Abstract
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.
Highlights
Whole body F-18 fluoro-2-deoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) has become an important method for detecting tumors, planning radiation treatment and evaluating response to therapy
PET/CT imaging of the lung and abdomen region is generally affected by patient respiratory motion, which can lead to underestimation of maximum standardized uptake value (SUVmax) of a region of interest, overestimation of tumor volume and mismatched PET and CT images that yield attenuation correction errors, registration errors and tumor mislocalization [1,2,3]
We investigated the effects of partial volume and respiratory motion using a phantom and the usefulness of a simple method to correct SUV for respiratory motion to know the actual malignancy in early lung cancer
Summary
Whole body F-18 fluoro-2-deoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) has become an important method for detecting tumors, planning radiation treatment and evaluating response to therapy. The effects of partial volume and respiratory motion on SUV were investigated in previous studies [1,2,3,4,5,6,7,8,9]. Guerra et al showed that the respiratory-gated PET/CT technique is a valuable clinical tool for diagnosing lung lesions, improving quantification and confidence in reporting, reducing 3D undermined findings and increasing the overall accuracy in lung lesion detection and characterization [10]. A study on 108 patients showed that SUVmax increased as much as 51.8% on average from free-breathing PET to deepinspiration-breathhold PET/CT for lesions in the lower lung region [11]. Though the usage is limited to lung cancer patients undergoing radiotherapy, we proposed a simple method for correction of SUV in the lung region using tumor size and motion displacement
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