Modulation factor (MF) and pitch have an impact on Helical TomoTherapy (HT) plan quality and HT u... more Modulation factor (MF) and pitch have an impact on Helical TomoTherapy (HT) plan quality and HT users mostly use vendor-recommended settings. This study analyses the effect of these two parameters on both plan quality and treatment time for plans made with TomoEdge planning software by using the concept of Pareto optimal fronts. More than 450 plans with different combinations of pitch [0.10-0.50] and MF [1.2-3.0] were produced. These HT plans, with a field width (FW) of 5 cm, were created for five head and neck patients and homogeneity index, conformity index, dose-near-maximum (D2), and dose-near-minimum (D98) were analysed for the planning target volumes, as well as the mean dose and D2 for most critical organs at risk. For every dose metric the median value will be plotted against treatment time. A Pareto-like method is used in the analysis which will show how pitch and MF influence both treatment time and plan quality. For small pitches (≤0.20), MF does not influence treatment t...
Conformal radiation therapy allows the possibility of delivering high doses at the tumor volume w... more Conformal radiation therapy allows the possibility of delivering high doses at the tumor volume whilst limiting the dose to the surrounding tissues and diminishing the secondary effects. With the example of the conformal radiation therapy used at the AZ VUB (3DCRT and tomotherapy), two treatment plans of a left ethmoid carcinoma will be evaluated and discussed in detail. The treatment of ethmoid cancer is technically difficult for both radiation therapy and surgery because of the anatomic constraints and patterns of local spread. A radiation therapy is scheduled to be delivered after surgical resection of the tumor. The treatment plan for the radiation therapy was calculated on a three-dimensional (3D) treatment planning system based on virtual simulation with a beam's eye view: George Sherouse's Gratis. An effort was made to make the plan as conformal and as homogeneous as possible to deliver a dose of 66 Gy in 33 fractions at the tumor bed with a maximum dose of 56 Gy to the right optic nerve and the chiasma. To establish the clinical utility and potential advantages of tomotherapy over 3DCRT for ethmoid carcinoma, the treatment of this patient was also planned with Peacock Plan. For both treatment plans the isodose distributions and cumulative dose volume histograms (CDVH) were computed. Superimposing the CDVHs yielded similar curves for the target and an obvious improvement for organs at risk such as the chiasma, brainstem and the left eye when applying tomotherapy. These results have also been reflected in the tumor control probabilities (equal for both plans) and the normal tissue complication probabilities (NTCP), yielded significant reductions in NTCP for tomotherapy. The probability of uncomplicated tumor control was 52.7% for tomotherapy against 38.3% for 3DCRT.
ABSTRACT The capability of radioluminescence (RL) dosimeters composed of carbon-doped aluminium o... more ABSTRACT The capability of radioluminescence (RL) dosimeters composed of carbon-doped aluminium oxide (Al2O3:C) detectors+optical fibre has been verified for absorbed dose-rate measurements during carbon radiotherapy. The RL signals from two separate Al2O3:C detectors (single crystal 'CG' and droplet 'P1') have been systematically measured and compared along the Bragg-curve and Spread-Out Bragg-Peak of 290 MeV/n carbon beams in the water. The absorbed dose response was assessed for the range of 0.5–10 Gy. For doses up to 6 Gy, we observed a linear response for both types of detectors, while for higher doses CG presented a more prominent supraliearity than P1. The RL response for low-LET protons in the entrance from the curve was found to closely resemble that observed for a clinical 6 MV X-ray beam, while it was found that P1 has a better agreement with the reference data from standard ionization chamber than CG. We observed a significant decrease in luminescence efficiency with LET in the Bragg peak region. The Al2O3:C RL luminescence efficiency differs from Al2O3:C OSL results, which implies that the signal can be corrected for LET dependency to match the correct SOBP and Bragg Peak.
A novel approach to dual-energy imaging for markerless tumor tracking was proposed consisting of ... more A novel approach to dual-energy imaging for markerless tumor tracking was proposed consisting of sequential dual-energy fluoroscopy, omitting the need for fast-switching kV generators. The implementation of this approach on a clinical tumor tracking system and its efficacy is shown feasible through optimization of the imaging parameters.
Objectives: Stereotactic radiosurgery is a well-established treatment technique for intracranial ... more Objectives: Stereotactic radiosurgery is a well-established treatment technique for intracranial benign and malignant lesions. However, a controversy remains about the best prescription isodose to use for treatment. The Gamma Knife approach generally uses the 50% prescription isodose while the Linac-based approach proposes higher isodose, usually the 80% isodose. A treatment plan is considered acceptable when a Paddick conformity index close to 1 is achieved, while the gradient index is kept below 3. The aim of this study was to investigate if the prescription isodose can be adjusted to achieve a better conformity and gradient. Methods: We enrolled 40 patients with vestibular schwannoma (Koos I-III) treated with Gamma Knife Perfexion (Elekta AB, Sweden) and replanned them with different prescription isodoses, both on Gamma Knife Perfexion system and a dedicated Linac-based system, the Novalis (Brainlab AG, Germany). The ideal prescription isodose for each case and treatment machine ...
ABSTRACT Purpose: Purpose: This study investigates the geometric accuracy of simultaneous Gantry/... more ABSTRACT Purpose: Purpose: This study investigates the geometric accuracy of simultaneous Gantry/Ring rotation during Dynamic Wave Arc (DWA) delivery.
Advances in radiation oncology evolved in parallel with advances in multimodality imaging. Both i... more Advances in radiation oncology evolved in parallel with advances in multimodality imaging. Both in the treatment planning process and during the actual treatment delivery, anatomical and biological information has become a necessity, which relies heavily on information ...
Modulation factor (MF) and pitch have an impact on Helical TomoTherapy (HT) plan quality and HT u... more Modulation factor (MF) and pitch have an impact on Helical TomoTherapy (HT) plan quality and HT users mostly use vendor-recommended settings. This study analyses the effect of these two parameters on both plan quality and treatment time for plans made with TomoEdge planning software by using the concept of Pareto optimal fronts. More than 450 plans with different combinations of pitch [0.10-0.50] and MF [1.2-3.0] were produced. These HT plans, with a field width (FW) of 5 cm, were created for five head and neck patients and homogeneity index, conformity index, dose-near-maximum (D2), and dose-near-minimum (D98) were analysed for the planning target volumes, as well as the mean dose and D2 for most critical organs at risk. For every dose metric the median value will be plotted against treatment time. A Pareto-like method is used in the analysis which will show how pitch and MF influence both treatment time and plan quality. For small pitches (≤0.20), MF does not influence treatment t...
Conformal radiation therapy allows the possibility of delivering high doses at the tumor volume w... more Conformal radiation therapy allows the possibility of delivering high doses at the tumor volume whilst limiting the dose to the surrounding tissues and diminishing the secondary effects. With the example of the conformal radiation therapy used at the AZ VUB (3DCRT and tomotherapy), two treatment plans of a left ethmoid carcinoma will be evaluated and discussed in detail. The treatment of ethmoid cancer is technically difficult for both radiation therapy and surgery because of the anatomic constraints and patterns of local spread. A radiation therapy is scheduled to be delivered after surgical resection of the tumor. The treatment plan for the radiation therapy was calculated on a three-dimensional (3D) treatment planning system based on virtual simulation with a beam's eye view: George Sherouse's Gratis. An effort was made to make the plan as conformal and as homogeneous as possible to deliver a dose of 66 Gy in 33 fractions at the tumor bed with a maximum dose of 56 Gy to the right optic nerve and the chiasma. To establish the clinical utility and potential advantages of tomotherapy over 3DCRT for ethmoid carcinoma, the treatment of this patient was also planned with Peacock Plan. For both treatment plans the isodose distributions and cumulative dose volume histograms (CDVH) were computed. Superimposing the CDVHs yielded similar curves for the target and an obvious improvement for organs at risk such as the chiasma, brainstem and the left eye when applying tomotherapy. These results have also been reflected in the tumor control probabilities (equal for both plans) and the normal tissue complication probabilities (NTCP), yielded significant reductions in NTCP for tomotherapy. The probability of uncomplicated tumor control was 52.7% for tomotherapy against 38.3% for 3DCRT.
ABSTRACT The capability of radioluminescence (RL) dosimeters composed of carbon-doped aluminium o... more ABSTRACT The capability of radioluminescence (RL) dosimeters composed of carbon-doped aluminium oxide (Al2O3:C) detectors+optical fibre has been verified for absorbed dose-rate measurements during carbon radiotherapy. The RL signals from two separate Al2O3:C detectors (single crystal 'CG' and droplet 'P1') have been systematically measured and compared along the Bragg-curve and Spread-Out Bragg-Peak of 290 MeV/n carbon beams in the water. The absorbed dose response was assessed for the range of 0.5–10 Gy. For doses up to 6 Gy, we observed a linear response for both types of detectors, while for higher doses CG presented a more prominent supraliearity than P1. The RL response for low-LET protons in the entrance from the curve was found to closely resemble that observed for a clinical 6 MV X-ray beam, while it was found that P1 has a better agreement with the reference data from standard ionization chamber than CG. We observed a significant decrease in luminescence efficiency with LET in the Bragg peak region. The Al2O3:C RL luminescence efficiency differs from Al2O3:C OSL results, which implies that the signal can be corrected for LET dependency to match the correct SOBP and Bragg Peak.
A novel approach to dual-energy imaging for markerless tumor tracking was proposed consisting of ... more A novel approach to dual-energy imaging for markerless tumor tracking was proposed consisting of sequential dual-energy fluoroscopy, omitting the need for fast-switching kV generators. The implementation of this approach on a clinical tumor tracking system and its efficacy is shown feasible through optimization of the imaging parameters.
Objectives: Stereotactic radiosurgery is a well-established treatment technique for intracranial ... more Objectives: Stereotactic radiosurgery is a well-established treatment technique for intracranial benign and malignant lesions. However, a controversy remains about the best prescription isodose to use for treatment. The Gamma Knife approach generally uses the 50% prescription isodose while the Linac-based approach proposes higher isodose, usually the 80% isodose. A treatment plan is considered acceptable when a Paddick conformity index close to 1 is achieved, while the gradient index is kept below 3. The aim of this study was to investigate if the prescription isodose can be adjusted to achieve a better conformity and gradient. Methods: We enrolled 40 patients with vestibular schwannoma (Koos I-III) treated with Gamma Knife Perfexion (Elekta AB, Sweden) and replanned them with different prescription isodoses, both on Gamma Knife Perfexion system and a dedicated Linac-based system, the Novalis (Brainlab AG, Germany). The ideal prescription isodose for each case and treatment machine ...
ABSTRACT Purpose: Purpose: This study investigates the geometric accuracy of simultaneous Gantry/... more ABSTRACT Purpose: Purpose: This study investigates the geometric accuracy of simultaneous Gantry/Ring rotation during Dynamic Wave Arc (DWA) delivery.
Advances in radiation oncology evolved in parallel with advances in multimodality imaging. Both i... more Advances in radiation oncology evolved in parallel with advances in multimodality imaging. Both in the treatment planning process and during the actual treatment delivery, anatomical and biological information has become a necessity, which relies heavily on information ...
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Papers by Dirk Verellen