4DCT and VMAT for lung patients with irregular breathing

Abstract

Irregular breathing in lung cancer patients is a common contraindication to 4D computerized tomography (4DCT), which may then limit radiotherapy treatment options. For irregular breathers, we investigated whether 3DCT or 4DCT (1) better represents tumor motion, (2) better represents average tumor densities, and (3) better allows for volumetric modulated arc threarpy (VMAT) plans delivered with acceptable dosimetric accuracy. Methods: Ten clinical breathing traces were identified with irregularities in phase and amplitude, and fed to a programmable moving platform incorporating an anthropomorphic lung tumor phantom. 3DCT and 4DCT data resorted by phase (4DCT-P) and amplitude (4DCT-A) were acquired for each trace. Tumors were delineated by Hounsfield unit (HU) thresholding and apparent motion range assessed. HU profiles were extracted from each image and agreement with calculated expected profiles quantified using area-under-curve (AUC) scoring. Clinically representative VMAT plans were created for each image, delivered to the irregularly moving phantom, and measured with a small-volume ion chamber at the tumor center. Results: Median difference from expected tumor motion range for 3DCT, 4DCT-P, and 4DCT-A was 2.

Accuracy of abdominal organ motion estimation in radiotherapy using the right hemidiaphragm top as a surrogate during prolonged breath‐holds quantified with MRI

“…This is prone to artefacts due to irregular breathing. 10,11 Secondly, there are substantial phase differences between diaphragm motion and motion of abdominal organs during FB. 12,13 Breath-holding might address these issues.…”

“…First, analyzing motion of entire organs in three dimensions, requires 4‐dimensional computed tomography (4DCT), that is, 3D images at, for instance, ten phases of respiration. This is prone to artefacts due to irregular breathing 10,11 . Secondly, there are substantial phase differences between diaphragm motion and motion of abdominal organs during FB 12,13 …”

Improving the Feasibility of Mitigating Phase Errors in 4DCT caused by a Random Reference Breathing Pattern in the Quasar Phantom and the Role of Slice Thickness

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In the context of binning 4DCT (4-Dimensional Computed Tomography) scans for lung patients, the occurrence of phase errors represents a persistent challenge. These errors, varying from minor discrepancies to significant inaccuracies, can compromise treatment planning quality and influence patient outcomes [1][2][3][4][5]. A primary contributor to these phase errors is the difficulty in consistently adhering to reference breathing patterns, especially when scans encompass the entire length of the lungs and liver.

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