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The effect of tumour geometry on the quantification accuracy of 123I in planar phantom images
S10
Abstracts/Physica Medica 31 (2015) S1–S14
completely different from that of the conventional treatment modality. The aim of the study was to re-calculate the patient workload for RapidArc treatment modality at Addington Hospital. Materials and Methods: Both bunkers at Addington Hospital are designed for linac energies up to 25 MV. Currently our linacs have a maximum energy of 18 MV. The NCRP 151 and McGinley formulation were used to carry out the patient workload. The bunker workload was assumed from both NCRP 49 and Mechalkos. The patient’s prescription from conventional therapy and IMRT was used to calculate the IMRT factor later incorporated into RapidArc factor. The averaging method was also used to deduce the RapidArc use factor (U) from IMRT U. Results: The number of patients to be treated per day was calculated to be 112 and 64 for both assumed NCRP49 and Mechalkos workload respectively. The RapidArc U and RapidArc factor were calculated to be 14.9% and 2.4 respectively. Conclusion: The Re-calculation of Patient workload for RapidArc treatment technique at Addington Hospital was carried out successfully, and served as the basis for therapists to introduce shifts in case of higher patient numbers. Keywords: Patient workload, IMRT factor, RapidArc use factor O.35 THE EFFECT OF TUMOUR GEOMETRY ON THE QUANTIFICATION ACCURACY OF 123I IN PLANAR PHANTOM IMAGES K. Ramonaheng *, J.A. van Staden, H. du Raan. Department of Medical Physics, University of the Free State, Bloemfontein, South Africa Introduction: Accurate activity quantification is important for its application in radiation dosimetry. Planar images play an important role for quantification of whole body images enabling comprehensive assessment of bio-distribution from radionuclide administrations. [123I]-MIBG quantification of neuroendocrine tumours is performed prior to therapeutic radionuclide treatment. The aim of this study was to evaluate the effect of tumour geometry on the quantification accuracy of 123I planar phantom images. The geometry investigated included: various tumour sizes, various tumour–liver distances and two tumour–background ratios. Materials and Methods: An in-house manufactured abdominal phantom was equipped with liver, cylindrical inserts of different diameters simulating tumours and a rod to vary the axial tumour–liver distance. The geometric mean method with corrections for scatter and attenuation was used for image processing. Scatter correction was performed using the triple energy window scatter correction technique. Attenuation correction was performed using a printed 99mTc transmission sheet source. Partial volume effect (PVE) was compensated using region definitions for tumour activity distribution. The activity measured in the dose calibrator served as reference for determining the quantification accuracy. Results: The largest percentage deviation was obtained for the smallest tumours with an average activity underestimation of 34.6 ± 1.2% attributed to PVE. Quantification for the largest tumour resulted in overestimations of 3.1 ± 3.0%. PVE compensation improved the quantification accuracy for all tumour sizes yielding accuracies of better than 12.4%. Scatter contribution to the tumours from the liver had minimal effect on the quantification accuracy at tumour–liver distances larger than 3 cm. An increased tumour–background ratio resulted in a % increase of up to 26.3% when PVE was compensated. Conclusion: When applying all relevant corrections for scatter, attenuation and PVE without significant background, quantification accuracy within 12% was obtained. This study has demonstrated the successful implementation of a practical technique to obtain accurate quantitative information from 123I planar images. Keywords: Planar images, Activity quantification, Tumour size, Scatter, Attenuation O.36 LINEAR ACCELERATOR MULTILEAF COLLIMATOR QUALITY CONTROL METHODOLOGIES IN RADIOTHERAPY: PRELIMINARY RESULTS
complex treatment, and resulted in an increase in patient setup speed. An MLC system thus requires a re-evaluation of the quality assurance requirements for beam collimation and techniques. This study surveyed, developed, performed and evaluated quality assurance efforts for conventional MLCs with the aim to determine efficacy and reproducibility of the quality control procedures. Materials and Methods: The performance of MLCs for an Elekta (Livingstone Hospital) and Siemens (Charlotte Makexe Johannesburg Academic Hospital) Linac was examined. The major quality control procedures studied were leaf matching, leaf position accuracy, inter-leaf leakage and transmission through abutting leaves. Three portal imaging devices (radiographic film, radio chromic film and an Electronic Portal Imaging Device) and a LA48 Linear array were used as detectors. Record and verify data management systems were used to set up and execute the procedures. The calibration of all the portal imaging devices was also performed. Results: The calibration procedure of the portal imaging devices is Linac specific in execution. The profiles obtained indicated consistency across device and time. A combined single execution procedure is viable and reproducible on all platforms. Conclusion: The preliminary results show that the calibration of imaging devices is of great importance. The MLC design influences the range and extent of quality control that can be performed. This may impact on the accuracy with which advanced technologies requiring high conformity and reproducible leaf movement can be delivered. Imaging devices each have specific resource requirement issues affecting the efficacy of their use. Keywords: Multileaf collimator, Quality control, Assurance O.37 INSTALLATION PROCESS FOR A PHILIPS INGENIA 3 TESLA MAGNETIC RESONANCE IMAGING UNIT AT UNIVERSITAS ACADEMIC HOSPITAL R.K. Segoenyane *, W.I.D. Rae, A. Conradie. Department of Medical Physics, University of the Free State, Bloemfontein, South Africa Introduction: Magnetic Resonance Imaging (MRI) uses strong magnetic fields and radio waves to produce cross-sectional images of patients. To achieve this, a large superconducting magnet, of mass approximately 4000 kg, is used to create a 1.5 Tesla (1.5T) or 3 Tesla (3T) magnetic field. Special precautions and planning are thus required during room design. The aim of this study is to review the installation process of the Philips Ingenia 3T MRI installed at Universitas Academic Hospital (UAH) in early 2015. Materials and Methods: Colour digital images were obtained during installation to record the process. Comparison was made between the Philips Ingenia 3T installation and the recent Siemens 1.5T Magnetrom Aera MRI installation at Pelonomi Tertiary Hospital (PTH). Acceptance testing was performed based on the American College of Radiology phantom protocol. The influence of the 3T MRI scanner on the adjacent GE 1.5T MRI unit was investigated. Results: Before installation, floor loading capacity was increased by the installation of T-bar support structures between the structural pillars. The walls where shielded using conductive cladding. The MRI unit was factory assembled and delivered intact. Installation included ramping the magnet and electrical installation. During installation, wraparound and zipper artefacts were identified on images acquired by the adjacent GE 1.5T unit, but were found to be unrelated to the 3T MRI. After installation, the unit passed acceptance testing. A metal detector was installed to ensure that no ferromagnetic objects enter the room. Conclusion: Installation of the 3T MRI at UAH was similar to that of the 1.5T MRI at PTH. Artefacts on 1.5T images ceased after installation. Installation records should be retained as a reference for installation of 3T units at other hospitals. Keywords: Magnetic resonance imaging, 3T, Installation, Artefacts O.38 TOTAL SCATTER FACTOR COMPARISON BETWEEN CC01, EFD3G ELECTRON DIODE AND PTW60019 MICRODIAMOND DETECTORS FOR SMALL FIELDS IN MEGAVOLTAGE PHOTON BEAMS
A.E. Rule *,a, D.G. van der Merwe b. a Department of Radiation Oncology, Livingstone Hospital, Port Elizabeth, South Africa; b Department of Medical Physics, Charlotte Maxeke Johannesburg Academic Hospital/University of the Witwatersrand, Johannesburg, South Africa
I.E. Setilo *, F.C.P. du Plessis. Department of Medical Physics, University of the Free State, Bloemfontein, South Africa
Introduction: The Multileaf collimator (MLC) system introduction into the Clinical Linear Accelerator (Linac) facilitated computer-control and verification of
Introduction: Small fields are characterized by the lack of electronic equilibrium, and therefore small detectors must be used for beam output
Abstracts/Physica Medica 31 (2015) S1–S14
completely different from that of the conventional treatment modality. The aim of the study was to re-calculate the patient workload for RapidArc treatment modality at Addington Hospital. Materials and Methods: Both bunkers at Addington Hospital are designed for linac energies up to 25 MV. Currently our linacs have a maximum energy of 18 MV. The NCRP 151 and McGinley formulation were used to carry out the patient workload. The bunker workload was assumed from both NCRP 49 and Mechalkos. The patient’s prescription from conventional therapy and IMRT was used to calculate the IMRT factor later incorporated into RapidArc factor. The averaging method was also used to deduce the RapidArc use factor (U) from IMRT U. Results: The number of patients to be treated per day was calculated to be 112 and 64 for both assumed NCRP49 and Mechalkos workload respectively. The RapidArc U and RapidArc factor were calculated to be 14.9% and 2.4 respectively. Conclusion: The Re-calculation of Patient workload for RapidArc treatment technique at Addington Hospital was carried out successfully, and served as the basis for therapists to introduce shifts in case of higher patient numbers. Keywords: Patient workload, IMRT factor, RapidArc use factor O.35 THE EFFECT OF TUMOUR GEOMETRY ON THE QUANTIFICATION ACCURACY OF 123I IN PLANAR PHANTOM IMAGES K. Ramonaheng *, J.A. van Staden, H. du Raan. Department of Medical Physics, University of the Free State, Bloemfontein, South Africa Introduction: Accurate activity quantification is important for its application in radiation dosimetry. Planar images play an important role for quantification of whole body images enabling comprehensive assessment of bio-distribution from radionuclide administrations. [123I]-MIBG quantification of neuroendocrine tumours is performed prior to therapeutic radionuclide treatment. The aim of this study was to evaluate the effect of tumour geometry on the quantification accuracy of 123I planar phantom images. The geometry investigated included: various tumour sizes, various tumour–liver distances and two tumour–background ratios. Materials and Methods: An in-house manufactured abdominal phantom was equipped with liver, cylindrical inserts of different diameters simulating tumours and a rod to vary the axial tumour–liver distance. The geometric mean method with corrections for scatter and attenuation was used for image processing. Scatter correction was performed using the triple energy window scatter correction technique. Attenuation correction was performed using a printed 99mTc transmission sheet source. Partial volume effect (PVE) was compensated using region definitions for tumour activity distribution. The activity measured in the dose calibrator served as reference for determining the quantification accuracy. Results: The largest percentage deviation was obtained for the smallest tumours with an average activity underestimation of 34.6 ± 1.2% attributed to PVE. Quantification for the largest tumour resulted in overestimations of 3.1 ± 3.0%. PVE compensation improved the quantification accuracy for all tumour sizes yielding accuracies of better than 12.4%. Scatter contribution to the tumours from the liver had minimal effect on the quantification accuracy at tumour–liver distances larger than 3 cm. An increased tumour–background ratio resulted in a % increase of up to 26.3% when PVE was compensated. Conclusion: When applying all relevant corrections for scatter, attenuation and PVE without significant background, quantification accuracy within 12% was obtained. This study has demonstrated the successful implementation of a practical technique to obtain accurate quantitative information from 123I planar images. Keywords: Planar images, Activity quantification, Tumour size, Scatter, Attenuation O.36 LINEAR ACCELERATOR MULTILEAF COLLIMATOR QUALITY CONTROL METHODOLOGIES IN RADIOTHERAPY: PRELIMINARY RESULTS
complex treatment, and resulted in an increase in patient setup speed. An MLC system thus requires a re-evaluation of the quality assurance requirements for beam collimation and techniques. This study surveyed, developed, performed and evaluated quality assurance efforts for conventional MLCs with the aim to determine efficacy and reproducibility of the quality control procedures. Materials and Methods: The performance of MLCs for an Elekta (Livingstone Hospital) and Siemens (Charlotte Makexe Johannesburg Academic Hospital) Linac was examined. The major quality control procedures studied were leaf matching, leaf position accuracy, inter-leaf leakage and transmission through abutting leaves. Three portal imaging devices (radiographic film, radio chromic film and an Electronic Portal Imaging Device) and a LA48 Linear array were used as detectors. Record and verify data management systems were used to set up and execute the procedures. The calibration of all the portal imaging devices was also performed. Results: The calibration procedure of the portal imaging devices is Linac specific in execution. The profiles obtained indicated consistency across device and time. A combined single execution procedure is viable and reproducible on all platforms. Conclusion: The preliminary results show that the calibration of imaging devices is of great importance. The MLC design influences the range and extent of quality control that can be performed. This may impact on the accuracy with which advanced technologies requiring high conformity and reproducible leaf movement can be delivered. Imaging devices each have specific resource requirement issues affecting the efficacy of their use. Keywords: Multileaf collimator, Quality control, Assurance O.37 INSTALLATION PROCESS FOR A PHILIPS INGENIA 3 TESLA MAGNETIC RESONANCE IMAGING UNIT AT UNIVERSITAS ACADEMIC HOSPITAL R.K. Segoenyane *, W.I.D. Rae, A. Conradie. Department of Medical Physics, University of the Free State, Bloemfontein, South Africa Introduction: Magnetic Resonance Imaging (MRI) uses strong magnetic fields and radio waves to produce cross-sectional images of patients. To achieve this, a large superconducting magnet, of mass approximately 4000 kg, is used to create a 1.5 Tesla (1.5T) or 3 Tesla (3T) magnetic field. Special precautions and planning are thus required during room design. The aim of this study is to review the installation process of the Philips Ingenia 3T MRI installed at Universitas Academic Hospital (UAH) in early 2015. Materials and Methods: Colour digital images were obtained during installation to record the process. Comparison was made between the Philips Ingenia 3T installation and the recent Siemens 1.5T Magnetrom Aera MRI installation at Pelonomi Tertiary Hospital (PTH). Acceptance testing was performed based on the American College of Radiology phantom protocol. The influence of the 3T MRI scanner on the adjacent GE 1.5T MRI unit was investigated. Results: Before installation, floor loading capacity was increased by the installation of T-bar support structures between the structural pillars. The walls where shielded using conductive cladding. The MRI unit was factory assembled and delivered intact. Installation included ramping the magnet and electrical installation. During installation, wraparound and zipper artefacts were identified on images acquired by the adjacent GE 1.5T unit, but were found to be unrelated to the 3T MRI. After installation, the unit passed acceptance testing. A metal detector was installed to ensure that no ferromagnetic objects enter the room. Conclusion: Installation of the 3T MRI at UAH was similar to that of the 1.5T MRI at PTH. Artefacts on 1.5T images ceased after installation. Installation records should be retained as a reference for installation of 3T units at other hospitals. Keywords: Magnetic resonance imaging, 3T, Installation, Artefacts O.38 TOTAL SCATTER FACTOR COMPARISON BETWEEN CC01, EFD3G ELECTRON DIODE AND PTW60019 MICRODIAMOND DETECTORS FOR SMALL FIELDS IN MEGAVOLTAGE PHOTON BEAMS
A.E. Rule *,a, D.G. van der Merwe b. a Department of Radiation Oncology, Livingstone Hospital, Port Elizabeth, South Africa; b Department of Medical Physics, Charlotte Maxeke Johannesburg Academic Hospital/University of the Witwatersrand, Johannesburg, South Africa
I.E. Setilo *, F.C.P. du Plessis. Department of Medical Physics, University of the Free State, Bloemfontein, South Africa
Introduction: The Multileaf collimator (MLC) system introduction into the Clinical Linear Accelerator (Linac) facilitated computer-control and verification of
Introduction: Small fields are characterized by the lack of electronic equilibrium, and therefore small detectors must be used for beam output