Diagnostic evaluation of separately acquired PET and CT images by nuclear medicine physicians and radiologists in cancer patients.

The aim of our study was to analyze how many oncology patients might benefit from a) integrated positron emission tomography - multidetector computed tomography (PET/MDCT) and additionally b) clinically relevant information provided by either the CT scan or PET scan. A total of 285 consecutive patients 164 male and 121 female, age range 17-84 years, 153 lung cancer, 112 lymphoma, 20 miscellaneous, referred for PET and separate CT scan, were included. The CT scan was performed after the intravenous injection of a soluble contrast media. Patients were retrospectively classified into six Groups: Group I: No pathological uptake on the PET scan, Group II: Suspected lesions were correctly identified by the PET scan alone, Group III: Side-by-side evaluation of PET and CT appeared sufficient to assess the localization of lesions, Group IV: Side-by-side reading was not sufficient and integrated PET/CT was considered beneficial. Additionally all patients with a CT scan with additional clinical relevant information (not visualized by the PET scan) were classified in Group V. Group VI was set for lesions detected by PET alone (not visualized by the CT scan). The CT scan was used as the gold standard to confirm or disprove PET lesion localization. Our results showed: A number of 77 patients, (Group I: 77/285, 27%) had no pathologic fluorine-18-fluorodeoxyglucose (18F-FDG)-uptake. Lesions were correctly localized by either conventional PET alone (Group II: 76/285, 27%) or side-by-side evaluation of PET and CT scans (Group III: 44/285, 15%). Integrated PET/CT or software fusion, was considered beneficial in 31% (88/285) of the patients with pathological 18F-FDG-uptake (Group IV). Additionally to the above, in 15% of all patients clinically relevant information, referring to disseminated small pulmonary lesions, abdominal aortic aneurysms >5 cm, thrombi or pulmonary emboli, was also provided by the CT scan (Group V). Also, in 7% of all patients, unsuspected pathological lesions, mainly bone metastases, were correctly detected by PET alone (Group VI). In conclusion, in 54% of all oncologic patients, PET alone was diagnostic. In 46% of all patients side-by-side reading (15%) or integrated PET/CT images (31%) were considered beneficial for more accurate anatomical localization of the lesions. Additionally, the CT scan added clinically relevant information in 15% of all patients and the PET scan showed unsuspected metastases in 7% of all studied patients. Therefore, integrated reading of PET and MDCT images by nuclear physicians and radiologists may gain quality in the staging of oncology patients.

Solitary splenic metastasis in a patient with a malignant melanoma diagnosed with F-18-FDG PET scanning.

A 71-year-old woman with a history of stage III melanoma was hospitalized for evaluating fever of unknown origin and severe left upper quadrant abdominal pain. A computed tomography scan of the abdomen revealed a solitary lesion in the spleen, 10.5 x 10.4 x 10.1-cm, causing splenomegaly. Fused F-18 FDG PET/CT images revealed a solitary splenic metastasis and a focus of increased uptake in the region of the previously removed melanoma at the right scapula. Based on the clinical findings and CT and PET scans, malignant melanoma (stage IV) was diagnosed. Splenectomy was performed subsequently. The histopathologic finding was consistent with a metastasis of a melanoma.

New post-imaging software provides fast and accurate volume data from CTA surveillance after endovascular aneurysm repair.

PURPOSE: To quantify intra- and interobserver variabilities when measuring total aneurysm volume after endovascular aneurysm repair using the Vitrea 2 System and to compare it in terms of accuracy and processing time with the gold standard methods using the Easy Vision workstation. METHODS: Total aneurysm volumes from 30 postendograft CTA datasets were randomly selected from a database consisting of approximately 400 CTA datasets recorded in 89 patients. The intra- and interobserver variabilities were measured on the Vitrea workstation by 2 investigators. The intermodality variability was calculated for the same measurements using the Easy Vision workstation. The differences of each pair of measurements were plotted against their mean, and the repeatability coefficient (RC) was calculated. The mean differences were also expressed as a percentage of the first measurements. RESULTS: The intraobserver mean difference was 1.6 mL (1.4%) with an RC of 10.8 mL (10.1%) and the interobserver mean difference was -1.4 mL (-1.4%) with an RC of 11.7 mL (10.2%). The intermodality mean difference was 1.8 mL (2.0%) with an RC of 15.8 mL (11.1%). The Vitrea workstation required a median of 8 minutes (interquartile range 7-10) for 1 observer and 6 minutes (interquartile range 5-8) for the other to perform a complete volume segmentation of each patient dataset compared to an estimated average of 30 minutes using the Easy Vision workstation. CONCLUSIONS: The Vitrea workstation provides fast and accurate volume data from spiral CTA follow-up of endovascular aneurysm repair. This software may enhance the acceptability of volume surveillance in daily practice.

Optimal scan delay in spiral CT for the diagnosis of acute pulmonary embolism.

PURPOSE: The purpose of this work was to assess whether easily obtained clinical parameters can predict optimal scan delay for contrast-enhanced spiral CT of pulmonary arteries and to compare image quality between individualized contrast timing versus a fixed scan delay. METHOD: We used an individualized delay in 85 patients by measuring the contrast transit time through the pulmonary circulation (Group A) and assessed the correlation between transit time and clinical parameters. In 56 patients (Group B), we used a 20 s fixed scan delay. The CT examinations of both groups were compared with regard to image quality. RESULTS: Contrast transit times (mean 10.5 s, range 4-26 s) did not correlate significantly with heart rate, blood pressure, body length, weight, body surface area, or cardiac function. Although contrast transit times were significantly related to gender and age, only 14.8% of the variation could be explained by these clinical parameters. Data of 57 patients in Group A and 50 patients in Group B were available for analysis. Image quality was not significantly different between Groups A and B, which was good, moderate, and poor in 61, 32, and 7% in Group A and 60, 34, and 6% in Group B, respectively (p = 1.0). CONCLUSION: One cannot predict individual scan delay from easily obtainable clinical parameters. Fortunately, a 20 s fixed scan delay provides equal image quality as individualized contrast timing.