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Sparse patch-based method applied to mri-only radiotherapy planning
Abstracts / Physica Medica 32 (2016) 284–339
CT-GUIDED SPINAL INFILTRATION: PATIENT DOSE EVALUATION Cretti Fabiola a,*, Lunghi Sandro b, Rizzi Pierluigi a a
ASST Papa Giovanni XXIII, Bergamo, Italy ASST Lecco, Lecco, Italy ⇑ Corresponding author. b
Introduction. In light of ICRP recommendations, Computer Tomography (CT) patient dose is considered, in interventional context. Objective. To evaluate patient dose for CT-guided spinal infiltration, using a multi-detector scanner Philips 64 Brillance. Methods. 211 dose reports were downloaded retrospectively from the digital archive, concerning 172 subjects, 91 males and 81 females (age 56 ± 17 years). Lateral (LL) and anterior-posterior (AP) thicknesses of the region of interest were measured from the images, in order to correct CTDI with size specific factors accordingly to AAPM report 204. Dose Length Product (DLP) values were converted to effective doses by using coefficients derived from CTDosimetry.xls (ImpaCTscan.org), SR250 data set and ICRP 103 tissue weighting factors. Also sex differences were considered. Skin doses were estimated too, using CTDIs and correction factors derived from film dosimetry. Results. Differences between corrected and uncorrected individual CTDI ranged from 12% to +78% (mean +32%). DLP was on average 192 (±104) mGy*cm, with no significant differences between males and females, whereas mean effective doses were 3.9 ± 2.2 mSv and 2.6 ± 1.5 mSv for females and males respectively. Mean peak skin dose was 62 (±27) mGy. Conclusion. In many cases CT-guided spinal injection represent the method of choice for back pain treatment. In lumbar disk herniation, because of the nature of the disease, surgery is rarely needed, so spinal injection is often the best way to obtain a long lasting pain relief. The relatively low radiation dose, assessed in our work for this procedure, confirms the safety of this minimally invasive technique. http://dx.doi.org/10.1016/j.ejmp.2016.07.171
HOUNSFIELD CT-VALUES CORRECTION WITH THE IMARÒ SOFTWARE, IMPACTS ON DOSIMETRICS CALCULATION FOR RADIATION THERAPY Muraro Stephane a, Galliano Geoffrey b a b
Physicist, France Student Physicist, France
Introduction. iMARÒ is a software developed by Siemens for the raw data reconstruction acquired with CT scan for dosimetry planification. This software is used in the event of presence of metal object which causes artefacts on the scan images. Purpose. Metal artifacts create uncertainty in contours, add time for manual correction, and might lead to inaccuracies in dose calculation. The iMARÒ algorithm used for this software must allow a depiction of the Hounsfield Units (HU) values getting closer to the reality, i.e without artefacts. To do that, several tests are conducted to demonstrate the efficiency of this product. Materials and methods. Siemens SOMATON Scope 24-slice is used for CT scan. Phantom created in the department of radiotherapy with a lot of inserts. These inserts come to QUASARTM phantom and CIRS Model 062. We compared several kind of acquisitions with different parameters of reconstructions while alternating the use, or not, of the iMAR algorithm. The dosimetry realized in the TPS EclipseÒ to process the treatment plan is based on the HU values calculated in the CT scan acquisition. Therefore an HU values comparison between images with/without iMARÒ software will be made to guaranty an optimal treatment.
309
Results. The first studies show a significant improvement of the UH values and the result are an optimization and precision of treatments processing. Conclusion. Use iMARÒ Siemens software can improve quality in the CT scan acquisition to enhanced contouring and more accurate dosimetry of the radiotherapy treatment. http://dx.doi.org/10.1016/j.ejmp.2016.07.172
SPARSE PATCH-BASED METHOD APPLIED TO MRI-ONLY RADIOTHERAPY PLANNING S. Aouadi, A. Vasic, S. Paloor, R.W. Hammoud, T. Torfeh, P. Petric, N. Al-Hammadi NCCCR, Hamad Medical Corporation, Doha, Qatar Introduction. Replacing CT/MRI in radiotherapy chain with MRIonly will remove CT/MRI fusion uncertainties and avoid the patient the dose of ionizing radiation from CT. Purpose. We propose to generate pseudo-CT (pCT) from conventional MRI and to assess it for MRI-only brain radiotherapy planning (RTP). Material/methods. In twelve patients with brain tumors, CT and contrast-enhanced T1-weighted MRI were registered. A library of patches was built by extracting 2D patches, defined as MRI squares of 5 5voxels, in each voxel location and labelling them with corresponding HU values. Each patch in target MRI was reconstructed from a sparse linear combination of database patches locally searched. The sparse coefficients were estimated by optimizing the Elastic-Net (EN) objective function. EN was enhanced by additional penalty term based on the structural similarity between target and database patches. Radiological and dosimetric assessments of pCT were done for all patients using leave one out cross-validation. Mean absolute error between CT and pCT radiological paths (MAEWEPL) over a grid were computed. VMAT planning was performed on CT and pCT for PTVs delineated in homogenous (PTV1) and heterogeneous regions (PTV2) and compared. Percentage of dose metrics deviations (PDMD) for PTVs and OARS were computed. Results. Radiological path estimation was accurate with MAEWEPL = 2.6 ± 0.4 mm. Good agreement with conventional planning techniques was obtained; the highest PDMD were D98% = 0.05 ± 0.1 for PTV1, D98% = 0.81 ± 0.47 for PTV2 and Dmean = 0.35 ± 0.7 for left lens. Conclusion. We presented a novel technique to generate pCT for MRI-only brain RTP. In the future, we will investigate its use for PET/MR attenuation correction. http://dx.doi.org/10.1016/j.ejmp.2016.07.173
NOWADAYS PROTON THERAPY: DOUBLE SCATTERING VERSUS PENCIL BEAM SCANNING MODE Anna Michaelidesová a,b,d,*, Jana Konírˇová a,c, Jana Vachelová a, Vladimír Vondrácˇek b, Marie Davídková a,d a Nuclear Physics Institute, Czech Academy of Sciences, Rˇezˇ, Czech Republic b Proton Therapy Center Czech, Prague, Czech Republic c Institute of Molecular Genetics, Czech Academy of Sciences, Prague, Czech Republic d Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Prague, Czech Republic ⇑ Corresponding author.
CT-GUIDED SPINAL INFILTRATION: PATIENT DOSE EVALUATION Cretti Fabiola a,*, Lunghi Sandro b, Rizzi Pierluigi a a
ASST Papa Giovanni XXIII, Bergamo, Italy ASST Lecco, Lecco, Italy ⇑ Corresponding author. b
Introduction. In light of ICRP recommendations, Computer Tomography (CT) patient dose is considered, in interventional context. Objective. To evaluate patient dose for CT-guided spinal infiltration, using a multi-detector scanner Philips 64 Brillance. Methods. 211 dose reports were downloaded retrospectively from the digital archive, concerning 172 subjects, 91 males and 81 females (age 56 ± 17 years). Lateral (LL) and anterior-posterior (AP) thicknesses of the region of interest were measured from the images, in order to correct CTDI with size specific factors accordingly to AAPM report 204. Dose Length Product (DLP) values were converted to effective doses by using coefficients derived from CTDosimetry.xls (ImpaCTscan.org), SR250 data set and ICRP 103 tissue weighting factors. Also sex differences were considered. Skin doses were estimated too, using CTDIs and correction factors derived from film dosimetry. Results. Differences between corrected and uncorrected individual CTDI ranged from 12% to +78% (mean +32%). DLP was on average 192 (±104) mGy*cm, with no significant differences between males and females, whereas mean effective doses were 3.9 ± 2.2 mSv and 2.6 ± 1.5 mSv for females and males respectively. Mean peak skin dose was 62 (±27) mGy. Conclusion. In many cases CT-guided spinal injection represent the method of choice for back pain treatment. In lumbar disk herniation, because of the nature of the disease, surgery is rarely needed, so spinal injection is often the best way to obtain a long lasting pain relief. The relatively low radiation dose, assessed in our work for this procedure, confirms the safety of this minimally invasive technique. http://dx.doi.org/10.1016/j.ejmp.2016.07.171
HOUNSFIELD CT-VALUES CORRECTION WITH THE IMARÒ SOFTWARE, IMPACTS ON DOSIMETRICS CALCULATION FOR RADIATION THERAPY Muraro Stephane a, Galliano Geoffrey b a b
Physicist, France Student Physicist, France
Introduction. iMARÒ is a software developed by Siemens for the raw data reconstruction acquired with CT scan for dosimetry planification. This software is used in the event of presence of metal object which causes artefacts on the scan images. Purpose. Metal artifacts create uncertainty in contours, add time for manual correction, and might lead to inaccuracies in dose calculation. The iMARÒ algorithm used for this software must allow a depiction of the Hounsfield Units (HU) values getting closer to the reality, i.e without artefacts. To do that, several tests are conducted to demonstrate the efficiency of this product. Materials and methods. Siemens SOMATON Scope 24-slice is used for CT scan. Phantom created in the department of radiotherapy with a lot of inserts. These inserts come to QUASARTM phantom and CIRS Model 062. We compared several kind of acquisitions with different parameters of reconstructions while alternating the use, or not, of the iMAR algorithm. The dosimetry realized in the TPS EclipseÒ to process the treatment plan is based on the HU values calculated in the CT scan acquisition. Therefore an HU values comparison between images with/without iMARÒ software will be made to guaranty an optimal treatment.
309
Results. The first studies show a significant improvement of the UH values and the result are an optimization and precision of treatments processing. Conclusion. Use iMARÒ Siemens software can improve quality in the CT scan acquisition to enhanced contouring and more accurate dosimetry of the radiotherapy treatment. http://dx.doi.org/10.1016/j.ejmp.2016.07.172
SPARSE PATCH-BASED METHOD APPLIED TO MRI-ONLY RADIOTHERAPY PLANNING S. Aouadi, A. Vasic, S. Paloor, R.W. Hammoud, T. Torfeh, P. Petric, N. Al-Hammadi NCCCR, Hamad Medical Corporation, Doha, Qatar Introduction. Replacing CT/MRI in radiotherapy chain with MRIonly will remove CT/MRI fusion uncertainties and avoid the patient the dose of ionizing radiation from CT. Purpose. We propose to generate pseudo-CT (pCT) from conventional MRI and to assess it for MRI-only brain radiotherapy planning (RTP). Material/methods. In twelve patients with brain tumors, CT and contrast-enhanced T1-weighted MRI were registered. A library of patches was built by extracting 2D patches, defined as MRI squares of 5 5voxels, in each voxel location and labelling them with corresponding HU values. Each patch in target MRI was reconstructed from a sparse linear combination of database patches locally searched. The sparse coefficients were estimated by optimizing the Elastic-Net (EN) objective function. EN was enhanced by additional penalty term based on the structural similarity between target and database patches. Radiological and dosimetric assessments of pCT were done for all patients using leave one out cross-validation. Mean absolute error between CT and pCT radiological paths (MAEWEPL) over a grid were computed. VMAT planning was performed on CT and pCT for PTVs delineated in homogenous (PTV1) and heterogeneous regions (PTV2) and compared. Percentage of dose metrics deviations (PDMD) for PTVs and OARS were computed. Results. Radiological path estimation was accurate with MAEWEPL = 2.6 ± 0.4 mm. Good agreement with conventional planning techniques was obtained; the highest PDMD were D98% = 0.05 ± 0.1 for PTV1, D98% = 0.81 ± 0.47 for PTV2 and Dmean = 0.35 ± 0.7 for left lens. Conclusion. We presented a novel technique to generate pCT for MRI-only brain RTP. In the future, we will investigate its use for PET/MR attenuation correction. http://dx.doi.org/10.1016/j.ejmp.2016.07.173
NOWADAYS PROTON THERAPY: DOUBLE SCATTERING VERSUS PENCIL BEAM SCANNING MODE Anna Michaelidesová a,b,d,*, Jana Konírˇová a,c, Jana Vachelová a, Vladimír Vondrácˇek b, Marie Davídková a,d a Nuclear Physics Institute, Czech Academy of Sciences, Rˇezˇ, Czech Republic b Proton Therapy Center Czech, Prague, Czech Republic c Institute of Molecular Genetics, Czech Academy of Sciences, Prague, Czech Republic d Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Prague, Czech Republic ⇑ Corresponding author.