Reproducibility of surface-based deep inspiration breath-hold technique for lung stereotactic body radiotherapy on a closed-bore gantry linac.

Background and purpose: Tumor motion and delivery efficiency are two main challenges of lung stereotactic body radiotherapy (SBRT). The present work implemented the deep inspiration breath hold technique (DIBH) with surface guided radiation therapy (SGRT) on closed-bore linacs and investigated the correlation between SGRT data and internal target position. Materials and methods: Thirteen lung SBRT patients treated in DIBH using a closed-bore gantry linac and a ring-mounted SGRT system were retrospectively analysed. Visual coaching was used to achieve DIBH with a ± 1 mm threshold window in the anterior-posterior direction. Three kV-CBCTs were added to the treatment workflow and examined offline to verify intra-fraction tumor position. Surface-based DIBH was analysed using SGRT treatment reports and an in-house python script. Data from 73 treatment sessions and 175 kV-CBCTs were studied. Correlations between target and surface positions were studied with Linear Mixed Models. Results: Median intra-fraction tumor motion was 0.8 mm (range: 0.7-1.3 mm) in the anterior-posterior direction, 1.2 mm (range: 1-1.7 mm) in the superior-inferior direction, and 1 mm (range: 0.7-1.1 mm) in the left-right direction, with rotations of <1° (range: 0.6°-1.1°) degree in all three directions. Planned target volumes and healthy lung volumes receiving 12.5 Gy and 13.5 Gy were reduced on average by 67% and 54%, respectively. Conclusions: Lung SBRT in DIBH with the ring-mounted SGRT system proved reproducible. The surface monitoring provided by SGRT was found to be a reliable surrogate for internal target motion. Moreover, the implementation of DIBH technique helped reduce target volumes and lung doses.

Investigating the robustness of the AlignRT InBore™ co-calibration process and determining the overall tracking errors.

OBJECTIVE: To determine the overall tracking errors inherent to the co-calibration procedure of AlignRT InBore™'s (Vision RT Ltd., London, UK) ceiling-mounted and ring-mounted cameras. METHODS: Extrinsic calibration errors related to the mismatch between ceiling and InBore cameras' isocentres and treatment isocentre were determined using MV images and the SRS package and compared to traditional plate-based error. Next, using a realistic anthropomorphic female phantom, intrinsic calibration errors were determined while varying source-skin distance (80 to 100 cm), breast board inclination (0° to 12.5°), room lighting conditions (0 to 258 lx), skin colour (dark, white and natural skin colour), and pod occlusion. RESULTS: MV images of the cube proved plate-based calibration to suffer from large errors especially in the vertical direction (up to 2 mm). Intrinsic calibration errors were considerably lower. Indeed, RTD values of ceiling and InBore cameras showed little variability with isocentre depth (within 1.0 mm/0.4°), surface orientation and breast board inclination (within 0.7 mm/0.3°), changing lighting conditions (within 0.1 mm/0.2°), skin colour/tone (within 0.3 mm/0.3°) and camera pod occlusion (within 0.3 mm/0.2°). CONCLUSION: The use of MV-images proved critical to maintain co-calibrating errors of ceiling and InBore cameras to Halcyon's treatment isocentre below 1 mm.

Commissioning and performance testing of the first prototype of AlignRT InBore™ a Halcyon™ and Ethos™-dedicated surface guided radiation therapy platform.

PURPOSE: To commission and assess the performance of AlignRT InBore™, a Halcyon™ and Ethos™-dedicated Surface Guided Radiation Therapy (SGRT) platform which combines ceiling-mounted cameras for patient setup and bore-mounted cameras for in-bore tracking. METHODS: To check the potential impact of InBore™ cameras on dose delivery, 16 SRS, H&N, breast and pelvis patients' quality assurance (QA) treatment plans were measured with/without AlignRT InBore™ and using ArcCHECK® and SRS MapCHECK®. Impact on image quality was determined using Catphan® 540 phantom and considering all available MV and CBCT protocols (head, breast, chest and pelvis). The stability, accuracy and overall performance of AlignRT InBore™ was assessed using an MV Cube and anthropomorphic phantoms. RESULTS: Comparison of 2D dose distributions with/without AlignRT InBore™ showed no impact on treatment delivery for all 16 QA checks (p-value > 0.25). 2D and CBCT images showed no artefacts or change in the contrast-to-noise ratio, resolution and noise values measured with Catphan® 540. Anti-collision sensors were unaffected by the bore-mounted cameras. Additionally, AlignRT InBore™ cameras allowed for motion detection with sub-0.5 mm accuracy and sub-0.4 mm stability with surface coverage of >50 × 60 × 35 cc. Accurate transition (sub-0.3 mm) from virtual to treatment isocentres was achieved. Finally, Halcyon™ rotations during CBCT and beam delivery resulted in limited camera vibrations with translation uncertainty <0.5 mm in left-right and anterior-posterior directions and <0.1 mm in head-feet direction. CONCLUSION: AlignRT InBore™ provides SGRT setup and intrafraction monitoring capabilities with a performance comparable to standard SGRT solutions while having no adverse effect on Halcyon™.

Epithelioid hemangioendothelioma of the spine treated with RapidArc volumetric-modulated radiotherapy.

Radiotherapy for epithelioid hemangioendothelioma (EHE) using volumetric intensity-modulated arc radiotherapy (VMAT). A 48-year-old woman was referred for curative irradiation of a vertebral EHE after failure of surgery. A comparison between VMAT and conventional conformal tridimensional (3D) dosimetry was performed and potential advantage of VMAT for sparing critical organs from irradiation's side effects was discussed. The total delivered dose on the planning target volume was 54 Gy in 27 fractions. The patient was finally treated with VMAT. The tolerance was excellent. There was no acute toxicity, including no increase in pain. With a follow-up of 18 months, no delayed toxicity was reported. The clinical response consisted of a decrease in the dorsal pain. The Dmax for the spinal cord was reduced from 55 Gy (3D-radiotherapy [RT]) (which would be an unacceptable dose to the spine because of the risk of myelopathy) to 42.8 Gy (VMAT), which remains below the recommended dose threshold (45 Gy). The dose delivered to 20% of organ volume (D20) was reduced from 47 Gy (3D-RT) to 3 Gy (VMAT) for the spinal cord. The study shows that VMAT allows the delivery of curative treatment for vertebral EHEs because of critical organ sparing.

Correlation of dosimetric parameters obtained with the analytical anisotropic algorithm and toxicity of chest chemoradiation in lung carcinoma.

The purpose of this study was to analyze and revisit toxicity related to chest chemoradiotherapy and to correlate these side effects with dosimetric parameters obtained using analytical anisotropic algorithm (AAA) in locally unresectable advanced lung cancer. We retrospectively analyzed data from 47 lung cancer patients between 2005 and 2008. All received conformal 3D radiotherapy using high-energy linear accelerator plus concomitant chemotherapy. All treatment planning data were transferred into Eclipse 8.05 (Varian Medical Systems, Palo Alto, CA) and dosimetric calculations were performed using AAA. Thirty-three patients (70.2%) developed acute pneumopathy after radiotherapy (grades 1 and 2). One patient (2.1%) presented with grade 3 pneumopathy. Thirty-one (66%) presented with grades 1-2 lung fibrosis, and 1 patient presented with grade 3 lung fibrosis. Thirty-four patients (72.3%) developed grade 1-2 acute oesophagic toxicity. Four patients (8.5%) presented with grades 3 and 4 dysphagia, necessitating prolonged parenteral nutrition. Median prescribed dose was 64 Gy (range 50-74) with conventional fractionation (2 Gy per fraction). Dose-volume constraints were respected with a median V20 of 23.5% (maximum 34%) and a median V30 of 17% (maximum 25%). The median dose delivered to healthy contralateral lung was 13.1 Gy (maximum 18.1 Gy). At univariate analysis, larger planning target volume and V20 were significantly associated with the probability of grade ≥2 radiation-induced pneumopathy (p = 0.022 and p = 0.017, respectively). No relation between oesophagic toxicity and clinical/dosimetric parameters could be established. Using AAA, the present results confirm the predictive value of the V20 for lung toxicity as already demonstrated with the conventional pencil beam convolution approach.

Feasibility and efficacy of high-dose three-dimensional-conformal radiotherapy in cirrhotic patients with small-size hepatocellular carcinoma non-eligible for curative therapies--mature results of the French Phase II RTF-1 trial.

PURPOSE: Hepatocellular carcinoma (HCC) is a poor prognosis tumor, and only 20% of patients will benefit from curative therapies (surgery, liver transplantation, percutaneous ablation). Although conventional radiotherapy has been traditionally regarded as inefficient and toxic for cirrhotic patients, three-dimensional conformal radiotherapy (3DCRT) has provided promising preliminary data for the treatment of HCC. METHODS AND MATERIALS: Prospective phase II trial including Child-Pugh A/B cirrhotic patients with small-size HCC (1 nodule < or =5 cm, or 2 nodules < or =3 cm) nonsuitable for curative treatments, to assess tolerance and efficacy of high-dose (66 Gy, 2 Gy/fraction) 3DCRT. RESULTS: Twenty-seven patients were enrolled. Among the 25 assessable patients, tumor response was observed for 23 patients (92%), with complete response for 20 patients (80%), and partial response for 3 patients (12%). Stable disease was observed in 2 patients (8%). Grade 4 toxicities occurred in 2 of 11 (22%) Child-Pugh B patients only. Child-Pugh A patients tolerated treatment well, and 3/16 (19%) developed asymptomatic Grade 3 toxicities. CONCLUSION: High-dose 3DCRT is a noninvasive, well-tolerated modality that is highly suitable for the treatment of small HCCs in cirrhotic patients, with promising results. However, additional trials are needed to optimize this technique and formally compare it with the usual curative approaches.

Potential benefits of using non coplanar field and intensity modulated radiation therapy to preserve the heart in irradiation of lung tumors in the middle and lower lobes.

PURPOSE: Investigate whether the use of non coplanar fields and intensity modulated radiation therapy (IMRT) reduces the dose to the heart, in irradiation of middle and lower lung tumors. MATERIALS AND METHODS: Four plans are compared on 10 CT scans: (1) a reference plan, corresponding to coplanar plan of 3D conformal radiotherapy (3DCRT); (2) a 3DCRT(noncopl) plan, differing from reference plan by the change of one field in non coplanar fields; (3) an IMRT(copl) plan optimized on the same coplanar plan as reference plan; and (4) an IMRT(noncopl) plan optimized on the same non coplanar beams as 3DCRT(noncopl) plan. The equivalent uniform dose (EUD) for PTV was 74 Gy in 37 fractions. RESULTS: In all plans, the 95% isodose surface covers at least 99% of the PTV with very similar conformity index values. A significant reduction in EUD, V30, V40 and V50 is observed for heart when either non coplanar fields or IMRT is used. IMRT also reduces the lung NTCP, V5, V13, V20 and V30 values and esophagus NTCP. CONCLUSION: Both the use of non coplanar fields and IMRT dramatically reduces the dose received by the heart. The largest benefit is seen when the two techniques are combined.