Noriyuki Kadoya, Yukio Fujita, Kengo Ito, Suguru Dobashi, Ken Takeda, Kazuma Kishi, Takaya Yamamoto, Rei Umezawa, Toshiyuki Sugawara, Tomohiro Kaneta, Haruo Matsushita and Keiichi Jingu
Objective: We investigated the effects of partial volume and respiratory motion using a National Electrical Manufacturers Association (NEMA) phantom and proposed a simple method for correction of maximum standardized uptake value (SUVmax) for respiratory motion in early lung cancer. Methods: The maximum recovery coefficient (RC) in static mode were measured using the NEMA phantom and a dynamic moving platform. The phantom on the platform was either at rest or moving sinusoidally along the longitudinal axis of the scanner to simulate respiratory motion. We also calculated estimated RC using our approximation. Results: RC of the sphere of 28mm in diameter decreased from 0.96 to 0.80 and 0.41 with 20 and 50 mm of motion amplitude, respectively. For the sphere of 10 mm in diameter, RC was decreased from 0.40 to 0.18 and 0.08 with 20 and 50 mm of motion amplitude, respectively. Our results showed that RC decreased with increase in motion amplitude. Average percentage differences between measurement and estimation in the sphere of 37, 28, 22, 17, 13 and 10 mm were -1.8 ± 3.7, -3.1 ± 11.3, -2.8 ± 10.5, -8.1 ± 6.6, -7.0 ± 12.3 and -1.8 ± 12.2 %, respectively. This result showed that our simple correction method could estimate SUVmax with moderate accuracy. Conclusions: Our results clearly demonstrated that RC decreases with increase in motion amplitude, as expected. Our simple correction with moderate accuracy method could not precisely estimate RC. However, the estimated values agreed with the measurements. Thus, our methods could be used in clinical practice to calculate the approximate SUVmax for lung cancer patients undergoing radiotherapy showing the malignancy grading for early lung cancer.
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