PT - JOURNAL ARTICLE AU - Richard Conwell AU - Chuanyong Bai AU - Peter Maffetone TI - Evaluation of the respiratory motion effect on transmission scans using an ultra-low dose x-ray-derived source DP - 2009 May 01 TA - Journal of Nuclear Medicine PG - 1475--1475 VI - 50 IP - supplement 2 4099 - http://jnm.snmjournals.org/content/50/supplement_2/1475.short 4100 - http://jnm.snmjournals.org/content/50/supplement_2/1475.full SO - J Nucl Med2009 May 01; 50 AB - 1475 Objectives The conventional transmission (TX) scans for PET/SPECT use either isotopic sources or X-ray. Using isotopic sources leads to long scan time due to source strength limits. Yet, using X-ray can lead to high patient dose and TX/emission (EM) misregistration due to the mismatch of respiratory motion (RM) phases in TX and EM scans. Recently, we introduced a new TX system that uses an X-ray-derived lead fluorescence source and a common set of solid-state detectors for both TX and EM scans. The count rate of TX blank scans is >6 kcps per 6 mm pixel. TX scans can be finished within 60 seconds with patient dose ~5.0μSv. In this work, we evaluate if RM can introduce TX/EM misregistration due to the short TX scans. Methods We assume RM can be fully averaged in scans (EM/TX) that include at least 10 RM cycles. We performed six 33-second TX scans of the same volunteer consecutively. The first two scans included 10.5 RM cycles while the volunteer breathed normally. The rest had 2.0 cycles, 3.5 cycles, shallow, and deep breath-holding, respectively. Images from the last five scans were compared to that from the first scan. Results None of the images showed RM introduced aliasing artifacts. Compared to the first image with normal breathing, the second normal breathing image was nearly identical to the first. The deep breath-holding image showed large cardiac shift (2.3 cm) and lung chamber enlargement; the shallow breath-holding image showed medium cardiac shift (0.9 cm) and lung chamber enlargement. The images with 2.0 and 3.5 RM cycles showed small cardiac shift (<0.3 cm) and no lung chamber enlargement. Conclusions The short transmission scans in the new transmission system are not likely to introduce TX/EM misregistration due to respiratory motion.