Background: Changes in maximum standardised uptake values (SUVmax) between serial PET/CT studies are used to\r\ndetermine disease progression or regression in oncologic patients. To measure these changes manually can be\r\ntime consuming in a clinical routine. A semi-automatic method for calculation of SUVmax in serial PET/CT studies\r\nwas developed and compared to a conventional manual method. The semi-automatic method first aligns the serial\r\nPET/CT studies based on the CT images. Thereafter, the reader selects an abnormal lesion in one of the PET\r\nstudies. After this manual step, the program automatically detects the corresponding lesion in the other PET study,\r\nsegments the two lesions and calculates the SUVmax in both studies as well as the difference between the SUVmax\r\nvalues. The results of the semi-automatic analysis were compared to that of a manual SUVmax analysis using a\r\nPhilips PET/CT workstation. Three readers did the SUVmax readings in both methods. Sixteen patients with lung\r\ncancer or lymphoma who had undergone two PET/CT studies were included. There were a total of 26 lesions.\r\nResults: Linear regression analysis of changes in SUVmax show that intercepts and slopes are close to the line of\r\nidentity for all readers (reader 1: intercept = 1.02, R2 = 0.96; reader 2: intercept = 0.97, R2 = 0.98; reader 3: intercept\r\n= 0.99, R2 = 0.98). Manual and semi-automatic method agreed in all cases whether SUVmax had increased or\r\ndecreased between the serial studies. The average time to measure SUVmax changes in two serial PET/CT\r\nexaminations was four to five times longer for the manual method compared to the semi-automatic method for\r\nall 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).\r\nConclusions: Good agreement was shown in assessment of SUVmax changes between manual and semi-automatic\r\nmethod. The semi-automatic analysis was four to five times faster to perform than the manual analysis. These\r\nfindings show the feasibility of using semi-automatic methods for calculation of SUVmax in clinical routine and\r\nencourage further development of programs using this type of methods.
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