyroid lesions. METHODS: Forty four patients with primary hyperparathyroidism, in whom histopathological correlation could be performed, were included in the study. Dual-phase Tc-99m parathyroid scintigraphy was performed 20 and 120 min after injection of 740 MBq Tc-99m MIBI in all patients. Tomographic images were acquired 120 min after the administration of radiopharmaceutical. The SPECT data were evaluated using an IR as well as a FBP algorithm. In 23 of 44 patients, SPECT acquisitions were performed in 64×64 matrix; in the remaining 21 patients, tomographic data were collected in 128×128 matrix. The imaging results were compared with pathological findings and sensitivities of both reconstruction algorithms, and planar views were calculated. RESULTS: Using planar MIBI scans, abnormal parathyroid glands were correctly localized in 75 per cent of the cases. Sensitivity increased to 77 per cent using SPECT with FBP and to 84 per cent with IR. When the sensitivities were calculated according to the acquisition matrix, these were 95 per cent (20/21) and 85 per cent (18/21) for IR and FBP, respectively in patients in whom 128×128 matrix was used. The sensitivities were lower in patients who were imaged with 64×64 matrix; these were calculated as 74 per cent (17/23) and 70 per cent (16/23) with IR and FBP, respectively. INTERPRETATION & CONCLUSIONS: Our findings showed that compared to planar scintigraphy, Tc-99m MIBI SPECT was more sensitive diagnostic modality in the detection of abnormal parathyroid tissues. Image quality and sensitivity may be improved further when larger matrices with IR are used instead of FBP algorithm.

Fluorodeoxyglucose positron emission tomography/computed tomography findings in a patient with cerebellar mutism after operation in posterior fossa.

Cerebellar mutism is a transient period of speechlessness that evolves after posterior fossa surgery in children. Although direct cerebellar and brain stem injury and supratentorial dysfunction have been implicated in the mediation of mutism, the pathophysiological mechanisms involved in the evolution of this kind of mutism remain unclear. Magnetic resonance imaging revealed dentatothalamocortical tract injuries and single photon emission computed tomography showed cerebellar and cerebral hypoperfusion in patients with cerebellar mutism. However, findings with 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in this group of patients have not been documented previously. In this clinical case, we report a patient who experienced cerebellar mutism after undergoing a posterior fossa surgery. Right cerebellar and left frontal lobe hypometabolism was shown using FDG PET/CT. The FDG metabolism of both the cerebellum and the frontal lobe returned to normal levels after the resolution of the mutism symptoms.

Differential diagnosis between secondary and tertiary hyperparathyroidism in a case of a giant-cell and brown tumor containing mass. Findings by (99m)Tc-MDP, (18)F-FDG PET/CT and (99m)Tc-MIBI scans.

Brown tumor is one of the skeletal manifestations of hyperparathyroidism. It is a benign but locally aggressive bone lesion and its differential diagnosis with giant cell containing skeletal tumors or metastases may be complicated. We present a male patient with chronic renal failure who was initially misdiagnosed as having a giant-cell rich neoplasm of bone in his right thumb. Diffusely increased fluorine-18 fluorodeoxyglucose ((18)F-FDG) uptake in the axial and appendicular skeleton and multiple (18)F-FDG avid lytic lesions suggesting multiple metastases were observed on the (18)F-FDG positron emission tomography/computed tomography (PET/CT) scan. On the usual technetium-99m methylene diphosphonate ((99m)Tc-MDP) bone scan we noticed diffusely increased uptake in the skeleton and two focuses with very much increased uptake, which suggested a metabolic bone disease rather than a multiple metastatic giant cell tumor or bone metastases. Additional investigation documentated increased levels of parathyroid hormone. Parathyroid hyperplasia was finally diagnosed with (99m)Tc-methoxyisobutylisonitrile (MIBI) parathyroid scintigraphy. Fluorine-18-FDG avid lytic lesions were attributed to hyerparathyroidism associated brown tumors instead of multiple metastases. In conclusion, we present a patient with chronic renal insufficiency, who suffered from secondary and later from tertiary HPT with polyostotic brown tumors, which were best shown by the (18)F-FDG PET/CT than by the (99m)Tc-MDP or the (99m)Tc-MIBI scans.

Marine-Lenhart syndrome in a young girl.

Graves' disease is the most common reason of hyperthyroidism in children. Graves' disease with accompanying functioning nodules is defined as Marine-Lenhart syndrome. This syndrome has not been described in children before. Here, a 15-year-old girl with Graves' disease and a coexisting cold nodule is presented. A thyroid scan showed diffuse uptake of Tc-99m pertechnatate in both lobes and decreased uptake in accordance with the left lobe nodule. The nodule was histologically diagnosed as benign. The patient was diagnosed with type 1 diabetes mellitus and polyglandular autoimmune syndrome during clinical follow-up. The differential diagnoses of Graves' disease with coexisting nodules should include the Marine-Lenhart syndrome. Treatment options should be determined taking this rare condition into account.

Undescended testis in inguinal canal detected incidentally on fluorodeoxyglucose PET/CT imaging.

The differential diagnosis at the inguinal region is very important for hypermetabolic foci because of the possibility of metastasis at this level in cancer patients ongoing PET imaging for detection of metastases. It is important to distinguish this activity from other possible malignant and benign conditions such as lymph node activity, testicular cancer, metastatic disease activity, inflammation and urine skin contamination artefact. A 66-year-old male patient with operated colon cancer and liver metastasis was referred for PET/CT examination for re-staging because of suspicious metastases. Findings of PET/CT imaging with undescended testis detected incidentally was presented.

FDG Uptake Pattern on PET/CT Imaging in Non-Infectious Graft of a Patient with Operated Abdominal Aortic Aneurysm.

UNLABELLED: Positron emission tomography using fluorodeoxyglucose is a well known diagnostic tool for routine assessment of the patients with carcinoma. Fluorodeoxyglucose uptake, as a marker of glucose metabolism, is increased in malignant conditions as well as infectious and inflammatory processes. In this case report, findings of postoperative changes in the graft on FDG PET/CT were presented in a patient on follow-up for operated renal cell carcinoma and aortic aneurysm graft surgery. The importance of the FDG uptake pattern has been pointed out for differential diagnosis of infectious and non-infectious conditions. CONFLICT OF INTEREST: None declared.

Evaluation of FDG uptake in pulmonary hila with FDG PET/CT and contrast-enhanced CT in patients with thoracic and non-thoracic tumors.

OBJECTIVE: Fluorine-18 fluorodeoxyglucose (FDG) uptake is frequently observed in lung hilus. This finding causes difficulties during the interpretation. Our objective was to evaluate the features of FDG uptake in lung hilus associated with benign or malignant etiology in patients with thoracic and non-thoracic tumors. METHODS: We retrospectively evaluated the files of 1172 patients who had undergone FDG positron emission tomography (PET)/computed tomography (CT) examination between January 2008 and June 2009. Forty-eight patients (21 males, 27 females, age range 12-80 years, mean 60.9 ± 15.82 years) with either unilateral or bilateral hilar FDG uptake and who had thorax contrast-enhanced computed tomography (CECT) performed within 1 month of the FDG PET/CT scan were enrolled in the study. Characteristics of FDG uptake were classified according to the pathology and CECT or PET/CT follow-up over 12 months. RESULTS: The characteristics of 71 hilar regions with FDG uptake could be classified. In 30 of 71 (42.3%) hilar regions, FDG uptake was considered to be physiological because no lymph node was observed on CECT. In 19 of 71 (26.8%), FDG uptake was secondary to benign lymph nodes and in 22 (30.9%) to malignant lymph nodes. Significant differences were observed between benign and malignant lymph nodes for SUVhilus and SUVhilus/SUVliver ratio. Using 4.49 as the cut-off value for SUVhilus, a sensitivity of 85.7% and a specificity of 86.4% were achieved (area under curve, AUC: 0.956). For SUVhilus/SUVliver ratio, sensitivity and specificity to detect malignant lymph nodes were 77.6 and 77.3% (AUC: 0.885), respectively, at a cut-off value of 1.75. CONCLUSION: SUVhilus and SUVhilus/SUVliver ratio were found to be significant parameters for determining malignancy in lung hilus. Combined interpretation with CECT is warranted during the evaluation of lung hilus with FDG PET/CT.

Differential renal function estimation by dynamic renal scintigraphy: influence of background definition and radiopharmaceutical.

OBJECTIVES: Differential renal function (DRF) calculation with 99mTc-diethylenetriamine-pentaacetic acid (DTPA) or mercaptoacetyltriglycine (MAG3) is gaining clinical importance in the evaluation of patients with ureteropelvic junction obstruction with hydronephrosis (HN). Although many decisions regarding surgery are based on the functional changes detected by serial diuretic renography, the reliability of DRF estimation has been questioned. Factors such as the correction of nonrenal activity included in the renal region of interest (background subtraction) and immature function resulting in poor renal extraction may cause unusual elevation in the differential function. The aim of this study is to evaluate the impact of the radiopharmaceutical and positioning of the background on the DRF. PATIENTS AND METHODS: A prospective study was undertaken in 83 patients (48 male, 35 female, median age 5 years) with unilateral or bilateral ureteropelvic junction obstruction with or without HN. Forty-five and 38 renograms were performed with 99mTc-DTPA and 99mTc-MAG3, respectively. DRF was calculated using two different regions of interest (subrenal and perirenal) for background subtraction. Of the 83 patients, 37 also had dimercaptosuccinic acid scans. The difference between DRF based on background selection, age, radiopharmaceutical, and correlation with dimercaptosuccinic acid uptake was analyzed. The difference in DRF between two background (BG) drawings (sebrenal and perirenal) and 95% confidence intervals were calculated. RESULTS: For 83 renograms, the mean difference was 4.82 (range -7 to +25, SD 5.26). The 95% confidence intervals were -3.67 to 5.97. Analysis of the data revealed that greater spread of DRF between the techniques was seen in patients with right HN (mean 7.96, P<0.001). In patients with right HN, when lower pole background activity was used, the right renal function was overestimated by an average of 4.67%. When MAG3 was used, all patients had statistically significant DRF for the different BG subtraction techniques, whereas the DRF values were only statistically different in those with right HN when DTPA was used. DISCUSSION: The current study supports the existence of BG-related variation in the DRF calculations. We found that the average counts in the perirenal BG more precisely represent nonrenal activity and recommend the use of semilunar-perirenal background region of interest to reduce the overlapping hepatic activity.

131I-MIBG therapy in metastatic phaeochromocytoma and paraganglioma.

PURPOSE: (131)Iodine metaiodobenzylguanidine ((131)I-MIBG) is a radiopharmaceutical used for scintigraphic localisation of phaeochromocytomas and paragangliomas. The experience with its therapeutic use is limited. We report our experience for the treatment of malignant phaeochromocytoma and paraganglioma. MATERIALS AND METHODS: The charts of 19 patients with malignant phaeochromocytoma (n = 12) or paraganglioma (n = 7), who were treated with (131)I-MIBG, were retrospectively reviewed. Four patients (21%) received radiotherapy, three (16%) chemotherapy, and in one patient (5%), both chemotherapy and radiotherapy was given before (131)I-MIBG therapy. Response to (131)I-MIBG treatment was evaluated by objective as tumour response, biochemical and subjective response. RESULTS: Of the 19 patients, 13 (68%) were men, 6 (32%) were women. Ages ranged from 22 to 68 years (median, 47). The median initial dose was 7.4 GBq (200 mCi; range, 6.7 GBq-25.9 GBq, 180-700 mCi); median cumulative dose was 22.2 GBq (600 mCi; range, 6.8 GBq-81.4 GBq, 183-2200 mCi). Objective tumour response was achieved in 47% of the patients. Biochemical response rate was 67%, and symptomatic response was seen in 89% of the patients. Overall median follow-up was 29 months, with a range of 3-93 months. Haematologic complications were the most common side effects and were observed in 26% of the patients. CONCLUSION: Our data support that symptomatic and biochemical response can be reached with (131)I-MIBG therapy in patients with metastatic phaeochromocytoma and paraganglioma. Although complete tumour response was not observed, the palliation and control of tumour function by (131)I-MIBG therapy may be valuable for the patients.

Unusual extracardiac findings detected on myocardial perfusion single photon emission computed tomography studies with Tc-99m sestamibi.

The authors describe the incidence and various uptake patterns of Tc-99m sestamibi (MIBI) in the extracardiac area due to unusual causes on myocardial perfusion single photon emission computed tomography (SPECT) studies. Seven patients are presented in whom incidental extracardiac findings were observed during the interpretation of the raw data besides the routine evaluation of myocardial reconstructed SPECT slices. These 7 patients were detected out of 582 consecutive patients (1.2%) who had myocardial perfusion SPECT with Tc-99m MIBI. The findings on the raw data led to additional reconstruction of thoracic SPECT images and eventually detailed examination of the extracardiac area. Two of the patients underwent surgery because of incidental extracardiac findings (thymoma and multinodular goiter) on cardiac scintigraphy. Other causes of increased extracardiac activity were the intestine protruded through the left hemithorax, uptake in the pulmonary arterial wall, and pulmonary interstitial fibrosis due to sarcoidosis. The reasons for decreased Tc-99m MIBI accumulation in the extracardiac area in the 2 other patients were significantly dilated pulmonary arteries and hydatic cyst, which were not defined before to our knowledge. Familiarity with the normal biodistribution and variable uptake patterns in the raw images becomes necessary during the interpretation of myocardial SPECT in order not to miss very unusual incidental extracardiac uptake or information that could lead to alteration in patient management. Potential underlying mechanisms of extracardiac Tc-99m MIBI accumulation are discussed, and the literature about noncardiac Tc-99m MIBI findings detected on myocardial perfusion SPECT studies was reviewed.

Visualization of gallbladder with In-111 labeled octreotide in post prandial state.

Somatostatin receptor scintigraphy is widely used in the management of neuroendocrine tumors. Somatostatin receptors are present in both neoplastic and normal tissues, which may lead to misinterpretation of the scans. Here, a patient with lung carcinoid imaged with In-111 octreotide is presented. Imaging was performed 4 and 24 hours after an intravenous injection of 185 MBq In-111 octreotide in the post prandial state. Whole body and SPECT images showed accumulation of radioactivity in the gallbladder. Imaging was repeated after fatty meal ingestion to differentiate abnormal activity and physiological uptake in the gallbladder. The abdominal SPECT studies at 28 hours revealed no uptake in the gallbladder, and the scintigraphic study was reported as normal so further excessive diagnostic procedures were prevented. Gallbladder can be visualized on somatostatin receptor scintigraphy even in the post prandial state. Delayed images after fatty meal administration are important for differential diagnosis.

Comparison of extraarticular leakage values of radiopharmaceuticals used for radionuclide synovectomy.

OBJECTIVES: Radionuclide synovectomy is a reliable therapy in patients with chronic synovitis. However, radiation doses delivered to non-target organ systems due to leakage of radioactive material from the articular cavity are an important disadvantage of this procedure. In this study we compared extraarticular leakage values of the 3 commonly used radiopharmaceuticals; 90Y-citrate, 90Y-silicate and 186Re-sulfide colloid. MATERIALS AND METHODS: Thirty-five patients with persistent synovitis were enrolled in the study. Twenty-two hemophilic, 8 rheumatoid arthritis and 5 patients with pigmented villonodular synovitis were studied. 90Y labeled silicate and citrate were used for knee joints and 186Re-sulfide for intermediate sized joints. Radiocolloid leakage values were evaluated using a gamma camera with 20% window centered over the bremsstrahlung photopeak of 90Y and a respective window over the 137 keV photopeak of 186Re. Regions of interest were drawn over the injection site, the regional lymph nodes and the background areas. Leakage of radiocolloid was calculated by dividing the counts/pixel in the regional lymph node area to the counts/pixel in the injection site. RESULTS: No visible leakage was observed. The median leakage values calculated for 90Y-citrate, 90Y-silicate and 186Re-sulfide were found as 1.9%, 2.4% and 2.7%, respectively. The difference between the variability of leakage values was not statistically significant (p > 0.05). CONCLUSION: There was no significant difference in terms of extraarticular leakage between 9Y-citrate, 9Y-silicate and 186Re-sulfide radiocolloids.

Is corticosteroid coinjection necessary for radiosynoviorthesis of patients with hemophilia?

PURPOSE: Radiation synovectomy is frequently combined with intraarticular corticosteroid injection in the treatment of rheumatoid arthritis to reduce local inflammation and lymphatic clearance of radiocolloid. However, this practice is not universally accepted because corticosteroids have local and systemic toxicity such as osteonecrosis and cartilage damage and whether simultaneous corticosteroid injection together with radiocolloids is necessary in other forms of chronic synovitis like patients with hemophilia remains to be determined. MATERIALS AND METHODS: In this study, we performed radiosynoviorthesis in 14 joints of 12 patients with hemophilia with chronic knee synovitis without corticosteroid coadministration and measured radiocolloid leakage from the joint space. Five mCi Y-90 radiocolloid was injected under local anesthesia and the needle was flushed with additional lidocaine injection instead of corticosteroid. The joint was then manipulated through a full range of extension and flexion to distribute the particles homogeneously throughout the joint space. The joint was then splinted for 48 hours to minimize leakage from the joint space. After the immobilization period, radiocolloid leakage was evaluated using a gamma camera with a 20% window centered over the maximum Bremsstrahlung photopeak of Y-90. Regions of interest were drawn to the injection site on the knee joint and to the ipsilateral inguinal lymph node area. Leakage of radiocolloid was calculated by dividing the background-corrected counts/pixel at the inguinal region by the counts/pixel at the injection site. RESULTS: One of 12 patients who had knee arthroplasty was previously found to have a high amount of leakage. In this patient, 70% of radiocolloid at the injection site drained into the pelvic lymph nodes. In the remaining 11 patients, no lymph nodes were visualized in the groin area and the measured average leakage for these patients was 2.3% (range, 0-13). CONCLUSION: We concluded that in cases of appropriate particle size and strict immobilization of knee joints, leakage of radiocolloid was minimal and steroid coinjection might not be necessary for radiosynoviorthesis of patients with hemophilia with chronic knee synovitis.