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Title: SU-G-JeP2-08: Image-Guided Radiation Therapy Using Synthetic CTs in Brain Cancer

Abstract

Purpose: Synthetic-CTs(synCTs) are essential for MR-only treatment planning. However, the performance of synCT for IGRT must be carefully assessed. This work evaluated the accuracy of synCT and synCT-generated DRRs and determined their performance for IGRT in brain cancer radiation therapy. Methods: MR-SIM and CT-SIM images were acquired of a novel anthropomorphic phantom and a cohort of 12 patients. SynCTs were generated by combining an ultra-short echo time (UTE) sequence with other MRI datasets using voxel-based weighted summation. For the phantom, DRRs from synCT and CT were compared via bounding box and landmark analysis. Planar (MV/KV) and volumetric (CBCT) IGRT performance were evaluated across several platforms. In patients, retrospective analysis was conducted to register CBCTs (n=34) to synCTs and CTs using automated rigid registration in the treatment planning system using whole brain and local registration techniques. A semi-automatic registration program was developed and validated to rigidly register planar MV/KV images (n=37) to synCT and CT DRRs. Registration reproducibility was assessed and margin differences were characterized using the van Herk formalism. Results: Bounding box and landmark analysis of phantom synCT DRRs were within 1mm of CT DRRs. Absolute 2D/2D registration shift differences ranged from 0.0–0.7mm for phantom DRRs on all treatment platformsmore » and 0.0–0.4mm for volumetric registrations. For patient planar registrations, mean shift differences were 0.4±0.5mm (range: −0.6–1.6mm), 0.0±0.5mm, (range: −0.9–1.2mm), and 0.1±0.3mm (range: −0.7–0.6mm) for the superior-inferior(S-I), left-right(L–R), and anterior-posterior(A-P) axes, respectively. Mean shift differences in volumetric registrations were 0.6±0.4mm (range: −0.2–1.6mm), 0.2±0.4mm (range: −0.3–1.2mm), and 0.2±0.3mm (range: −0.2–1.2mm) for S-I, L–R, and A–P axes, respectively. CT-SIM and synCT derived margins were within 0.3mm. Conclusion: DRRs generated via synCT agreed well with CT-SIM. Planar and volumetric registrations to synCT-derived targets were comparable to CT. This validation is the next step toward clinical implementation of MR-only planning for the brain. The submitting institution has research agreements with Philips Healthcare. Research sponsored by a Henry Ford Health System Internal Mentored Grant.« less

Authors:
;  [1];  [2]; ; ;  [3]
  1. Wayne State School of Medicine, Detroit, MI (United States)
  2. (United States)
  3. Henry Ford Health System, Detroit, MI (United States)
Publication Date:
OSTI Identifier:
22649374
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; BRAIN; COMPUTERIZED TOMOGRAPHY; NEOPLASMS; NMR IMAGING; PATIENTS; PERFORMANCE; PHANTOMS; PLANNING; RADIOTHERAPY

Citation Formats

Price, R.G., Glide-Hurst, C., Henry Ford Health System, Detroit, MI, Kim, J., Zheng, W., and Chetty, I.J. SU-G-JeP2-08: Image-Guided Radiation Therapy Using Synthetic CTs in Brain Cancer. United States: N. p., 2016. Web. doi:10.1118/1.4957028.
Price, R.G., Glide-Hurst, C., Henry Ford Health System, Detroit, MI, Kim, J., Zheng, W., & Chetty, I.J. SU-G-JeP2-08: Image-Guided Radiation Therapy Using Synthetic CTs in Brain Cancer. United States. doi:10.1118/1.4957028.
Price, R.G., Glide-Hurst, C., Henry Ford Health System, Detroit, MI, Kim, J., Zheng, W., and Chetty, I.J. 2016. "SU-G-JeP2-08: Image-Guided Radiation Therapy Using Synthetic CTs in Brain Cancer". United States. doi:10.1118/1.4957028.
@article{osti_22649374,
title = {SU-G-JeP2-08: Image-Guided Radiation Therapy Using Synthetic CTs in Brain Cancer},
author = {Price, R.G. and Glide-Hurst, C. and Henry Ford Health System, Detroit, MI and Kim, J. and Zheng, W. and Chetty, I.J.},
abstractNote = {Purpose: Synthetic-CTs(synCTs) are essential for MR-only treatment planning. However, the performance of synCT for IGRT must be carefully assessed. This work evaluated the accuracy of synCT and synCT-generated DRRs and determined their performance for IGRT in brain cancer radiation therapy. Methods: MR-SIM and CT-SIM images were acquired of a novel anthropomorphic phantom and a cohort of 12 patients. SynCTs were generated by combining an ultra-short echo time (UTE) sequence with other MRI datasets using voxel-based weighted summation. For the phantom, DRRs from synCT and CT were compared via bounding box and landmark analysis. Planar (MV/KV) and volumetric (CBCT) IGRT performance were evaluated across several platforms. In patients, retrospective analysis was conducted to register CBCTs (n=34) to synCTs and CTs using automated rigid registration in the treatment planning system using whole brain and local registration techniques. A semi-automatic registration program was developed and validated to rigidly register planar MV/KV images (n=37) to synCT and CT DRRs. Registration reproducibility was assessed and margin differences were characterized using the van Herk formalism. Results: Bounding box and landmark analysis of phantom synCT DRRs were within 1mm of CT DRRs. Absolute 2D/2D registration shift differences ranged from 0.0–0.7mm for phantom DRRs on all treatment platforms and 0.0–0.4mm for volumetric registrations. For patient planar registrations, mean shift differences were 0.4±0.5mm (range: −0.6–1.6mm), 0.0±0.5mm, (range: −0.9–1.2mm), and 0.1±0.3mm (range: −0.7–0.6mm) for the superior-inferior(S-I), left-right(L–R), and anterior-posterior(A-P) axes, respectively. Mean shift differences in volumetric registrations were 0.6±0.4mm (range: −0.2–1.6mm), 0.2±0.4mm (range: −0.3–1.2mm), and 0.2±0.3mm (range: −0.2–1.2mm) for S-I, L–R, and A–P axes, respectively. CT-SIM and synCT derived margins were within 0.3mm. Conclusion: DRRs generated via synCT agreed well with CT-SIM. Planar and volumetric registrations to synCT-derived targets were comparable to CT. This validation is the next step toward clinical implementation of MR-only planning for the brain. The submitting institution has research agreements with Philips Healthcare. Research sponsored by a Henry Ford Health System Internal Mentored Grant.},
doi = {10.1118/1.4957028},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • Purpose: The development of synthetic computed tomography (CT) (synCT) derived from magnetic resonance (MR) images supports MR-only treatment planning. We evaluated the accuracy of synCT and synCT-generated digitally reconstructed radiographs (DRRs) relative to CT and determined their performance for image guided radiation therapy (IGRT). Methods and Materials: Magnetic resonance simulation (MR-SIM) and CT simulation (CT-SIM) images were acquired of an anthropomorphic skull phantom and 12 patient brain cancer cases. SynCTs were generated using fluid attenuation inversion recovery, ultrashort echo time, and Dixon data sets through a voxel-based weighted summation of 5 tissue classifications. The DRRs were generated from the phantommore » synCT, and geometric fidelity was assessed relative to CT-generated DRRs through bounding box and landmark analysis. An offline retrospective analysis was conducted to register cone beam CTs (n=34) to synCTs and CTs using automated rigid registration in the treatment planning system. Planar MV and KV images (n=37) were rigidly registered to synCT and CT DRRs using an in-house script. Planar and volumetric registration reproducibility was assessed and margin differences were characterized by the van Herk formalism. Results: Bounding box and landmark analysis of phantom synCT DRRs were within 1 mm of CT DRRs. Absolute planar registration shift differences ranged from 0.0 to 0.7 mm for phantom DRRs on all treatment platforms and from 0.0 to 0.4 mm for volumetric registrations. For patient planar registrations, the mean shift differences were 0.4 ± 0.5 mm (range, −0.6 to 1.6 mm), 0.0 ± 0.5 mm (range, −0.9 to 1.2 mm), and 0.1 ± 0.3 mm (range, −0.7 to 0.6 mm) for the superior-inferior (S-I), left-right (L-R), and anterior-posterior (A-P) axes, respectively. The mean shift differences in volumetric registrations were 0.6 ± 0.4 mm (range, −0.2 to 1.6 mm), 0.2 ± 0.4 mm (range, −0.3 to 1.2 mm), and 0.2 ± 0.3 mm (range, −0.2 to 1.2 mm) for the S-I, L-R, and A-P axes, respectively. The CT-SIM and synCT derived margins were <0.3 mm different. Conclusion: DRRs generated by synCT were in close agreement with CT-SIM. Planar and volumetric image registrations to synCT-derived targets were comparable with CT for phantom and patients. This validation is the next step toward MR-only planning for the brain.« less
  • Purpose: Evaluate a large-field MRI phantom for assessment of geometric distortion in whole-body MRI for real-time MR guided radiation therapy. Methods: A prototype CIRS large-field MRI distortion phantom consisting of a PMMA cylinder (33 cm diameter, 30 cm length) containing a 3D-printed orthogonal grid (3 mm diameter rods, 20 mm apart), was filled with 6 mM NiCl{sub 2} and 30 mM NaCl solution. The phantom was scanned at 1.5T and 3.0T on a GE HDxt and Discovery MR750, respectively, and at 0.35T on a ViewRay system. Scans were obtained with and without 3D distortion correction to demonstrate the impact ofmore » such corrections. CT images were used as a reference standard for analysis of geometric distortion, as determined by a fully automated gradient-search method developed in Matlab. Results: 1,116 grid points distributed throughout a cylindrical volume 28 cm in diameter and 16 cm in length were identified and analyzed. With 3D distortion correction, average/maximum displacements for the 1.5, 3.0, and 0.35T systems were 0.84/2.91, 1.00/2.97, and 0.95/2.37 mm, respectively. The percentage of points with less than (1.0, 1.5, 2.0 mm) total displacement were (73%, 92%, 97%), (54%, 85%, 97%), and (55%, 90%, 99%), respectively. A reduced scan volume of 20 × 20 × 10 cm{sup 3} (representative of a head and neck scan volume) consisting of 420 points was also analyzed. In this volume, the percentage of points with less than (1.0, 1.5, 2.0 mm) total displacement were (90%, 99%, 100%), (63%, 95%, 100%), and (75%, 96%, 100%), respectively. Without 3D distortion correction, average/maximum displacements were 1.35/3.67, 1.67/4.46, and 1.51/3.89 mm, respectively. Conclusion: The prototype large-field MRI distortion phantom and developed software provide a thorough assessment of 3D spatial distortions in MRI. The distortions measured were acceptable for RT applications, both for the high field strengths and the system configuration developed by ViewRay.« less
  • Purpose: To present local control, complications, and cosmetic outcomes of intraoperative radiation therapy (IORT) for early breast cancer, as well as technical aspects related to the use of a nondedicated linear accelerator. Methods and Materials: This prospective trial began in May of 2004. Eligibility criteria were biopsy-proven breast-infiltrating ductal carcinoma, age >40 years, tumor <3 cm, and cN0. Exclusion criteria were in situ or lobular types, multicentricity, skin invasion, any contraindication for surgery and/or radiation therapy, sentinel lymph node involvement, metastasis, or another malignancy. Patients underwent classic quadrantectomy with intraoperative sentinel lymph node and margins evaluation. If both free, the patient wasmore » transferred from operative suite to linear accelerator room, and IORT was delivered (21 Gy). Primary endpoint: local recurrence (LR); secondary endpoints: toxicities and aesthetics. Quality assurance involved using a customized shield for chest wall protection, applying procedures to minimize infection caused by patient transportation, and using portal films to check collimator-shield alignment. Results: A total of 152 patients were included, with at least 1 year follow-up. Median age (range) was 58.3 (40-85.4) years, and median follow-up time was 50.7 (12-110.5) months. The likelihood of 5-year local recurrence was 3.7%. There were 3 deaths, 2 of which were cancer related. The Kaplan-Meier 5-year actuarial estimates of overall, disease-free, and local recurrence-free survivals were 97.8%, 92.5%, and 96.3%, respectively. The overall incidences of acute and late toxicities were 12.5% and 29.6%, respectively. Excellent, good, fair, and bad cosmetic results were observed in 76.9%, 15.8%, 4.3%, and 2.8% of patients, respectively. Most treatments were performed with a 5-cm collimator, and in 39.8% of the patients the electron-beam energy used was ≥12 MeV. All patients underwent portal film evaluation, and the shielding was repositioned in 39.9% of cases. No infection or anesthesia complications were observed. Conclusions: Local control with IORT was adequate, with low complication rates and good cosmetic outcomes. More than one-third of patients benefited from the “image-guidance” approach, and almost 40% benefited from the option of higher electron beam energies.« less
  • Purpose: Kilovoltage intrafraction monitoring (KIM) is a new real-time 3-dimensional image guidance method. Unlike previous real-time image guidance methods, KIM uses a standard linear accelerator without any additional equipment needed. The first prospective clinical trial of KIM is underway for prostate cancer radiation therapy. In this paper we report on the measured motion accuracy and precision using real-time KIM-guided gating. Methods and Materials: Imaging and motion information from the first 200 fractions from 6 patient prostate cancer radiation therapy volumetric modulated arc therapy treatments were analyzed. A 3-mm/5-second action threshold was used to trigger a gating event where the beammore » is paused and the couch position adjusted to realign the prostate to the treatment isocenter. To quantify the in vivo accuracy and precision, KIM was compared with simultaneously acquired kV/MV triangulation for 187 fractions. Results: KIM was successfully used in 197 of 200 fractions. Gating events occurred in 29 fractions (14.5%). In these 29 fractions, the percentage of beam-on time, the prostate displacement was >3 mm from the isocenter position, reduced from 73% without KIM to 24% with KIM-guided gating. Displacements >5 mm were reduced from 16% without KIM to 0% with KIM. The KIM accuracy was measured at <0.3 mm in all 3 dimensions. The KIM precision was <0.6 mm in all 3 dimensions. Conclusions: Clinical implementation of real-time KIM image guidance combined with gating for prostate cancer eliminates large prostate displacements during treatment delivery. Both in vivo KIM accuracy and precision are well below 1 mm.« less
  • Purpose: Image-guided intensity modulated radiation therapy (IG-IMRT) allows significant dose reductions to organs at risk in prostate cancer patients. However, clinical data identifying the benefits of IG-IMRT in daily practice are scarce. The purpose of this study was to compare dose distributions to organs at risk and acute gastrointestinal (GI) and genitourinary (GU) toxicity levels of patients treated to 78 Gy with either IG-IMRT or 3D-CRT. Methods and Materials: Patients treated with 3D-CRT (n=215) and IG-IMRT (n=260) receiving 78 Gy in 39 fractions within 2 randomized trials were selected. Dose surface histograms of anorectum, anal canal, and bladder were calculated. Identical toxicitymore » questionnaires were distributed at baseline, prior to fraction 20 and 30 and at 90 days after treatment. Radiation Therapy Oncology Group (RTOG) grade ≥1, ≥2, and ≥3 endpoints were derived directly from questionnaires. Univariate and multivariate binary logistic regression analyses were applied. Results: The median volumes receiving 5 to 75 Gy were significantly lower (all P<.001) with IG-IMRT for anorectum, anal canal, and bladder. The mean dose to the anorectum was 34.4 Gy versus 47.3 Gy (P<.001), 23.6 Gy versus 44.6 Gy for the anal canal (P<.001), and 33.1 Gy versus 43.2 Gy for the bladder (P<.001). Significantly lower grade ≥2 toxicity was observed for proctitis, stool frequency ≥6/day, and urinary frequency ≥12/day. IG-IMRT resulted in significantly lower overall RTOG grade ≥2 GI toxicity (29% vs 49%, respectively, P=.002) and overall GU grade ≥2 toxicity (38% vs 48%, respectively, P=.009). Conclusions: A clinically meaningful reduction in dose to organs at risk and acute toxicity levels was observed in IG-IMRT patients, as a result of improved technique and tighter margins. Therefore reduced late toxicity levels can be expected as well; additional research is needed to quantify such reductions.« less