Radiation dose verification using real tissue phantom in modern radiotherapy techniques

Gurjar, Om Prakash; Mishra, Smita; Bhandari, Virendra; Pathak, Pankaj; Patel, Prapti; Shrivastav, Garima

doi:10.4103/0971-6203.125504

Cited by 26 publications

(20 citation statements)

References 10 publications

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“…We embarked on a series of experiments to validate the MC doses vs doses measured in the near‐reality phantoms for different geometries. Using animal tissues to validate dose calculations is a common method and yielded great results as described by Zheng, Grassberger, and Gurjar, though most of this work was done for passively scattered or uniformly scanned proton beams. Our aim was to develop phantoms that can validate the calculated dose “inside” the phantom and not “on the other side,” that is, a transmission‐type measurement.…”

Section: Introductionmentioning

confidence: 99%

Validation of the RayStation Monte Carlo dose calculation algorithm using realistic animal tissue phantoms

Schreuder

Bridges

Rigsby

et al. 2019

J Applied Clin Med Phys

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Purpose Our purposes are to compare the accuracy of RaySearch's analytical pencil beam (APB) and Monte Carlo (MC) algorithms for clinical proton therapy and to present clinical validation data using a novel animal tissue lung phantom. Methods We constructed a realistic lung phantom composed of a rack of lamb resting on a stack of rectangular natural cork slabs simulating lung tissue. The tumor was simulated using 70% lean ground lamb meat inserted in a spherical hole with diameter 40 ± 5 mm carved into the cork slabs. A single‐field plan using an anterior beam and a two‐field plan using two anterior‐oblique beams were delivered to the phantom. Ion chamber array measurements were taken medial and distal to the tumor. Measured doses were compared with calculated RayStation APB and MC calculated doses. Results Our lung phantom enabled measurements with the MatriXX PT at multiple depths in the phantom. Using the MC calculations, the 3%/3 mm gamma index pass rates, comparing measured with calculated doses, for the distal planes were 74.5% and 85.3% for the APB and 99.1% and 92% for the MC algorithms. The measured data revealed up to 46% and 30% underdosing within the distal regions of the target volume for the single and the two field plans when APB calculations are used. These discrepancies reduced to less than 18% and 7% respectively using the MC calculations. Conclusions RaySearch Laboratories' Monte Carlo dose calculation algorithm is superior to the pencil‐beam algorithm for lung targets. Clinicians relying on the analytical pencil‐beam algorithm should be aware of its pitfalls for this site and verify dose prior to delivery. We conclude that the RayStation MC algorithm is reliable and more accurate than the APB algorithm for lung targets and therefore should be used to plan proton therapy for patients with lung cancer.

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Section: Introductionmentioning

confidence: 99%

Validation of the RayStation Monte Carlo dose calculation algorithm using realistic animal tissue phantoms

Schreuder

Bridges

Rigsby

et al. 2019

J Applied Clin Med Phys

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“…[14] In addition, the physical density of pinewood was measured by weighing one slab of dimension of 30 × 30 × 2 cm 3 .…”

Section: Methodsmentioning

confidence: 99%

A dosimetric study on slab-pinewood-slab phantom for developing the heterogeneous chest phantom mimicking actual human chest

2017

Self Cite

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The aim is to study the density, isodose depths, and doses at different points in slab-pinewood-slab (SPS) phantom, solid phantom SP34 (made up of polystyrene), and chest level of actual patient for developing heterogeneous chest phantom mimicking thoracic region of human body. A 6 MV photon beam of field size of 10 cm × 10 cm was directed perpendicular to the surface of computed tomography (CT) images of chest level of patient, SPS phantom, and SP34 phantom. Dose was calculated using anisotropic analytical algorithm. Hounsfield units were used to calculate the density of each medium. Isodose depths in all the three sets of CT images were measured. Variations between planned doses on treatment planning system (TPS) and measured on linear accelerator (LA) were calculated for three points, namely, near slab–pinewood interfaces (6 and 18 cm depths) and 10 cm depth in SPS phantom and at the same depths in SP34 phantom. Density of pinewood, SP34 slabs, chest wall, lung, and soft tissue behind lung was measured as 0.329 ± 0.08, 0.999 ± 0.02, 0.898 ± 0.02, 0.291 ± 0.12, and 1.002 ± 0.03 g/cc, respectively. Depths of 100% and 90% isodose curves in all the three sets of CT images were found to be similar. Depths of 80%, 70%, 60%, 50%, and 40% isodose lines in SPS phantom images were found to be equivalent to that in chest images, while it was least in SP34 phantom images. Variations in doses calculated at 6, 10, and 18 cm depths on TPS and measured on LA were found to be 0.36%, 1.65%, and 2.23%, respectively, in case of SPS phantom, while 0.24%, 0.90%, and 0.93%, respectively, in case of SP34 slab phantom. SPS phantom seemed equivalent to the chest level of human body. Dosimetric results of this study indicate that patient-specific quality assurance can be done using chest phantom mimicking thoracic region of human body, which has been fabricated using polystyrene and pinewood.

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“…For the lung, fitting the LKB model to clinical complication data usually yields values of "n" close to unity. The initial and readjusted radiobiological parameters for AAA were used and then the NTCP were compared (16)(17)(18)(19). The initial radiobiological parameters were: n=0.87, m=0.18 and TD 50 =24.5 Gy.…”

Section: Ntcpmentioning

confidence: 99%

Correlation between pneumonitis risk in radiation oncology and lung density measured with X-ray computed tomography

Chaikh

Balosso

2016

Quant. Imaging Med. Surg.

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Background: The risk of toxicity with radiation oncology for lung cancer limits the maximal radiation dose that can be delivered to thoracic tumors. This study aims at investigating the correlation between normal tissue complication probability (NTCP) and physical lung density by analyzing the computed tomography (CT) scan imaging used for radiotherapy dose planning.Methods: Data from CT of lung cancer patients (n=10), treated with three dimensional radiotherapy, were selected for this study. The dose was calculated using analytical anisotropic algorithm (AAA). Dose volume histograms (DVH) for healthy lung (lung excluding targets) were calculated. The NTCP for lung radiation induced pneumonitis was computed using initial radiobiological parameters from Lyman-Kutcher and Burman (LKB) model and readjusted parameters for AAA, with α/β=3. The correlation coefficient "rho" was calculated using Spearman's rank test. The bootstrap method was used to estimate the 95% confidence interval (95% CI). Wilcoxon paired test was used to calculate P values.Results: Bootstrapping simulation revealed significant difference between NTCP computed with the initial radiobiological parameters and that computed with the parameters readjusted for AAA (P=0.03). The results of simulations based on 1,000 replications showed no correlation for NTCP with density, with "rho" <0.3.Conclusions: For a given set of patients, we assessed the correlation between NTCP and lung density using bootstrap analysis. The lack of correlation could result either from a very accurate dose calculation, by AAA, whatever the lung density yielding a NTCP result only dependant of the dose and not any more of the density; or to the very limited range of natural variation of relative electronic density (0.15 to 0.20) observed in this small series of patients. Another important parameter is the bootstrap simulation with 1,000 random samplings may have underestimated the correlation, since the initial data (n=10) showed a weak correlation.Keywords: Normal tissue complication probability (NTCP); radiotherapy; bootstrap; physical density of lung and statistical concepts, to estimate the tumor control probability (TCP) as well as the normal tissue complication probability (NTCP) (2-9). Most theoretical models, that have been developed to estimate the benefits/risks balance, are based on physical dose distribution and the biological effect in normal tissue. However, the accuracy of the estimated TCP/NTCP depends on the accuracy of the assessment of the delivered dose as well as uncertainties related to the clinical data and dose calculation methods. The purpose of this paper is to evaluate and quantify the correlation between NTCP estimates and physical lung density. The NTCP was computed using dosimetric data derived from the patients' dose volume histograms (DVH) with Lyman model. Methods Clinical cases and dose calculationData from computed tomography (CT-scans) in ten lung cancer patients, treated with 3-dimensional radiotherapy, were selected for this study. The clini...

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Radiation dose verification using real tissue phantom in modern radiotherapy techniques

Cited by 26 publications

References 10 publications

Validation of the RayStation Monte Carlo dose calculation algorithm using realistic animal tissue phantoms

Validation of the RayStation Monte Carlo dose calculation algorithm using realistic animal tissue phantoms

A dosimetric study on slab-pinewood-slab phantom for developing the heterogeneous chest phantom mimicking actual human chest

Correlation between pneumonitis risk in radiation oncology and lung density measured with X-ray computed tomography

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