Bojan Štrbac - Academia.edu (original) (raw)
Papers by Bojan Štrbac
Biomedical Physics & Engineering Express, May 24, 2018
Radiation Protection Dosimetry, Feb 18, 2008
Application of a quality control (QC) programme is very important when optimisation of image qual... more Application of a quality control (QC) programme is very important when optimisation of image quality and reduction of patient exposure is desired. QC surveys of diagnostics imaging equipment in Republic of Srpska (entity of Bosnia and Herzegovina) has been systematically performed since 2001. The presented results are mostly related to the QC test results of X-ray tubes and generators for diagnostic radiology units in 92 radiology departments. In addition, results include workplace monitoring and usage of personal protective devices for staff and patients. Presented results showed the improvements in the implementation of the QC programme within the period 2001--2005. Also, more attention is given to appropriate maintenance of imaging equipment, which was one of the main problems in the past. Implementation of a QC programme is a continuous and complex process. To achieve good performance of imaging equipment, additional tests are to be introduced, along with image quality assessment and patient dosimetry. Training is very important in order to achieve these goals.
Social Science Research Network, 2021
Journal of biomedical physics & engineering, 2023
Background: Mobility of lung tumors is induced by respiration and causes inadequate dose coverage... more Background: Mobility of lung tumors is induced by respiration and causes inadequate dose coverage. Objective: This study quantified lung tumor motion, velocity, and stability for small (≤5 cm) and large (>5 cm) tumors to adapt radiation therapy techniques for lung cancer patients. Material and Methods: In this retrospective study, 70 patients with lung cancer were included that 50 and 20 patients had a small and large gross tumor volume (GTV). To quantify the tumor motion and velocity in the upper lobe (UL) and lower lobe (LL) for the central region (CR) and a peripheral region (PR), the GTV was contoured in all ten respiratory phases, using 4D-CT. Results: The amplitude of tumor motion was greater in the LL, with motion in the superior-inferior (SI) direction compared to the UL, with an elliptical motion for small and large tumors. Tumor motion was greater in the CR, rather than in the PR, by 63% and 49% in the UL compared to 50% and 38% in the LL, for the left and right lung. The maximum tumor velocity for a small GTV was 44.1 mm/s in the LL (CR), decreased to 4 mm/s for both ULs (PR), and a large GTV ranged from 0.4 to 9.4 mm/s. Conclusion: The tumor motion and velocity depend on the tumor localization and the greater motion was in the CR for both lobes due to heart contribution. The tumor velocity and stability can help select the best technique for motion management during radiation therapy.
Radiation and Environmental Biophysics
Polish Journal of Medical Physics and Engineering, 2020
Purpose: To evaluate the breathing amplitude, tumor motion, patient positioning, and treatment vo... more Purpose: To evaluate the breathing amplitude, tumor motion, patient positioning, and treatment volumes among consecutive four-dimensional computed tomography (4D-CT) scans, during the simulation for lung stereotactic body radiation therapy (SBRT). Material and methods: The variation and shape of the breathing amplitude, patient positioning, and treatment volumes were evaluated for 55 lung cancer patients after consecutive 4D-CT acquisitions, scanned at one-week intervals. The impact of variation in the breathing amplitude on lung tumor motion was determined for 20 patients. The gross tumor volume (GTV) was contoured from a free-breathing CT scan and at ten phases of the respiratory cycle, for both 4D-CTs (440 phases in total). Results: Breathing amplitude decreased by 3.6 (3.4-4.9) mm, tumor motion by 3.2 (0.4-5.0) mm while breathing period increased by 4 (2-6) s, inter-scan for 20 patients. Intra-scan variation was 4 times greater for the breathing amplitude, 5 times for the breath...
Physica Medica, 2017
Quality Assurance is an important part of a safe radiotherapy service. The End to End (E2E) test ... more Quality Assurance is an important part of a safe radiotherapy service. The End to End (E2E) test assesses the overall spatial targeting accuracy of the integrated CyberKnife system for multiple beams delivered isocentrically. The targeting accuracy is quantified based on the dose distribution recorded on film. The complexity of the entire process suggests that data-driven approaches can provide robust solutions for the detection and prediction of errors. Regression analysis is a statistical technique for determining the relationship between a single dependent (criterion) variable (in this analysis: total targeting error) and one or more independent (predictor) variables, which are specific error components from the Anterior-Posterior(AP), Left–Right(LR) or Superior–Inferior(SI) directions. Dominance analysis (DA) was used as a method to find whether one independent variable contributes more variance to the regression effect than another independent variable on average across all pos...
Iranian Journal of Medical Physics, 2020
Purpose: To evaluate internal (lung, heart and diaphragm) and external (nine glass marbles) marke... more Purpose: To evaluate internal (lung, heart and diaphragm) and external (nine glass marbles) marker motion in correlation with lung tumor motion, to determine potential surrogate for respiratory gating radiation therapy (RGRT) depending on tumor localization, upper lobe (UL) vs lower lobe (LL).Methods: This study included 58 patients (34 male and 24 female) with small lung cancer (≤ 5cm), who underwent Stereotactic Body Radiation Therapy (SBRT). All patients were scanned and contoured in all ten phases (Varian Eclipse 13.7) after four-dimensional computed tomography simulation (4D-CT). The motion of internal markers and external markers were analyzed and correlated with tumor motion. The Pearson correlation coefficient (PCC) was used to evaluate the correlation between internal and external marker motion with tumor motion. Results: The median (range) values of tumor motion were 3.2 (0.6-11.0) vs 8.6 (4.0-24.0) mm in the UL vs LL. The median (range) values of organs motion and PCC com...
Australasian physical & engineering sciences in medicine, Jan 27, 2017
Intrafraction prostate motion degrades the accuracy of radiation therapy (RT) delivery. Whilst a ... more Intrafraction prostate motion degrades the accuracy of radiation therapy (RT) delivery. Whilst a number of metrics in the literature have been used to quantify intrafraction prostate motion, it has not been established whether these metrics reflect the effect of motion on the RT dose delivered to the patients. In this study, prostate motion during volumetric modulated arc therapy (VMAT) treatment of 18 patients and a total of 294 fractions was quantified through novel metrics as well as those available in the literature. The impact of the motion on VMAT dosimetry was evaluated using these metrics and dose reconstructions based on a previously validated and published method. The dosimetric impact of the motion on planning target volume (PTV) and clinical target volume (CTV) coverage and organs at risk (OARs) was correlated with the motion metrics, using the coefficient of determination (R (2) ), to evaluate their utility. Action level threshold for the prostate motion metric that bes...
Physica Medica, 2016
In a previous work, phase-space data files (phsp) provided by the International Atomic Energy Age... more In a previous work, phase-space data files (phsp) provided by the International Atomic Energy Agency (IAEA) were used to develop a hybrid virtual source model (VSM) for clinical photon beams. Very good agreement with dosimetric measurements performed on linear accelerators was obtained for field sizes up to 15×15cm(2). In the present work we extend the VSM to larger field sizes, for which phsp are not available. We incorporate a virtual flattening filter to our model, which can be determined from dose measurements for larger fields. In this way a fully functional VSM can be built, from publicly available IAEA's phsps and standard dose measurements, for fields of any size and tailored to a particular linac.
International Journal of Radiation Oncology*Biology*Physics, 2015
Physica Medica, 2014
In the present work, phase-space data files (phsp) provided by the International Atomic Energy Ag... more In the present work, phase-space data files (phsp) provided by the International Atomic Energy Agency (IAEA) for different accelerators were used in order to develop a Virtual Source Model (VSM) for clinical photon beams. Spectral energy distributions extracted from supplied phsp files were used to define the radiation pattern of a virtual extended source in a hybrid model which is completed with a virtual diaphragm used to simulate both electron contamination and the shape of the penumbra region. This simple virtual model was used as the radiation source for dosimetry calculations in a water phantom. The proposed model proved easy to build and test, and good agreement with clinical accelerators dosimetry measurements were obtained for different field sizes. Our results suggest this simple method could be useful for treatment planning systems (TPS) verification purposes.
Journal of Radiation Oncology, 2020
Purpose To evaluate the amplitude of lung tumor motion and impact of tumor motion on dose deliver... more Purpose To evaluate the amplitude of lung tumor motion and impact of tumor motion on dose delivered to the organs at risk (OARs) during lung stereotactic body radiation therapy (SBRT). Materials and methods This study included 55 patients (30 males and 25 females) with lung cancer who had a small gross tumor volume (GTV). SBRT lung cancer patients were treated with a prescribed dose of 60 Gy in 4 to 8 fractions. Radiotherapy plans were planned in Pinnacle 9.10 with two partial dynamic conformal arcs (DCAs) for the peripheral region (PR) and three to four partial DCAs for the central region (CR). The amplitude of tumor motion and their impact on the maximum dose delivered (D max) to the OARs were evaluated in the upper lobe (UL) and lower lobe (LL) in cases of CR and PR tumor's localizations. Results The median tumor motions between CR and PR were 4.5 vs 2.2 mm in the UL and 12.5 vs 7.0 mm in the LL. Max dose delivered to the OARs between CR and PR in the UL and LL were as follows: 6.7 vs 8.9 Gy and 9.1 vs 11.7 Gy for the spinal cord; 15.2 vs 0.6 Gy and 22.4 vs 7.6 Gy for the heart; and 11.7 vs 10.8 Gy and 14.8 vs 9.8 Gy for the esophagus, respectively. Conclusion The dose received by the OARs depends on the amplitude of tumor motion and is relative to the OAR's location and motion, due to patient respiration and heart contribution.
Radiotherapy and Oncology, 2011
Purpose: To determine the likely benefit from introduction of IGRT to prostate radiotherapy pract... more Purpose: To determine the likely benefit from introduction of IGRT to prostate radiotherapy practice with current CTV-PTV margins of 5-10mm delivered either concomitantly or in two phases. Also to determine the feasibility of a potential clinical trial to resolve the expected difference in TCP between IGRT and non-IGRT arms for these margin sizes. Materials: Real systematic error data collected from 50 patients undergoing daily fiducial marker localisation was used together with a random error of σ=3mm to model non-IGRT treatment. IGRT was modelled with residual systematic and random errors of Σ=σ=1.5mm. Motion of the target relative to a
Medical Dosimetry, 2021
The aim of this study is to investigate the robustness of our institutionally applied clinical ta... more The aim of this study is to investigate the robustness of our institutionally applied clinical target volume (CTV)-to-planning target volume (PTV) margins in cervical cancer patients in terms of an equivalent uniform dose (EUD) based on tumor control probability (TCP). We simulated target motion using 25 IMRT cervical cancer plans to demonstrate the effect of geometrical uncertainties on the EUD and TCP. The different components of the total geometrical uncertainties budget were estimated. The biological effects were compared by calculating the EUDs from the trial DVHs. The impact of geometric uncertainties was calculated as a percentage of the difference between 〖EUD〗_static and 〖EUD〗_motion, where the 〖EUD〗_static is the EUD calculated from the target DVHs and 〖EUD〗_motion is averaged, over a 1000 calculated EUDs for each of the analyzed IMRT treatment plans. The multivariate nonlinear regression was used to find the predicted difference between the static and motion EUD. The estimate of the systematic and random motion errors were Σ_(total(SI,LR,AP)) (mm)=(2.6; 2.5; 1.8) and σ_(total(SI,LR,AP)) (mm)=(3.4; 1.4; 3.4). For average 〈EUD〉_motion=44.3 Gy (over 25 patients) we have found a TCP decrease of about 1%, %(ΔTCP)≈1% for predefined PTV margin. According to the calculated EUD motion-distributions, for particular patients, the CTV does receive the prescribed EUD of 45 Gy. The predicted difference in EUD showed that our isotropic margin of 10 mm is large enough to absorb geometric uncertainties and ensure dose coverage of the moving CTV in the cervical cancer patients.
Medical Dosimetry
The aim of this study was to evaluate thoracic surface motion from chest wall expansion during fr... more The aim of this study was to evaluate thoracic surface motion from chest wall expansion during free breathing (FB) and deep inspiration breath hold (DIBH) methods, measured with and without 4-dimensional computed tomography (4D-CT) simulation, using equipment developed in-house. The respiratory amplitude and chest wall expansion were evaluated at 5 levels of the thorax, (the sterno-clavicular joint (SCJ), the second level, the intermammary line (IML), the fourth level and the caudal end of the xiphoid process (XP)) using radiopaque wires and potentiometers, with a CT scan simultaneously. This study included 25 examinees (10 volunteers performed FB, 10 volunteers performed DIBH and 5 patients performed FB). For low and irregular respiration, coaching was used, and its impact was evaluated for both breathing methods, FB and DIBH. The breathing amplitude performed with FB between volunteers and patients was not detectable at the SCJ; increasing to the abdomen, 3 mm vs 2 mm (p = 0.326) at the second level; 6 mm vs 4 mm (p = 0.042) at the IML; 10 mm vs 8 mm (p < 0.01) at the fourth level; and 23 mm vs 19 mm (p < 0.001) at the XP. Contrary to the DIBH, where breathing amplitude was greater at 2 first levels 18 mm (SCJ) and 20 mm (second level), decreasing to the abdomen, 14 mm (IML); 11 mm (fourth level); and 10 mm (XP). Chest wall expansion was not detected at the SCJ, while at other levels measured from 1 to 7 mm. Coaching was improve breathing amplitude, for both methods, FB (3 mm) and DIBH (5 mm). The location of amplification is different depending on the breathing method and the in-house phantom was useful to check the amplification level.
Radiotherapy and Oncology, 2011
Purpose: To determine the likely benefit from introduction of IGRT to prostate radiotherapy pract... more Purpose: To determine the likely benefit from introduction of IGRT to prostate radiotherapy practice with current CTV-PTV margins of 5-10mm delivered either concomitantly or in two phases. Also to determine the feasibility of a potential clinical trial to resolve the expected difference in TCP between IGRT and non-IGRT arms for these margin sizes. Materials: Real systematic error data collected from 50 patients undergoing daily fiducial marker localisation was used together with a random error of σ=3mm to model non-IGRT treatment. IGRT was modelled with residual systematic and random errors of Σ=σ=1.5mm. Motion of the target relative to a
Biomedical Physics & Engineering Express, May 24, 2018
Radiation Protection Dosimetry, Feb 18, 2008
Application of a quality control (QC) programme is very important when optimisation of image qual... more Application of a quality control (QC) programme is very important when optimisation of image quality and reduction of patient exposure is desired. QC surveys of diagnostics imaging equipment in Republic of Srpska (entity of Bosnia and Herzegovina) has been systematically performed since 2001. The presented results are mostly related to the QC test results of X-ray tubes and generators for diagnostic radiology units in 92 radiology departments. In addition, results include workplace monitoring and usage of personal protective devices for staff and patients. Presented results showed the improvements in the implementation of the QC programme within the period 2001--2005. Also, more attention is given to appropriate maintenance of imaging equipment, which was one of the main problems in the past. Implementation of a QC programme is a continuous and complex process. To achieve good performance of imaging equipment, additional tests are to be introduced, along with image quality assessment and patient dosimetry. Training is very important in order to achieve these goals.
Social Science Research Network, 2021
Journal of biomedical physics & engineering, 2023
Background: Mobility of lung tumors is induced by respiration and causes inadequate dose coverage... more Background: Mobility of lung tumors is induced by respiration and causes inadequate dose coverage. Objective: This study quantified lung tumor motion, velocity, and stability for small (≤5 cm) and large (>5 cm) tumors to adapt radiation therapy techniques for lung cancer patients. Material and Methods: In this retrospective study, 70 patients with lung cancer were included that 50 and 20 patients had a small and large gross tumor volume (GTV). To quantify the tumor motion and velocity in the upper lobe (UL) and lower lobe (LL) for the central region (CR) and a peripheral region (PR), the GTV was contoured in all ten respiratory phases, using 4D-CT. Results: The amplitude of tumor motion was greater in the LL, with motion in the superior-inferior (SI) direction compared to the UL, with an elliptical motion for small and large tumors. Tumor motion was greater in the CR, rather than in the PR, by 63% and 49% in the UL compared to 50% and 38% in the LL, for the left and right lung. The maximum tumor velocity for a small GTV was 44.1 mm/s in the LL (CR), decreased to 4 mm/s for both ULs (PR), and a large GTV ranged from 0.4 to 9.4 mm/s. Conclusion: The tumor motion and velocity depend on the tumor localization and the greater motion was in the CR for both lobes due to heart contribution. The tumor velocity and stability can help select the best technique for motion management during radiation therapy.
Radiation and Environmental Biophysics
Polish Journal of Medical Physics and Engineering, 2020
Purpose: To evaluate the breathing amplitude, tumor motion, patient positioning, and treatment vo... more Purpose: To evaluate the breathing amplitude, tumor motion, patient positioning, and treatment volumes among consecutive four-dimensional computed tomography (4D-CT) scans, during the simulation for lung stereotactic body radiation therapy (SBRT). Material and methods: The variation and shape of the breathing amplitude, patient positioning, and treatment volumes were evaluated for 55 lung cancer patients after consecutive 4D-CT acquisitions, scanned at one-week intervals. The impact of variation in the breathing amplitude on lung tumor motion was determined for 20 patients. The gross tumor volume (GTV) was contoured from a free-breathing CT scan and at ten phases of the respiratory cycle, for both 4D-CTs (440 phases in total). Results: Breathing amplitude decreased by 3.6 (3.4-4.9) mm, tumor motion by 3.2 (0.4-5.0) mm while breathing period increased by 4 (2-6) s, inter-scan for 20 patients. Intra-scan variation was 4 times greater for the breathing amplitude, 5 times for the breath...
Physica Medica, 2017
Quality Assurance is an important part of a safe radiotherapy service. The End to End (E2E) test ... more Quality Assurance is an important part of a safe radiotherapy service. The End to End (E2E) test assesses the overall spatial targeting accuracy of the integrated CyberKnife system for multiple beams delivered isocentrically. The targeting accuracy is quantified based on the dose distribution recorded on film. The complexity of the entire process suggests that data-driven approaches can provide robust solutions for the detection and prediction of errors. Regression analysis is a statistical technique for determining the relationship between a single dependent (criterion) variable (in this analysis: total targeting error) and one or more independent (predictor) variables, which are specific error components from the Anterior-Posterior(AP), Left–Right(LR) or Superior–Inferior(SI) directions. Dominance analysis (DA) was used as a method to find whether one independent variable contributes more variance to the regression effect than another independent variable on average across all pos...
Iranian Journal of Medical Physics, 2020
Purpose: To evaluate internal (lung, heart and diaphragm) and external (nine glass marbles) marke... more Purpose: To evaluate internal (lung, heart and diaphragm) and external (nine glass marbles) marker motion in correlation with lung tumor motion, to determine potential surrogate for respiratory gating radiation therapy (RGRT) depending on tumor localization, upper lobe (UL) vs lower lobe (LL).Methods: This study included 58 patients (34 male and 24 female) with small lung cancer (≤ 5cm), who underwent Stereotactic Body Radiation Therapy (SBRT). All patients were scanned and contoured in all ten phases (Varian Eclipse 13.7) after four-dimensional computed tomography simulation (4D-CT). The motion of internal markers and external markers were analyzed and correlated with tumor motion. The Pearson correlation coefficient (PCC) was used to evaluate the correlation between internal and external marker motion with tumor motion. Results: The median (range) values of tumor motion were 3.2 (0.6-11.0) vs 8.6 (4.0-24.0) mm in the UL vs LL. The median (range) values of organs motion and PCC com...
Australasian physical & engineering sciences in medicine, Jan 27, 2017
Intrafraction prostate motion degrades the accuracy of radiation therapy (RT) delivery. Whilst a ... more Intrafraction prostate motion degrades the accuracy of radiation therapy (RT) delivery. Whilst a number of metrics in the literature have been used to quantify intrafraction prostate motion, it has not been established whether these metrics reflect the effect of motion on the RT dose delivered to the patients. In this study, prostate motion during volumetric modulated arc therapy (VMAT) treatment of 18 patients and a total of 294 fractions was quantified through novel metrics as well as those available in the literature. The impact of the motion on VMAT dosimetry was evaluated using these metrics and dose reconstructions based on a previously validated and published method. The dosimetric impact of the motion on planning target volume (PTV) and clinical target volume (CTV) coverage and organs at risk (OARs) was correlated with the motion metrics, using the coefficient of determination (R (2) ), to evaluate their utility. Action level threshold for the prostate motion metric that bes...
Physica Medica, 2016
In a previous work, phase-space data files (phsp) provided by the International Atomic Energy Age... more In a previous work, phase-space data files (phsp) provided by the International Atomic Energy Agency (IAEA) were used to develop a hybrid virtual source model (VSM) for clinical photon beams. Very good agreement with dosimetric measurements performed on linear accelerators was obtained for field sizes up to 15×15cm(2). In the present work we extend the VSM to larger field sizes, for which phsp are not available. We incorporate a virtual flattening filter to our model, which can be determined from dose measurements for larger fields. In this way a fully functional VSM can be built, from publicly available IAEA's phsps and standard dose measurements, for fields of any size and tailored to a particular linac.
International Journal of Radiation Oncology*Biology*Physics, 2015
Physica Medica, 2014
In the present work, phase-space data files (phsp) provided by the International Atomic Energy Ag... more In the present work, phase-space data files (phsp) provided by the International Atomic Energy Agency (IAEA) for different accelerators were used in order to develop a Virtual Source Model (VSM) for clinical photon beams. Spectral energy distributions extracted from supplied phsp files were used to define the radiation pattern of a virtual extended source in a hybrid model which is completed with a virtual diaphragm used to simulate both electron contamination and the shape of the penumbra region. This simple virtual model was used as the radiation source for dosimetry calculations in a water phantom. The proposed model proved easy to build and test, and good agreement with clinical accelerators dosimetry measurements were obtained for different field sizes. Our results suggest this simple method could be useful for treatment planning systems (TPS) verification purposes.
Journal of Radiation Oncology, 2020
Purpose To evaluate the amplitude of lung tumor motion and impact of tumor motion on dose deliver... more Purpose To evaluate the amplitude of lung tumor motion and impact of tumor motion on dose delivered to the organs at risk (OARs) during lung stereotactic body radiation therapy (SBRT). Materials and methods This study included 55 patients (30 males and 25 females) with lung cancer who had a small gross tumor volume (GTV). SBRT lung cancer patients were treated with a prescribed dose of 60 Gy in 4 to 8 fractions. Radiotherapy plans were planned in Pinnacle 9.10 with two partial dynamic conformal arcs (DCAs) for the peripheral region (PR) and three to four partial DCAs for the central region (CR). The amplitude of tumor motion and their impact on the maximum dose delivered (D max) to the OARs were evaluated in the upper lobe (UL) and lower lobe (LL) in cases of CR and PR tumor's localizations. Results The median tumor motions between CR and PR were 4.5 vs 2.2 mm in the UL and 12.5 vs 7.0 mm in the LL. Max dose delivered to the OARs between CR and PR in the UL and LL were as follows: 6.7 vs 8.9 Gy and 9.1 vs 11.7 Gy for the spinal cord; 15.2 vs 0.6 Gy and 22.4 vs 7.6 Gy for the heart; and 11.7 vs 10.8 Gy and 14.8 vs 9.8 Gy for the esophagus, respectively. Conclusion The dose received by the OARs depends on the amplitude of tumor motion and is relative to the OAR's location and motion, due to patient respiration and heart contribution.
Radiotherapy and Oncology, 2011
Purpose: To determine the likely benefit from introduction of IGRT to prostate radiotherapy pract... more Purpose: To determine the likely benefit from introduction of IGRT to prostate radiotherapy practice with current CTV-PTV margins of 5-10mm delivered either concomitantly or in two phases. Also to determine the feasibility of a potential clinical trial to resolve the expected difference in TCP between IGRT and non-IGRT arms for these margin sizes. Materials: Real systematic error data collected from 50 patients undergoing daily fiducial marker localisation was used together with a random error of σ=3mm to model non-IGRT treatment. IGRT was modelled with residual systematic and random errors of Σ=σ=1.5mm. Motion of the target relative to a
Medical Dosimetry, 2021
The aim of this study is to investigate the robustness of our institutionally applied clinical ta... more The aim of this study is to investigate the robustness of our institutionally applied clinical target volume (CTV)-to-planning target volume (PTV) margins in cervical cancer patients in terms of an equivalent uniform dose (EUD) based on tumor control probability (TCP). We simulated target motion using 25 IMRT cervical cancer plans to demonstrate the effect of geometrical uncertainties on the EUD and TCP. The different components of the total geometrical uncertainties budget were estimated. The biological effects were compared by calculating the EUDs from the trial DVHs. The impact of geometric uncertainties was calculated as a percentage of the difference between 〖EUD〗_static and 〖EUD〗_motion, where the 〖EUD〗_static is the EUD calculated from the target DVHs and 〖EUD〗_motion is averaged, over a 1000 calculated EUDs for each of the analyzed IMRT treatment plans. The multivariate nonlinear regression was used to find the predicted difference between the static and motion EUD. The estimate of the systematic and random motion errors were Σ_(total(SI,LR,AP)) (mm)=(2.6; 2.5; 1.8) and σ_(total(SI,LR,AP)) (mm)=(3.4; 1.4; 3.4). For average 〈EUD〉_motion=44.3 Gy (over 25 patients) we have found a TCP decrease of about 1%, %(ΔTCP)≈1% for predefined PTV margin. According to the calculated EUD motion-distributions, for particular patients, the CTV does receive the prescribed EUD of 45 Gy. The predicted difference in EUD showed that our isotropic margin of 10 mm is large enough to absorb geometric uncertainties and ensure dose coverage of the moving CTV in the cervical cancer patients.
Medical Dosimetry
The aim of this study was to evaluate thoracic surface motion from chest wall expansion during fr... more The aim of this study was to evaluate thoracic surface motion from chest wall expansion during free breathing (FB) and deep inspiration breath hold (DIBH) methods, measured with and without 4-dimensional computed tomography (4D-CT) simulation, using equipment developed in-house. The respiratory amplitude and chest wall expansion were evaluated at 5 levels of the thorax, (the sterno-clavicular joint (SCJ), the second level, the intermammary line (IML), the fourth level and the caudal end of the xiphoid process (XP)) using radiopaque wires and potentiometers, with a CT scan simultaneously. This study included 25 examinees (10 volunteers performed FB, 10 volunteers performed DIBH and 5 patients performed FB). For low and irregular respiration, coaching was used, and its impact was evaluated for both breathing methods, FB and DIBH. The breathing amplitude performed with FB between volunteers and patients was not detectable at the SCJ; increasing to the abdomen, 3 mm vs 2 mm (p = 0.326) at the second level; 6 mm vs 4 mm (p = 0.042) at the IML; 10 mm vs 8 mm (p < 0.01) at the fourth level; and 23 mm vs 19 mm (p < 0.001) at the XP. Contrary to the DIBH, where breathing amplitude was greater at 2 first levels 18 mm (SCJ) and 20 mm (second level), decreasing to the abdomen, 14 mm (IML); 11 mm (fourth level); and 10 mm (XP). Chest wall expansion was not detected at the SCJ, while at other levels measured from 1 to 7 mm. Coaching was improve breathing amplitude, for both methods, FB (3 mm) and DIBH (5 mm). The location of amplification is different depending on the breathing method and the in-house phantom was useful to check the amplification level.
Radiotherapy and Oncology, 2011
Purpose: To determine the likely benefit from introduction of IGRT to prostate radiotherapy pract... more Purpose: To determine the likely benefit from introduction of IGRT to prostate radiotherapy practice with current CTV-PTV margins of 5-10mm delivered either concomitantly or in two phases. Also to determine the feasibility of a potential clinical trial to resolve the expected difference in TCP between IGRT and non-IGRT arms for these margin sizes. Materials: Real systematic error data collected from 50 patients undergoing daily fiducial marker localisation was used together with a random error of σ=3mm to model non-IGRT treatment. IGRT was modelled with residual systematic and random errors of Σ=σ=1.5mm. Motion of the target relative to a