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Bilateral kidney sparing in treatment of pancreatic malignancies by VMAT vs. IMRT strategies using Real Time Tumor Tracking System |
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PP: 75-86 |
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doi:10.18576/jrna/110110
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Author(s) |
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Wafaa Rashed,
Rania Abdelrahman,
Hany El-Gamal,
Mostafa Abd el-wanis,
Khaled. M. El-Shahat,
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Abstract |
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| A dosimetric study was conducted to compare two high-intensity modulated treatment planning strategies (Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Radiotherapy (IMRT)) for pancreatic malignancies. The study incorporated a Real-Time Tumor-Tracking Radiation Therapy (RTRT) system to enhance treatment precision. Its primary goal was to evaluate which technique provides superior tumor dose coverage and early tumor response while minimizing severe radiation toxicities to organs at risk (OAR), particularly for bilateral kidney preservation. This dosimetric analysis was performed in 30 patients who had undergone radiotherapy for pancreatic carcinoma at our institution. We compared 9-field IMRT and 2 arcs RapidArc (RA) plans for each patient of 30s. Each treatment plan was designed in such a way that standard fractionation consists of 1.8 Gy daily fraction in 28 fractions to deliver a total dose of 50.4 Gy to the planning target volume (PTV). Treatment planning objectives were ensuring that 95% of the PTV received ≥ 95% of the radical prescribed dose and no more than 2% of the PTV received more than 107%; this involves assessing treatment plans using metrics like dose-volume histograms (DVH), homogeneity index (HI), and conformity index (CI) to obtain the optimum strategy as appropriate for the treatment of pancreatic cancer. The DVH for each IMRT & RA plans in terms of the target volume and the radiosensitive organs (right and left kidneys) were compared, in addition to the monitor units (MUs) and delivery treatment time, which were also reported. All of these comparative plans achieved the treatment plan objectives as D95% for IMRT = 48.9 Gy and for RA = 48.6 Gy, while RA exhibited superiority in protecting bilateral kidneys from the probability of injury as it decreased the mean tolerance dose irradiated to both kidneys (for the left kidney: the RA Dmean (4.5-5.2) Gy vs. (9.2-10.5) Gy in the IMRT plans; for the right kidney: the RA Dmean (3.4-4.1) Gy vs. (8.2-9.1) Gy in the IMRT plans). The results provide evidence of potential benefits of RapidArc with real-time tumor-tracking in pancreatic carcinoma treatment, as RA allows significant dose reduction for bilateral kidneys while enhancing dose conformity, improving targeting accuracy, and reducing treatment time and monitor units. |
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