Comparison of 80 and 120 kVp contrast-enhanced CT for attenuation correction in PET/CT, using quantitative analysis and reporter assessment of PET image quality.

AIM: To determine the effect of low tube voltage on positron-emission tomography (PET) image quality, quantitative analysis, and radiation dose in a combined PET/computed tomography (CT) study in patients with normal body mass index (BMI). MATERIALS AND METHODS: One hundred and twenty-nine examinations performed in 46 patients (mean age 57 years), who had at least two separate studies were retrospectively evaluated; at least one with 120 kVp and one with 80 kVp. Three independent readers reviewed all PET images and graded the image quality. PET signal and noise were recorded on the liver, spleen, fat, bone marrow, and aorta. CT dose index (CTDI) and the dose-length product (DLP) were used for CT radiation dose estimation. A mixed-effects model analysis was used for comparison of estimated radiation dose and PET data. RESULTS: There was a significant decrease of 15% in the radiation dose estimates between 80 and 120 kVp (DLP 946.2 ± 189 versus 1157.0 ± 236, respectively; p < 0.001). There was an increase of 12% in PET signal in the normal liver with 80 kVp. The average score of PET image quality obtained between 80 and 120 kVp was 4.85 ± 0.42 versus 4.90 ± 0.27, respectively (p = 0.47). CONCLUSION: PET/80 kVp CT has no statistically significant difference in the PET image quality and quantitative analysis compared to PET/120 kVp and may be used in selected patients to reduce the radiation dose.

The value of Ga-67 scintigraphy and F-18 fluorodeoxyglucose positron emission tomography in staging and monitoring the response of lymphoma to treatment.

Gallium-67 scintigraphy (GS) has the ability to provide important diagnostic and prognostic information for the evaluation of patients with lymphoma. GS is superior to morphologic imaging techniques because of its affinity to viable lymphoma cells. The value of GS lies not in the initial diagnosis but primarily in assessing the results of treatment and in the follow-up of patients with lymphoma. Nevertheless, GS has not gained the expected wide acceptance, possibly because of the meticulous technique required and the expertise needed for optimal interpretation. The introduction of positron emission tomography (PET) with F-18 fluorodeoxyglucose (FDG) as a tumor-seeking agent, which provides images of superior quality, may have an impact on the current role of GS in the management of patients with lymphoma. FDG-PET seems to share with GS the advantages of a tumor viability agent. It appears to be more sensitive for detecting nodal and extranodal sites of disease than GS and may have predictive value during and after therapy for lymphoma. These potential clinical and economic advantages of FDG-PET need to be confirmed in systematic, large-scale prospective studies.