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Title: Sci—Thur AM: YIS - 08: Constructing an Attenuation map for a PET/MR Breast coil

Abstract

In 2013, around 23000 Canadian women and 200 Canadian men were diagnosed with breast cancer. An estimated 5100 women and 55 men died from the disease. Using the sensitivity of MRI with the selectivity of PET, PET/MRI combines anatomical and functional information within the same scan and could help with early detection in high-risk patients. MRI requires radiofrequency coils for transmitting energy and receiving signal but the breast coil attenuates PET signal. To correct for this PET attenuation, a 3-dimensional map of linear attenuation coefficients (μ-map) of the breast coil must be created and incorporated into the PET reconstruction process. Several approaches have been proposed for building hardware μ-maps, some of which include the use of conventional kVCT and Dual energy CT. These methods can produce high resolution images based on the electron densities of materials that can be converted into μ-maps. However, imaging hardware containing metal components with photons in the kV range is susceptible to metal artifacts. These artifacts can compromise the accuracy of the resulting μ-map and PET reconstruction; therefore high-Z components should be removed. We propose a method for calculating μ-maps without removing coil components, based on megavoltage (MV) imaging with a linear accelerator that hasmore » been detuned for imaging at 1.0MeV. Containers of known geometry with F18 were placed in the breast coil for imaging. A comparison between reconstructions based on the different μ-map construction methods was made. PET reconstructions with our method show a maximum of 6% difference over the existing kVCT-based reconstructions.« less

Authors:
 [1];  [2];  [2];  [1];  [2];  [2];  [3];  [4];  [1];  [2];  [2];  [1];  [2];  [1];  [2];  [2];  [1];  [2];  [2];  [2]
  1. Department of Medical Biophysics, Western University, Knoxville, TN (United States)
  2. (United States)
  3. Imaging, Lawson Health Research Institute, Knoxville, TN (United States)
  4. Siemens Healthcare Molecular Imaging, Knoxville, TN (United States)
Publication Date:
OSTI Identifier:
22409504
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 41; Journal Issue: 8; Other Information: (c) 2014 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; ACCURACY; CANADA; COMPARATIVE EVALUATIONS; GEOMETRY; MAMMARY GLANDS; MEN; NEOPLASMS; NMR IMAGING; POSITRON COMPUTED TOMOGRAPHY; THREE-DIMENSIONAL CALCULATIONS; WOMEN

Citation Formats

Patrick, John C., Imaging, Lawson Health Research Institute, Knoxville, TN, London Regional Cancer Program, Knoxville, TN, So, Aaron, Imaging, Lawson Health Research Institute, Knoxville, TN, Imaging Laboratories - Robarts Research Institute, Knoxville, TN, Butler, John, Faul, David, Yartsev, Slav, Department of Oncology, Western University, Knoxville, TN, London Regional Cancer Program, Knoxville, TN, Thompson, Terry, Imaging, Lawson Health Research Institute, Knoxville, TN, Prato, Frank S., Imaging, Lawson Health Research Institute, Knoxville, TN, Diagnostic Imaging St Joseph's Health Care London, Knoxville, TN, Gaede, Stewart, Department of Oncology, Western University, Knoxville, TN, Imaging, Lawson Health Research Institute, Knoxville, TN, and London Regional Cancer Program, Knoxville, TN. Sci—Thur AM: YIS - 08: Constructing an Attenuation map for a PET/MR Breast coil. United States: N. p., 2014. Web. doi:10.1118/1.4894949.
Patrick, John C., Imaging, Lawson Health Research Institute, Knoxville, TN, London Regional Cancer Program, Knoxville, TN, So, Aaron, Imaging, Lawson Health Research Institute, Knoxville, TN, Imaging Laboratories - Robarts Research Institute, Knoxville, TN, Butler, John, Faul, David, Yartsev, Slav, Department of Oncology, Western University, Knoxville, TN, London Regional Cancer Program, Knoxville, TN, Thompson, Terry, Imaging, Lawson Health Research Institute, Knoxville, TN, Prato, Frank S., Imaging, Lawson Health Research Institute, Knoxville, TN, Diagnostic Imaging St Joseph's Health Care London, Knoxville, TN, Gaede, Stewart, Department of Oncology, Western University, Knoxville, TN, Imaging, Lawson Health Research Institute, Knoxville, TN, & London Regional Cancer Program, Knoxville, TN. Sci—Thur AM: YIS - 08: Constructing an Attenuation map for a PET/MR Breast coil. United States. doi:10.1118/1.4894949.
Patrick, John C., Imaging, Lawson Health Research Institute, Knoxville, TN, London Regional Cancer Program, Knoxville, TN, So, Aaron, Imaging, Lawson Health Research Institute, Knoxville, TN, Imaging Laboratories - Robarts Research Institute, Knoxville, TN, Butler, John, Faul, David, Yartsev, Slav, Department of Oncology, Western University, Knoxville, TN, London Regional Cancer Program, Knoxville, TN, Thompson, Terry, Imaging, Lawson Health Research Institute, Knoxville, TN, Prato, Frank S., Imaging, Lawson Health Research Institute, Knoxville, TN, Diagnostic Imaging St Joseph's Health Care London, Knoxville, TN, Gaede, Stewart, Department of Oncology, Western University, Knoxville, TN, Imaging, Lawson Health Research Institute, Knoxville, TN, and London Regional Cancer Program, Knoxville, TN. Fri . "Sci—Thur AM: YIS - 08: Constructing an Attenuation map for a PET/MR Breast coil". United States. doi:10.1118/1.4894949.
@article{osti_22409504,
title = {Sci—Thur AM: YIS - 08: Constructing an Attenuation map for a PET/MR Breast coil},
author = {Patrick, John C. and Imaging, Lawson Health Research Institute, Knoxville, TN and London Regional Cancer Program, Knoxville, TN and So, Aaron and Imaging, Lawson Health Research Institute, Knoxville, TN and Imaging Laboratories - Robarts Research Institute, Knoxville, TN and Butler, John and Faul, David and Yartsev, Slav and Department of Oncology, Western University, Knoxville, TN and London Regional Cancer Program, Knoxville, TN and Thompson, Terry and Imaging, Lawson Health Research Institute, Knoxville, TN and Prato, Frank S. and Imaging, Lawson Health Research Institute, Knoxville, TN and Diagnostic Imaging St Joseph's Health Care London, Knoxville, TN and Gaede, Stewart and Department of Oncology, Western University, Knoxville, TN and Imaging, Lawson Health Research Institute, Knoxville, TN and London Regional Cancer Program, Knoxville, TN},
abstractNote = {In 2013, around 23000 Canadian women and 200 Canadian men were diagnosed with breast cancer. An estimated 5100 women and 55 men died from the disease. Using the sensitivity of MRI with the selectivity of PET, PET/MRI combines anatomical and functional information within the same scan and could help with early detection in high-risk patients. MRI requires radiofrequency coils for transmitting energy and receiving signal but the breast coil attenuates PET signal. To correct for this PET attenuation, a 3-dimensional map of linear attenuation coefficients (μ-map) of the breast coil must be created and incorporated into the PET reconstruction process. Several approaches have been proposed for building hardware μ-maps, some of which include the use of conventional kVCT and Dual energy CT. These methods can produce high resolution images based on the electron densities of materials that can be converted into μ-maps. However, imaging hardware containing metal components with photons in the kV range is susceptible to metal artifacts. These artifacts can compromise the accuracy of the resulting μ-map and PET reconstruction; therefore high-Z components should be removed. We propose a method for calculating μ-maps without removing coil components, based on megavoltage (MV) imaging with a linear accelerator that has been detuned for imaging at 1.0MeV. Containers of known geometry with F18 were placed in the breast coil for imaging. A comparison between reconstructions based on the different μ-map construction methods was made. PET reconstructions with our method show a maximum of 6% difference over the existing kVCT-based reconstructions.},
doi = {10.1118/1.4894949},
journal = {Medical Physics},
number = 8,
volume = 41,
place = {United States},
year = {Fri Aug 15 00:00:00 EDT 2014},
month = {Fri Aug 15 00:00:00 EDT 2014}
}
  • Purpose: To develop quality assurance (QA) standards and tolerance levels for image quality of small animal irradiators. Methods: A fully automated in-house QA software for image analysis of a commercial microCT phantom was created. Quantitative analyses of CT linearity, signal-to-noise ratio (SNR), uniformity and noise, geometric accuracy, modulation transfer function (MTF), and CT number evaluation was performed. Phantom microCT scans from seven institutions acquired with varying parameters (kVp, mA, time, voxel size, and frame rate) and five irradiator units (Xstrahl SARRP, PXI X-RAD 225Cx, PXI X-RAD SmART, GE explore CT/RT 140, and GE Explore CT 120) were analyzed. Multi-institutional datamore » sets were compared using our in-house software to establish pass/fail criteria for each QA test. Results: CT linearity (R2>0.996) was excellent at all but Institution 2. Acceptable SNR (>35) and noise levels (<55HU) were obtained at four of the seven institutions, where failing scans were acquired with less than 120mAs. Acceptable MTF (>1.5 lp/mm for MTF=0.2) was obtained at all but Institution 6 due to the largest scan voxel size (0.35mm). The geometric accuracy passed (<1.5%) at five of the seven institutions. Conclusion: Our QA software can be used to rapidly perform quantitative imaging QA for small animal irradiators, accumulate results over time, and display possible changes in imaging functionality from its original performance and/or from the recommended tolerance levels. This tool will aid researchers in maintaining high image quality, enabling precise conformal dose delivery to small animals.« less
  • Introduction: Long-term cardiac side effects in left-sided breast cancer patients (BREL) after post-operative radiotherapy has become one of the most debated issues in radiation oncology. Through breathing-adapted radiotherapy the volume of the heart exposed to radiation can be significantly reduced by delivering the radiation only at the end of inspiration phase of the respiratory cycle, this is referred to as inspiration gating (IG). The purpose of this study is to quantify the potential reduction in cardiac exposure during IG compared to conventional BREL radiotherapy and to assess the dosimetric impact of cardiac motion due to natural breathing. Methods: 24 BRELmore » patients treated with tangential parallel opposed photon beams were included in this study. All patients received a standard fast helical planning CT (FH-CT) and a 4D-CT. Treatment plans were created on the FH-CT using a clinical treatment planning system. The original treatment plan was then superimposed onto the end of inspiration CT and all 10 phases of the 4D-CT to quantify the dosimetric impact of respiratory motion and IG through 4D dose accumulation. Results: Through IG the mean dose to the heart, left ventricle, and left anterior descending artery (LAD) can be reduced in comparison to the clinical standard BREL treatment by as much as 8.39%, 10.11%, and 13.71% respectively (p < 0.05). Conclusion: Failure to account for respiratory motion can lead to under or overestimation in the calculated DVH for the heart, and it's sub-structures. IG can reduce cardiac exposure especially to the LAD during BREL radiotherapy.« less
  • Inter-patient radiation sensitivity variability has recently been shown to have a genetic component. This genetic component may play a key role in explaining the fluctuating rates of radiation-induced toxicities (RITs). Single nucleotide polymorphisms (SNPs) have thus far yielded inconsistent results in delineating RITs while copy number variations (CNVs) have not yet been investigated for such purposes. We explore a radiogenomic modeling approach to investigate the association of CNVs and SNPs, along with clinical and dosimetric variables, in radiation induced rectal bleeding (RB) and erectile dysfunction (ED) in prostate cancer patients treated with curative hypofractionated irradiation. A cohort of 62 prostatemore » cancer patients who underwent hypofractionated radiotherapy (66 Gy in 22 fractions) between 2002 to 2010 were retrospectively genotyped for CNV and SNP rs5489 in the xrcc1 DNA repair gene. Late toxicity rates for RB grade 2 and 3 and grade 3 alone were 29.0% and 12.9%, respectively. ED toxicity was found to be 62.9%. Radiogenomic model performance was evaluated using receiver operating characteristic area under the curve (AUC) and resampling by cross-validation. Binary variables were evaluated using Chi-squared contingency table analysis and multivariate models by Spearman's rank correlation coefficient (rs). Ten patients were found to have three copies of xrcc1 CNV (RB: χ{sup 2}=14.6, p<0.001 and ED: χ{sup 2}=4.88, p=0.0272) and twelve had heterozygous rs25489 SNP (RB: χ{sup 2}=0.278, p=0.599 and ED: χ{sup 2}=0.112, p=0.732). Radiogenomic modeling yielded significant, cross-validated NTCP models for RB (AUC=0.665) and ED (AUC=0.754). These results indicate that CNVs may be potential predictive biomarkers of both late ED and RB.« less
  • In peptide receptor radionuclide therapy (PRRT), huge inter-patient variability in absorbed radiation doses per administered activity mandates the utilization of individualized dosimetry to evaluate therapeutic efficacy and toxicity. We created a reliable GPU-calculated dosimetry code (irtGPUMCD) and assessed {sup 177}Lu-octreotate renal dosimetry in eight patients (4 cycles of approximately 7.4 GBq). irtGPUMCD was derived from a brachytherapy dosimetry code (bGPUMCD), which was adapted to {sup 177}Lu PRRT dosimetry. Serial quantitative single-photon emission computed tomography (SPECT) images were obtained from three SPECT/CT acquisitions performed at 4, 24 and 72 hours after {sup 177}Lu-octreotate administration, and registered with non-rigid deformation of CTmore » volumes, to obtain {sup 177}Lu-octreotate 4D quantitative biodistribution. Local energy deposition from the β disintegrations was assumed. Using Monte Carlo gamma photon transportation, irtGPUMCD computed dose rate at each time point. Average kidney absorbed dose was obtained from 1-cm{sup 3} VOI dose rate samples on each cortex, subjected to a biexponential curve fit. Integration of the latter time-dose rate curve yielded the renal absorbed dose. The mean renal dose per administered activity was 0.48 ± 0.13 Gy/GBq (range: 0.30–0.71 Gy/GBq). Comparison to another PRRT dosimetry code (VRAK: Voxelized Registration and Kinetics) showed fair accordance with irtGPUMCD (11.4 ± 6.8 %, range: 3.3–26.2%). These results suggest the possibility to use the irtGPUMCD code in order to personalize administered activity in PRRT. This could allow improving clinical outcomes by maximizing per-cycle tumor doses, without exceeding the tolerable renal dose.« less
  • Introduction: The use of gold nanoparticles (GNPs) in radiotherapy has shown promise for therapeutic enhancement. In this study, we explore the feasibility of enhancing radiotherapy with GNPs in an arc-therapy context. We use Monte Carlo simulations to quantify the macroscopic dose-enhancement ratio (DER) and tumour to normal tissue ratio (TNTR) as functions of photon energy over various tumour and body geometries. Methods: GNP-enhanced arc radiotherapy (GEART) was simulated using the PENELOPE Monte Carlo code and penEasy main program. We simulated 360° arc-therapy with monoenergetic photon energies 50 – 1000 keV and several clinical spectra used to treat a spherical tumourmore » containing uniformly distributed GNPs in a cylindrical tissue phantom. Various geometries were used to simulate different tumour sizes and depths. Voxel dose was used to calculate DERs and TNTRs. Inhomogeneity effects were examined through skull dose in brain tumour treatment simulations. Results: Below 100 keV, DERs greater than 2.0 were observed. Compared to 6 MV, tumour dose at low energies was more conformai, with lower normal tissue dose and higher TNTRs. Both the DER and TNTR increased with increasing cylinder radius and decreasing tumour radius. The inclusion of bone showed excellent tumour conformality at low energies, though with an increase in skull dose (40% of tumour dose with 100 keV compared to 25% with 6 MV). Conclusions: Even in the presence of inhomogeneities, our results show promise for the treatment of deep-seated tumours with low-energy GEART, with greater tumour dose conformality and lower normal tissue dose than 6 MV.« less