Planning 4-dimensional computed tomography (4DCT) cannot adequately represent daily intrafractional motion of abdominal tumors.

To evaluate whether planning 4-dimensional computed tomography (4DCT) can adequately represent daily motion of abdominal tumors in regularly fractionated and stereotactic body radiation therapy (SBRT) patients. Intrafractional tumor motion of 10 patients with abdominal tumors (4 pancreas-fractionated and 6 liver-stereotactic patients) with implanted fiducials was measured based on daily orthogonal fluoroscopic movies over 38 treatment fractions. The needed internal margin for at least 90% of tumor coverage was calculated based on a 95th and fifth percentile of daily 3-dimensional tumor motion. The planning internal margin was generated by fusing 4DCT motion from all phase bins. The disagreement between needed and planning internal margin was analyzed fraction by fraction in 3 motion axes (superior-inferior [SI], anterior-posterior [AP], and left-right [LR]). The 4DCT margin was considered as an overestimation/underestimation of daily motion when disagreement exceeded at least 3 mm in the SI axis and/or 1.2 mm in the AP and LR axes (4DCT image resolution). The underlying reasons for this disagreement were evaluated based on interfractional and intrafractional breathing variation. The 4DCT overestimated daily 3-dimensional motion in 39% of the fractions in 7 of 10 patients and underestimated it in 53% of the fractions in 8 of 10 patients. Median underestimation was 3.9 mm, 3.0 mm, and 1.7 mm in the SI axis, AP axis, and LR axis, respectively. The 4DCT was found to capture irregular deep breaths in 3 of 10 patients, with 4DCT motion larger than mean daily amplitude by 18 to 21 mm. The breathing pattern varied from breath to breath and day to day. The intrafractional variation of amplitude was significantly larger than intrafractional variation (2.7 mm vs 1.3 mm) in the primary motion axis (ie, SI axis). The SBRT patients showed significantly larger intrafractional amplitude variation than fractionated patients (3.0 mm vs 2.1 mm, P<.05). It may not be appropriate to use 4DCT without monitoring of patient motion on a regular basis for patients with abdominal tumors, especially SBRT patients.

Ge J ，Santanam L ，Noel C ，Parikh PJ ... -  《-》

Tumor motion changes in stereotactic body radiotherapy for liver tumors: an evaluation based on four-dimensional cone-beam computed tomography and fiducial markers.

Shimohigashi Y ，Toya R ，Saito T ，Ikeda O ，Maruyama M ，Yonemura K ，Nakaguchi Y ，Kai Y ，Yamashita Y ，Oya N ，Araki F ... -  《Radiation Oncology》

Evaluation of the intra- and interfractional tumor motion and variability by fiducial-based real-time tracking in liver stereotactic body radiation therapy.

Tumor motion amplitude varies during treatment. The purpose of the study was to evaluate the intra- and interfraction tumor motion and variability in patients with liver cancer treated with fiducial-based real-time tracking stereotactic body radiotherapy (SBRT). Fourteen liver patients were treated with SBRT using a CyberKnife. Two to four fiducial markers implanted near the tumor were used for real-time monitoring using the Synchrony system. The tumor motion information during treatment was extracted from the log files recorded by the Synchrony system. Logfile-based amplitudes in the superior-posterior (SI), left-right (LR) and anterior-posterior (AP) directions were compared to the 4DCT-based amplitudes. The intra- and interfraction amplitude variations and the incidence of baseline shifts were analyzed for 66 fractions administered to 14 patients. The median (range) logfile-based liver motion amplitudes for all patients were 11.9 (5.1-17.3) mm, 1.3 (0.4-4) mm and 3.8 (0.9-7.7) mm in the SI, LR and AP directions, respectively. Compared with the logfile-based amplitude, the 4DCT-based amplitude was underestimated (P < 0.05). The median (range) intra- and interfraction liver motion amplitude variations were 4.3 (1.6-6.0) mm (SI), 0.5 (0.2-2.2) mm(LR) and 1.5 (0.3-3.3) mm (AP) and 1.7 (0.5-4.6) mm (SI), 0.3 (0.1-3.0) mm (LR) and 0.7 (0.3-2.7) mm (AP), respectively. Baseline shifts exceeding 2 mm, 3 mm and 5 mm were observed in 27.3%, 7.6% and 3% of the measurements, respectively, within 10 min, and in 66.7%, 38.1% and 19%, respectively, within 30 min for the square root of the sum of the squares of the distances in the SI, LR and AP directions (3D). The tumor motion amplitude was found to be correlated with the baseline shift. Most patients showed significant intra- and interfraction liver motion amplitude variations over the entire course of radiation. More caution is needed for patients with large tumor motion amplitudes.

Liang Z ，Liu H ，Xue J ，Hu B ，Zhu B ，Li Q ，Zhang S ，Wu G ... -  《Journal of Applied Clinical Medical Physics》

Differences in respiratory-induced pancreatic tumor motion between 4D treatment planning CT and daily cone beam CT, measured using intratumoral fiducials.

Lens E ，van der Horst A ，Kroon PS ，van Hooft JE ，Dávila Fajardo R ，Fockens P ，van Tienhoven G ，Bel A ... -  《-》

Inter- and Intrafractional Variation in the 3-Dimensional Positions of Pancreatic Tumors Due to Respiration Under Real-Time Monitoring.

To quantify the 3-dimensional pancreatic tumor motion during the overall treatment course using real-time orthogonal kilovoltage X-ray imaging. This study included 10 patients with pancreatic cancer who underwent 6-port static intensity modulated radiation therapy with real-time tumor tracking in 15 fractions, except for 1 patient (5 fractions). The tumor and abdominal wall positions were acquired simultaneously during the overall treatment course. Then the tumor motion amplitude and reference positions were determined. The mean tumor amplitudes were 4.9, 6.5, and 13.4 mm in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions, respectively. The intrafractional variations of the reference tumor position were up to 5.4, 10.2, and 10.7 mm in the LR, AP, and SI directions, and those of the reference abdominal position were up to 10.5 mm. The reference tumor position drifted significantly in the AP and SI directions after 10 minutes, and that of abdominal wall motion drifted during the first 15 minutes (P<.05). The interfractional variation of the reference tumor position after setup correction, based on bony structures, was up to 8.9, 9.8, and 11.0 mm in the LR, AP, and SI directions, respectively. Appropriate respiratory motion management techniques should be applied for the accurate localization of pancreatic tumors.

Akimoto M ，Nakamura M ，Nakamura A ，Mukumoto N ，Kishi T ，Goto Y ，Mizowaki T ，Hiraoka M ... -  《-》