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Dosimetric effects of oral contrast in the planning of conventional radiotherapy and IMRT, for rectal cancer treatment. JOURNAL OF RADIOTHERAPY IN PRACTICE 2022. [DOI: 10.1017/s1460396922000243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Abstract
Introduction:
Contrast media are frequently used during radiation therapy simulation. However, there are concerns about dosimetric variations when dose calculation is done on contrast-enhanced computed tomography (CT). This study evaluates the dosimetric effect of oral contrast during three-dimensional conformal radiotherapy (3D-CRT) and volumetric modulated arc radiotherapy (VMAT) planning.
Methods:
Rectal cancer patients were consecutively enrolled. For each patient, one unenhanced CT and one contrast-enhanced CT were taken using oral and intravenous contrast. Then, a 3D-CRT plan and an Intensity-modulated radiation therapy (IMRT)/VMAT plan were generated in the enhanced CT, and the dose distribution was recalculated in the respective unenhanced CT. The beam intensities were kept the same as for the enhanced CT plans. Finally, the unenhanced and enhanced plans were compared by calculating the gamma index.
Results:
For 3D-CRT plans, there were statistically significant differences in second phase planning target volume (PTV) D2% (Mean difference (MD) between unenhanced and enhanced CT 0·01 Gy, 95% CI [0·003 to 0·02 Gy]) and in maximum doses to the bladder (MD 0·26 Gy, 95% CI [0·05 to 0·47 Gy]). For IMRT/VMAT plans, there were statistically significant differences in small intestine V45 Gy (MD 3·1 cc, 95% CI [0·81 to 5·4 cc]), bladder V45 Gy (MD 2·9%, 95% CI [1·4 to 4·3%]) and maximum dose to the bladder (MD 0·65 Gy, 95% CI [0·46 Gy to 0·85 Gy]). In addition, for PTV D98% the MD between unenhanced and enhanced CT was 0·22 Gy 95% CI [0·05 to 0·39].
Conclusions:
For most of the dose metrics, the differences were not clinically meaningful. The greatest differences were found in VMAT plans, especially in V45 Gy of the small intestine. This difference could lead to an underestimation of dose–volume metrics when the plan is based on an enhanced CT. The use of small bowel oral contrast does not significantly influence dose calculations and may not affect the acceptability of plans when adhering to constraints.
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Application of virtual noncontrast CT generation technology from intravenous enhanced CT based on deep learning in proton radiotherapy. JOURNAL OF RADIATION RESEARCH AND APPLIED SCIENCES 2022. [DOI: 10.1016/j.jrras.2022.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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3
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Kruis MF. Improving radiation physics, tumor visualisation, and treatment quantification in radiotherapy with spectral or dual-energy CT. J Appl Clin Med Phys 2021; 23:e13468. [PMID: 34743405 PMCID: PMC8803285 DOI: 10.1002/acm2.13468] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 10/13/2021] [Accepted: 10/19/2021] [Indexed: 12/11/2022] Open
Abstract
Over the past decade, spectral or dual‐energy CT has gained relevancy, especially in oncological radiology. Nonetheless, its use in the radiotherapy (RT) clinic remains limited. This review article aims to give an overview of the current state of spectral CT and to explore opportunities for applications in RT. In this article, three groups of benefits of spectral CT over conventional CT in RT are recognized. Firstly, spectral CT provides more information of physical properties of the body, which can improve dose calculation. Furthermore, it improves the visibility of tumors, for a wide variety of malignancies as well as organs‐at‐risk OARs, which could reduce treatment uncertainty. And finally, spectral CT provides quantitative physiological information, which can be used to personalize and quantify treatment.
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Bhushan M, Tripathi D, Yadav G, Kumar L, Dewan A, Tandon S, Kumar G, Wahi IK, Gairola M. Effect of contrast medium on treatment modalities planned with different photon beam energies: a planning study. Rep Pract Oncol Radiother 2021; 26:688-711. [PMID: 34760305 PMCID: PMC8575357 DOI: 10.5603/rpor.a2021.0103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Accepted: 09/16/2021] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Routinely, patient's planning scans are acquired after administration of iodinized contrast media but they will be treated in the absence of that. Similarly, high energy photons have a better penetrating power, while low energy photons will result in tighter dose distribution and negligible neutron contamination. The aim of the study was to investigate a suitable photon beam energy in the presence of intravenous contrast medium. MATERIALS AND METHODS An indigenously made original-contrast (OC) phantom was mentioned as virtual-contrast (VC) and virtual-without-contrast (VWC) phantom were generated by assigning the Hounsfield Units (HU) to different structures. Intensity-modulated (IMRT) and volumetric-modulated-arc (VMAT) plans were generated as per criteria of the TG-119 protocol. RESULTS It was observed that the maximum dose to the spinal cord was better with 6 mega-voltage (MV) in IMRT. The coverage of Prostate PTV (PR PTV) was similar with all the photon energies and was comparable with TG-119, except for original-contrast (OC) phantom using the VMAT technique. Homogeneity-index (HI) was comparatively better for VMAT plans. CONCLUSION The contrast CT images lower the dose to targets. IMRT or VMAT plans, generated on such CT images will be delivered with higher doses than evaluated. However, the overdose remains non-significant.
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Affiliation(s)
- Manindra Bhushan
- Division of Medical Physics and Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
- Amity School of Applied Sciences, Amity University (AUUP), NOIDA, Mumbai, India
| | - Deepak Tripathi
- Amity School of Applied Sciences, Amity University (AUUP), NOIDA, Mumbai, India
| | - Girigesh Yadav
- Division of Medical Physics and Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
| | - Lalit Kumar
- Division of Medical Physics and Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
| | - Abhinav Dewan
- Division of Medical Physics and Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
| | - Sarthak Tandon
- Division of Medical Physics and Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
| | - Gourav Kumar
- Division of Medical Physics and Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
| | - Inderjit Kaur Wahi
- Division of Medical Physics and Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
| | - Munish Gairola
- Division of Medical Physics and Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India
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Oulhouq Y, Bakari D, Krim DE, Zerfaoui M, Rrhioua A, Berhili S, Mezouar L. Dosimetric study of Hounsfield number correction effect in areas influenced by contrast product in lungs case. Rep Pract Oncol Radiother 2021; 26:590-597. [PMID: 34434575 PMCID: PMC8382071 DOI: 10.5603/rpor.a2021.0083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 02/27/2021] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND The aim of the study was dosimetric effect quantification of exclusive computed tomography (CT) use with an intravenous (IV) contrast agent (CA ), on dose distribution of 3D-CRT treatment plans for lung cancer. Furthermore, dosimetric advantage investigation of manually contrast-enhanced region overriding, especially the heart. MATERIALS AND METHODS Ten patients with lung cancer were considered. For each patient two planning CT sets were initially taken with and without CA. Treatment planning were optimized based on CT scans without CA. All plans were copied and recomputed on scans with CA. In addition, scans with IV contrast were copied and density correction was performed for heart contrast enhanced. Same plans were copied and replaced to undo dose calculation errors that may be caused by CA. Eventually, dosimetric evaluations based on dose volume histograms (DVHs) of planning target volumes (PTV) and organs at-risk were studied and analyzed using the Wilcoxon's signed rank test. RESULTS There is no statistically significant difference in dose calculation for the PTV maximum, mean, minimum doses, spinal cord maximum doses and lung volumes that received 20 and 30 Gy, between planes calculated with and without contrast scans (p > 0.05) and also for contrast scan, with manual regions overriding. CONCLUSIONS Dose difference caused by the contrast agent is negligible and not significant. Therefore, there is no justification to perform two scans, and using an IV contrast enhanced scan for dose calculation is sufficient.
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Affiliation(s)
- Yassine Oulhouq
- LPMR, Faculty of Sciences, University Mohamed 1st, Oujda, Morocco,HASSAN II Oncology Center, University Hospital Mohammed VI, Oujda, Morocco
| | - Dikra Bakari
- National School of Applied Sciences, University Mohamed 1st, Oujda, Morocco
| | - Deae-Eddine Krim
- LPMR, Faculty of Sciences, University Mohamed 1st, Oujda, Morocco
| | | | - Abdeslem Rrhioua
- LPMR, Faculty of Sciences, University Mohamed 1st, Oujda, Morocco
| | - Soufiane Berhili
- HASSAN II Oncology Center, University Hospital Mohammed VI, Oujda, Morocco
| | - Loubna Mezouar
- HASSAN II Oncology Center, University Hospital Mohammed VI, Oujda, Morocco
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6
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Lalonde A, Bobić M, Winey B, Verburg J, Sharp GC, Paganetti H. Anatomic changes in head and neck intensity-modulated proton therapy: Comparison between robust optimization and online adaptation. Radiother Oncol 2021; 159:39-47. [PMID: 33741469 PMCID: PMC8205952 DOI: 10.1016/j.radonc.2021.03.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 03/08/2021] [Accepted: 03/08/2021] [Indexed: 11/18/2022]
Abstract
BACKGROUND/PURPOSE Setup variations and anatomical changes can severely affect the quality of head and neck intensity-modulated proton therapy (IMPT) treatments. The impact of these changes can be alleviated by increasing the plan's robustness a priori, or by adapting the plan online. This work compares these approaches in the context of head and neck IMPT. MATERIALS/METHODS A representative cohort of 10 head and neck squamous cell carcinoma (HNSCC) patients with daily cone-beam computed tomography (CBCT) was evaluated. For each patient, three IMPT plans were created: 1- a classical robust optimization (cRO) plan optimized on the planning CT, 2- an anatomical robust optimization (aRO) plan additionally including the two first daily CBCTs and 3- a plan optimized without robustness constraints, but online-adapted (OA) daily, using a constrained spot intensity re-optimization technique only. RESULTS The cumulative dose following OA fulfilled the clinical objective of both the high-risk and low-risk clinical target volumes (CTV) coverage in all 10 patients, compared to 8 for aRO and 4 for cRO. aRO did not significantly increase the dose to most organs at risk compared to cRO, although the integral dose was higher. OA significantly reduced the integral dose to healthy tissues compared to both robust methods, while providing equivalent or superior target coverage. CONCLUSION Using a simple spot intensity re-optimization, daily OA can achieve superior target coverage and lower dose to organs at risk than robust optimization methods.
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Affiliation(s)
- Arthur Lalonde
- Department of Radiation Oncology, Massachusetts General Hospital & Harvard Medical School, Boston, USA.
| | - Mislav Bobić
- Department of Radiation Oncology, Massachusetts General Hospital & Harvard Medical School, Boston, USA; ETH Zürich, Zürich, Switzerland
| | - Brian Winey
- Department of Radiation Oncology, Massachusetts General Hospital & Harvard Medical School, Boston, USA
| | - Joost Verburg
- Department of Radiation Oncology, Massachusetts General Hospital & Harvard Medical School, Boston, USA
| | - Gregory C Sharp
- Department of Radiation Oncology, Massachusetts General Hospital & Harvard Medical School, Boston, USA
| | - Harald Paganetti
- Department of Radiation Oncology, Massachusetts General Hospital & Harvard Medical School, Boston, USA
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Elter A, Hellwich E, Dorsch S, Schäfer M, Runz A, Klüter S, Ackermann B, Brons S, Karger CP, Mann P. Development of phantom materials with independently adjustable CT- and MR-contrast at 0.35, 1.5 and 3 T. Phys Med Biol 2021; 66:045013. [PMID: 33333496 DOI: 10.1088/1361-6560/abd4b9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Quality assurance in magnetic resonance (MR)-guided radiotherapy lacks anthropomorphic phantoms that represent tissue-equivalent imaging contrast in both computed tomography (CT) and MR imaging. In this study, we developed phantom materials with individually adjustable CT value as well as [Formula: see text]- and [Formula: see text]-relaxation times in MR imaging at three different magnetic field strengths. Additionally, their experimental stopping power ratio (SPR) for carbon ions was compared with predictions based on single- and dual-energy CT. Ni-DTPA doped agarose gels were used for individual adjustment of [Formula: see text] and [Formula: see text] at [Formula: see text] and 3.0 T. The CT value was varied by adding potassium chloride (KCl). By multiple linear regression, equations for the determination of agarose, Ni-DTPA and KCl concentrations for given [Formula: see text] [Formula: see text] and CT values were derived and employed to produce nine specific soft tissue samples. Experimental [Formula: see text] [Formula: see text] and CT values of these soft tissue samples were compared with predictions and additionally, carbon ion SPR obtained by range measurements were compared with predictions based on single- and dual-energy CT. The measured CT value, [Formula: see text] and [Formula: see text] of the produced soft tissue samples agreed very well with predictions based on the derived equations with mean deviations of less than [Formula: see text] While single-energy CT overestimates the measured SPR of the soft tissue samples, the dual-energy CT-based predictions showed a mean SPR deviation of only [Formula: see text] To conclude, anthropomorphic phantom materials with independently adjustable CT values as well as [Formula: see text] and [Formula: see text] relaxation times at three different magnetic field strengths were developed. The derived equations describe the material specific relaxation times and the CT value in dependence on agarose, Ni-DTPA and KCl concentrations as well as the chemical composition of the materials based on given [Formula: see text] and CT value. Dual-energy CT allows accurate prediction of the carbon ion range in these materials.
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Affiliation(s)
- A Elter
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), INF 280, Heidelberg, Germany. National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany. Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany
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Ates O, Hua CH, Zhao L, Shapira N, Yagil Y, Merchant TE, Krasin M. Feasibility of using post-contrast dual-energy CT for pediatric radiation treatment planning and dose calculation. Br J Radiol 2021; 94:20200170. [PMID: 33201728 DOI: 10.1259/bjr.20200170] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
OBJECTIVES When iodinated contrast is administered during CT simulation, standard practice requires a separate non-contrast CT for dose calculation. The objective of this study is to validate our hypothesis that since iodine affects Hounsfield units (HUs) more than electron density (ED), the information from post-contrast dual-layer CT (DLCT) would be sufficient for accurate dose calculation for both photon and proton therapy. METHODS AND MATERIALS 10 pediatric patients with abdominal tumors underwent DLCT scans before and after iodinated contrast administration for radiotherapy planning. Dose distributions with these DLCT-based methods were compared to those with conventional calibration-curve methods that map HU images to ED and stopping-power ratio (SPR) images. RESULTS For photon plans, conventional and DLCT approaches based on post-contrast scans underestimated the PTV D99 by 0.87 ± 0.70% (p = 0.18) and 0.36 ± 0.31% (p = 0.34), respectively, comparing to their non-contrast optimization plans. Renal iodine concentration was weakly associated with D99 deviation for both conventional (R2 = 0.10) and DLCT (R2 = 0.02) approaches. For proton plans, the clinical target volume D99 errors were 3.67 ± 2.43% (p = 0.0001) and 0.30 ± 0.25% (p = 0.40) for conventional and DLCT approaches, respectively. The proton beam range changed noticeably with the conventional approach. Renal iodine concentration was highly associated with D99 deviation for the conventional approach (R2 = 0.83) but not for DLCT (R2 = 0.007). CONCLUSION Conventional CT with iodine contrast resulted in a large dosimetric error for proton therapy, compared to true non-contrast plans, but the error was less for photon therapy. These errors can be greatly reduced in the case of the proton plans if DLCT is used, raising the possibility of using only a single post-contrast CT for radiotherapy dose calculation, thus reducing the time and imaging dose required. ADVANCES IN KNOWLEDGE This study is the first to compare directly the differences in the calculated dose distributions between pre- and post-contrast CT images generated by single-energy CT and dual-energy CT methods for photon and proton therapy.
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Affiliation(s)
- Ozgur Ates
- Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Chia-Ho Hua
- Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Li Zhao
- Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Nadav Shapira
- Department of Radiology, University of Pennsylvania, Philadelphia, PA, USA.,Global Advanced Technology, Philips Medical Systems, Haifa, Israel
| | - Yoad Yagil
- Global Advanced Technology, Philips Medical Systems, Haifa, Israel
| | - Thomas E Merchant
- Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Matthew Krasin
- Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, TN, USA
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Oral contrast agents lead to underestimation of dose calculation in volumetric-modulated arc therapy planning for pelvic irradiation. Chin Med J (Engl) 2020; 133:2061-2070. [PMID: 32810050 PMCID: PMC7478501 DOI: 10.1097/cm9.0000000000001025] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Supplemental Digital Content is available in the text Background The effects of oral contrast agents (OCAs) on dosimetry have not been studied in detail. Therefore, this study aimed to examine the influence of OCAs on dose calculation in volumetric-modulated arc therapy plans for rectal cancer. Methods From 2008 to 2016, computed tomography (CT) images were obtained from 33 rectal cancer patients administered OCA with or without intravenous contrast agent (ICA) and 14 patients who received no contrast agent. CT numbers of organs at risk were recorded and converted to electronic densities. Volumetric-modulated arc therapy plans were designed before and after the original densities were replaced with non-enhanced densities. Doses to the planned target volume (PTV) and organs at risk were compared between the plans. Results OCA significantly increased the mean and maximum densities of the bowels, while the effects of ICA on these parameters depended on the blood supply of the organs. With OCA, the actual doses for PTV were significantly higher than planned and doses to the bowel increased significantly although moderately. However, the increase in the volume receiving a high-range doses was substantial (the absolute change of intestine volume receiving ≥52 Gy: 1.46 [0.05−3.99, cubic centimeter range: −6.74 to 128.12], the absolute change of colon volume receiving ≥50 Gy: 0.34 [0.01−1.53 cc, range: −0.08 to 3.80 cc]. Dose changes due to ICA were insignificant. Pearson correlation showed that dose changes were significantly correlated with a high intestinal volume within or near the PTV (ρ > 0.5, P < 0.05) and with the density of enhanced intestine (ρ > 0.3, P < 0.05). Conclusions Contrast agents applied in simulation cause underestimation of doses in actual treatment. The overdose due to ICA was slight, while that due to OCA was moderate. The bowel volume receiving ≥50Gy was dramatically increased when OCA within the bowel was absent. Physicians should be aware of these issues if the original plan is barely within clinical tolerance or if a considerable volume of enhanced intestine is within or near the PTV.
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Lalonde A, Xie Y, Burgdorf B, O'Reilly S, Ingram WS, Yin L, Zou W, Dong L, Bouchard H, Teo BKK. Influence of intravenous contrast agent on dose calculation in proton therapy using dual energy CT. Phys Med Biol 2019; 64:125024. [PMID: 31044743 DOI: 10.1088/1361-6560/ab1e9d] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of this study is to evaluate the effect of an intravenous (IV) contrast agent on proton therapy dose calculation using dual-energy computed tomography (DECT). Two DECT methods are considered. The first one, [Formula: see text], attempts to accurately predict the proton stopping powers relative to water (SPR) of contrast enhanced (CE) DECT images, while the second generates a virtual non-contrast (VNC) volume that can be processed as a native non-contrast (NC) one. Both methods are compared against single-energy computed tomography (SECT). The accuracy of SPR predicted for different concentrations of IV contrast diluted in water is first evaluated using simulated data. Results then are validated in an experimental set-up comparing SPR predictions for both NC and CE images to measurements made with a multi-layer ionisation chamber (MLIC). Finally, the impact of IV contrast on dose calculation using both SECT and DECT is evaluated for one liver and one head and neck patient. Using simulated data, DECT is shown to be less sensitive to the presence of IV contrast than SECT, although the performance of the [Formula: see text] method is sensitive to the level of beam hardening considered. For different concentrations of IV contrast diluted in water, experimental MLIC measurement of SPR agrees with DECT predictions within 3% while SECT introduce errors above 20%. This error in the SPR value results in a range error of up to 3.2 mm (2.6%) for proton beams calculated on SECT CE patient images. The error is reduced below 1 mm using DECT with the [Formula: see text] and VNC methods. Globally, it is observed that the influence of IV contrast on proton therapy dose calculation is mitigated using DECT over SECT. In patient anatomies, the VNC approach provides the best agreement with the reference dose distribution.
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Affiliation(s)
- Arthur Lalonde
- Département de Physique, Université de Montréal, Pavillon Roger-Gaudry, 2900 Boulevard Édouard-Montpetit, Montréal, Québec H3T 1J4, Canada. Author to whom any correspondence should be addressed
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Eekers DBP, Roelofs E, Cubillos-Mesías M, Niël C, Smeenk RJ, Hoeben A, Minken AWH, Granzier M, Janssens GO, Kaanders JHAM, Lambin P, Troost EGC. Intensity-modulated proton therapy decreases dose to organs at risk in low-grade glioma patients: results of a multicentric in silico ROCOCO trial. Acta Oncol 2019; 58:57-65. [PMID: 30474448 DOI: 10.1080/0284186x.2018.1529424] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND AND PURPOSE Patients with low-grade glioma (LGG) have a prolonged survival expectancy due to better discriminative tumor classification and multimodal treatment. Consequently, long-term treatment toxicity gains importance. Contemporary radiotherapy techniques such as intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), tomotherapy (TOMO) and intensity-modulated proton therapy (IMPT) enable high-dose irradiation of the target but they differ regarding delivered dose to organs at risk (OARs). The aim of this comparative in silico study was to determine these dosimetric differences in delivered doses. MATERIAL AND METHODS Imaging datasets of 25 LGG patients having undergone postoperative radiotherapy were included. For each of these patients, in silico treatment plans to a total dose of 50.4 Gy to the target volume were generated for the four treatment modalities investigated (i.e., IMRT, VMAT, TOMO, IMPT). Resulting treatment plans were analyzed regarding dose to target and surrounding OARs comparing IMRT, TOMO and IMPT to VMAT. RESULTS In total, 100 treatment plans (four per patient) were analyzed. Compared to VMAT, the IMPT mean dose (Dmean) for nine out of 10 (90%) OARs was statistically significantly (p < .02) reduced, for TOMO this was true in 3/10 (30%) patients and for 1/10 (10%) patients for IMRT. IMPT was the prime modality reducing dose to the OARs followed by TOMO. DISCUSSION The low dose volume to the majority of OARs was significantly reduced when using IMPT compared to VMAT. Whether this will lead to a significant reduction in neurocognitive decline and improved quality of life is to be determined in carefully designed future clinical trials.
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Affiliation(s)
- Daniëlle B. P. Eekers
- Department of Radiation Oncology (MAASTRO), GROW – School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
- Proton Therapy Centre South-East Netherlands (ZON-PTC), Maastricht, The Netherlands
| | - Erik Roelofs
- Department of Radiation Oncology (MAASTRO), GROW – School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
- Department of Radiation Oncology (The D-Lab), GROW – School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Macarena Cubillos-Mesías
- OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Cal Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden, Rossendorf, Dresden, Germany
| | - Charles Niël
- Department of Radiation Oncology, Radiotherapiegroep, Deventer, The Netherlands
| | - Robert Jan Smeenk
- Department of Radiation Oncology, RadboudUMC, Nijmegen, The Netherlands
| | - Ann Hoeben
- Department of Medical Oncology, GROW – School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Andre W. H. Minken
- Department of Radiation Oncology, Radiotherapiegroep, Deventer, The Netherlands
| | - Marlies Granzier
- Department of Radiation Oncology (MAASTRO), GROW – School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Geert O. Janssens
- Department of Radiation Oncology, RadboudUMC, Nijmegen, The Netherlands
- Princess Maxima Center for Pediatric Oncology, Utrecht, The Netherlands
- Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Philippe Lambin
- Department of Radiation Oncology (The D-Lab), GROW – School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Esther G. C. Troost
- OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Cal Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden, Rossendorf, Dresden, Germany
- Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Helmholtz-Zentrum Dresden – Rossendorf, Institute of Radiooncology – OncoRay, Dresden, Germany
- German Cancer Consortium (DKTK), Partner Site Dresden, and German Cancer Research Center (DKFZ), Heidelberg, Germany
- mNational Center for Tumor Diseases (NCT) Partner Site Dresden, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, and Helmholtz Association/Helmholtz-Zentrum Dresden, Rossendorf (HZDR), Dresden, Germany
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Xie Y, Ainsley C, Yin L, Zou W, McDonough J, Solberg TD, Lin A, Teo BKK. Ex vivo validation of a stoichiometric dual energy CT proton stopping power ratio calibration. Phys Med Biol 2018. [PMID: 29513647 DOI: 10.1088/1361-6560/aaae91] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A major source of uncertainty in proton therapy is the conversion of Hounsfield unit (HU) to proton stopping power ratio relative to water (SPR). In this study, we measured and quantified the accuracy of a stoichiometric dual energy CT (DECT) SPR calibration. We applied a stoichiometric DECT calibration method to derive the SPR using CT images acquired sequentially at [Formula: see text] and [Formula: see text]. The dual energy index was derived based on the HUs of the paired spectral images and used to calculate the effective atomic number (Z eff), relative electron density ([Formula: see text]), and SPRs of phantom and biological materials. Two methods were used to verify the derived SPRs. The first method measured the sample's water equivalent thicknesses to deduce the SPRs using a multi-layer ion chamber (MLIC) device. The second method utilized Gafchromic EBT3 film to directly compare relative ranges between sample and water after proton pencil beam irradiation. Ex vivo validation was performed using five different types of frozen animal tissues with the MLIC and three types of fresh animal tissues using film. In addition, the residual ranges recorded on the film were used to compare with those from the treatment planning system using both DECT and SECT derived SPRs. Bland-Altman analysis indicates that the differences between DECT and SPR measurement of tissue surrogates, frozen and fresh animal tissues has a mean of 0.07% and standard deviation of 0.58% compared to 0.55% and 1.94% respectively for single energy CT (SECT) and SPR measurement. Our ex vivo study indicates that the stoichiometric DECT SPR calibration method has the potential to be more accurate than SECT calibration under ideal conditions although beam hardening effects and other image artifacts may increase this uncertainty.
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Affiliation(s)
- Yunhe Xie
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104, United States of America
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Feasibility Study on Cardiac Arrhythmia Ablation Using High-Energy Heavy Ion Beams. Sci Rep 2016; 6:38895. [PMID: 27996023 PMCID: PMC5171237 DOI: 10.1038/srep38895] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 11/09/2016] [Indexed: 01/19/2023] Open
Abstract
High-energy ion beams are successfully used in cancer therapy and precisely deliver high doses of ionizing radiation to small deep-seated target volumes. A similar noninvasive treatment modality for cardiac arrhythmias was tested here. This study used high-energy carbon ions for ablation of cardiac tissue in pigs. Doses of 25, 40, and 55 Gy were applied in forced-breath-hold to the atrioventricular junction, left atrial pulmonary vein junction, and freewall left ventricle of intact animals. Procedural success was tracked by (1.) in-beam positron-emission tomography (PET) imaging; (2.) intracardiac voltage mapping with visible lesion on ultrasound; (3.) lesion outcomes in pathohistolgy. High doses (40–55 Gy) caused slowing and interruption of cardiac impulse propagation. Target fibrosis was the main mediator of the ablation effect. In irradiated tissue, apoptosis was present after 3, but not 6 months. Our study shows feasibility to use high-energy ion beams for creation of cardiac lesions that chronically interrupt cardiac conduction.
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Heydarheydari S, Farshchian N, Haghparast A. Influence of the contrast agents on treatment planning dose calculations of prostate and rectal cancers. Rep Pract Oncol Radiother 2016; 21:441-6. [PMID: 27489514 DOI: 10.1016/j.rpor.2016.04.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 03/07/2016] [Accepted: 04/13/2016] [Indexed: 01/22/2023] Open
Abstract
AIM The aim of the present study is to quantify differences in dose calculations caused by using CA and determine if the resulting differences are clinically significant. BACKGROUND The influence of contrast agents (CA) on radiation dose calculations must be taken into account in treatment planning. MATERIALS AND METHODS Eleven patients with pelvic cancers were included in this study and two sets of CTs were taken for each patient (without and with CA) in the same position and coordinates. Both sets of images were transferred to the DosiSoft ISOgray treatment planning system for contouring and calculating the dose distribution and monitor units (MUs) with Collapsed Cone and Superposition algorithms, respectively. All plans were generated on pre-contrast CT and subsequently copied to the post-contrast CT. Radiation dose calculations from the two sets of CTs were compared using a paired sample t-test. RESULTS The results showed a statistically insignificant difference between pre- and post-contrast CT treatment plans for target volume and OARs (p > 0.05), except bladder organ in the prostate region (p < 0.05) but the relative mean dose and MU differences were less than 2% in any patient for 18 MV photon beam. CONCLUSIONS Treatment planning on contrasted images generally showed a lower radiation dose to both target volume and OARs than plans on non-contrasted images. The results of this research showed that the small radiation dose differences between the plans for the CT scans with and without CA seem to be clinically insignificant; therefore, contrast-enhanced CT can be used for both target delineation and treatment planning of prostate and rectal cancers.
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Affiliation(s)
- Sahel Heydarheydari
- Department of Biomedical Physics and Engineering, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Negin Farshchian
- Department of Radiation Oncology, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Abbas Haghparast
- Department of Biomedical Physics and Engineering, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
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Constantinescu A, Lehmann HI, Packer DL, Bert C, Durante M, Graeff C. Treatment Planning Studies in Patient Data With Scanned Carbon Ion Beams for Catheter-Free Ablation of Atrial Fibrillation. J Cardiovasc Electrophysiol 2016; 27:335-44. [PMID: 26638826 DOI: 10.1111/jce.12888] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 11/12/2015] [Accepted: 11/25/2015] [Indexed: 01/08/2023]
Abstract
INTRODUCTION Catheter ablation with isolation of the pulmonary veins is a common treatment option for atrial fibrillation but still has insufficient success rates and carries several interventional risks. These treatment planning studies assessed if high-dose single fraction treatment with scanned carbon ions (12C) can be reliably delivered for AF ablation, while sparing risk structures and considering respiratory and contractile target motion. METHODS AND RESULTS Time resolved CT scans of complete respiratory and cardiac cycles of 9 and 5 patients, respectively, were obtained. Ablation lesions and organs at risk for beam delivery were contoured. Single fraction intensity-modulated particle therapy with target doses of 25 and 40 Gy were studied and motion influences on these deliveries mitigated. Respiration had a large influence on lesion displacement (≤ 2 cm). End expiration could be exploited as a stable gating window. Smaller, but less predictable, heartbeat displacements (< 6 mm) remained to be mitigated because cardiac contraction resulted in insufficient dose coverage (V95 < 90%) if uncompensated. Repeated irradiation (12C beam rescanning) during breath hold was used to accommodate contractile motion, resulting in good dose coverage. Dose depositions to all organs at risk were carefully examined and did not exceed values for X-ray cancer treatment. CONCLUSION Treatment planning of 12C with delivery of physical ionizing radiation doses that have been described to induce complete block is feasible for AF ablation, considering human anatomy, dose constraints, and encasing underlying motion patterns from respiration and cardiac contraction at the LA-PV junction into treatment planning.
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Affiliation(s)
- Anna Constantinescu
- Department of Biophysics, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany
| | - H Immo Lehmann
- Mayo Clinic Translational Interventional Electrophysiology Laboratory, Rochester, Minnesota, USA
| | - Douglas L Packer
- Mayo Clinic Translational Interventional Electrophysiology Laboratory, Rochester, Minnesota, USA
| | - Christoph Bert
- Department of Biophysics, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany.,Department of Radiation Oncology, Friedrich-Alexander University Erlangen-Nürnberg and University Hospital, Erlangen, Germany
| | - Marco Durante
- Department of Biophysics, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany
| | - Christian Graeff
- Department of Biophysics, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany
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Joseph K, Liu D, Severin D, Dickey M, Polkosnik LA, Warkentin H, Mihai A, Ghosh S, Field C. Dosimetric effect of small bowel oral contrast on conventional radiation therapy, linear accelerator–based intensity modulated radiation therapy, and helical tomotherapy plans for rectal cancer. Pract Radiat Oncol 2015; 5:e95-102. [DOI: 10.1016/j.prro.2014.07.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Revised: 07/22/2014] [Accepted: 07/25/2014] [Indexed: 12/31/2022]
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Liu AJ, Vora N, Suh S, Liu A, Schultheiss TE, Wong JY. Effect of CT contrast on volumetric arc therapy planning (RapidArc and helical tomotherapy) for head and neck cancer. Med Dosim 2015; 40:32-6. [DOI: 10.1016/j.meddos.2014.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 07/28/2014] [Accepted: 07/29/2014] [Indexed: 01/20/2023]
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Yamada S, Ueguchi T, Ogata T, Mizuno H, Ogihara R, Koizumi M, Shimazu T, Murase K, Ogawa K. Radiotherapy treatment planning with contrast-enhanced computed tomography: feasibility of dual-energy virtual unenhanced imaging for improved dose calculations. Radiat Oncol 2014; 9:168. [PMID: 25070169 PMCID: PMC4118618 DOI: 10.1186/1748-717x-9-168] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 07/22/2014] [Indexed: 11/10/2022] Open
Abstract
Background In radiotherapy treatment planning, intravenous administration of an iodine-based contrast agent during computed tomography (CT) improves the accuracy of delineating target volumes. However, increased tissue attenuation resulting from the high atomic number of iodine may result in erroneous dose calculations because the contrast agent is absent during the actual procedure. The purpose of this proof-of-concept study was to present a novel framework to improve the accuracy of dose calculations using dual-energy virtual unenhanced CT in the presence of an iodine-based contrast agent. Methods Simple phantom experiments were designed to assess the feasibility of the proposed concept. By utilizing a “second-generation” dual-source CT scanner equipped with a tin filter for improved spectral separation, four CT datasets were obtained using both a water phantom and an iodine phantom: “true unenhanced” images with attenuation values of 2 ± 11 Hounsfield Units (HU), “enhanced” images with attenuation values of 274 ± 23 HU, and two series of “virtual unenhanced” images synthesized from dual-energy scans of the iodine phantom, each with a different combination of tube voltages. Two series of virtual unenhanced images demonstrated attenuation values of 12 ± 29 HU (with 80 kVp/140 kVp) and 34 ± 10 HU (with 100 kVp/140 kVp) after removing the iodine component from the contrast-enhanced images. Dose distributions of the single photon beams calculated from the enhanced images and two series of virtual unenhanced images were compared to those from true unenhanced images as a reference. Results The dose distributions obtained from both series of virtual unenhanced images were almost equivalent to that from the true unenhanced images, whereas the dose distribution obtained from the enhanced images indicated increased beam attenuation caused by the high attenuation characteristics of iodine. Compared to the reference dose distribution from the true unenhanced images, the dose distribution pass rates from both series of virtual unenhanced images were greater than 90%, while those from the enhanced images were less than approximately 50–60%. Conclusions Dual-energy virtual unenhanced CT improves the accuracy of dose distributions in radiotherapy treatment planning by removing the iodine component from contrast-enhanced images.
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Affiliation(s)
- Sachiko Yamada
- Department of Radiology, Osaka University Hospital, 2-15 Yamadaoka, Suita, Osaka 565-0871, Japan.
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Tu SJ, Yang PY, Hong JH, Lo CJ. Quantitative dosimetric assessment for effect of gold nanoparticles as contrast media on radiotherapy planning. Radiat Phys Chem Oxf Engl 1993 2013. [DOI: 10.1016/j.radphyschem.2013.03.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Intravenous Contrast Agent Influence on Thoracic Computed Tomography Simulation Investigated Through A Heterogeneous Dose Calculation Method Using 5-Bulk Densities. Am J Clin Oncol 2012; 35:110-4. [DOI: 10.1097/coc.0b013e318209a910] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Hwang UJ, Shin DH, Kim TH, Moon SH, Lim YK, Jeong H, Rah JE, Kim SS, Kim JY, Kim DY, Park SY, Cho KH. The Effect of a Contrast Agent on Proton Beam Range in Radiotherapy Planning Using Computed Tomography for Patients With Locoregionally Advanced Lung Cancer. Int J Radiat Oncol Biol Phys 2011; 81:e317-24. [DOI: 10.1016/j.ijrobp.2011.02.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2010] [Revised: 02/06/2011] [Accepted: 02/09/2011] [Indexed: 10/18/2022]
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Lim YK, Hwang UJ, Shin D, Kim DW, Kwak J, Yoon M, Lee DH, Lee SB, Lee SY, Park SY, Pyo HR. Proton Range Uncertainty Due to Bone Cement Injected Into the Vertebra in Radiation Therapy Planning. Med Dosim 2011; 36:299-305. [DOI: 10.1016/j.meddos.2010.05.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Accepted: 05/27/2010] [Indexed: 10/18/2022]
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Shin D, Kim TH, Park SY, Kwak J, Moon SH, Yoon M, Lee SB, Park S, Shin KH, Kim DY, Cho KH, Park JW, Kim CM. Influence of Lipiodol Agent on Proton Beam Range in Radiotherapy Planning Using Computed Tomography for Hepatocellular Carcinoma. Int J Radiat Oncol Biol Phys 2008; 72:687-94. [DOI: 10.1016/j.ijrobp.2008.01.059] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2007] [Revised: 01/28/2008] [Accepted: 01/29/2008] [Indexed: 01/14/2023]
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Létourneau D, Finlay M, O'Sullivan B, Waldron JN, Cummings BJ, Ringash J, Kim JJ, Bayley AJ, Dawson LA. Lack of influence of intravenous contrast on head and neck IMRT dose distributions. Acta Oncol 2008; 47:90-4. [PMID: 17934894 DOI: 10.1080/02841860701418861] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
PURPOSE Intravenous (i.v.) contrast at the time of CT-Simulation facilitates radiotherapy contouring, but may introduce a discrepancy between planned and delivered dose due to density variation in blood vessels. Here, the effect of physiologic and non-physiologic extremes of i.v. contrast densities on intensity modulated radiotherapy (IMRT) plans for patients with head and neck cancer was investigated. METHODS AND MATERIALS This planning study was conducted using i.v. contrast CT scans of ten patients with squamous cell cancer of the head and neck treated with IMRT. The target volumes and normal tissues, including the blood vessels of the head and neck, were contoured and IMRT plans were created according to RTOG Protocol 0022. The density within the blood vessels was then virtually altered to mimic non-contrast and extreme (bone and air) densities. The dose was then recalculated using the same IMRT plan. Plans obtained with and without density overrides were then compared. RESULTS The change in planning target volume (PTV) coverage for plans with and without i.v. contrast was minimal. The volume of the PTVs covered by the 93% and 100% isodoses changed on average by 0.57%. The minimum dose to PTVs varied by a maximum of 0.17 Gy. The maximum point dose to critical organs changed by a maximum of 0.12 Gy (brainstem). Non-physiologic extremes of density within blood vessels also resulted in minimal changes in tumor or normal tissue dosimetry. CONCLUSION The use of i.v. contrast at time of CT-simulation does not significantly affect dose calculation in head and neck IMRT plans.
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Burridge NA, Rowbottom CG, Burt PA. Effect of contrast enhanced CT scans on heterogeneity corrected dose computations in the lung. J Appl Clin Med Phys 2006; 7:1-12. [PMID: 17533351 PMCID: PMC5722395 DOI: 10.1120/jacmp.v7i4.2240] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2006] [Revised: 07/27/2006] [Accepted: 12/31/1969] [Indexed: 11/23/2022] Open
Abstract
The aim of this study was to investigate and, if possible, compensate for the effect of intravenous contrast‐enhanced CT scans on the treatment planning dose distributions for lung patients. The contrast and noncontrast CT scans of 3 patients were registered, and the effect of contrast on the Hounsfield units (HU) was assessed. The effect of contrast was then simulated in the CT scans of 18 patients receiving radiotherapy of the lung by modification of the CT numbers for relevant sections of noncontrast‐enhanced CT scans. All treatment planning was performed on the Pinnacle3 planning system. The dose distributions computed from simulated contrast CT scans were compared to the original dose distributions by comparison of the monitor units (MUs) for each beam in the treatment plan required to deliver the prescribed dose to the isocenter as well as a comparison of the total MUs for each patient, a percentage change in required MUs being equivalent to a percentage change in the dose. A correction strategy to enable the use of contrast‐enhanced CT scans in treatment planning was developed, and the feasibility of applying the strategy was investigated by calculating dose distributions for both the original and simulated contrast CT scans. A mean increase in the overall patient MUs of 1.0 ± 0.8% was found, with a maximum increase of 3.3% when contrast was simulated on the original CT scans. The simulated contrast scans confirmed that the use of contrast‐enhanced CT scans for routine treatment planning would result in a systematic change in the dose delivered to the isocenter. The devised correction strategy had no clinically relevant effect on the dose distribution for the original CT scans. The application of the correction strategy to the simulated contrast CT scans led to a reduction of the mean difference in the overall MUs to 0.1 ± 0.2% compared to the original scan, demonstrating that the effect of contrast was eliminated with the correction strategy. This work has highlighted the problems associated with using contrast‐enhanced CT scans in heterogeneity corrected dose computation. Contrast visible in the CT scan is transient and should not be accounted for in the treatment plan. A correction strategy has been developed that minimizes the effect of intravenous contrast while having no clinical effect on noncontrast CT scans. The correction strategy allows the use of contrast without detriment to the treatment plan. PACS number: 87.53.Tf
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Affiliation(s)
- Nichola A Burridge
- North Western Medical Physics, Christie Hospital NHS Trust, Manchester, United Kingdom.
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Choi Y, Kim JK, Lee HS, Hur WJ, Hong YS, Park S, Ahn K, Cho H. Influence of intravenous contrast agent on dose calculations of intensity modulated radiation therapy plans for head and neck cancer. Radiother Oncol 2006; 81:158-62. [PMID: 17050020 DOI: 10.1016/j.radonc.2006.09.010] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Revised: 09/19/2006] [Accepted: 09/22/2006] [Indexed: 11/22/2022]
Abstract
BACKGROUND AND PURPOSE To evaluate the effect of an intravenous contrast agent (CA) on dose calculations and its clinical significance in intensity modulated radiation therapy (IMRT) plans for head and neck cancer. MATERIALS AND METHODS Fifteen patients with head and neck cancer and involved neck nodes were enrolled. Each patient took two sets of computerized tomography (CT) in the same position before and after intravenous CA injections. Target volumes and organs at risk (OAR) were contoured on the enhanced CT, and then an IMRT plan of nine equiangular beams with a 6 MV X-ray was created. After the fusion of non-enhanced and enhanced CTs, the contours and the IMRT plan created from the enhanced CT were copied and placed to the non-enhanced CT. Doses were calculated again from the non-enhanced CT by the same IMRT plan. The radiation doses calculated from the two sets of CTs were compared with regard to planning target volumes (PTV) and the three OARs, both parotid glands and the spinal cord, by Wilcoxon's signed rank test. RESULTS The doses (maximum, mean, and the dose of 95% of PTV received (D95%)) of PTV70 and PTV59.4 calculated from the enhanced CTs were lower than those from the non-enhanced CTs (p < 0.05), but the dose differences were less than 1% compared to the doses calculated from the enhanced CTs. The doses of PTV50.4, parotid glands, and spinal cord were not significantly different between the non-enhanced and enhanced CTs. CONCLUSIONS The difference between the doses calculated from the CTs with and without CA enhancement was tolerably small, therefore using intravenous CA could be recommended for the planning CT of head and neck IMRT.
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Affiliation(s)
- Youngmin Choi
- Department of Radiation Oncology, College of Medicine, Dong-A University Hospital, Sugu, Busan, South Korea.
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