Accumulation of the delivered treatment dose in volumetric modulated arc therapy with breath‐hold for pancreatic cancer patients based on daily cone beam computed tomography images with limited field‐of‐view

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.

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

10.21203/rs.3.rs-19263/v1 ◽

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.

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

Cancers ◽

10.3390/cancers13071651 ◽

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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Time-Resolved Versus Integrated Transit Planar Dosimetry for Volumetric Modulated Arc Therapy

Technology in Cancer Research & Treatment ◽

10.1177/1533034615617668 ◽

2016 ◽

Vol 15 (6) ◽

pp. NP79-NP87 ◽

Cited By ~ 12

Author(s):

L.C.G.G. Persoon ◽

M. Podesta ◽

S.M.J.J.G. Nijsten ◽

E.G.C. Troost ◽

F. Verhaegen

Keyword(s):

Computed Tomography ◽

Pleural Effusion ◽

Tumor Regression ◽

Control Point ◽

Volumetric Modulated Arc Therapy ◽

Time Resolved ◽

Treatment Dose ◽

Arc Therapy ◽

Geometrical Change ◽

Radiation Treatments

Purpose: It is desirable that dosimetric deviations during radiation treatments are detected. Integrated transit planar dosimetry is commonly used to evaluate external beam treatments such as volumetric-modulated arc therapy. This work focuses on patient geometry changes which result in differences between the planned and the delivered radiation dose. Integrated transit planar dosimetry will average out some deviations. Novel time-resolved transit planar dosimetry compares the delivered dose of volumetric-modulated arc therapy to the planned dose at various time points. Four patient cases are shown where time-resolved transit planar dosimetry detects patient geometry changes during treatment. Methods: A control point to control point comparison between the planned dose and the treatment dose of volumetric-modulated arc therapy beams is calculated using the planning computed tomography and the kV cone-beam computed tomography of the day and evaluated with a time-resolved γ function. Results were computed for 4 patients treated with volumetric-modulated arc therapy, each showing an anatomical change: pleural effusion, rectal gas pockets, and tumor regression. Results: In all cases, the geometrical change was detected by time-resolved transit planar dosimetry, whereas integrated transit planar dosimetry showed minor or no indication of the dose discrepancy. Both tumor regression cases were detected earlier in the treatment with time-resolved planar dosimetry in comparison to integrated transit planar dosimetry. The pleural effusion and the gas pocket were detected exclusively with time-resolved transit planar dosimetry. Conclusions: Clinical cases were presented in this proof-of-principle study in which integrated transit planar dosimetry did not detect dosimetrically relevant deviations to the same extent time-resolved transit planar dosimetry was able to. Time-resolved transit planar dosimetry also provides results that can be presented as a function of arc delivery angle allowing easier interpretation compared to integrated transit planar dosimetry.

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