Lesion concordance, image quality and artefacts in PET/CT: results of a multicenter study.

AIM: This study had three major objectives: 1.) to record the number of concordant (both in PET and CT) pathological lesions in different body regions/organs, 2.) to evaluate the image quality and 3.) to determine both, the quantity and the quality of artefacts in whole body FDG PET/CT scans. PATIENTS, METHODS: Routine whole body scans of 353 patients referred to FDG-PET/CT exams at 4 university hospitals were employed. All potentially malignant lesions in 13 different body regions/organs were classified as either concordant or suspicious in FDG-PET or CT only. In the latter case the diagnostic relevance of this disparity was judged. The image quality in PET and CT was rated as a whole and separately in 5 different body regions. Furthermore we investigated the frequency and site of artefacts caused by metal implants and oral or intravenous contrast media as well as the subjective co-registration quality (in 4 body regions) and the diagnostic impact of such artefacts or misalignment. In addition, the readers rated the diagnostic gain of adding the information from the other tomographic method. RESULTS: In total 1941 lesions (5.5 per patient) were identified, 1094 (56%) out of which were concordant. 602 (71%) out of the 847 remaining lesions were detected only with CT, 245 (29%) were only PET-positive. As expected, CT particularly depicted the majority of lesions in the lungs and abdominal organs. However, the diagnostic relevance was greater with PET-only positive lesions. Most of the PET/CT scans were performed with full diagnostic CT including administration of oral and intravenous contrast media (> 80%). The image quality in PET and CT was rated excellent. Artefacts occurred in more than 60% of the scans and were mainly due to (dental) metal implants and contrast agent. Nevertheless there was almost no impact on diagnostic confidence if reading of the non attenuation corrected PET was included. The co-registration quality in general was also rated as excellent. Misalignment mostly occurred due to patient motion and breathing and led to diagnostic challenges in about 4% of all exams. The diagnostic gain of adding PET to a CT investigation was rated higher than vice versa. CONCLUSIONS: As the image quality in both PET and CT was more than satisfying, CT-artefacts almost never led to diagnostic uncertainties and serious misalignment rarely occurred, PET/CT can be considered as suitable for routine use and may replace single PET- and CT-scans. However, additional reading of the non attenuation corrected PET is mandatory to assure best possible diagnostic confidence in PET. Since approximately half of all lesions found in PET/CT were not concordant, at least in a setting with a diagnostic CT the exams need to be reported by both a nuclear medicine physician and a radiologist in consensus.

[18F] FDG-PET/CT as a new and sensitive imaging method for the diagnosis of large vessel vasculitis.

OBJECTIVE: To determine the value of the new imaging modality positron-emission tomography/computed tomography (PET/CT) for the diagnosis and re-evaluation of large vessel vasculitis. METHODS: Thirteen patients newly diagnosed or re-evaluated for suspected clinical disease activity of Takayasu arteritis (TA, 3 patients) or giant cell arteritis (GCA, 10 patients) underwent PET/CT. Clinical activity status, serological markers, and alternative imaging methods were evaluated. RESULTS: In patients with clinical activity despite nearly normal erythrocyte sedimentation rate (ESR) and C reactive protein (CRP), disease activity could be shown by PET-CT. A long segmental, increased fluoro-deoxyglucose (FDG) uptake in the vessel wall served as confirmation of the vascular inflammation. The aortic arch was involved in all patients with active disease (n=12). In the complementary CT scans, stenotic lesions were found in 8 out of 13 patients. Duplex ultrasonography was performed in 11/13 patients and was positive in nine of these patients at least at one site. Magnetic resonance imaging (MRI) was done for confirmation in 10 patients. CONCLUSION: Doppler ultrasonography is a very useful and widely available method to confirm a first suspicion of vasculitis, but it has limitations especially at the large thoracic vessels, which are affected in many cases. ESR and CRP alone are not sufficient to evaluate disease activity. The new imaging modality PET/CT provides the additional information. It allows the evaluation of disease activity and vessel morphology as well as the localization of the inflammatory process in the same session.

Comparison of 11C-choline-PET/CT and whole body-MRI for staging of prostate cancer.

UNLABELLED: Aim of this study was to compare the diagnostic accuracy of positron emission tomography and computed tomography with (11)C-Choline (Cho-PET/CT) and whole body magnetic resonance imaging (WB-MRI) for diagnostic work-up of prostate cancer. PATIENTS, METHODS: We evaluated retrospectively 42 patients with untreated prostate cancer (n = 17), or increasing levels of prostate-specific antigen (PSA) after curative therapy (n = 25) who had been investigated by both Cho-PET/CT and WB-MRI. MRI, CT, and PET images were separately analyzed by experienced radiologists or nuclear medicine experts, followed by consensus reading. Validation was established by histology, follow-up, or consensus reading. RESULTS: 88/103 detected lesions were considered as malignant: 44 bone metastases, 22 local tumor, 15 lymph node metastases, 3 lung, and 3 brain metastases. One further lesion was located in the adrenal gland, which was a second tumor. Overall sensitivity, specificity and accuracy for Cho-PET/CT were 96.6%, 76.5%, and 93.3%, resp., and for WB-MRI 78.4%, 94.1%, and 81.0%, resp. 3 vertebral metastases had initially been missed by Cho-PET/CT and were found retrospectively. MRI identified 2 bone metastases and 1 lymph node metastasis after being informed about the results of Cho-PET/CT. CONCLUSIONS: Cho-PET/CT and WB-MRI both presented high accuracy in the detection of bone and lymph node metastases. The strength of MRI is excellent image quality providing detailed anatomical information whereas the advantage of Cho-PET/CT is high image contrast of pathological foci.

Value of contrast-enhanced multiphase CT in combined PET/CT protocols for oncological imaging.

To evaluate the additional value of contrast-enhanced multiphase CT in comparison with low-dose non-contrast CT in combined positron emission tomography (PET)/CT protocols for oncological imaging, we retrospectively analysed 100 patients with different malignant tumours. All patients underwent a PET/CT consisting of a multiphase CT protocol including a low-dose non-enhanced attenuation scan and an arterial and portal-venous contrast-enhanced scan followed by a whole-body PET. PET/CT studies were analysed by different categories to determine the added value of contrast-enhanced CT. The additional value was defined as new information provided by diagnostic CT and not available from the low-dose CT, resulting in change of PET/CT interpretation. The results were validated either by histopathology or by clinical-radiological follow up at > or =6 months. The clinical impact was evaluated with respect to changes in patient management. Diagnostic multiphase CT was of additional value in 52 out of 100 patients with 85 suspected lesions. In 40 out of 100 patients, no additional value could be detected. Eight patients were excluded due to inconclusive diagnosis in both methods including fusion. The analysis showed the greatest benefit of diagnostic CT in the categories localization of pathological fluorodeoxyglucose (FDG) uptake and precise tumour delineation, changing PET/CT interpretation in 42% and 31% of patients, respectively. The benefit of diagnostic CT was influenced by the tumour type demonstrating the highest impact in gastrointestinal, lung and neuroendocrine tumours. Diagnostic CT changed clinical management in 21 patients (21%). Diagnostic multiphase CT as part of the combined PET/CT protocol has the potential to provide considerable additional value in specific clinical conditions with resultant change of management in a substantial proportion of patients.

Dual-phase multidetector thin-section CT in detecting duodenal gastrinoma.

Preoperative localization of gastrinomas, especially of extrapancreatic origin, remains a challenge to the radiologist. Most patients with extrapancreatic gastrinomas undergo surgery without preoperative identification of the primary tumor. The appropriate imaging modality to localize gastrinomas is under continuing debate. We report a case of a duodenal gastrinoma with regional lymph node metastases that presented with Zollinger-Ellison syndrome. The small primary tumor was detected noninvasively by dual-phase multidetector thin-section computed tomography with adequate bowel distention and confirmed by endoscopy and histopathologic examination. The case illustrates that appropriate computed tomographic technique and scanning protocol are crucial for success in localizing extrapancreatic gastrinoma.

[Early prediction of treatment response to high-dose chemotherapy in patients with relapsed germ cell tumors using [18F]FDG-PET, CT or MRI, and tumor marker]. / [ ¹8F]FDG-PET, CT/MRT und Tumormarker als prädiktive Indikatoren für das Ansprechen unter Hochdosis-Chemotherapie bei Patienten mit metastasierten Keimzelltumoren.

PURPOSE: To assess the ability of [(18)F]FDG-PET, CT/MRI and serum tumor marker (TM) for the early prediction of response in patients with metastatic germ cell tumors (GCT) undergoing salvage high-dose chemotherapy (HD-CTX). MATERIALS AND METHODS: Before commencement of HD-CTX, 19 patients with metastases from GCT were evaluated with [(18)F]FDG-PET, CT or MRI and TM after 2-3 cycles of induction chemotherapy and the results compared with those of the baseline examinations. PET was analyzed visually and quantitatively by calculating the standard uptake value (SUV). CT or MRI was evaluated for changes in tumor size (progressive disease/stable disease PD/SD = viable lesion; partial remission/complete remission PR/CR = nonviable lesion), density or signal intensity, homogeneity and contrast enhancement. For the prognosis, the worse case, i.e., the most vital lesion detected in a patient, was considered. The reference standard was the result of the histology after resection of any residual masses (N = 10) and/or the clinical-radiological follow-up for at least 6 months after completion of the treatment (N = 9). RESULTS: Six of nineteen patients (32 %) remained progression-free for over 6 months following treatment, whereas 13 (68 %) progressed. The outcome of HD-CTX was correctly predicted by PET, CT and TM in 89 %, 67 % and 88 %, respectively. In 5 of 6 patients with successful HD-CTX, PET was negative (mean SUV = 1.8), with CT or MRI showing a partial regression of the tumor in 4 of 5 patients. Of the 13 patients not cured by HD-CTX, the PET data were positive in all (mean SUV = 2.7), and the CT/MRI results were true positive (PD or SD) in 8 and false negative (PR) in 5 patients. The combined assessment of CT and TM corrected 3 false negative prognoses and 1 false positive CT prognosis. Two patients with unfavorable outcome despite a favorable response by CT and TM criteria were exclusively identified by PET. The resultant sensitivities and specificities for the prediction of therapy response are as follows: PET 100% and 67%; CT/MRI 62% and 80%; TM 83% and 100%; CT+TM 85% and 83%. CONCLUSION: FDG-PET has a high prognostic value for predicting the response to chemotherapy in patients with metastatic GCT early in the course of treatment and may improve patient selection for subsequent HD-CTX protocols. Especially in patients with response to induction chemotherapy according to CT or TM evaluation, PET offers additional information to detect patients with an overall unfavorable outcome.