Virginia Commonwealth University VCU Scholars Compass Theses and Dissertations Graduate School 2010 REAL TIME 3-D TRACKING OF THE HIGH DOSE RATE RADIATION SOURCE USING A FLAT PANEL DETECTOR Aditya Bondal Virginia Commonwealth University Follow this and additional works at: https://scholarscompass.edu/etd Part of the Biomedical Engineering and Bioengineering Commons © The Author Downloaded from https://scholarscompass.edu/etd/2236 This Thesis is brought to you for free and open access by the Graduate School at VCU Scholars Compass. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of VCU Scholars Compass. For more information, please contact libcompass@vcu. © Aditya Bondal 2010 All Rights Reserved REAL TIME 3-D TRACKING OF THE HIGH DOSE RATE RADIATION SOURCE USING A FLAT PANEL DETECTOR A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University.
by ADITYA BONDAL Bachelor of Engineering, Mumbai University, India 2006 Director: DORIN TODOR, PH. ASSOCIATE PROFESSOR, RADIATION ONCOLOGY Director: DING-YU FEI, PH. ASSOCIATE PROFESSOR, BIOMEDICAL ENGINEERING Virginia Commonwealth University Richmond, Virginia August, 2010 ii Acknowledgement Firstly, I would like to thank my research advisor and mentor, Dr. Dorin Todor, who has supported me throughout my thesis with his patience, knowledge and occasional humor.
I attribute the level of my Masters degree to his encouragement and effort and without him this thesis, would not have been completed or written. I would also like to thank Dr Ding-Yu Fei for being my academic advisor and guiding me with course work and my research. His unconditional guidance and support during the Biomedical Instrumentation and Imaging class helped me understand crucial concepts essential for my project and ultimately my thesis. I would like to thank Dr Ou Bai for agreeing to be on my master‟s defense committee.
I am very grateful to Dr Williamson for providing financial support during my masters and giving me the opportunity to work with Dr Todor. I am extremely thankful to Chris, Lynn, Tatjana and Chem for helping me operate the Acuity machine. Without you guys I would have no data to play around with. Most importantly I would like to thank my family.
Without their love and support none of this would have been possible. My dad Ashwin Bondal, who has been the one person I look up to, my role model and one day I hope to be just like him and my mom Kumud Bondal who raised me to be the man I am today, I dedicate this thesis to the two iii of you. I would also like to thank my sister for being there when I missed my family and supporting me in every possible way. Last but not least I would like to thank all my friends in Richmond and as well as back home who have always been there during my ups and downs in life.
Especially my friends in Richmond for being my family away from home, thanks guys. Above all, I would like to thank God for helping me in every walk of life. iv Table of Contents Page Acknowledgements. ii List of Tables.
vii List of Figures. viii List of Abbreviations. xi Chapter 1 Introduction .2 Objective of the Study .2 Treatment of Breast Cancer .4 Breast Conservation Treatment Followed by RT .5 Accelerated Partial Breast Irradiation .1 Multicatheter Interstitial Brachytherapy.2 MammoSite Balloon Brachytherapy .8 High Dose Rate Radiation Source .9 Radiation Treatment Planning Workflow .3 Quality Assurance Procedures. 24 3 Methods and Materials .1 Testing Imaging Geometry and Image Quality .3 Calibrating the System .2 Calculate the Coordinates of the Markers.2 Second and Third Trial .6 Morphological Image Processing .7 Reconstruction of the Source.
84 B File From the Planning System containing the 3D Coordinates of the Treatment Plan. 90 vii List of Tables Page Table 1: Height between marker and detector. 62 Table 2: Mean and standard deviation of the shortest distance D and the x, y and z coordinates of points P and Q for Test Plan 1 for each dwell position. 65 Table 3: Mean and standard deviation of the shortest distance D and the x, y and z coordinates of points P and Q for Test Plan 2 for each dwell position.
65 Table 4: Mean and standard deviation of the shortest distance D and the x, y and z coordinates of points P and Q for Test Plan 1 for each dwell position. 66 Table 5: Comparison of planned dwell position against reconstructed dwell position. 69 viii List of Figures Page Figure 1: Multicatheter interstitial brachytherapy. 2 Figure 2: Structure of the female breast.
8 Figure 3: MammoSite balloon brachytherapy. 17 Figure 4: VariSource remote afterloader (Varian Medical Inc. 18 Figure 5: Ir-192 source by Varian Medical Systems Inc. 19 Figure 6: Tumor outline and planning for catheter placement.
20 Figure 7: Multicatheter implants for APBI treatments. 21 Figure 8: Contouring of tumor cavity and target volumes. 22 Figure 9: Explaining outlining of applicator and definition of dwell positions. 23 Figure 10: QA chart for treatment delivery.
25 Figure 11: Explaining the schematic of the experiment. 27 Figure 12: Explaining position of the markers for a good imaging geometry. 30 Figure 13: Explaining the area of interest for the position of the markers. 31 Figure 14: Grey scale image acquired using the HDR source and flat panel detector with source – detector distance 50cm to test imaging geometry and quality.
33 Figure 15: Binary image obtained after morphologically processing and segmenting the grey scale image. 35 Figure 16: Representation of the experimental setup. 36 ix Figure 17: Representing the arrangement of well defined matrix of markers. 37 Figure 18: Explaining the correct positioning of the flat panel detector.
39 Figure 19: Grey scale calibration image, red dotted lined representing the central axes. 41 Figure 20: Represents a schematic diagram used to calculate the height. 42 Figure 21: Represents a schematic for the calculating the coordinates of the markers from the calibration image. 45 Figure 22: Represents a schematic explaining the positioning of the test catheter and the test plan.
48 Figure 23: 3D representation of the first test plan. 50 Figure 24: 3D representation of the second test plan. 51 Figure 25: 3D representation of the third test plan. 52 Figure 26: Grey scale image acquired using the HDR source and flat panel detector for the first dwell position of test plan 1.
53 Figure 27: Binary image obtained after morphologically processing and segmenting the grey scale image. 57 Figure 28: Schematic explaining intersection of two lines in 3D. 59 Figure 29: 3D plot of the markers and its projection for the first dwell position of the second test plan. 62 Figure 30: Scatter plot of P‟s and Q‟s for Test Plan 2.
63 x Figure 31: Representation of the reconstructed 3D coordinates of the dwell position for (a) Test Plan 1, (b) Test Plan 2 and (c) Test Plan 3. 67 xi List of Abbreviations APBI – Accelerated Partial Breast Irradiation BCS – Breast Conservation Surgery CT – Computed Tomography DHI – Dose Homogeneity Index EBRT – External beam radiation therapy FPD – Flat Panel Detector HDR – High Dose Rate MIB – Multicatheter Interstitial Brachytherapy RT – Radiation Therapy TPS – Treatment Planning System QA – Quality Assurance Abstract REAL TIME 3D TRACKING OF THE HIGH DOSE RATE RADIATION SOURCE USING A FLAT PANEL DETECTOR By Aditya Bondal, B. A Thesis submitted in partial fulfillment of the requirements for the degree of Masters of Science at Virginia Commonwealth University. Virginia Commonwealth University, 2010 Major Director: Dorin Todor, Ph.
Associate Professor, Radiation Oncology A number of QA procedures have been developed for Breast Brachytherapy treatments, yet none guarantee accurate dose delivery or allow conformation of the actual source position leading to errors sometimes going unnoticed. The objective of this study is to track the exact path the HDR source would follow in real time. The exit radiation of the HDR source was used to image a well defined matrix of markers. The images were acquired using FPD and were processed to obtain projection coordinates while an x-ray calibration image was processed to obtain marker coordinates.
Each marker along with its xii xiii projection represents a line in 3D. A mathematical solution for the „near-intersection‟ of two 3D lines was implemented and used to determine the „true‟ 3D source position. A matrix with N markers will produce N*(N-1)/2 points of intersection and their mean will result in a more accurate source position. This study has proved that the accuracy of source position detection using a FPD is sub-millimeter.1 Background Radiation Therapy (RT) has been used for over a century as a treatment for cancer 1.
Within a few years of the discovery of radium by the Curie‟s, the importance of the medical use of radioactive substances was realized, which lead to an increase interest in radiobiology and the beginning of brachytherapy1. Educating women against breast cancer through various health promotion campaigns has spread the awareness of the disease 2. The 1980‟s and 1990‟s saw a sharp rise in the occurrence of early stage breast cancer that was tumors of less than 4cm in dimension being detected 3. This was mainly due to the introduction and application of new breast cancer diagnostic techniques along with greater number of women obtaining mammography scans4.
Breast brachytherapy is a Radiation Therapy procedure, which in the current era is typically delivered after lumpectomy as part of the breast conservation solution in Accelerated Partial Breast Irradiation (APBI) treatments. Brachytherapy as defined by the American Brachytherapy Society (ABS) is “the therapeutic use of encapsulated radionuclides within or close to a tumor 5”, that is the radiation source is placed within the tumor bed or in very close proximity to the area requiring treatment 6. Brachytherapy is 1 2 derived from the Greek "brachios" which stands for short, as the radiation source is placed at very short distances from the tumor5. Lumpectomy is the surgical removal of only the part of the breast containing the cancer tumor2,7.
Although the tumor is excised, microscopic residual of the tumor may exist on the borders of the tumor cavity. Radiation kills these microscopic residual thus reducing the chances of reoccurrence of the cancer tumor. A number of studies have proven that one of the most efficient radiation therapy methods for the treatment of breast cancer is Brachytherapy. Once the cancer tumor has been excised, catheters are inserted inside the area surrounding the tumor cavity in the breast (Figure 1) 8.
Figure 1: Multicatheter interstitial brachytherapy8 Catheters are cylindrical hollow tubes through which the radiation source can travel within the breast. The number of catheters depends on the size of the tumor. The catheters 3 are placed such that it assures optimal coverage to the radiation source of the target volume. Based on these images the TPS would define positions and times for the radiation source to be placed.
A dwell position for each catheter defines the exact location the radiation source will be positioned during the actual treatment and a dwell time defines the precise amount of time source will remain at that position. The TPS creates an optimal treatment plan made up of dwell positions for each catheter and dwell times for each position such that the radiation dose is delivered only to the area under treatment. In Breast Brachytherapy, radiation is delivered by placing a High Dose Rate (HDR) Ir-192 source inside the body of the patient at precise locations in the tumor bed for precise amounts of time. The HDR source is located at the tip of a wire which is stored in a device known as the remote afterloader and the movement of the HDR source is controlled by a remote computer.