Clinical impact of anisotropic analytical algorithm and Acuros XB dose calculation algorithms for intensity modulated radiation therapy in lung cancer patients

OBJECTIVE: To evaluate dose differences predicted between using Anisotropic Analytical Algorithm (AAA) and Acuros XB (AXB) in patients diagnosed with locally advanced non-small cell lung cancer (NSCLC) treated with intensity modulated radiation therapy (IMRT). METHODS: A phantom study was done to evaluate the dose prediction accuracy of AXB and AAA beyond low-density medium by comparing the calculated measurement results. Thirty-two advanced NSCLC patients were subjected to IMRT. The dose regimen was 60 Gy over 30 fractions. Effects on planning target volume (PTV) and organ-at-risk (OAR) were evaluated. Clinically acceptable treatment plans with AAA were re-calculated using AXB algorithms with two modes Dw and Dm at the same beam arrangements and multileaf collimator leaf settings as with AAA. RESULTS: Using AXB yielded better agreement with the measurements and the average dose difference for all points was about 0.5%. Conversely, using AAA showed a larger disagreement with measured values and the average difference was up to 5.9%. The maximum relative difference was between AXB_Dm and AAA for PTV dose (D98 %). The percentage dose differences of plans calculated by AAA, AXB_Dw and AAA, AXB_Dm revealed that AAA overestimated the dose than AXB. Regarding OAR, results showed significant difference for lungs-PTV. CONCLUSIONS: AXB algorithm yields more accurate dose prediction than AAA in heterogeneous medium. Differences in dose distribution are observed when plans re-calculated with AXB indicating that AAA apparently overestimates dose, particularly the PTV dose. Thus, AXB algorithm should be used in preference to AAA for cases in which PTVs are involved with tissues of highly different densities, such as lung.

The dependence of inhomogeneity correction factors on photon beam quality index performed with the Anisotropic Analytical Algorithm

Purpose: The purpose of the study was to investigate the dependence of tissue inhomogeneity correction factors (ICFs) on the photon beam quality index (QI).Materials and Methods: Heterogeneous phantoms, comprising semi-infinite slabs of the lung (0.10, 0.20, 0.26 and 0.30 g/cm3), adipose tissue (0.92 g/cm3) and bone (1.85 g/cm3) in water, were constructed in the Eclipse treatment planning system. Several calculation models of 6 MV and 15 MV photon beams for quality index (TPR20,10) = 0.670±k*0.01 and TPR20,10 = 0.760±k*0.01, k = -3, -2, -1, 0, 1, 2, 3 respectively were built in the Eclipse. The ICFs were calculated with the anisotropic analytical algorithm (AAA) for several beam sizes and points lying at several depths inside of and below inhomogeneities of different thicknesses.Results: The ICFs increased for lung and adipose tissues with increasing beam quality (TPR20,10), while decreased for bone. Calculations with AAA predict that the maximum difference in ICFs of 1.0% and 2.5% for adipose and bone tissues, respectively. For lung tissue, changes of ICFs of a maximum of 9.2% (6 MV) and 13.8% (15 MV). For points where charged particle equilibrium exists, a linear dependence of ICFs on TPR20,10 was observed. If CPE doesn’t exist, the dependence became more complex. For points inside of the low-density inhomogeneity, the dependence of the ICFs on energy was not linear but the changes of ICFs were smaller than 3.0%. Measurements results carried out with the CIRS phantom were consistent with the calculation results.Conclusions: A negligible dependence of the ICFs on energy was found for adipose and bone tissue. For lung tissue, in the CPE region, the dependence of ICFs on different beam quality indexes with the same nominal energy may not be neglected, however, this dependence was linear. Where there is no CPE, the dependence of the ICFs on energy was more complicated.

TREATMENT PLANNING SYSTEM (TPS) KANKER PAYUDARA MENGGUNAKAN TEKNIK 3DCRT

ABSTRAKPenelitian ini bertujuan untuk mengevaluasi hasil simulasi TPS teknik 3DCRT pada kasus kanker payudara agar sesuai dengan standar yang diizinkan International Commission on Radiation Units and Measurements (ICRU). Proses TPS menggunakan program Eclipse dengan algoritma Anisotropic Analytical Algorithm. Kurva histogram dosis volume kumulatif 3DCRT dianalisis untuk mendapatkan dosis radiasi yang diterima organ at risk (OAR) paru-paru kiri, paru-paru kanan dan jantung. Hasil TPS menunjukkan dosis yang diterima OAR berada di bawah batas ambang yang ditentukan yaitu paru-paru kiri dengan mean dose 54,7 cGy yang melingkupi volume 1238,5 cm3 dan pada paru-paru kanan dosis mean dose 2113,2 cGy melingkupi volume 1474,5 cm3 serta pada jantung mean dose 96,5 cGy melingkupi volume 175,5 cm3. Simulasi TPS yang dilakukan berhasil mendapatkan data perencanaan penyinaran kasus kanker payudara yang memenuhi syarat dosis relatif yang melingkupi volume PTV yang diizinkan ICRU (volume terlingkupi 95%-107%) yaitu besarnya dosis relatif untuk target sebesar 95% yang melingkupi 95,5% volume target. Kata kunci: radioterapi, TPS, dosis, PTV, OAR. ABSTRACTThis study objective is to evaluate the simulation results of the 3DCRT technique TPS in breast cancer cases to conform to the standards permitted by the International Commission on Radiation Units and Measurements (ICRU). The TPS process uses the Eclipse program with the Anisotropic Analytical Algorithm algorithm. The 3DCRT cumulative dose-volume histogram curve was analyzed to obtain the absorbed dose received by the organ at risk (OAR) of the left lung, right lung and heart. The TPS results show that the dose received by OAR was below the prescribed threshold of the left lung with a mean dose of 54.7 cGy covering a volume of 1238.5 cm3 and to the right lung the mean dose of 2113.2 cGy surrounding the volume of 1474, 5 cm3 and at the heart the mean dose of 96.5 cGy covers a volume of 175.5 cm 3. TPS simulation carried out successfully obtained data on the planning of radiation from breast cancer cases that met the relative dosage requirements that covered the volume of PTV permitted by ICRU (95% -107% enclosed volume), that is, the relative dose for the target of 95% which covered 95.5% of the target volume. Keywords: radiotherapy, TPS, dose, PTV, OAR.