Miltiadis G. Delichas

Comparison of the helical tomotherapy against the multileaf collimator-based intensity-modulated radiotherapy and 3D conformal radiation modalities in lung cancer radiotherapy

OBJECTIVES The aim of this study was to compare three-dimensional (3D) conformal radiotherapy and the two different forms of IMRT in lung cancer radiotherapy. METHODS Cases of four lung cancer patients were investigated by developing a 3D conformal treatment plan, a linac MLC-based step-and-shoot IMRT plan and an HT plan for each case. With the use of the complication-free tumour control probability (P(+)) index and the uniform dose concept as the common prescription point of the plans, the different treatment plans were compared based on radiobiological measures. RESULTS The applied plan evaluation method shows the MLC-based IMRT and the HT treatment plans are almost equivalent over the clinically useful dose prescription range; however, the 3D conformal plan inferior. At the optimal dose levels, the 3D conformal treatment plans give an average P(+) of 48.1% for a effective uniform dose to the internal target volume (ITV) of 62.4 Gy, whereas the corresponding MLC-based IMRT treatment plans are more effective by an average ΔP(+) of 27.0% for a Δ effective uniform dose of 16.3 Gy. Similarly, the HT treatment plans are more effective than the 3D-conformal plans by an average ΔP(+) of 23.8% for a Δ effective uniform dose of 11.6 Gy. CONCLUSION A radiobiological treatment plan evaluation can provide a closer association of the delivered treatment with the clinical outcome by taking into account the dose-response relations of the irradiated tumours and normal tissues. The use of P - effective uniform dose diagrams can complement the traditional tools of evaluation to compare and effectively evaluate different treatment plans.

Comparison of the helical tomotherapy and MLC-based IMRT radiation modalities in treating brain and cranio-spinal tumors

The investigation of the clinical efficacy and effectiveness of Intensity Modulated Radiotherapy (IMRT) using Multileaf Collimators (MLC) and Helical Tomotherapy (HT) has been an issue of increasing interest over the past few years. In order to assess the suitability of a treatment plan, dosimetric criteria such as dose-volume histograms (DVH), maximum, minimum, mean, and standard deviation of the dose distribution are typically used. Nevertheless, the radiobiological parameters of the different tumors and normal tissues are often not taken into account. The use of the biologically effective uniform dose (D̿) together with the complication-free tumor control probability (P+) were applied to evaluate the two radiation modalities. Two different clinical cases of brain and cranio-spinal axis cancers have been investigated by developing a linac MLC-based step-and-shoot IMRT plan and a Helical Tomotherapy plan. The treatment plans of the MLC-based IMRT were developed on the Philips treatment planning station using the Pinnacle 7.6 software release while the dedicated Tomotherapy treatment planning station was used for the HT plan. With the use of the P+ index and the D̿ concept as the common prescription point, the different treatment plans were compared based on radiobiological measures. The tissue response probabilities were plotted against D̿ for a range of prescription doses. The applied plan evaluation method shows that in the brain cancer, the HT treatment gives slightly better results than the MLC-based IMRT in terms of optimum expected clinical outcome (P+ of 66.1% and 63.5% for a D̿ to the PTV of 63.0 Gy and 62.0 Gy, respectively). In the cranio-spinal axis cancer, the HT plan is significantly better compared to the MLC-based IMRT plan over the clinically useful dose prescription range (P+ of 84.1% and 28.3% for a D̿ to the PTV of 50.6 Gy and 44.0 Gy, respectively). If a higher than 5% risk for complications could be allowed, the complication-free tumor control could be increased by almost 30% compared to the initial dose prescription. In comparison to MLC based-IMRT, HT can better encompass the often large PTV while minimizing the volume of the OARs receiving high dose. A radiobiological treatment plan evaluation can provide a closer association of the delivered treatment with the clinical outcome by taking into account the dose-response relations of the irradiated tumors and normal tissues. The use of P — D̿ diagrams can complement the traditional tools of evaluation such as DVHs, in order to compare and effectively evaluate different treatment plans.

The dependence of patient dose on factors relating to the technique and complexity of Interventional Cardiology procedures

Dose-area product (DAP) measurements were conducted for 168 coronary angiography (CA) and 89 single vessel percutaneous transluminal coronary angioplasty (PTCA) to examine the factors influencing patient dose beyond the X-ray exposure parameters. It was found that for CA, the DAP increases with the number of catheters used and with the number of vessels with stenosis. DAP values for patients with a prior bypass surgery, were higher compared to those without such a medical record to surgery. In PTCA, the use of coronary stents did not enhance the patient radiation dose significantly. Noticeable differences were found in the percentage contribution of each projection to the total DAP between the three types of single vessel PTCA. Finally low variations in DAP were found among the cardiologists performing both procedures.

SU‐GG‐T‐422: Radiobiological Effectiveness of 3D‐Conformal Radiotherapy, MLC‐Based IMRT and Helical Tomotherapy in Lung Cancer

Purpose: To investigate the clinical efficacy and effectiveness of 3D‐Conformal radiotherapy,Intensity Modulated Radiotherapy(IMRT) using Multileaf Collimators(MLC) and Helical Tomotherapy (HT), by evaluating dosimetric and radiobiological measures of a lungcancer case. Method and Materials: A typical case of lungcancer has been investigated by developing a 3D‐Conformal treatment plan, a linac MLC‐based step‐and‐shoot IMRT plan and a Helical Tomotherapy plan. The treatment plans of the 3D‐Conformal and the MLC‐based IMRT were developed on the Philips treatment planning station using the Pinnacle 7.6 software release while the dedicated Tomotherapy treatment planning station was used for the HT plan. With the use of the complication‐free tumorcontrol probability, P + and the biologically effective uniform dose,D concept as the common prescription point of the plans, the three different treatment plans were compared based on radiobiological measures. Results: The applied plan evaluation method shows that in this lungcancer case the MLC‐based IMRT and the HT treatment plans are almost equivalent over the clinically useful dose prescription range, whereas the 3D‐Conformal plan appears to be quite inferior than the other two modalities. More specifically, the 3D‐Conformal, MLC‐based IMRT and HT treatment plans give a P + of 55.4%, 72.9% and 66.9%, for a D to the target volume of 57.0Gy, 66.9Gy and 64.0Gy, respectively. If a higher than 5% risk for complications could be allowed, the complication‐free tumorcontrol could be increased by almost 5% compared to the initial dose prescription. Conclusion: In comparison to 3D‐Conformal radiotherapy, both the MLC based‐IMRT and HT can better encompass the often large ITV while minimizing the volume of the OARs receiving high dose. The use of P ‐ D diagrams can compliment the traditional tools of evaluation such as DVHs, in order to compare and effectively evaluate different treatment plans.