1
|
Paoletti L, Ceccarelli C, Menichelli C, Aristei C, Borghesi S, Tucci E, Bastiani P, Cozzi S. Special stereotactic radiotherapy techniques: procedures and equipment for treatment simulation and dose delivery. Rep Pract Oncol Radiother 2022; 27:1-9. [PMID: 35402024 PMCID: PMC8989452 DOI: 10.5603/rpor.a2021.0129] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 11/14/2021] [Indexed: 12/25/2022] Open
Abstract
Stereotactic radiotherapy (SRT ) is a multi-step procedure with each step requiring extreme accuracy. Physician-dependent accuracy includes appropriate disease staging, multi-disciplinary discussion with shared decision-making, choice of morphological and functional imaging methods to identify and delineate the tumor target and organs at risk, an image-guided patient set-up, active or passive management of intra-fraction movement, clinical and instrumental follow-up. Medical physicist-dependent accuracy includes use of advanced software for treatment planning and more advanced Quality Assurance procedures than required for conventional radiotherapy. Consequently, all the professionals require appropriate training in skills for high-quality SRT. Thanks to the technological advances, SRT has moved from a “frame-based” technique, i.e. the use of stereotactic coordinates which are identified by means of rigid localization frames, to the modern “frame-less” SRT which localizes the target volume directly, or by means of anatomical surrogates or fiducial markers that have previously been placed within or near the target. This review describes all the SRT steps in depth, from target simulation and delineation procedures to treatment delivery and image-guided radiation therapy. Target movement assessment and management are also described.
Collapse
Affiliation(s)
- Lisa Paoletti
- Radiotherapy Unit, AUSL Toscana Centro, Florence, Italy
| | | | | | - Cynthia Aristei
- Radiation Oncology Section, University of Perugia and Perugia General Hospital, Italy
| | - Simona Borghesi
- Radiation Oncology Unit of Arezzo-Valdarno, Azienda USL Toscana Sud Est, Italy
| | - Enrico Tucci
- Radiation Oncology Unit of Arezzo-Valdarno, Azienda USL Toscana Sud Est, Italy
| | | | - Salvatore Cozzi
- Radiation Oncology Unit, Azienda Unità Sanitaria Locale - IRCCS di Reggio Emilia, Italy
| |
Collapse
|
2
|
Worm ES, Hansen R, Høyer M, Weber B, Mortensen H, Poulsen PR. Uniform versus non-uniform dose prescription for proton stereotactic body radiotherapy of liver tumors investigated by extensive motion-including treatment simulations. Phys Med Biol 2021; 66. [PMID: 34544071 DOI: 10.1088/1361-6560/ac2880] [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: 04/08/2021] [Accepted: 09/20/2021] [Indexed: 12/24/2022]
Abstract
Compared to x-ray-based stereotactic body radiotherapy (SBRT) of liver cancer, proton SBRT may reduce the normal liver tissue dose. For an optimal trade-off between target and liver dose, a non-uniform dose prescription is often applied in x-ray SBRT, but lacks investigation for proton SBRT. Also, proton SBRT is prone to breathing-induced motion-uncertainties causing target mishit or dose alterations by interplay with the proton delivery. This study investigated non-uniform and uniform dose prescription in proton-based liver SBRT, including effects of rigid target motion observed during planning-4DCT and treatment. The study was based on 42 x-ray SBRT fractions delivered to 14 patients under electromagnetic motion-monitoring. For each patient, a non-uniform and uniform proton plan were made. The uniform plan was renormalized to be iso-toxic with the non-uniform plan using a NTCP model for radiation-induced liver disease. The motion data were used in treatment simulations to estimate the delivered target dose with rigid motion. Treatment simulations were performed with and without a repainting scheme designed to mitigate interplay effects. Including rigid motion, the achieved CTV mean dose after three fractions delivered without repainting was on average (±SD) 24.8 ± 8.4% higher and the D98%was 16.2 ± 11.3% higher for non-uniform plans than for uniform plans. The interplay-induced increase in D2%relative to the static plans was reduced from 3.2 ± 4.1% without repainting to -0.5 ± 1.7% with repainting for non-uniform plans and from 1.5 ± 2.0% to 0.1 ± 1.3% for uniform plans. Considerable differences were observed between estimated CTV doses based on 4DCT motion and intra-treatment motion. In conclusion, non-uniform dose prescription in proton SBRT may provide considerably higher tumor doses than uniform prescription for the same complication risk. Due to motion variability, target doses estimated from 4DCT motion may not accurately reflect the delivered dose. Future studies including modelling of deformations and associated range uncertainties are warranted to confirm the findings.
Collapse
Affiliation(s)
| | - Rune Hansen
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark
| | - Morten Høyer
- Danish Center for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - Britta Weber
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.,Danish Center for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - Hanna Mortensen
- Danish Center for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - Per Rugaard Poulsen
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark.,Danish Center for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| |
Collapse
|
3
|
Thaper D, Singh G, Kamal R, Oinam AS, Yadav HP, Kumar R, Kumar V. Impact of dose heterogeneity in target on TCP and NTCP for various radiobiological models in liver SBRT: different isodose prescription strategy. Biomed Phys Eng Express 2021; 7:015020. [PMID: 33522499 DOI: 10.1088/2057-1976/abd3f0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
INTRODUCTION The impact of dose heterogeneity within the tumor on TCP and NTCP was studied using various radiobiological models. The effect of the degree of heterogeneity index (HI) on TCP was also analyzed. MATERIALS AND METHODS Thirty-seven pre-treated liver SBRT cases were included in this study. Two different kinds of treatment techniques were employed. In both arms, the prescribed dose was received by 95% of the PTV. Initially, the inhomogeneous treatment plans (IHTP) were made in which the spatial change of dose within the PTV was high and the maximum dose within the PTV can go up to 160%. Subsequently, in another arm, homogeneous treatment plans (HTP) were generated in which PTV was covered with the same prescription isodose and the maximum dose can go up to 120%. As per RTOG 1112, all organs at risk (OAR's) were considered while optimization of the treatment plans. TCP was calculated using the Niemierko and Poisson model. NTCP was calculated using the Niemierko and LKB fractionated model. RESULTS For the IHTP, TCP was decreasing as 'a' value decreased in the Niemierko model whereas, for HTP, TCP was found to be the same. NTCP of the normal liver was less in IHTP as compared to HTP, and the Niemierko model overestimates the NTCP as compared to LKB fractionated model. NTCP for all other OAR's was <1% in both kinds of treatment plans. CONCLUSION IHTP is found to be clinically better than HTP because NTCP of the normal liver was significantly less and TCP was more for certain 'a' values of the Niemierko model and the Poisson model. There is not any effect of HI on TCP was observed. Advances in knowledge: IHTP could be used clinically because of the dose-escalation and subsequently, leads to an increase in the TCP.
Collapse
Affiliation(s)
- Deepak Thaper
- Centre for Medical Physics, Panjab University, Chandigarh, India. Department of Radiation Oncology, Institute of Liver and Biliary Sciences, New Delhi, India
| | | | | | | | | | | | | |
Collapse
|
4
|
Hansen AT, Poulsen PR, Høyer M, Worm ES. Isotoxic dose prescription level strategies for stereotactic liver radiotherapy: the price of dose uniformity. Acta Oncol 2020; 59:558-564. [PMID: 31833432 DOI: 10.1080/0284186x.2019.1701200] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Introduction: To find the optimal dose prescription strategy for liver SBRT, this study investigated the tradeoffs between achievable target dose and healthy liver dose for a range of isotoxic uniform and non-uniform prescription level strategies.Material and methods: Nine patients received ten liver SBRT courses with intrafraction motion monitoring during treatment. After treatment, five VMAT treatment plans were made for each treatment course. The PTV margin was 5 mm (left-right, anterior-posterior) and 10 mm (cranio-caudal). All plans had a mean CTV dose of 56.25 Gy in three fractions, while the PTV was covered by 50%, 67%, 67 s% (steep dose gradient outside CTV), 80%, and 95% of this dose, respectively. The 50%, 67 s%, 80%, and 95% plans were then renormalized to be isotoxic with the standard 67% plan according to a Lyman-Kutcher-Burman normal tissue complication probability model for radiation induced liver disease. The CTV D98 and mean dose of the iso-toxic plans were calculated both without and with the observed intrafraction motion, using a validated method for motion-including dose reconstruction.Results: Under isotoxic conditions, the average [range] mean CTV dose per fraction decreased gradually from 21.2 [20.5-22.7] Gy to 15.5 [15.0-16.6] Gy and the D98 dose per fraction decreased from 20.4 [19.7-21.7] Gy to 15.0 [14.5-15.5] Gy, as the prescription level to the PTV rim was increased from 50% to 95%. With inclusion of target motion the mean CTV dose was 20.5 [16.5-22.5] Gy (50% PTV rim dose) and 15.4 [13.9-16.7] Gy (95% rim dose) while D98 was 17.8 [7.4-20.6] Gy (50% rim dose) and 14.6 [8.8-15.7] Gy (95% rim dose).Conclusion: Requirements of a uniform PTV dose come at the price of excess normal tissue dose. A non-uniform PTV dose allows increased CTV mean dose at the cost of robustness toward intrafraction motion. The increase in planned CTV dose by non-uniform prescription outbalanced the dose deterioration caused by motion.
Collapse
Affiliation(s)
- Anders T. Hansen
- Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark
| | - Per R. Poulsen
- Department of Oncology, Aarhus University Hospital, Aarhus, Denmark
- The Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - Morten Høyer
- The Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark
| | - Esben S. Worm
- Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark
| |
Collapse
|
5
|
Hillman Y, Kim J, Chetty I, Wen N. Refinement of MLC modeling improves commercial QA dosimetry system for SRS and SBRT patient-specific QA. Med Phys 2018; 45:1351-1359. [DOI: 10.1002/mp.12808] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 01/15/2018] [Accepted: 01/23/2018] [Indexed: 01/17/2023] Open
Affiliation(s)
- Yair Hillman
- Department of Radiation Oncology; Karmanos Cancer Institute at McLaren Macomb; Mt. Clemens MI USA
| | - Josh Kim
- Department of Radiation Oncology; Henry Ford Hospital; Detroit MI USA
| | - Indrin Chetty
- Department of Radiation Oncology; Henry Ford Hospital; Detroit MI USA
| | - Ning Wen
- Department of Radiation Oncology; Henry Ford Hospital; Detroit MI USA
| |
Collapse
|
6
|
Yeo UA, Taylor ML, Supple JR, Siva S, Kron T, Pham D, Franich RD. Evaluation of dosimetric misrepresentations from 3D conventional planning of liver SBRT using 4D deformable dose integration. J Appl Clin Med Phys 2014; 15:4978. [PMID: 25493523 PMCID: PMC5711129 DOI: 10.1120/jacmp.v15i6.4978] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2014] [Revised: 07/27/2014] [Accepted: 07/18/2014] [Indexed: 12/25/2022] Open
Abstract
The purpose of this study is to evaluate dosimetric errors in 3D conventional planning of stereotactic body radiotherapy (SBRT) by using a 4D deformable image registration (DIR)‐based dose‐warping and integration technique. Respiratory‐correlated 4D CT image sets with 10 phases were acquired for four consecutive patients with five liver tumors. Average intensity projection (AIP) images were used to generate 3D conventional plans of SBRT. Quasi‐4D path‐integrated dose accumulation was performed over all 10 phases using dose‐warping techniques based on DIR. This result was compared to the conventional plan in order to evaluate the appropriateness of 3D (static) dose calculations. In addition, we consider whether organ dose metrics derived from contours defined on the average intensity projection (AIP), or on a reference phase, provide the better approximation of the 4D values. The impact of using fewer (<10) phases was also explored. The AIP‐based 3D planning approach overestimated doses to targets by 1.4% to 8.7% (mean 4.2%) and underestimated dose to normal liver by up to 8% (mean −5.5%; range −2.3% to −8.0%), compared to the 4D methodology. The homogeneity of the dose distribution was overestimated when using conventional 3D calculations by up to 24%. OAR doses estimated by 3D planning were, on average, within 10% of the 4D calculations; however, differences of up to 100% were observed. Four‐dimensional dose calculation using 3 phases gave a reasonable approximation of that calculated from the full 10 phases for all patients, which is potentially useful from a workload perspective. 4D evaluation showed that conventional 3D planning on an AIP can significantly overestimate target dose (ITV and GTV+5mm), underestimate normal liver dose, and overestimate dose homogeneity. Implementing nonadaptive quasi‐4D dose calculation can highlight the potential limitation of 3D conventional SBRT planning and the resultant misrepresentations of dose in some regions affected by motion and deformation. Where the 4D approach is unavailable, contouring on the full expiration phase may yield more accurate dose calculations, most relevant in the case of the healthy liver, but the absolute dose differences are in general small for the other healthy organs. The technique has the potential to quantify under‐ and over‐dosage and improve treatment plan evaluation, retrospective plan analysis, and clinical outcome correlation. PACS numbers: 87.55.‐x, 87.55.D‐, 87.55.de, 87.55.dk, 87.55.Qr, 87.57.nj
Collapse
Affiliation(s)
- Unjin A Yeo
- Radiation Oncology Victoria and RMIT University.
| | | | | | | | | | | | | |
Collapse
|
7
|
Poulsen PR, Worm ES, Petersen JBB, Grau C, Fledelius W, Høyer M. Kilovoltage intrafraction motion monitoring and target dose reconstruction for stereotactic volumetric modulated arc therapy of tumors in the liver. Radiother Oncol 2014; 111:424-30. [PMID: 24997991 DOI: 10.1016/j.radonc.2014.05.007] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Revised: 04/30/2014] [Accepted: 05/24/2014] [Indexed: 12/21/2022]
Abstract
PURPOSE To use intrafraction kilovoltage (kV) imaging during liver stereotactic body radiotherapy (SBRT) delivered by volumetric modulated arc therapy (VMAT) to estimate the intra-treatment target motion and to reconstruct the delivered target dose. METHODS Six liver SBRT patients with 2-3 implanted gold markers received SBRT in three fractions of 18.75 Gy or 25 Gy. CTV-to-PTV margins of 5 mm in the axial plane and 10 mm in the cranio-caudal directions were applied. A VMAT plan was designed to give minimum target doses of 95% (CTV) and 67% (PTV). At each fraction, the 3D marker trajectory was estimated by fluoroscopic kV imaging throughout treatment delivery and used to reconstruct the actually delivered CTV dose. The reduction in D95 (minimum dose to 95% of the CTV) relative to the planned D95 was calculated. RESULTS The kV position estimation had mean root-mean-square errors of 0.36 mm and 0.47 mm parallel and perpendicular to the kV imager, respectively. Intrafraction motion caused a mean 3D target position error of 2.9 mm and a mean D95 reduction of 6.0%. The D95 reduction correlated with the mean 3D target position error during a fraction. CONCLUSIONS Kilovoltage imaging for detailed motion monitoring with dose reconstruction of VMAT-based liver SBRT was demonstrated for the first time showing large dosimetric impact of intrafraction tumor motion.
Collapse
Affiliation(s)
- Per Rugaard Poulsen
- Department of Oncology, Aarhus University Hospital, Denmark; Institute of Clinical Medicine, Aarhus University, Denmark.
| | - Esben S Worm
- Department of Oncology, Aarhus University Hospital, Denmark; Department of Medical Physics, Aarhus University Hospital, Denmark
| | | | - Cai Grau
- Department of Oncology, Aarhus University Hospital, Denmark; Institute of Clinical Medicine, Aarhus University, Denmark
| | - Walther Fledelius
- Department of Oncology, Aarhus University Hospital, Denmark; Department of Medical Physics, Aarhus University Hospital, Denmark
| | - Morten Høyer
- Department of Oncology, Aarhus University Hospital, Denmark; Institute of Clinical Medicine, Aarhus University, Denmark
| |
Collapse
|
8
|
Stereotactic ablative body radiation therapy with dynamic conformal multiple arc therapy for liver tumors: Optimal isodose line fitting to the planning target volume. Pract Radiat Oncol 2014; 4:e7-e13. [DOI: 10.1016/j.prro.2013.04.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Revised: 03/07/2013] [Accepted: 04/04/2013] [Indexed: 12/31/2022]
|
9
|
Eccles CL, Lindsay PE, Craig TD, Kim JJ, Dawson LA. Dosimetric Impact of Image-Guided Radiotherapy in Liver Stereotactic Radiotherapy. J Med Imaging Radiat Sci 2013; 44:5-13. [DOI: 10.1016/j.jmir.2012.09.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 08/29/2012] [Accepted: 09/06/2012] [Indexed: 11/28/2022]
|
10
|
Hypofraction radiotherapy of liver tumor using cone beam computed tomography guidance combined with active breath control by long breath-holding. Radiother Oncol 2012; 104:379-85. [DOI: 10.1016/j.radonc.2011.11.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 11/07/2011] [Accepted: 11/22/2011] [Indexed: 12/25/2022]
|
11
|
Breedveld S, Storchi PRM, Voet PWJ, Heijmen BJM. iCycle: Integrated, multicriterial beam angle, and profile optimization for generation of coplanar and noncoplanar IMRT plans. Med Phys 2012; 39:951-63. [PMID: 22320804 DOI: 10.1118/1.3676689] [Citation(s) in RCA: 222] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To introduce iCycle, a novel algorithm for integrated, multicriterial optimization of beam angles, and intensity modulated radiotherapy (IMRT) profiles. METHODS A multicriterial plan optimization with iCycle is based on a prescription called wish-list, containing hard constraints and objectives with ascribed priorities. Priorities are ordinal parameters used for relative importance ranking of the objectives. The higher an objective priority is, the higher the probability that the corresponding objective will be met. Beam directions are selected from an input set of candidate directions. Input sets can be restricted, e.g., to allow only generation of coplanar plans, or to avoid collisions between patient/couch and the gantry in a noncoplanar setup. Obtaining clinically feasible calculation times was an important design criterium for development of iCycle. This could be realized by sequentially adding beams to the treatment plan in an iterative procedure. Each iteration loop starts with selection of the optimal direction to be added. Then, a Pareto-optimal IMRT plan is generated for the (fixed) beam setup that includes all so far selected directions, using a previously published algorithm for multicriterial optimization of fluence profiles for a fixed beam arrangement Breedveld et al. [Phys. Med. Biol. 54, 7199-7209 (2009)]. To select the next direction, each not yet selected candidate direction is temporarily added to the plan and an optimization problem, derived from the Lagrangian obtained from the just performed optimization for establishing the Pareto-optimal plan, is solved. For each patient, a single one-beam, two-beam, three-beam, etc. Pareto-optimal plan is generated until addition of beams does no longer result in significant plan quality improvement. Plan generation with iCycle is fully automated. RESULTS Performance and characteristics of iCycle are demonstrated by generating plans for a maxillary sinus case, a cervical cancer patient, and a liver patient treated with SBRT. Plans generated with beam angle optimization did better meet the clinical goals than equiangular or manually selected configurations. For the maxillary sinus and liver cases, significant improvements for noncoplanar setups were seen. The cervix case showed that also in IMRT with coplanar setups, beam angle optimization with iCycle may improve plan quality. Computation times for coplanar plans were around 1-2 h and for noncoplanar plans 4-7 h, depending on the number of beams and the complexity of the site. CONCLUSIONS Integrated beam angle and profile optimization with iCycle may result in significant improvements in treatment plan quality. Due to automation, the plan generation workload is minimal. Clinical application has started.
Collapse
Affiliation(s)
- Sebastiaan Breedveld
- Department of Radiation Oncology, Erasmus MC Rotterdam, Groene Hilledijk 301, 3075 EA Rotterdam, The Netherlands.
| | | | | | | |
Collapse
|
12
|
Bujold A, Dawson LA. Stereotactic radiation therapy and selective internal radiation therapy for hepatocellular carcinoma. Cancer Radiother 2011; 15:54-63. [PMID: 21239204 DOI: 10.1016/j.canrad.2010.11.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 07/21/2010] [Indexed: 12/17/2022]
Abstract
Recent technological advances allow precise and safe radiation delivery in hepatocellular carcinoma. Stereotactic body radiotherapy is a conformal external beam radiation technique that uses a small number of relatively large fractions to deliver potent doses of radiation therapy to extracranial sites. It requires stringent breathing motion control and image guidance. Selective internal radiotherapy or radioembolization refers to the injection of radioisotopes, usually delivered to liver tumors via the hepatic artery. Clinical results for both treatments show that excellent local control is possible with acceptable toxicity. Most appropriate patient populations and when which type of radiation therapy should be best employed in the vast therapeutic armamentarium of hepatocellular carcinoma are still to be clarified.
Collapse
Affiliation(s)
- A Bujold
- Radiation Medicine Program, Princess Margaret Hospital, 610 University Avenue, Toronto, Ontario, Canada
| | | |
Collapse
|
13
|
Stereotactic Body Radiation Therapy for Liver Tumors: Impact of Daily Setup Corrections and Day-to-Day Anatomic Variations on Dose in Target and Organs at Risk. Int J Radiat Oncol Biol Phys 2009; 75:1201-8. [DOI: 10.1016/j.ijrobp.2008.12.020] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2008] [Revised: 12/07/2008] [Accepted: 12/09/2008] [Indexed: 11/20/2022]
|
14
|
Richter A, Baier K, Meyer J, Wilbert J, Krieger T, Flentje M, Guckenberger M. Influence of increased target dose inhomogeneity on margins for breathing motion compensation in conformal stereotactic body radiotherapy. BMC MEDICAL PHYSICS 2008; 8:5. [PMID: 19055768 PMCID: PMC2637830 DOI: 10.1186/1756-6649-8-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Accepted: 12/03/2008] [Indexed: 12/25/2022]
Abstract
Background Breathing motion should be considered for stereotactic body radiotherapy (SBRT) of lung tumors. Four-dimensional computer tomography (4D-CT) offers detailed information of tumor motion. The aim of this work is to evaluate the influence of inhomogeneous dose distributions in the presence of breathing induced target motion and to calculate margins for motion compensation. Methods Based on 4D-CT examinations, the probability density function of pulmonary tumors was generated for ten patients. The time-accumulated dose to the tumor was calculated using one-dimensional (1D) convolution simulations of a 'static' dose distribution and target probability density function (PDF). In analogy to stereotactic body radiotherapy (SBRT), different degrees of dose inhomogeneity were allowed in the target volume: minimum doses of 100% were prescribed to the edge of the target and maximum doses varied between 102% (P102) and 150% (P150). The dose loss due to breathing motion was quantified and margins were added until this loss was completely compensated. Results With the time-weighted mean tumor position as the isocentre, a close correlation with a quadratic relationship between the standard deviation of the PDF and the margin size was observed. Increased dose inhomogeneity in the target volume required smaller margins for motion compensation: margins of 2.5 mm, 2.4 mm and 1.3 mm were sufficient for compensation of 11.5 mm motion range and standard deviation of 3.9 mm in P105, P125 and P150, respectively. This effect of smaller margins for increased dose inhomogeneity was observed for all patients. Optimal sparing of the organ-at-risk surrounding the target was achieved for dose prescriptions P105 to P118. The internal target volume concept over-compensated breathing motion with higher than planned doses to the target and increased doses to the surrounding normal tissue. Conclusion Treatment planning with inhomogeneous dose distributions in the target volume required smaller margins for compensation of breathing induced target motion with the consequence of lower doses to the surrounding organs-at-risk.
Collapse
Affiliation(s)
- Anne Richter
- Julius-Maximilians-University, Department of Radiation Oncology, Wuerzburg, Germany.
| | | | | | | | | | | | | |
Collapse
|
15
|
de Pooter JA, Méndez Romero A, Wunderink W, Storchi PRM, Heijmen BJM. Automated non-coplanar beam direction optimization improves IMRT in SBRT of liver metastasis. Radiother Oncol 2008; 88:376-81. [PMID: 18585809 DOI: 10.1016/j.radonc.2008.06.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Revised: 05/29/2008] [Accepted: 06/09/2008] [Indexed: 11/19/2022]
Abstract
PURPOSE To investigate whether automatically optimized coplanar, or non-coplanar beam setups improve intensity modulated radiotherapy (IMRT) treatment plans for stereotactic body radiotherapy (SBRT) of liver tumors, compared to a reference equi-angular IMRT plan. METHODS For a group of 13 liver patients, an in-house developed beam selection algorithm (Cycle) was used for generation of 3D-CRT plans with either optimized coplanar-, or non-coplanar beam setups. These 10 field, coplanar and non-coplanar setups, and an 11 field, equi-angular coplanar reference setup were then used as input for generation of IMRT plans. For all plans, the PTV dose was maximized in an iterative procedure by increasing the prescribed PTV dose in small steps until further increase was prevented by constraint violation(s). RESULTS For optimized non-coplanar setups, D(PTV, max) increased by on average 30% (range 8-64%) compared to the corresponding reference IMRT plan. Similar increases were observed for D(PTV, 99%) and gEUD(a). For optimized coplanar setups, mean PTV dose increases were only approximately 4%. After re-scaling all plans to the clinically applied dose, optimized non-coplanar configurations resulted in the best sparing of organs at risk (healthy liver, spinal cord, bowel). CONCLUSION Compared to an equi-angular beam setup, computer optimized non-coplanar setups do result in substantial improvements in IMRT plans for SBRT of liver tumors.
Collapse
Affiliation(s)
- Jacco A de Pooter
- Department of Radiation Oncology, Erasmus MC - Daniel den Hoed Cancer Center, Rotterdam, The Netherlands.
| | | | | | | | | |
Collapse
|
16
|
Georg D, Hillbrand M, Stock M, Dieckmann K, Pötter R. Can protons improve SBRT for lung lesions? Dosimetric considerations. Radiother Oncol 2008; 88:368-75. [PMID: 18405986 DOI: 10.1016/j.radonc.2008.03.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Revised: 03/05/2008] [Accepted: 03/06/2008] [Indexed: 10/22/2022]
Abstract
BACKGROUND AND PURPOSE The aim of the present study was to investigate potential dosimetric benefits of proton therapy for hypofractionated stereotactic body radiotherapy (SBRT). MATERIALS AND METHOD Twelve patients undergoing hypofractionated SBRT at the Medical University Vienna were selected. Passively scattered protons (PT) and intensity modulated proton therapy (IMPT) were evaluated against a conformal photon technique (3D-CRT), assuming a fractionation of 3x15Gy, prescribed to the 65% isodose. For all treatment techniques shallow breathing with abdominal compression (SB+AC) was compared with a deep inspiration breath hold technique (DIBH). Treatment planning was done with XiO (CMS, USA). Target conformity, dose-volume histograms (DVH) and various associated dosimetric parameters were considered for the planning target volume (PTV), lung, heart and esophagus. RESULTS For both breathing conditions conformity indices were very similar. They were between 0.75 and 0.78 for IMPT and 3D-CRT and around 0.55 for PT using 2-3 beams. Irrespective of treatment modality, DVHs for the ipsilateral lung were improved with the DIBH technique. For the PT technique, the 2Gy isodose (V2Gy) covered on average 7-9% less lung volume compared to 3D-CRT, for IMPT this reduction was more than 10%. Volumes covered the 4 and 6Gy isodoses were 2-4% smaller for IMPT, but very similar for PT and 3D-CRT. Both proton techniques achieved full sparing of the contralateral lung and superior sparing of the heart. Maximum doses to the heart and esophagus were on average around 3Gy for 3D-CRT and almost 0Gy for both proton techniques. For 3D-CRT average V2Gy values for the heart could be reduced from 64% in shallow breathing to 34% in DIBH. V2Gy for protons was negligible. CONCLUSIONS Only small dosimetric differences were found between photons and protons for SBRT of lung lesions. Whether these small dosimetric benefits translate in reduced side effects or have the potential to improve local control rates remains to be demonstrated in clinical studies.
Collapse
Affiliation(s)
- Dietmar Georg
- Department of Radiotherapy, Medical University Vienna/AKH Vienna, Vienna, Austria.
| | | | | | | | | |
Collapse
|
17
|
Woudstra E, Heijmen BJM, Storchi PRM. A comparison of an algorithm for automated sequential beam orientation selection (Cycle) with simulated annealing. Phys Med Biol 2008; 53:2003-18. [DOI: 10.1088/0031-9155/53/8/001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|