Comparison of four commercial dose calculation algorithms in different evaluation tests.

BACKGROUND: Accurate and fast dose calculation is crucial in modern radiation therapy. Four dose calculation algorithms (AAA, AXB, CCC, and MC) are available in Varian Eclipse and RaySearch Laboratories RayStation Treatment Planning Systems (TPSs). OBJECTIVES: This study aims to evaluate and compare dosimetric accuracy of the four dose calculation algorithms applying to homogeneous and heterogeneous media, VMAT plans (based on AAPM TG-119 test cases), and the surface and buildup regions. METHODS: The four algorithms are assessed in homogeneous (IAEA-TECDOCE 1540) and heterogeneous (IAEA-TECDOC 1583) media. Dosimetric evaluation accuracy for VMAT plans is then analyzed, along with the evaluation of the accuracy of algorithms applying to the surface and buildup regions. RESULTS: Tests conducted in homogeneous media revealed that all algorithms exhibit dose deviations within 5% for various conditions, with pass rates exceeding 95% based on recommended tolerances. Additionally, the tests conducted in heterogeneous media demonstrate high pass rates for all algorithms, with a 100% pass rate observed for 6 MV and mostly 100% pass rate for 15 MV, except for CCC, which achieves a pass rate of 94%. The results of gamma index pass rate (GIPR) for dose calculation algorithms in IMRT fields show that GIPR (3% /3 mm) for all four algorithms in all evaluated tests based on TG119, are greater than 97%. The results of the algorithm testing for the accuracy of superficial dose reveal variations in dose differences, ranging from -11.9% to 7.03% for 15 MV and -9.5% to 3.3% for 6 MV, respectively. It is noteworthy that the AXB and MC algorithms demonstrate relatively lower discrepancies compared to the other algorithms. CONCLUSIONS: This study shows that generally, two dose calculation algorithms (AXB and MC) that calculate dose in medium have better accuracy than other two dose calculation algorithms (CCC and AAA) that calculate dose to water.

Dosimetry procedure to verify dose in High Dose Rate (HDR) brachytherapy treatment of cancer patients: A systematic review.

High dose rate (HDR) brachytherapy is a widely accepted cancer treatment method which provides high cure rates. In a HDR brachytherapy treatment, high radiation doses are delivered to the tumor area by placing the radioactive sources in the close proximity to the region of interest. The brachytherapy dose delivery follows the inverse square law with rapid dose fall of leading to minimal damage to the surrounding normal tissue. The safe direct delivery of the radiation dose to the tumour leads to good treatment outcomes comparable to other modalities of treatment. Hence, it is crucial to maintain a sharp drop in the radiation dose distribution within very short distances. Treatment planning system (TPS) which is controlled by a computer algorithm plays a significant role in calculating the optimum doses to the tumour area during a typical HDR brachytherapy treatment. However, the optimum dose calculated by the TPS must be verified by using an independent testing method in order to eliminate under/over irradiation of the tumor region and as quality assurance. In general, two types of independent dose verification methods(experimental and computational) are used to crosscheck the doses calculated by TPS. This systematic review aims to summarize the studies done in the past ten years on HDR brachytherapy treatment planning verification and to analyze the reliability and limitations.

A preliminary study on modeling and commissioning method of the treatment planning system used in the first domestic proton therapy device / 中华放射医学与防护杂志

Objective:To introduce the method and result of the modeling and preliminary dose verification of the treatment planning system used in the first domestic proton therapy device of China (Raystation 10B, a system of scientific research version with no available registration certificate) and to verify the modeling accuracy using dose verification result.Methods:The modeling method for a treatment planning system (TPS) mainly included the data acquisition and modeling of integrated depth dose (IDD) curves, the data acquisition and modeling of beam spot profiles in air, and the calibration and modeling of absolute dose by scanning a 10 cm ×10 cm square field with a spot spacing of 2.5 mm. By measuring the dose distributions in three cases with different complexity levels and comparing them with the dose distributions calculated using the TPS, this study verified and analyzed the modeling accuracy and proposed the requirements for beam parameters and the commissioning suggestions of the proton device.Results:The peak values of the IDD curves of low-energy regions fitted using the TPS model were less than the measured values, while those of medium- and high-energy regions fitted using the TPS model approximated the measured values. The range in all energy regions fitted accurately. For the three cases with different complexity levels, the deviation between the average dose calculated by the TPS and that measured was within ±5% (national standard for type tests of medical devices). Moreover, the DTA of high-dose-gradient areas was less than 3 mm.Conclusions:The modeling accuracy of the TPS generally meets the verification requirements. However, due to the low resolution of IDDs obtained by Monte Carlo simulation in the TPS model and the sharp Bragg peaks of low-energy regions, the IDD modeling accuracy of low-energy regions is insufficient.

SABR pre-treatment checks using alanine and nanoDot dosimeters.

Stereotactic Ablative Radiotherapy (SABR) remains one of the preferred treatment techniques for early-stage cancer. It can be extended to more treatment locales involving the sternum, scapula and spine. This work investigates SABR checks using Alanine and nanoDot dosimeter for three treatment sites, including sternum, spine and scapula. Alanine and nanoDot dosimeters' performances were verified using a 6 MV photon beam before SABR pretreatment verifications. Each dosimeter was placed inside customized designed inserts into a Rod Phantom (in-house phantom) made of Perspex that mimics the human body for a SABR check. Electron Paramagnetic Resonance (EPR) spectrometer, Bruker EleXsys E500 (9.5 GHz) and Microstar (Landauer Inc.) Reader was employed to acquire the irradiated alanine and nanoDot dosimeters' signal, respectively. Both dosimeters treatment sites are expressed as mean ± standard deviation (SD) of the measured and Eclipse calculated dose Alanine (19.59 ± 0.24, 17.98 ± 0.15, 17.95 ± 0.18) and nanoDot (19.70 ± 0.43, 17.05 ± 0.08, 17.95 ± 0.98) for spine, scapula and sternum, respectively. The percentage difference between alanine and nanoDot dosimeters was within 2% for sternum and scapula but 2.4% for spine cases. These results demonstrate Alanine and nanoDot dosimeters' potential usefulness for SABR pretreatment quality assurance (QA).

Monte Carlo as quality control tool of stereotactic body radiation therapy treatment plans.

PURPOSE/OBJECTIVE: The objective of this study was to verify the accuracy of treatment plans of stereotactic body radiation therapy (SBRT) and to verify the feasibility of the use of Monte Carlo (MC) as quality control (QC) on a daily basis. MATERIAL/METHODS: Using EGSnrc, a MC model of Agility™ linear accelerator was created. Various measurements (Percentage depth dose (PDD), Profiles and Output factors) were done for different fields sizes from 1x1 up to 40x40 (cm2). An iterative model optimization was performed to achieve adequate parameters of MC simulation. 40 SBRT patient's dosimetry plans were calculated by Monaco™ 3.1.1. CT images, RT-STRUCT and RT-PLAN files from Monaco™ being used as input for Moderato MC code. Finally, dose volume histogram (DVH) and paired t-tests for each contour were used for dosimetry comparison of the Monaco™ and MC. RESULTS: Validation of MC model was successful, as <2% difference comparing to measurements for all field's sizes. The main energy of electron source incident on the target was 5.8 MeV, and the full width at half maximum (FWHM) of Gaussian electron source were 0.09 and 0.2 (cm) in X and Y directions, respectively. For 40 treatment plan comparisons, the minimum absolute difference of mean dose of planning treatment planning (PTV) was 0.1% while the maximum was 6.3%. The minimum absolute difference of Max dose of PTV was 0.2% while the maximum was 8.1%. CONCLUSION: SBRT treatment plans of Monaco agreed with MC results. It possible to use MC for treatment plans verifications as independent QC tool.

Measurement of Dosimetric Parameters and Dose Verifi cation in Stereotactic Radiosurgery (SRS) / Jurnal Sains Kesihatan Malaysia

The fi rst part of this study was about measurement of dosimetric parameters for small photon beams to be used as input data for treatment planning computer system (TPS) and to verify the dose calculated by TPS in Stereotactic Radiosurgery (SRS) procedure. The beam data required were percentage depth dose (PDD), off-axis ratio (OAR) and scattering factor. Small beams of 5 mm to 45 mm diameter from a circular cone collimator in SRS were used for beam data measurements. Measurements were made using pinpoint ionisation chamber (0.016cc). In the second part of this study, we reported the important of carrying out quality assurance (QA) procedures before SRS treatment which were found to infl uence the accuracy of dose delivery. These QA procedures consisted of measurements on the accuracy in target localization and treatment room laser alignment. The calculated TPS dose for treatment was verifi ed using pinpoint ionisation chamber and thermoluminescent detector (TLD) 100H. The deviation mean between measured and calculated dose was -3.28%. The measured dose obtained from pinpoint ionisation chamber is in good agreement with the calculated dose from TPS with deviation mean of 2.17%. In conclusion, pinpoint ionisation chamber gives a better accuracy in dose calculation compared to TLD 100H. The results are acceptable as recommended by International Commission on Radiation Units and Measurements (ICRU) Report No. 50 (1994) that dose delivered to the target volume must be within ± 5% error.

Methods of verification and measurement of MLC-defined small field output factors for eight medical accelerators in Henan province / 中华放射医学与防护杂志

Objective To investigate muli-leaf collimator (MLC)-defined small field output factors calculated by the treatment planning system (TPS), and to study the measuring method of small field output factors verified by 0.015 cc PinPoint ionization chamber.Methods Eight medical accelerators for intensity-modulated radiation therapy (IMRT) were investigated in Henan province, and TPS-calculated output factors for various small fields (6 cm ×6 cm,4 cm ×4 cm,3 cm ×3 cm and 2 cm ×2 cm) were compared with published values recommended by IAEA.If the relative deviation was more than ± 3％ for the 2 cm ×2 cm field size and ±2％ for the fields of 6 cm ×6 cm, 4 cm ×4 cm and 3 cm ×3 cm, which was beyond the scope of IAEA allowed, the output factors will be measured and verified using 0.015 cc PinPoint ionization chamber and Unidos electrometer.Results TPS-calculated small field output factors for eight medical accelerators were compared with published values.The relative deviation of small field output factors for five pieces of equipment, which accounted for 62.5％ of the total, met the IAEA's requirement, while the other three, which accounted for 37.5％ of the total, did not.After measuring with PinPoint ionization chamber, the results from only three pieces of equipment met minimum IAEA's requirement.Conclusions MLC-defined small field output factors calculated by TPS for some medical accelerators in Henan need to be measured and corrected using micro-ionization chamber, and the measured values could be taken as the basis of radiation treatment planning.

Development of the measurement method for MLC small field output factor in intensity modulated radiation therapy (IMRT) / 中华放射医学与防护杂志

Objective To develop the methods for using 0.015 cc pinpoint chambers, 0.007 cc miniature chambers and diode detector to measure Multi-leaf collimator (MLC) small field in IMRT.Methods MAX4000 and Unidos electrometers were connected with different types of small chambers and diode detectors.MLC shaped fields of10 cm×10 cm, 6 cm×6 cm, 4 cm×4 cm, 3 cm×3 cm, 2 cm× 2 cm were defined at 100 cm SSD.The field sizes for the Varian accelerator were defined by the tertiary MLC, while the secondary jaws were kept at 10 cm × 10 cm field, with the monitor units of 250 MU.Each field was measured three times to obtain the average value.The readings of all small fields were normalized to 10 cm × 10 cm field values for comparison of measured and published output factors.Results The relative deviations of the MLC small field output factors from the published outputs are 1.0％ , 1.7％ , 1.5％ and 2.4％, respectively, for Unidos electrometer connected with 0.015 cc pinpoint chamber;0.2％, 0.8％, 0.8％ and 1.4％, respectively, for Unidos electrometer connected with 0.007 cc miniature chamber;and 0.1％, 0.5％, 0.5％ and 0.9％, respectively, for MAX4000 electrometer connected with 0.007 cc miniature chamber.Conclusions The 0.015 cc chamber-measured MLC output factors for 3 cm × 3 cm and 2 cm × 2 cm fields are excellent.As required by IAEA, the relative deviations of the measured output factor from the published output factor are within ± 2％ for 2 cm × 2 cm fields and ± 3％ for larger fields.The results measured using 0.007 cc chamber are better than those measured using 0.015 cc chamber.The measured results using the diode detector, normalized to the 10 cm × 10 cm field, are consistent with the minimum requirements and excellent when being normalized to the 4 cm × 4 cm field.For dosimetric consideration, MLC small field output factor should be measured using small chamber and diode detector.The method is accurate and reliable, therefore, all measured output factors for MLC small fields should be input into radiation treatment plan system.

Clinical verification of Neptune 3D-RTPS-A treatment planning system compared to Prowess TPS / 中华放射医学与防护杂志

Objective To investigate the safety and validity of Neptune 3D-RTPS-A treatment planning system compared to Prowess TPS.Methods A total of 30 clinical tumor cases with radiotherapy planning on Prowess TPS from September 2009 to May 2010 were used.The contours, organs at risk and target volumes in Prowess TPS were transported into Neptune TPS, the same parameters setted in the two treatment planning systems.The results of comparison of the two TPS were calculated.Results All cases of clinical treatment planning were completed successfully by Neptune TPS, and the various functions of the design were achieved for fitting tumor conformal radiation therapy.The key parameters on radiation treatment were compared.The results are as follows:the differences of source skin distance ( SSD ) ＜0.5% , differences of Monitor Unites ＜0.5%, the differences of dose at isocenter ＜2%, the differences of five isodose lines surrounding area ＜ 3%, and the mean difference of distances of five isodose lines was 0.43 mm, the differences of the volume of PTV on 90% isodose line ＜ 2%, and the differences in V30of organs at risk ＜ 3%.Conclusions Neptune TPS could be qualified for clinical validity and safety by clinical verification.