An assessment of cone beam CT in the adaptive radiotherapy planning process for non-small-cell lung cancer patients

Duffton, A.; Harrow, Stephen; McJury, M.

doi:10.1259/bjr.20150492

Cited by 18 publications

(15 citation statements)

References 30 publications

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“…Michenzi et al assessed the accuracy of CB-CT for quantifying NSCLC tumor volume changes and reported a high correlation between CB-CT and the gold standard contrast-enhanced diagnostic CT ( 42 ). In our study, continuous tumor shrinkage during radiotherapy was detected to an extent in line with other studies reporting residual volumes of 49–75% and volume decreases of 1.2–1.5% per fraction ( 15 , 16 , 43 , 44 ). However, detection of treatment response and volume changes of mediastinal lymph node involvement was found to be challenging on CB-CT. Berkovic et al also emphasized that CB-CTs lack contrast to truly distinguish between lymph node and other surrounding tissue, which only allows for adaptation on the lung-lymph node boundary ( 17 ).…”

Section: Discussionsupporting

confidence: 92%

Cone-Beam-CT Guided Adaptive Radiotherapy for Locally Advanced Non-small Cell Lung Cancer Enables Quality Assurance and Superior Sparing of Healthy Lung

et al. 2020

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PurposeTo evaluate the potential of cone-beam-CT (CB-CT) guided adaptive radiotherapy (ART) for locally advanced non-small cell lung cancer (NSCLC) for sparing of surrounding organs-at-risk (OAR).Materials and MethodsIn 10 patients with locally advanced NSCLC, daily CB-CT imaging was acquired during radio- (n = 4) or radiochemotherapy (n = 6) for simulation of ART. Patients were treated with conventionally fractionated intensity-modulated radiotherapy (IMRT) with total doses of 60–66 Gy (pPlan) (311 fraction CB-CTs). OAR were segmented on every daily CB-CT and the tumor volumes were modified weekly depending on tumor changes. Doses actually delivered were recalculated on daily images (dPlan), and voxel-wise dose accumulation was performed using a deformable registration algorithm. For simulation of ART, treatment plans were adapted using the new contours and re-optimized weekly (aPlan).ResultsCB-CT showed continuous tumor regression of 1.1 ± 0.4% per day, leading to a residual gross tumor volume (GTV) of 65.3 ± 13.4% after 6 weeks of radiotherapy (p = 0.005). Corresponding PTVs decreased to 83.7 ± 7.8% (p = 0.005). In the actually delivered plans (dPlan), both conformity (p = 0.005) and homogeneity (p = 0.059) indices were impaired compared to the initial plans (pPlan). This resulted in higher actual lung doses than planned: V20Gy was 34.6 ± 6.8% instead of 32.8 ± 4.9% (p = 0.066), mean lung dose was 19.0 ± 3.1 Gy instead of 17.9 ± 2.5 Gy (p = 0.013). The generalized equivalent uniform dose (gEUD) of the lung was 18.9 ± 3.1 Gy instead of 17.8 ± 2.5 Gy (p = 0.013), leading to an increased lung normal tissue complication probability (NTCP) of 15.2 ± 13.9% instead of 9.6 ± 7.3% (p = 0.017). Weekly plan adaptation enabled decreased lung V20Gy of 31.6 ± 6.2% (−3.0%, p = 0.007), decreased mean lung dose of 17.7 ± 2.9 Gy (−1.3 Gy, p = 0.005), and decreased lung gEUD of 17.6 ± 2.9 Gy (−1.3 Gy, p = 0.005). Thus, resulting lung NTCP was reduced to 10.0 ± 9.5% (−5.2%, p = 0.005). Target volume coverage represented by conformity and homogeneity indices could be improved by weekly plan adaptation (CI: p = 0.007, HI: p = 0.114) and reached levels of the initial plan (CI: p = 0.721, HI: p = 0.333).ConclusionIGRT with CB-CT detects continuous GTV and PTV changes. CB-CT-guided ART for locally advanced NSCLC is feasible and enables superior sparing of healthy lung at high levels of plan conformity.

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Section: Discussionsupporting

confidence: 92%

Cone-Beam-CT Guided Adaptive Radiotherapy for Locally Advanced Non-small Cell Lung Cancer Enables Quality Assurance and Superior Sparing of Healthy Lung

et al. 2020

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“…tumour shrinkage, atelectasis or pleural effusion), or displacements of anatomical structures (e.g. a baseline shift of the tumour or a shift of the mediastinal structures) needing adaptations occur in approximately 12-27% of the patients during fractionated radiotherapy [1][2][3][4][5][6][7]. As a result, the delivered dose to the tumour or organs at risk may deviate from the planned dose and become unacceptable [4,8].…”

Section: Introductionmentioning

confidence: 99%

Automatic selection of lung cancer patients for adaptive radiotherapy using cone-beam CT imaging

Bosch

Öllers

Reymen

et al. 2017

Physics and Imaging in Radiation Oncology

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Background and purpose: Anatomical changes in non-small cell lung cancer (NSCLC) patients may lead to unacceptable treatment results, requiring adaptive radiotherapy (ART). The method proposed in this study describes the proof-of-principle to automatically select patients eligible for ART. Materials and methods: A method was developed flagging patients potentially requiring replanning using changes in density information between the planning CT and cone-beam CT (CBCT) scan. Potential candidates were defined based on anatomical changes in the primary tumour, mediastinum and a region including the lungs. In total, CBCTs of 70 NSCLC patients were retrospectively scored by two independent experts for the need of replanning using the clinical guidelines. Expert evaluation was used as benchmark for the automatic method and accuracy was quantified using a leave-one-out cross-validation strategy. Results: The automatic method correctly selected 79%, 71%, and 89% of the pre-defined candidates based on anatomical change in the tumour, mediastinum and lungs, respectively. The false positive rate was 27%, 9%, and 19% for these regions, respectively. If a single criterion ('flag') per patient is sufficient for replanning, the overall sensitivity was 89% with a false positive rate of 34%. Most common reasons for false positives were changes in breathing pattern or anatomical shifts outside the evaluated region. Excluding these reasons, the false positive rate dropped to 21% and the accuracy was almost similar to expert evaluation: overall sensitivity of approx. 95% with a false positive rate below 19%. Conclusion: Our method based on daily CBCT allows automatic selection of patients that should be investigated for treatment adaptation.

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“…Modern linear accelerators are integrated with a kilovoltage imaging system capable of cone-beam computed tomography (kV-CBCT), 1 which is increasingly utilized for verification of patient alignment, 2 evaluation of organ motion using pre-and posttreatment imaging, 3 and implementing adaptive radiotherapy planning. 4 It has also enabled sufficiently small margins for SBRT, often making dose escalation possible. 5,6 Onboard kV-CBCT is also increasingly being used for accurate patient setup in stereotactic radiosurgery (SRS).…”

Section: Introductionmentioning

confidence: 99%

Comprehensive radiation and imaging isocenter verification using NIPAM kV‐CBCT dosimetry

et al. 2020

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Purpose To develop and demonstrate a comprehensive method to directly measure radiation isocenter uncertainty and coincidence with the cone‐beam computed tomography (kV‐CBCT) imaging coordinate system that can be carried out within a typical quality assurance (QA) time slot. Methods An N‐isopropylacrylamide (NIPAM) three‐dimensional (3D) dosimeter for which dose is observed as increased electron density in kV‐CBCT is irradiated at eight couch/gantry combinations which enter the dosimeter at unique orientations. One to three CBCTs are immediately acquired, radiation profile is detected per beam, and displacement from imaging isocenter is quantified. We performed this test using a 5 mm diameter MLC field, and 7.5 and 4 mm diameter cones, delivering approximately 16 Gy per beam. CBCT settings were 1035–4050 mAs, 80–125 kVs, smooth filter, 1 mm slice thickness. The two‐dimensional (2D) displacement of each beam from the imaging isocenter was measured within the planning system, and Matlab code developed in house was used to quantify relevant parameters based on the actual beam geometry. Detectability of the dose profile in the CBCT was quantified as the contrast‐to‐noise ratio (CNR) of the irradiated high‐dose regions relative to the surrounding background signal. Our results were compared to results determined by the traditional Winston‐Lutz test, film‐based “star shots,” and the vendor provided machine performance check (MPC). The ability to detect alignment errors was demonstrated by repeating the test after applying a 0.5 mm shift to the MLCs in the direction of leaf travel. In addition to radiation isocenter and coincidence with CBCT origin, the analysis also calculated the actual gantry and couch angles per beam. Results Setup, MV irradiation, and CBCT readout were carried out within 38 min. After subtracting the background signal from the pre‐CBCT, the CNR of the dosimeter signal from the irradiation with the MLCs (125 kVp, 1035 mAs, n = 3), 7.5 mm cone (125 kVp, 1035 mAs, n = 3), and 4 mm cone (80 kVp, 4050 mAs, n = 1) was 5.4, 5.9, and 2.9, respectively. The minimum radius that encompassed all beams calculated using the automated analysis was 0.38, 0.48, and 0.44 mm for the MLCs, 7.5 mm cone, and 4 mm cone, respectively. When determined manually, these values were slightly decreased at 0.28, 0.41, and 0.40 mm. For comparison, traditional Winston‐Lutz test with MLCs and MPC measured the 3D isocenter radius to be 0.24 mm. Lastly, when a 0.5 mm shift to the MLCs was applied, the smallest radius that intersected all beams increased from 0.38 to 0.90 mm. The mean difference from expected value for gantry angle was 0.19 ± 0.29°, 0.17 ± 0.23°, and 0.12 ± 0.14° for the MLCs, 7.5 mm cone, and 4 mm cone, respectively. The mean difference from expected for couch angle was −0.07 ± 0.28°, −0.08 ± 0.66°, and 0.04 ± 0.25°. Conclusions This work demonstrated the feasibility of a comprehensive isocenter verification using a NIPAM dosimeter with sub‐mm accuracy which incorporates evaluation of coincidence with imaging coordin...

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An assessment of cone beam CT in the adaptive radiotherapy planning process for non-small-cell lung cancer patients

Cited by 18 publications

References 30 publications

Cone-Beam-CT Guided Adaptive Radiotherapy for Locally Advanced Non-small Cell Lung Cancer Enables Quality Assurance and Superior Sparing of Healthy Lung

Cone-Beam-CT Guided Adaptive Radiotherapy for Locally Advanced Non-small Cell Lung Cancer Enables Quality Assurance and Superior Sparing of Healthy Lung

Automatic selection of lung cancer patients for adaptive radiotherapy using cone-beam CT imaging

Comprehensive radiation and imaging isocenter verification using NIPAM kV‐CBCT dosimetry

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