The 111In-granulocyte scan in prosthetic vascular graft infections: imaging technique and results

Fourteen patients were examined between 3 weeks and 11 years after implantation of an aortobifemoral vascular graft with 111In labelled leukocytes isolated with discontinuous gradient centrifugation. The camera acquisition was performed with a three phase technique (acquisitions at 30 min, 4 h and 24 h p.i.). The presence and extent of a graft or perigraft infection including complicating fistulas could be correctly diagnosed in six of eight patients with surgically proven infections. Leukocyte uptake index was calculated as 1.77 +/- 0.4 (30 min p.i.) and 2.4 +/- 0.7 (24 h p.i.). All infections could be diagnosed by 30 min p.i., fistulas only could be seen 24 h p.i. In two of eight patients, false positive results were observed. These patients suffered from suspected perigraft hematomas and noninfected aortic graft aneurysms. Both had a negative 30 min scan and a slight uptake in the late scans comparable to bone marrow activity. Six patients with fever of unknown origin showed true negative scans. There were no false negative scans. We conclude that only the leukocyte scan can diagnose the presence and the extent, including fistulas, of vascular graft infections. The three phase technique is recommended to localize the blood pool in the 30 min scan and to diagnose complications 24 h p.i. In cases of a negative 30 min scan and positive 4 h and 24 h scans, false positive results should be suspected. All infections have a leukocyte uptake index higher than 1.2.     

Brain tumour imaging with PET: a comparison between [18F]fluorodopa and [11C]methionine

Imaging of amino acid transport in brain tumours is more sensitive than fluorine-18 2-fluoro-deoxyglucose positron emission tomography (PET). The most frequently used tracer in this field is carbon-11 methionine (MET), which is unavailable for PET centres without a cyclotron because of its short half-life. The purpose of this study was to evaluate the performance of 3,4-dihydroxy-6-[¹⁸F]fluoro-phenylalanine (FDOPA) in this setting, in comparison with MET. Twenty patients with known supratentorial brain lesions were referred for PET scans with FDOPA and MET. The diagnoses were 18 primary brain tumours, one metastasis and one non-neoplastic cerebral lesion. All 20 patients underwent PET with FDOPA (100 MBq, 20 min p.i.), and 19 of them also had PET scans with MET (800 MBq, 20 min p.i.). In all but one patient a histological diagnosis was available. In 15 subjects, histology was known from previous surgical interventions; in five of these patients, as well as in four previously untreated patients, histology was obtained after PET. In one untreated patient, confirmation of PET was possible solely by correlation with MRI; a histological diagnosis became available 10 months later. MET and FDOPA images matched in all patients and showed all lesions as hot spots with higher uptake than in the contralateral brain. Standardised uptake value ratios, tumour/contralateral side (mean±SD), were 2.05±0.91 for MET and 2.04±0.53 for FDOPA (NS). The benign lesion, which biopsy revealed to be a focal demyelination, was false positive, showing increased uptake of MET and FDOPA. We conclude that FDOPA is accurate as a surrogate for MET in imaging amino acid transport in malignant cerebral lesions for the purpose of visualisation of vital tumour tissue. It combines the good physical properties of ¹⁸F with the pharmacological properties of MET and might therefore be a valuable PET radiopharmaceutical in brain tumour imaging.     

Utility of<Superscript>99m</Superscript>Tc dextran scintigraphy in diabetic patients with suspected osteomyelitis of the foot

PURPOSE: Osteomyelitis of the foot is a frequent complication of diabetes mellitus and its diagnosis is often difficult. The goal of this study was to demonstrate the utility of 99mTc dextran scintigraphy in suspected diabetic foot infections. MATERIALS AND METHODS: Twenty-six patients (20 males, 6 females, age range 18-80 years) with diabetes mellitus who had a total of 36 foot ulcers or necrosis were studied. All the patients underwent both three phase bone scan and 99mTc dextran scintigraphy. Final diagnosis was based upon either pathologic examination or clinical follow-up at least four months. RESULTS: On bone scan increased uptake was seen in 55 sites, and among these there were 11 lesions of proven osteomyelitis. There were 11 true-positive, 0 false negative, 0 true negative and 44 false positive results for bone scan. The sensitivity, specificity and accuracy of bone scan were 100%, 0% and 20%, respectively. With regard to 99mTc dextran scan, nine lesions produced true-positive results with two lesions indicating false negatives resulting in a sensitivity of 82%. Thirty-six true negative and eight false positive results produced a specificity of 82%, and an accuracy 82% from 99mTc dextran studies was obtained. Eight false-positive results were possibly due to neuroarthropathy, pressure points and deep penetrating ulcers. A patient with one false-negative result had angiopathy while other had neither neuropathy nor angiopathy. CONCLUSIONS: According to these results, 99mTc dextran scintigraphy seems to be a sensitive and specific diagnostic method, and because of its advantages over other radiopharmaceuticals (shorter preparation time, highly stability in vivo/in vitro, early diagnostic imaging and low cost), it may be a radiopharmaceutical of choice for diagnosing in diabetic foot infections.     

Accuracy of transmission CT and FDG-PET in the detection of small pulmonary nodules with integrated PET/CT

Purpose The purpose of this study was to determine the accuracy of detection of small pulmonary nodules on quiet breathing attenuation correction CT (CTAC) and FDG-PET when performing integrated PET/CT, as compared with a diagnostic inspiratory CT scan acquired in the same imaging session.Methods PET/CT scans of 107 patients with a history of carcinoma (54 male and 53 female, mean age 57.3 years) were analyzed. All patients received an integrated PET/CT scan including a CTAC acquired during quiet respiration and a contrast-enhanced CT acquired during inspiration in the same session. Breathing CTAC scans were reviewed by two thoracic radiologists for the presence of pulmonary nodules. FDG-PET scans were reviewed to determine accuracy of nodule detection. Diagnostic CT was used as the gold standard to confirm or refute the presence of nodules.Results On the CTAC scans 200 nodules were detected, of which 183 were true positive (TP) and 17, false positive. There were 109 false negatives (FN). Overall, 51 (48%) patients had a false interpretation, including 19 in whom CT was interpreted as normal for lung nodules. The average size of the nodules missed was 3.8±2 mm (range 2–12 mm). None of the nodules missed on the CTAC scans were detected by PET. In the right lung there were 20 TP, 42 true negative (TN), 11 FP, and 34 FN interpretations with a sensitivity in nodule detection of 37% (CI 24–51%) and a specificity of 79% (CI 66–89%). In the left lungs there were 16 TP, 65 TN, 3 FP, and 23 FN interpretations, with a sensitivity of 41% (CI 26–58%) and a specificity of 96% (CI 88–99%).Conclusion The detection of small pulmonary nodules by breathing CTAC and FDG-PET is relatively poor. Therefore an additional diagnostic thoracic CT scan obtained during suspended inspiration is recommended for thorough evaluation of those patients in whom detection of pulmonary metastases is necessary for management.     

The single late 99Tcm granulocyte antibody scan in inflammatory diseases.

Immunoscintigraphy using 555-740 MBq 99Tcm-labelled monoclonal antigranulocyte antibodies (IgG1 against NCA-95) (BW250/183) was performed in 56 patients. In 32 of them inflammatory or infectious lesions were proven or excluded histologically. Gamma camera scans were performed 4 to 6 and 20 h postinjection (p.i.). Eight of 14 infectious or inflammatory lesions could be detected in the early scan (4-6 h p.i.). Sensitivity, specificity and diagnostic accuracy of the early scan were 57, 89 and 75%. Sensitivity, specificity and diagnostic accuracy in 19 patients with bone or prosthetic bone infections (87, 81 and 84%, respectively) were lower than in patients with abdominal or soft tissue infections (100%). The overall sensitivity, specificity and diagnostic accuracy of the 20 h scan was 86, 89 and 88%, respectively. It is concluded that the high diagnostic accuracy of immunoscintigraphy justifies a broader application of the scan in the diagnosis of infectious diseases. It is recommended that only late scans (20 h p.i.) are necessary.     

131I-meta-iodobenzylguanidine scintigraphy in patients with a suspected pheochromocytoma. A comparison with CT and biohumoral parameters]

The results of 131I metaiodobenzylguanidine (MIBG) and Computed Tomography (CT) scans in a group of patients with clinically suspected pheochromocytoma were evaluated and compared with biohumoral parameters. We studied 24 consecutive patients (7 M and 17 F; age range 20-66 years). 131I-MIBG scintigraphy and CT were in agreement in 19 patients (79%): of them 7 cases were true positive, and 12 were true negative. Disagreement between the two imaging techniques was observed in 5 patients (21%). In this group, one patient, with positive CT scan, had false negative MIBG study, while 4 patients with negative MIBG scan, had false positive CT. MIBG showed significantly higher (p less than 0.05) specificity (100%), positive predictive value (100%), and accuracy (96%) than CT (75%, 67%, and 83%, respectively). 131I-MIBG scintigraphy is an accurate, noninvasive technique for localizing pheochromocytoma and providing direct tissue characterization, while CT provides more accurate spatial information. In conclusion, CT and MIBG studies are complementary in the evaluation of patients with suspected pheochromocytoma.     

The clinical impact of18F-FDG PET in papillary thyroid carcinoma with a negative131I whole body scan: A single-center study of 108 patients

OBJECTIVE: To assess whether FDG PET could localize the recurrent or metastatic lesions in papillary thyroid cancer patients with negative radioiodine scan. METHODS: Whole body PET was performed after injecting 370-555 MBq of 18F-FDG in 108 patients, who were suspected of having recurrence or metastasis and whose 131I whole body scans were negative. Recurrence or metastasis occurred in 63 patients by pathology or clinical assessment, whereas 45 patients remained in remission. RESULTS: FDG PET revealed recurrence or metastases in 59 patients (sensitivity 93.7%), whereas thyroglobulin (Tg) levels were elevated in 41 (sensitivity 65.1%). In 35 of 45 patients in remission, FDG PET was negative (specificity 77.8%). When patients positive for antithyroglobulin antibody were excluded, the sensitivity and specificity of serum Tg became 84.8% and 46.9%, respectively. Compared to Tg measurement, FDG PET detected more metastatic lesions in cervical lymph nodes. Of 40 patients with a negative radioiodine scan showing diffuse hepatic uptake, metastases occurred in 23 patients and remission in 17. FDG PET showed 100% sensitivity and 76.5% specificity in the detection of recurrence in these 40 patients. CONCLUSION: FDG PET is useful for localizing recurrent or metastatic lesions in 131I scan-negative thyroid cancer patients. In particular, it is superior to serum Tg measurement for identifying metastases to cervical lymph nodes. We recommend its use in cases of negative radioiodine scan with diffuse hepatic uptake.     

Relations Between Pathological Markers and Radioiodine Scan and 18F-FDG PET/CT Findings in Papillary Thyroid Cancer Patients With Recurrent Cervical Nodal Metastases

Purpose

The aim of this study was to investigate relationships between the immunohistochemical results and radioiodine scan and ¹⁸F-FDG PET findings in papillary thyroid cancer (PTC) patients with recurrent cervical nodal metastases.

Methods

A total of 46 PTC patients who had undergone a radioiodine scan and/or ¹⁸F-FDG PET/CT and a subsequent operation on recurrent cervical lymph nodes were enrolled. Twenty-seven patients underwent ¹⁸F-FDG PET/CT, 8 underwent radioiodine scans, and 11 underwent both scans. In all surgical specimens, the immunoexpressions of thyroglobulin (Tg), sodium-iodide symporter (NIS), glucose transporter 1 (Glut-1), and somatostatin receptor 1 and 2A (SSTR1 and SSTR2A) were assessed, and associations between these expressions and radioiodine scan and ¹⁸F-FDG PET findings were evaluated.

Results

Of the 38 patients who underwent ¹⁸F-FDG PET/CT, all patients with weak Tg expression had positive ¹⁸F-FDG uptake, while only 45 % of the patients with moderate or strong Tg expression showed positive uptake (p = 0.01). The proportion of patients with positive ¹⁸F-FDG uptake increased as the degree of Glut-1 expression with luminal accentuation increased. Of the 19 patients who underwent a radioiodine scan, the proportion with positive radioiodine uptake was greater among patients with strong NIS and SSTR2A expression than among patients expressing these markers at weak levels (p = 0.04 for all). All three patients with weak Tg expression were negative for radioiodine uptake.

Conclusion

The ¹⁸F-FDG uptakes of recurrent cervical nodes are related to strong Glut-1 expression with luminal accentuation and weak Tg expression, whereas radioiodine uptake is related to the strong expressions of NIS and SSTR2A.     

90Y microsphere treatment of unresectable liver metastases: changes in 18F-FDG uptake and tumour size on PET/CT

Purpose The intra-arterial administration of ⁹⁰Y microspheres is a new palliative treatment option for unresectable liver metastases. The aim of this study was to quantitatively assess changes in FDG uptake and tumour size following ⁹⁰Y microsphere treatment (SIR-Spheres) using ¹⁸F-fluorodeoxyglucose (FDG) PET/CT imaging.Methods Five patients with unresectable liver metastases who had failed multiple prior chemotherapy regimens received seven ⁹⁰Y microsphere treatments to a single liver lobe. All patients underwent a baseline PET/CT scan prior to treatment, as well as up to four follow-up PET/CT scans. The tumour area of 30 liver metastases was measured on CT and the FDG uptake was semiquantitatively assessed by calculation of standardised uptake values (SUVs). A total of 18 FDG-PET/CT scans were performed.Results The SUVs in the 30 treated liver metastases decreased from 6.5±2.3 at baseline to 4.2±1.8 after the first follow-up PET/CT scan (p=0.001). In contrast, the SUVs of untreated metastases increased slightly from 7.2±2.3 to 8.0±0.8. There was no difference in FDG uptake in treated versus untreated normal liver tissue. Using a previously defined threshold of 20% decrease in SUV from baseline to determine response, 20 out of 30 liver metastases were considered to have responded at the first follow-up PET/CT scan approximately 1 month after treatment. In these metastases, the SUV decreased by 47±12%, compared with a slight increase by 5.9±19% in ten non-responding metastases (p=0.0001). The changes in tumour size did not correlate with changes in FDG uptake. On the first follow-up PET/CT scan, the tumour area on CT increased by 3.1±57% in treated metastases compared with 23.3±32% in untreated metastases. A wide range of post-treatment changes of target lesions was observed on CT, including an increase in the size of hypodense lesions, necrotic features and complete resolution of CT abnormalities.Conclusion The metabolic information obtained from FDG-PET/CT seems to provide a more accurate and earlier assessment of therapy response following ⁹⁰Y microsphere treatment than does the anatomical CT information.     

MR imaging of complications of aortic surgery

Sixteen patients with a variety of complications of aortic surgery were evaluated with magnetic resonance (MR) imaging. More than one complication occurred in seven patients, resulting in the following types of abnormalities: graft occlusions, two; graft infections; five; pseudoaneurysms or aneurysmal dilatation of graft anastomoses, 10; perigraft hemorrhages, four; and aortoenteric fistulas, two. The MR findings were verified by surgery in 10, by CT in four, and by angiography in 11 patients. The size and extent of pseudoaneurysm or anastomotic dilatation, the presence of thrombus and vessel occlusion, the extent of abscesses, and the effect of pseudoaneurysms and abscesses on adjacent structures were readily demonstrated by MR. The size of the residual lumen in the case of thrombosis could be assessed. Abscesses were identified by their characteristic signal increase with long repetition rates and long echo delays. Magnetic resonance was also able to exclude suspected complications such as perigraft infection, hemorrhage, and graft occlusion in four patients.     

18F-FDG PET in malignant lymphoma: significance of positive findings

Purpose The aim of this study was to evaluate the significance of increased uptake of ¹⁸F-fluorodeoxyglucose (FDG) in patients with malignant lymphoma (ML) studied by positron emission tomography (PET).Methods A total of 1,120 consecutive scans carried out in 848 patients were reviewed; all patients had a diagnosis of ML [574 non-Hodgkins lymphoma (NHL) and 274 Hodgkins disease (HD)] and were studied at completion of therapy, for suspected recurrence or during follow-up. PET was carried out after intravenous injection of 370 MBq of ¹⁸F-FDG; images were recorded after 60–90 min. Patients were selected whose reports indicated areas of increased FDG uptake. PET findings were considered positive for lymphomatous localisation when uptake occurred at sites of previous disease, in asymmetrical lymph nodes or in nodes unlikely to be affected by inflammation (mediastinal, except for hilar, and abdominal). PET findings were adjudged negative for neoplastic localisations in the following instances: physiological uptake (urinary, muscular, thymic or gastrointestinal in patients without MALT), symmetrical nodal uptake, uptake in lesions unrelated to lymphoma that had already been identified by other imaging methods at the time of PET scan, uptake at sites atypical for lymphoma, very low uptake and non-focal uptake. PET findings were compared with the results of other diagnostic procedures (including CT and ultrasound), biopsy findings and follow-up data.Results Overall, 354 scans (in 256 patients) showed increased FDG uptake (244 scans in NHL and 110 in HD): in 286 cases, FDG uptake was considered pathological and indicative of ML, in 41 cases the findings were described as uncertain or equivocal and in 37 cases, FDG uptake was considered unrelated to ML (in ten scans, concurrent findings of abnormal FDG uptake attributed to ML and uptake assigned to other causes were obtained) . Of the 286 patients with positive PET findings, 274 (95.8%) were found to have residual or recurrent ML (i.e. true positives). Four of the 41 patients with inconclusive findings turned out to have ML, while in 13 patients, pathological processes other than ML could be identified as the cause of FDG uptake. ML was excluded in all patients with findings reported as non-pathological (100% true-negative rate). Therefore, the false-positive rate in our series was about 5%. The main cause of increased FDG uptake mimicking ML was inflammation.Conclusion Our data confirm that ¹⁸F-FDG-PET has very high but not absolute specificity for ML. As already suggested, increased FDG uptake may also be observed in patients without active disease; in most cases, however, non-pathological FDG accumulation is properly identified. Less frequently, inconclusive scans are encountered; these cases are usually caused by inflammation, which subsequently resolves.     

Whole-body kinetics and dosimetry ofl-3-[123I]iodo-α-methyltyrosine

The synthetic amino acidl-3-[¹²³I]iodo--methyltyrosine (IMT) is currently under clinical evaluation as a single-photon emission tomography (SPET) tracer of amino acid uptake in brain tumours. So far, dosimetric data in respect of IMT are not available. Therefore we investigated the whole-body distribution of IMT in six patients with cerebral gliomas and the radiation doses were estimated. Whole-body scans were acquired at 1.5, 3 and 5 h after i.v. injection of 370–550 MBq IMT. The bladder was voided prior to each scan and the radioactivity excreted in the urine was measured. Based on the MIRD-11 method and the updated MIRDOSE3, the mean absorbed doses for various organs and the effective dose were calculated from geometric means of the anterior and posterior whole-body scans using seven source organs and the residence time. IMT was predominantly excreted by the kidneys (52.8%±11.5% at 1.5 h p.i., 63.0%±15.7% at 3 h p.i. and 74.6%±9.8% at 5 h p.i.). No organ system other than the urinary tract showed significant retention of the tracer. Early whole-body scans revealed slightly increased tracer uptake in the liver and in the bowel. Highest absorbed doses were found for the urinary bladder wall (0.047 mGy/MBq), the kidneys (0.010 mGy/MBq), the lower large intestinal wall (0.011 mGy/MBq) and the upper large intestinal wall (0.008 mGy/MBq). The effective dose according to ICRP 60 was estimated to be 0.0073 mSv/MBq for adults. This leads to an effective dose of 3.65 mSv in a typical brain SPET study using 500 MBq IMT. The MIRDOSE3 scheme yielded similar results. Thus, in spite of the relatively high tracer dose required for optimal brain scanning, radiation exposure in SPET studies with IMT is in the normal range of routine nuclear medicine investigations.     

Iodine-123 as a diagnostic imaging agent in differentiated thyroid carcinoma: a comparison with iodine-131 post-treatment scanning and serum thyroglobulin measurement

Purpose Using ¹²³I for diagnostic purposes avoids the risk of stunning for subsequent radioiodine treatment and affords an excellent image quality. In this study we assessed the role of ¹²³I in comparison with ¹³¹I post-treatment imaging in patients with thyroid cancer. Methods We compared a total of 292 ¹²³I scans with their corresponding post-treatment ¹³¹I images. Patients received a therapeutic dose of ¹³¹I following diagnostic scanning with 50–111 MBq of ¹²³I. All patients were in a hypothyroid state (>30 μIU/l) before radioiodine administration for either diagnostic or therapeutic purposes. Results In 228 out of 263 patients with a positive diagnostic scan, ¹²³I whole-body scan findings were concordant with those of corresponding post-treatment ¹³¹I images (concordance rate 87%). However, there were 44 additional foci of abnormal uptake on post-treatment ¹³¹I scans in 22 discordant cases with no impact on therapeutic management of the patients. In 13 patients, there was at least one new site on post-treatment images that had been missed on pretreatment ¹²³I images. Twenty-nine patients with a negative diagnostic scan were treated with ¹³¹I owing to a high serum thyroglobulin level (range 11.3–480 ng/ml). Radioiodine uptake sites were seen in eight post-treatment scans. In 21 pairs of whole-body scans, both the pre- and the post-treatment scan were negative (concordance rate 72.4%). Conclusion ¹²³I scanning is comparable to high-dose ¹³¹I post-treatment imaging in thyroid carcinoma patients, and ¹²³I offers excellent image quality as a diagnostic agent. It avoids disadvantages such as stunning before treatment and delivery of a high radiation dose to patients.     

Hepatic 123I-insulin binding kinetics in non-insulin-dependent (Type 2) diabetic patients after i.v. bolus administration

Insulin binding kinetics in the liver were studied in non insulin dependent (Type 2) diabetic patients, by i.v. bolus administration of ¹²³I-insulin. Eight Type 2 diabetic patients were compared with six male volunteers. Uptake of ¹²³I-insulin by liver and kidneys was measured by dynamic scintigraphy with a gamma camera during 30 min. Images of liver and kidneys appeared within 2–3 min after administration of ¹²³I-insulin at a dose of 1 mCi (37 MBq). Peak radioactivity for the liver was found 7.5±0.2 and 6.9±0.3 min after injection for the healthy and the diabetic subjects, respectively (N.S.). The percentage ¹²³I-insulin hepatic uptake was not significantly different for the diabetic and the healthy subjects.Although a large variation exists for maximal uptake of radioactivity within both groups, the data suggest that binding differences in the liver in Type 2 diabetic patients, as compared to healthy subjects, may not account for hepatic insulin resistance.     

Immunoscintigraphy using 111Indium-labeled antimyosin in suspected myocarditis

111Indium-monoclonal antimyosin scans were carried out in 21 patients with suspected myocarditis, confirmed by reduced ejection volume, pericardial effusion and clinical follow up in 12 patients. Coronary heart disease was excluded angiographically in all cases. Quantitative evaluation of myocardial 111In-antimyosin accumulation 48 hours after injection showed a pathological uptake in 10/12 patients with increased heart/lung ratios (Q48 greater than 1.58). Ratios were also elevated in 2 patients with cardiomyopathy, 2 suffering from vasculitis and 1 with dermatomyositis. Four patients without proven cardiac disease had normal ratios (Q48 less than or equal to 1.58). Examination after 24 hours was of limited value, depending on the residual blood pool activity. Visual analysis of the scans showed a high interobserver variation despite a positive correlation with quantitative analysis (48 h p.i.: r = 0.72; p less than 0.001), and is not recommended. The results show the value of the 111In-antimyosin scan as a screening method prior to myocardial biopsy. However, scintigraphy cannot definitely elucidate the cause of myocardial damage. Therefore, myocardial biopsy is still recommended after positive antimyosin scans.     

Diagnostics of “non-acute” vascular prosthesis infection using <Superscript>18</Superscript>F-FDG PET/CT: our experience with 96 prostheses

Introduction  Vascular prosthesis infection (VPI) is a life-threatening complication that occurs in 0.5–5% of prostheses. Low-grade infections in non-acute patients are a diagnostic challenge requiring a new method with good diagnostic accuracy. The aim of this work was to define the accuracy of ¹⁸F-FDG PET/CT in these settings and to identify essential parameters of the evaluation. Material and methods  PET/CT was performed prospectively in 76 consecutive patients with a total of 96 vascular prosthetic grafts in which infection was suspected. PET/CT scans were analysed in terms of the presence and intensity of focal and diffuse FDG uptake, the presence of an anastomotic pseudoaneurysm, the presence of an irregular boundary of infiltration, a combination of these, and the uptake ratio between the graft and blood background. The gold standard was based on operative/histopathological finding or a clinical follow up of >6 months. Results  Among the various assessed parameters only focal FDG uptake and an irregular graft boundary were significant predictors of VPI. Focal intense FDG uptake together with an irregular boundary of the lesion on CT scan predicted VPI with 97% probability, while smooth lesion boundaries and no focal FDG uptake predicted a probability of VPI of less than 5%. Even in lesions with nondiagnostic inhomogeneous focal FDG uptake (18/96) an irregular boundary effectively helped in decision-making with a probability of 28% (smooth) or 77% (irregular) for VPI. Conclusion  PET/CT gave reliable results with an accuracy >95% in 75% of prostheses. PET/CT can identify those prostheses (25% of prosthesis) for which its diagnostic accuracy is diminished to 70–75%. In our series PET/CT was an excellent diagnostic modality for suspected VPI.     

Evaluation of 111In leukocyte whole body scanning.

Indium-111 oxine, polymorphonuclear cells isolated and labeled with 111In were used for studying absecesses and inflammatory conditions. There were 64 total scans done in 59 patients, 32 male and 27 female, aged 3-81 years (average, 51). The original clinical diagnosis was abscess in 33 patients. The whole blood cell scan was abnormal in 12 (36%) of these, and a good clinical correlation was obtained in 11 of the 12. In the 21 with a normal scan, 18 had no evidence of abscess, yielding one false-positive and three false-negative interpretations in the abscess group. Thirteen patients had fever of unknown origin, nine had negative scans and no subsequent evidence of abscess, and four had positive scans with good correlation in three. Acute bone and joint infections were positive on scan (4/4), whereas chronic osteomyelitis was negative (0/2). Three patients with acute myocardial infarction and three of four with subacute bacterial endocarditis had normal scans. All three studies in renal transplant rejection showed positive uptake in the pelvic kidneys. Indium-111 white blood cell scans have proved useful to diagnose or exclude a diagnosis of abscess or inflammatory condition infiltrated with polymorphonuclear leukocytes.     

Diagnostic value of <Superscript>18</Superscript>F-FDG PET/CT in trauma patients with suspected chronic osteomyelitis

Purpose To retrospectively evaluate the diagnostic value of ¹⁸F-FDG PET/CT in trauma patients with suspected chronic osteomyelitis. Methods Thirty-three partial body ¹⁸F-FDG PET/CT scans were performed in 33 patients with trauma suspected of having chronic osteomyelitis. In 10 and 23 patients, infection was suspected in the axial and appendicular skeleton, respectively. In 18 patients, PET/CT was performed in the presence of metallic implants. Histopathology or bacteriological culture was used as the standard of reference. For statistical analysis, sensitivity, specificity and accuracy were calculated in relation to findings of the reference standard. Results Of 33 PET/CT scans, 17 were true positive, 13 true negative, two false positive and one false negative. Eighteen patients had chronic osteomyelitis and 15 had no osseous infection according to the reference standard. Sensitivity, specificity and accuracy for ¹⁸F-FDG PET/CT was 94%, 87% and 91% for the whole group, 88%, 100% and 90% for the axial skeleton and 100%, 85% and 91% for the appendicular skeleton, respectively. Conclusion ¹⁸F-FDG PET/CT is a highly sensitive and specific method for the evaluation of chronic infection in the axial and appendicular skeleton in patients with trauma. PET/CT allows precise anatomical localisation and characterisation of the infectious focus and demonstrates the extent of chronic osteomyelitis with a high degree of accuracy.     

Indium-111 labeled purified granulocytes in the diagnosis of synthetic vascular graft infection

Indium-111 labeled leukocytes have been shown to be useful in the diagnosis of synthetic vascular graft infection. To minimize the potential effects of labeled red blood cells and platelets on image interpretation, the authors prepared purified autologous granulocytes (PG) from 84 ml of blood using Volex enhanced gravity sedimentation and Ficoll-Hypaque double density centrifugation. The labeling efficiency of PG with In-111 tropolone was 90 +/- 9% (mean +/- SD). Imaging was performed 18-24 hours following injection of approximately 445 microcuries of In-111 PG in 26 patients with suspected infection of vascular grafts that had been implanted 12 days to 12 years prior to the study. In ten patients with proven graft infection, seven had positive In-111 PG scans. Ten of 11 patients without infection had negative scans. In five patients with clinically equivocal findings, scan results were positive in one, negative in one, and equivocal in three. A false-positive scan occurred in a patient with an uninfected inflammatory pseudoaneurysm of an aortic graft. These results confirm an earlier report that In-111 PG imaging is a useful technique in the diagnosis of synthetic vascular graft infection.     

Ga-67 citrate scan in vascular graft infection

The clinical utility of the Ga-67 scan has been studied in 9 patients with clinical suspicion of vascular graft infection. Eleven grafts were analyzed: 4 aortobifemoral, 2 iliofemoral, 3 femoropopliteal, 1 axillofemoral, and 1 axillobifemoral. The Ga-67 scan was positive in 8 grafts with bacteriological proof of infection and negative in 3 grafts in which infection was ruled out by clinical follow-up. A Ga-67 scan also demonstrated the spread of infection to the thigh in two patients and to the pelvis in another two patients. In 4 patients CT was performed. The CT findings included graft thrombosis, perigraft fluid collection and thickened graft wall. No discrepancies were found between the CT scan and Ga-67 scan. In three patients a control Ga-67 scan was carried out after specific antibiotic and surgical treatment. Two of these showed increased Ga-67 uptake and spreading of infection along the graft; in the other patient, a Ga-67 scan revealed normalization after resolution of an abdominal abscess. In conclusion, the Ga-67 scan proved useful in the diagnosis of vascular graft infection, the definition of location of the extent of the disease and in the evaluation of the efficiency of treatment.