scholarly journals Positional repeatability and variation in internal and external markers during volumetric-modulated arc therapy under end-exhalation breath-hold conditions for pancreatic cancer patients

2020 ◽  
Vol 61 (5) ◽  
pp. 755-765
Author(s):  
Makoto Sasaki ◽  
Mitsuhiro Nakamura ◽  
Tomohiro Ono ◽  
Ryo Ashida ◽  
Michio Yoshimura ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Cancer Patients ◽  
Volumetric Modulated Arc Therapy ◽  
Breath Hold ◽  
Reference Position ◽  
Marker Position ◽  
Positional Variation ◽  
Arc Therapy ◽  
The Difference ◽  
Internal Marker

Abstract The purpose of this study was to assess the positional repeatability of internal and external markers among multiple breath-hold (BH) sessions and evaluate the positional variation of these markers within BH sessions for volumetric-modulated arc therapy (VMAT) for pancreatic cancer patients. A total of 13 consecutive pancreatic cancer patients with an internal marker were enrolled. Single full-arc coplanar VMAT was delivered under end-exhalation BH conditions while monitoring the internal marker with kilovoltage (kV) X-ray fluoroscopy. Positional repeatability of the internal and external markers was determined by the difference between the reference and zero position in all BH sessions, and positional variation was defined by the displacement from the reference position in each BH session during megavolt beam delivery. The overall positional repeatability was 0.6 ± 1.5 mm in the X-axis for the centroid of the internal marker (CoIM), −0.1 ± 2.2 mm in the Y-axis for the CoIM, and 0.8 ± 2.2 mm for the external marker. The frequency of an internal marker position appearing > 2 mm from the reference position in the Y-axis, despite the external marker position being ≤2 mm from the reference position, ranged from 0.0 to 39.9% for each patient. Meanwhile, the proportion of sessions with positional variation ≤2 mm was 93.2 and 98.7% for the CoIM and external marker, respectively. External marker motion can be used as a surrogate for pancreatic tumor motion during BH-VMAT delivery; however, margins of ~5 mm were required to ensure positional repeatability.

scholarly journals Positional repeatability and variation in internal and external markers during volumetric-modulated arc therapy under end-exhalation breath-hold conditions for pancreatic cancer patients

2020 ◽  
Author(s):  
Makoto Sasaki ◽  
Mitsuhiro Nakamura ◽  
Tomohiro Ono ◽  
Ryo Ashida ◽  
Michio Yoshimura ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Cancer Patients ◽  
Volumetric Modulated Arc Therapy ◽  
Breath Hold ◽  
Maximum Displacement ◽  
Reference Position ◽  
Marker Position ◽  
Positional Variation ◽  
Arc Therapy ◽  
Internal Marker

Abstract Background: To assess the positional repeatability of internal and external markers among multiple breath-hold (BH) sessions and assess the positional variation of these markers within BH sessions for volumetric-modulated arc therapy (VMAT) for pancreatic cancer patients. Methods: A total of 13 consecutive pancreatic cancer patients with an internal marker were enrolled. Single full-arc coplanar VMAT was delivered under end-exhalation (EE) BH conditions, while monitoring the internal marker with kilovoltage (kV) X-ray fluoroscopy. Positional repeatability of internal and external markers was indicated by the difference between the reference marker position and the marker position at the beginning of each BH session, and positional variation was indicated by the maximum displacement of the marker during each BH session. Results: The overall positional repeatability was 0.6 ± 1.5 mm in the X-axis for the centroid of the internal marker (CoIM), -0.1 ± 2.2 mm in the Y-axis for the CoIM, and 0.8 ± 2.2 mm for the external marker. An internal marker position > 2 mm from the reference position in the Y-axis was observed in 19.1% of all BH sessions, despite the external marker position being ≤ 2 mm from the reference position. Meanwhile, the proportion of sessions with positional variation ≤ 2 mm was 93.2% and 98.7% for the CoIM and external marker, respectively. Conclusions: External marker motion can be used as a surrogate for pancreatic tumor motion during BH-VMAT; however, an optimal internal margin is required to ensure positional repeatability.

Stereotactic radiation treatment planning with volumetric modulated arc therapy: Impact of duodenal sparing on pancreatic tumor coverage.

2011 ◽  
Vol 29 (4_suppl) ◽  
pp. 301-301
Author(s):  
R. Kumar ◽  
J. Kang ◽  
J. M. Herman ◽  
R. Tuli ◽  
T. M. Pawlik ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Treatment Planning ◽  
Radiation Treatment ◽  
Volumetric Modulated Arc Therapy ◽  
High Dose ◽  
Stereotactic Radiation ◽  
Radiation Delivery ◽  
Delivery Times ◽  
Arc Therapy ◽  
The Difference

301 Background: Volumetric modulated arc therapy (VMAT) allows for intensity-modulated radiation delivery with faster treatment times and fewer delivered monitor units (MU). The dose-limiting structure for pancreatic stereotactic body radiation therapy (SBRT) is the duodenum. We evaluate VMAT dose distribution, delivery times, and the effect of duodenal sparing (DS) for pancreas SBRT. Methods: Plans of 15 patients with unresectable pancreatic cancer (14 head/1 tail) were selected. VMAT treatment planning with the “SmartArc” function of Pinnacle v. 8.9 was used to plan one fraction of 25 Gy to the PTV (gross tumor + 2 mm expansion) normalized to the 80% isodose line. Two VMAT SBRT plans were conducted for each case; the first did not attempt to spare the duodenum (non DS) while the second did (DS). Constraints were stomach/duodenum any point max <30 Gy (for DS plan), liver D50 < 5 Gy, ipsilateral kidney D25 < 5 Gy, cord Dmax < 5 Gy and stomach D4 < 22.5 Gy. Results: Gross tumor volume ranged from 58.4cm3 to 320.3 cm3. The average overlap volume between PTV and the duodenum was 8.4 cm3. In 10/15 non-DS plans, the duodenal Dmax exceeded 30 Gy. With DS optimization, only 1/15 plans exceeded the 30 Gy threshold. These differences were statistically significant (p<0.001). Typical MU and delivery times, as calculated by the planning software, were 5494 MU and 775 secs vs. 5296 MU and 703 secs for the DS and non-DS plans, respectively. The difference in delivery times was significant (p=0.01), but amounted to only 1.2 min on average. The average duodenal Dmax for non-DS plans was 30.4Gy, D4% was 23.4 Gy. With DS, the average Dmax was reduced to 28.1Gy and D4% to <19.7 Gy (p<0.001). As expected, VMAT plans with greater overlap between the duodenum and PTV had a higher duodenal Dmax. Conclusions: This study demonstrates the feasibility of VMAT for high-dose SBRT treatment of pancreatic cancer incorporating constraints to limit the dose to the duodenum. Future studies will evaluate whether VMAT with fractionated SBRT results in improved duodenal sparing more efficiently than traditional IMRT. No significant financial relationships to disclose.

scholarly journals Clinical Implications of Geometric and Dosimetric Uncertainties of Inter- and Intra-Fractional Movement during Volumetric Modulated Arc Therapy for Breast Cancer Patients

Cancers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1651
Author(s):  
Jason Joon Bock Lee ◽  
Ik Jae Lee ◽  
Yeonho Choi ◽  
Mi Jin Jeon ◽  
Il Hun Jung ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Patients ◽  
Volumetric Modulated Arc Therapy ◽  
Fold Increase ◽  
Cone Beam ◽  
Breath Hold ◽  
Breast Cancer Patients ◽  
Deep Inspiration Breath Hold ◽  
Arc Therapy ◽  
Pre Treatment

With the introduction of modern sophisticated radiotherapy (RT) techniques, the significance of accuracy has increased considerably. This study evaluated the necessity of pre-treatment and intra-fractional cone-beam computed tomography (CBCT) by analyzing inter- and intra-fractional CBCT images of breast cancer patients receiving RT. From 57 patients, 1206 pre-treatment CBCT and 1067 intra-fractional CBCT images were collected. Geometric movements of patients were measured quantitively in both inter- and intra-fractional CBCT, and changes in dosimetric parameters were evaluated in selected patients with extreme intra-fractional movement. For right-sided breast cancer patients, left-sided breast cancer patients treated using deep-inspiration breath hold (DIBH), and left-sided breast cancer patients treated using continuous positive airway pressure (CPAP), median inter-fractional deviations were 0.53 (range 0.06–2.98) cm, 0.66 (range 0.08–4.41) cm, and 0.69 (range 0.04–3.80) cm, and median intra-fractional deviations were 0.14 (range 0.00–0.62) cm, 0.23 (range 0.02–0.96) cm, and 0.24 (0.00–1.15) cm, respectively. Modified plans reflecting large changes in intra-fractional position in 10 selected cases revealed insufficient target coverage in seven cases and more than 20-fold increase in the volume of heart receiving at least 25 Gy in two cases. Intra-fractional verification, as well as pre-treatment verification, might be considered in patients using DIBH or CPAP.

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