Mid-ventilation CT scan construction from four-dimensional respiration-correlated CT scans for radiotherapy planning of lung cancer patients

Wolthaus, J.; Schneider, Christoph; Sonke, Jan‐Jakob; Herk, Marcel van; Belderbos, J.; Rossi, Maddalena; Lebesque, Joos V.; Damen, E.

doi:10.1016/j.ijrobp.2006.04.031

Cited by 242 publications

(197 citation statements)

References 38 publications

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“…This reduces respiratory motion artifacts and yields a 3D image at different tumor positions within the respiratory cycle. The tumor position can be compared to the planning phase (e.g., midventilation CT phase) (3) . The tumor motion verification and the correction of the tumor baseline shift based on a registration between the planning 4D CT and 4D CBCT is made prior to delivery, thus improving the precision of dose delivery.…”

Section: Introductionmentioning

confidence: 99%

Difference in performance between 3D and 4D CBCT for lung imaging: a dose and image quality analysis

Thengumpallil

Smith

Monnin

et al. 2016

J Applied Clin Med Phys

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The study was to describe and to compare the performance of 3D and 4D CBCT imaging modalities by measuring and analyzing the delivered dose and the image quality. The 3D (Chest) and 4D (Symmetry) CBCT Elekta XVI lung IGRT protocols were analyzed. Dose profiles were measured with TLDs inside a dedicated phantom. The dosimetric indicator cone‐beam dose index (CBDI) was evaluated. The image quality analysis was performed by assessing the contrast transfer function (CTF), the noise power spectrum (NPS) and the noise‐equivalent quanta (NEQ). Artifacts were also evaluated by simulating irregular breathing variations. The two imaging modalities showed different dose distributions within the phantom. At the center, the 3D CBCT delivered twice the dose of the 4D CBCT. The CTF was strongly reduced by motion compared to static conditions, resulting in a CTF reduction of 85% for the 3D CBCT and 65% for the 4D CBCT. The amplitude of the NPS was two times higher for the 4D CBCT than for the 3D CBCT. In the presence of motion, the NEQ of the 4D CBCT was 50% higher than the 3D CBCT. In the presence of breathing irregularities, the 4D CBCT protocol was mainly affected by view‐aliasing artifacts, which were typically cone‐beam artifacts, while the 3D CBCT protocol was mainly affected by duplication artifacts. The results showed that the 4D CBCT ensures a reasonable dose and better image quality when moving targets are involved compared to 3D CBCT. Therefore, 4D CBCT is a reliable imaging modality for lung free‐breathing radiation therapy.PACS number(s): 87.57.C‐, 87.57.uq, 87.53.Ly

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Section: Introductionmentioning

confidence: 99%

Difference in performance between 3D and 4D CBCT for lung imaging: a dose and image quality analysis

Thengumpallil

Smith

Monnin

et al. 2016

J Applied Clin Med Phys

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“…Other breathing adaptation techniques include breath-hold techniques (voluntary and controlled) [41] and dynamic motion tracking in which the beam ''chases'' the target during its respiratory motion [12,24]. In the simpler end, motion inclusion techniques can be based on 4DCT scans to cover the target respiratory motion with treatment field margins on a patient individual basis [40].…”

Section: Discussionmentioning

confidence: 99%

The role of image guidance in respiratory gated radiotherapy

et al. 2008

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“…All ITV and MTV treatment plans were designed on the reference phase. Finally, a midV plan was generated on the midV phase as described by Wolthaus et al 5 The PTV midV for these plans was generated by expanding the GTV by 4.4–7.6 mm depending on the intrafractional motion observed in the 4DCT scan. All plans were designed for step‐and‐shoot IMRT with nine equidistant beams according to RTOG 1021 (3‐Fx) with a D 95 prescription of 18 Gy/Fx.…”

Section: Methodsmentioning

confidence: 99%

“…Although this straight‐forward approach guarantees target coverage for the whole breathing cycle (as long as the motion in treatment and imaging sessions coincide), the high‐dose volume is unnecessarily large and potentially toxic to surrounding normal tissues. A refinement of this approach is the midventilation (midV)/midposition (midP) approach 5 , 6 which is based on the average tumor position resulting in smaller target margins. Especially for hypofractionated treatment regimens, moving away from the very conservative ITV‐based PTV is expected to reduce toxicity.…”

Section: Introductionmentioning

confidence: 99%

Real‐time 4D dose reconstruction for tracked dynamic MLC deliveries for lung SBRT

et al. 2016

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PurposeThis study provides a proof of concept for real‐time 4D dose reconstruction for lung stereotactic body radiation therapy (SBRT) with multileaf collimator (MLC) tracking and assesses the impact of tumor tracking on the size of target margins.MethodsThe authors have implemented real‐time 4D dose reconstruction by connecting their tracking and delivery software to an Agility MLC at an Elekta Synergy linac and to their in‐house treatment planning software (TPS). Actual MLC apertures and (simulated) target positions are reported to the TPS every 40 ms. The dose is calculated in real‐time from 4DCT data directly after each reported aperture by utilization of precalculated dose‐influence data based on a Monte Carlo algorithm. The dose is accumulated onto the peak‐exhale (reference) phase using energy‐mass transfer mapping. To investigate the impact of a potentially reducible safety margin, the authors have created and delivered treatment plans designed for a conventional internal target volume (ITV) + 5 mm, a midventilation approach, and three tracking scenarios for four lung SBRT patients. For the tracking plans, a moving target volume (MTV) was established by delineating the gross target volume (GTV) on every 4DCT phase. These were rigidly aligned to the reference phase, resulting in a unified maximum GTV to which a 1, 3, or 5 mm isotropic margin was added. All scenarios were planned for 9‐beam step‐and‐shoot IMRT to meet the criteria of RTOG 1021 (3 × 18 Gy). The GTV 3D center‐of‐volume shift varied from 6 to 14 mm.ResultsReal‐time dose reconstruction at 25 Hz could be realized on a single workstation due to the highly efficient implementation of dose calculation and dose accumulation. Decreased PTV margins resulted in inadequate target coverage during untracked deliveries for patients with substantial tumor motion. MLC tracking could ensure the GTV target dose for these patients. Organ‐at‐risk (OAR) doses were consistently reduced by decreased PTV margins. The tracked MTV + 1 mm deliveries resulted in the following OAR dose reductions: lung V 20 up to 3.5%, spinal cord D 2 up to 0.9 Gy/Fx, and proximal airways D 2 up to 1.4 Gy/Fx.ConclusionsThe authors could show that for patient data at clinical resolution and realistic motion conditions, the delivered dose could be reconstructed in 4D for the whole lung volume in real‐time. The dose distributions show that reduced margins yield lower doses to healthy tissue, whilst target dose can be maintained using dynamic MLC tracking.

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Mid-ventilation CT scan construction from four-dimensional respiration-correlated CT scans for radiotherapy planning of lung cancer patients

Cited by 242 publications

References 38 publications

Difference in performance between 3D and 4D CBCT for lung imaging: a dose and image quality analysis

Difference in performance between 3D and 4D CBCT for lung imaging: a dose and image quality analysis

The role of image guidance in respiratory gated radiotherapy

Real‐time 4D dose reconstruction for tracked dynamic MLC deliveries for lung SBRT

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