Is a Single Respiratory Correlated 4D-CT Study Sufficient for Evaluation of Breathing Motion?

• Published in: International journal of radiation oncology, biology, physics Vol. 67; no. 5; pp. 1352 - 1359
• Main Authors: Guckenberger, Matthias, M.D, Wilbert, Juergen, Ph.D, Meyer, Juergen, Ph.D, Baier, Kurt, Richter, Anne, Flentje, Michael, M.D
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.04.2007
• Subjects: AMPLITUDES; CARCINOMAS; COMPRESSION; COMPUTERIZED TOMOGRAPHY; ERRORS; Four-dimensional CT (4D-CT); Hematology, Oncology and Palliative Medicine; Humans; Intrafractional errors; Lung Neoplasms - diagnostic imaging; Lung Neoplasms - radiotherapy; Lung Neoplasms - secondary; LUNGS; Mean tumor position; METASTASES; Movement; PATIENTS; Radiology; RADIOLOGY AND NUCLEAR MEDICINE; Radiotherapy Planning, Computer-Assisted - methods; RESPIRATION; Stereotactic body radiotherapy (SBRT); Stereotaxic Techniques; Tomography, X-Ray Computed - methods; Tumor breathing motion; Stereotactic body radiotherapy (SBRT); Intrafractional errors; Four-dimensional CT (4D-CT); Mean tumor position; Tumor breathing motion
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/j.ijrobp.2006.11.025

Purpose: Respiratory correlated computed tomography has been shown to be effective for evaluation of breathing-induced motion of pulmonary tumors. This study investigated whether a single four-dimensional CT study (4D-CT) is representative and sufficient for treatment planning in stereotactic body radiotherapy (SBRT). Methods and Materials: Four repeated helical 4D-CT studies were acquired every 10 min for 10 patients with 14 pulmonary metastases. Patients remained immobilized in a stereotactic body frame (SBF) for 30 min; abdominal compression was applied to seven patients. Using amplitude based sorting, eight phases equally distributed over the breathing cycle were reconstructed for each 4D-CT study. Tumor position was defined in a total of 406 CT series and variability of breathing motion and mean tumor position were evaluated. Results: Peak-to-peak tumor motion was 9.9 mm ± 6.8 mm (mean ± standard deviation) and 9.0 mm ± 7.4 mm at time point 0 min (t0 ) and t30 , respectively. In one patient with poor pulmonary function, continuous increase of breathing motion from 17.4 mm at t0 to 28.3 mm at t30 was seen. In five and two lesions, respectively, a drift of the mean tumor position greater than 3 mm and 5 mm was observed. A borderline significance was calculated for larger tumor position variability in midventilation phases compared with peak-ventilation phases of the breathing cycle ( p = 0.08). Conclusion: Treatment planning based on a single 4D-CT study is reliable for the majority of patients. Increased intrafractional uncertainties were seen for patients with poor pulmonary function and with tumors located in the lower lobe.