RECOGNITION OF SUBSEGMENTAL SCINTIGRAPHIC DEFECTS IN VIRTUAL LUNG SCINTIGRAPHY

A virtual model of the segmental scintigraphic anatomy of the lungs wa s used to investigate the threshold at which small defects are percept ible. A model of the segmental anatomy of the lungs was developed from a number of sources and counts generated within the phantom by Monte- Carlo simulation of photon emission. Multiple subsegmental defects wer e created in both lungs and submitted for blinded reporting to detect the presence of any defect. A total of 36 of the 47 (77%) defects were seen. Of those defects in the lower lobes, 16 of 22 (73%) were visibl e. All the defects in the left lung (n = 21) were visible, while 15 of 26 (58%) of the defects on the right were visible. In the lower lobe of the right lung, 4 of 10 defects were visible. The defects that were not visible were all in the right lung. We conclude that absolute siz e and location are critical in the perception of defects. The percepti on of defects was dependent on absolute defect size rather than the pr oportion of a segment involved. Defects less than 3% of the volume of a lung were not detected.