Jorge Daniel Oldan MD, Presenter: Nothing to Disclose

Bennett B. Chin MD, Abstract Co-Author: Nothing to Disclose

Standardized uptake value (SUV) measurements on PET can be used to assess response to drug therapies, but image acquisition and processing variables such as time-of-flight (TOF) data acquisition may affect their quantitative accuracy. The purpose of this study is to compare SUV measurements in TOF and conventional non TOF reconstructions in 18F sodium fluoride (NaF) PET / CT.

SUV measurements in 45 prostate cancer patients with both TOF and non-TOF 18F NaF PET-CT data were analyzed for differences. SUV mean and maximum were measured in normal soft tissue (n=276 total regions; liver, aorta, posterior abdominal fat, bladder, brain, and paraspinal muscles) and osseous structures (n=184; T12 vertebral body, femoral diaphyseal cortex, femoral head, and lateral rib); degenerative changes (DJD; n=281) and metastatic lesions (n=159) were also measured. Data were examined for outliers and remeasured when registration was found to produce unusual results. TOF and non-TOF SUV were compared with paired t-test with Bonferroni correction and linear correlation.

Soft tissue showed lower SUV for TOF compared to non-TOF in liver (0.50±0.13 vs 0.65±0.17; p < 0.0001), brain (0.15 ± 0.04 vs 0.2 ± 0.05; p < .0001), and adipose (0.18 ± 0.05 vs 0.2 ± 0.05; p < 0.0001). Osseous structures showed higher SUV for TOF compared to non-TOF in T12 (6.74 ± 1.48 vs 6.65 ± 1.43; p < 0.0001), femoral head (2.3 ± 0.96 vs 2.16 ± 0.88, p < 0.0001), rib (3.45 ± 0.83 vs 3.26 ± 0.8; p < 0.0001), DJD (11.07 ± 3.78 vs 10.67 ± 3.74; p< 0.0001), and metastases (16.38 ± 13.05 vs 16.18 ± 13.22; p <0.0001). Also higher on TOF was the bladder (42.6 ± 24.2 vs 42.3 ± 24.4, p=.0021). Paraspinal muscles (0.71 ± 0.11 vs 0.68 ± 0.11, p=.024), femoral cortex (1.69 ± 0.66 vs 1.58 ± 0.64; p=.008), and aorta (1.21 ± 0.25 vs 1.25 ± 0.26, p=.0047) were not significantly different. Degenerative changes tended to increase by about 3% on TOF images, whereas metastases increased about 2.5%.

Most osseous structures (as well as structures brighter than their surroundings such as the bladder) have higher SUV values, and background tissues have lower SUV values, on TOF images. While these differences are statistically significant, they are small in magnitude.

These results suggest that TOF compared to non-TOF SUV measurements in 18F NaF PET / CT will have an overall minor effect in multicenter clinical trials and in clinical practice.

Oldan, J, Chin, B, Time-of-Flight and non-Time-of-Flight Sodium Fluoride PET-CT.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14045518.html