Semi-automatic analysis of standard uptake values in serial PET/CT studies in patients with lung cancer and lymphoma

BACKGROUND: Changes in maximum standardised uptake values (SUV(max)) between serial PET/CT studies are used to determine disease progression or regression in oncologic patients. To measure these changes manually can be time consuming in a clinical routine. A semi-automatic method for calculation of SUV(max )in serial PET/CT studies was developed and compared to a conventional manual method. The semi-automatic method first aligns the serial PET/CT studies based on the CT images. Thereafter, the reader selects an abnormal lesion in one of the PET studies. After this manual step, the program automatically detects the corresponding lesion in the other PET study, segments the two lesions and calculates the SUV(max )in both studies as well as the difference between the SUV(max )values. The results of the semi-automatic analysis were compared to that of a manual SUV(max )analysis using a Philips PET/CT workstation. Three readers did the SUV(max )readings in both methods. Sixteen patients with lung cancer or lymphoma who had undergone two PET/CT studies were included. There were a total of 26 lesions. RESULTS: Linear regression analysis of changes in SUV(max )show that intercepts and slopes are close to the line of identity for all readers (reader 1: intercept = 1.02, R(2 )= 0.96; reader 2: intercept = 0.97, R(2 )= 0.98; reader 3: intercept = 0.99, R(2 )= 0.98). Manual and semi-automatic method agreed in all cases whether SUV(max )had increased or decreased between the serial studies. The average time to measure SUV(max )changes in two serial PET/CT examinations was four to five times longer for the manual method compared to the semi-automatic method for all readers (reader 1: 53.7 vs. 10.5 s; reader 2: 27.3 vs. 6.9 s; reader 3: 47.5 vs. 9.5 s; p < 0.001 for all). CONCLUSIONS: Good agreement was shown in assessment of SUV(max )changes between manual and semi-automatic method. The semi-automatic analysis was four to five times faster to perform than the manual analysis. These findings show the feasibility of using semi-automatic methods for calculation of SUV(max )in clinical routine and encourage further development of programs using this type of methods.