Radiation Oncology Department - UCSF Comprehensive Cancer Center - Pouliot's Group

IPSA-HDR is an optimization algorithm for inverse treatment planning of cancer treatment with High Dose Rate Brachytherapy.

High dose rate brachytherapy (HDR) is a promising radiation treatment modality that uses temporarily implanted catheters to deliver the curative dose directly in the tumor. A programmable robotic device (the afterloader) moves a single tiny radioactive source (192Ir) along the catheters using a flexible cable attached to the source. With this flexible system, a wide variety of dose distributions can be generated from a given implant simply by adjusting the length of time (dwell time) that the source dwells at any location within the implanted catheters (dwell position). The challenge is to select the optimal sequence of dwell times related to the unique clinical situation of each patient.  This sequence of dwell times defines the volume and shape of the dose distribution hence ultimately the treatment outcome.

IPSA is an optimization algorithm that determines the optimal sequence of dwell times based on the physician’s clinical objectives, the given anatomy of the patient and the actual position of the implanted catheters or applicators. It follows the philosophy of inverse planning optimization and used simulated annealing to perform the search.

IPSA has been designed for 3D image-guided HDR treatment planning.  The optimization process is guided by dose objectives define for each organ extracted from 3D images.  It can take into account multiple targets (e.g. prostate, dominant intra prostatic lesion) and multiple organs at risk (e.g. urethra, rectum, bladder, etc.).  The adjustment of weighting factors sets the relative importance of dose objectives for each organ and between dose conformality and dose homogeneity.  Once the anatomy and the catheters are digitized, IPSA automatically selects the active dwell positions, use a unique strategy to generate thousands of dose calculation points and optimizes the dwell times to fulfill the dose objectives.  A simulated annealing engine, based on a unique search space probing scheme and an adapted cooling sequence, was specially designed to solve this optimization problem in a short time for clinical application.

The dose objectives are normally setup to maximize the target dose coverage while taking into account other clinical objectives such as the dose homogeneity and the organs at risk protection.  Using IPSA the dosimetrist has to play directly with the compromises between target coverage, dose homogeneity and organs at risk protection instead of playing with dwell positions and dwell times.  This change of perspective focuses the attention on the anatomy bringing the planning process closer to the real clinical issues.

 

CLINICAL APPLICATION

The advent of computerized tomography (CT), positron emission tomography (PET), magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS) and 3D treatment planning software improves the delineation of the anatomical structures and the localization of the cancerous cells.  Most treatment planning optimization tools were developed at the time when x-ray films were the only piece of information.  The goal was to maximize the dose distribution homogeneity within the tumor volume based on the catheter locations.  These tools fail to use the anatomical information and this result in an approximation of the shape of the anatomy.  A geometrical representation of the tumor cannot guarantee the complete dose coverage of the tumor.  Moreover, the surrounding normal tissues and organs at risk may be unnecessarily overdosed.  This in turn can lead to late side effects and complications. 

Therefore, the dwell times have to be carefully adjusted after the optimization to improve the tumor dose coverage and reduce the dose deliver to the organs at risk.  With hundreds of dwell positions, irregularly shaped tumor volumes, multiple tumor volumes and organs at risk, multiple organ sensitivities, this approach requires time and skills and the final treatment planning quality is often limited by the tight schedule of the clinical staff.  IPSA has been developed to execute this task automatically and in a short time for clinical application. 

Several independent beta sites validated the clinical efficiency of the algorithm.  First at UCSF, then at the Centre Hospitalier Universitaire de Quebec and at NIH-Bethesda. Today 10 beta sites have access to IPSA, and six are using it clinically.  So far, more than a thousand patients have been planned and treated with IPSA since 1999 at UCSF and at the beta sites.  The clinical experiences were reported in several scientific publications (see the attached list).  IPSA is efficient for all clinical sites and independent of the tumor size and shape.  IPSA reduced significantly the treatment planning time and produced improved treatment plans with reduced dose to the organs at risk compare to conventional treatment planning methods.  This anatomy based optimization achieved conformal dose coverage to the target opening the possibility to deliver higher dose while reducing the dose deliver to the organs at risk and normal tissues. 

 

Main Advantages

• Over 7 years of development (since 1999),
  
  
• Proven to produce better treatment plans for prostate brachytherapy (simultaneous better sparing of organ at risk, better target coverage and shortened planning time),
  
  
• The clinical experiences were reported in several of publications,
  
  
• The clinical efficiency was validated by several American and European beta sites,
  
  
• IPSA is well known to the international radiation oncology community,
  
  
• In the United States and Canada, centers who received IPSA immediately use it and abandon previous approach,
  
  
• Produces a treatment plan in few seconds,
  
  
• Optimizes the dwell time values to generate dose distribution based on user defined dose constraints,
  
  
• Introduce the concept of class solution in brachytherapy,
  
  
• Brings consistency from patient to patient,
  
  
• Works for all anatomical sites,
  
  
• Works for High Dose Rate and Pulsed Dose Rate Brachytherapy,
  
  
• Uses a unique routine to automatically generate thousands of dose points to evaluate the dose strategically during the optimization process,
  
  
• Determines automatically the active dwell positions based on the digitized catheters, the anatomy and the clinical objectives,
  
  
• Uses a unique simulated annealing search engine specially designed for HDR that accelerates the optimization,
  
  
• Uses a unique simulated annealing cooling schedule (between fast and quenching annealing) fine-tuned for HDR that accelerate the optimization.

 

SCIENTIFIC PUBLICATIONS IN REFEREED JOURNALS

1. Lessard E. and Pouliot J., Inverse Planning Anatomy-based dose optimization for HDR-Brachytherapy of the prostate using fast simulated annealing algorithm and dedicated objective function, Med. Phys. 28 (5), 773-779, 2001.
   
   
2. Lachance, B., B.-Nadeau, D., Lessard, E., Chrétien, M., Hsu, I.C., Pouliot, J., Beaulieu, L. and Vigneault E. Early Clinical Experience with anatomy-based inverse planning dose optimization for HDR boost of the prostate,  Int. J. Radiation Oncology Biol. Phys. 54 (1), pp86-100, 2002.
   
   
3. Lessard, E., Hsu I-C.  and Pouliot J., Inverse Planning For Interstitial Gynecological Template Brachytherapy: Truly Anatomy Based Planning, Int. J. Radiation Oncology Biol. Phys. 54 (4) pp1243-1251, 2002.
   
   
4. Lessard E., "Development and clinical introduction of an inverse planning dose optimization by simulated annealing (IPSA) for high dose rate brachytherapy" Thesis abstract, Med. Phys. 31(10), pp 2935 (October 2004)
   
   
5. Hsu I-C., Lessard E., Weinberg V., Pouliot J., Comparison of Inverse Planning Simulated Annealing and Geometrical Optimization for Prostate High Dose Rate Brachytherapy, Brachytherapy, 3(3) 147-152; 2004.
   
   
6. Ménard C., Susil R., Choyke P., Gustafson G., Kammerer W., Ning H., Miller R., Ullman K., Sears-Course N., Smith S., Lessard E., Pouliot J., Wright V., McVeigh E., Coleman N. and Camphausen K., MRI-Guided HDR Prostate Brachytherapy in a Standard 1.5T Scanner, Int. J. Radiation Oncology Biol. Phys. 59(5) 1414-1423; 2004.
   
   
7. Pouliot, J.,  Kim, Y., Lessard E., Hsu, I-C. Vigneron D. and Kurhanewicz, J.  Inverse Planning For HDR Prostate Brachytherapy Use to Boost Dominant Intra-Prostatic Lesion Defined by Magnetic-Resonance Spectroscopy Imaging. Int. J. Radiation Oncology Biol. Phys. 59 (4) 1196-1207; 2004.
   
   
8. Taschereau R. Stauffer P., Hsu I-C, Schlorff J.L., Milligan A.J. and Pouliot J., Radiation Dosimetry of a Conformal Heat-Brachytherapy Applicator, Technology in Cancer Research and Treatment, ISSN 1533-0346, Volume 3, (4); 347-358, 2004.
   
   
9. DeWitt K.D., Hsu I-C., Weinberg V.K., Lessard E., and Pouliot J, 3-D Inverse Treatment Planning for the Tandem and Ovoid Applicator in Cervical Cancer, Int. J. Radiation Oncology Biol. Phys. 63(4); 1270-1274, 2005.
   
   
10. Mamoudieh A., Tremblay C., Beaulieu L., Lachance B., Harel F., Lessard E., Pouliot J. and Vigneault E, Anatomy-Based Inverse Planning dose optimization in HDR prostate implant:  A toxicity study, Radiotherapy and Oncology, 75; 318-324, 2005.
    
    
11. Citrin D., Ning H., Guion P. Li G., Susil R.C. Miller R.W., Lessard E., Pouliot J., Huchen X., Capala J., Coleman C.N. Camphausen K., and Ménard C., Inverse treatment planning based on MRI for HDR prostate brachytherapy, Int. J. Radiation Oncology Biol. Phys. 61 (4); 1267-1275, 2005
    
    
12. Lessard E., Kwa S.L.S., Pickett B., Roach III, M., and Pouliot J., Class Solution for Inversly Planned Permanent Prostate Implants to Mimic An Experienced Dosimetrist for Pre And Real-Time Treatment Planning, Med. Phys. 33(8), August 2006
    
    
13. Alterovitz R., Lessard E., Pouliot J., Hsu I-C., O’Brien J.F., and Goldberg K., Optimization of high-dose-rate brachytherapy dose distribution using linear programming with penalty costs, Med. Phys. 33(11), 4012-4019, 2006

 

BOOK CHAPTERS

1. Advanced 3D Planning in Brachytherapy, Chap. 21, Pouliot J., Lessard E. and Hsu I.C. Brachytherapy Physics, 2^nd Edition, Eds. B.R.Thomadsen, M.J. Rivard, W.M. Butler, AAPM, Medical Physics Monograph No. 31, Seattle, Wa, 2005. ISBN-13: 978-1-930524-24-8.
   
   
2. Modern Technology of Radiation Therapy, Supplement: Chapter 10,  Prostate Brachytherapy: permanent and HDR temporary implants, Pickett B. and Pouliot J.. Ed. J. Van Dyke, Medical Physics Publishing, 2005.
   
   
3. HDR Prostate Brachytherapy: (part of) Chapter 13: Leibel, 2nd Edition, 2004.
   

Oral presentations AT SCIENTIFIC MEETINGS

1. Pouliot J., Lessard E., Hsu I-C., Lachance B., and Vigneault E., “Anatomy-based inverse planning dose optimization for HDR-Brachytherapy of the prostate” 10^th Annual International Brachytherapy Conference, Madrid, Spain, 2000.
   
   
2. Pouliot, J., Lessard, E., Oral E., and Taschereau, R. Anatomy conformal dose delivery for prostate brachytherapy. FRONTIER-SCIENCE RESEARCH CONFERENCES La Jolla International School of Science, The Institute for Advanced Physics Studies. 2000.
   
   
3. Lessard E., Hsu I-C., and Pouliot J., “Inverse Planning Anatomy conformal dose optimization for HDR-brachytherapy using fast simulated annealing algorithm and adaptable objective function”  43^rd AAPM Annual Meeting, Salt Lake City, Utah, 2001.
   
   
4. Lessard E., Lachance B., Vigneault E., and Pouliot J., “Inverse Planning Anatomy conformal dose optimization for high dose rate brachytherapy using fast simulated annealing algorithm and adaptable objective function” CAP Annual Meeting, Victoria, British Colombia, Canada, 2001. (1^st place young investigator competition)
   
   
5. Lachance B.,  Nadeau D., Lessard E., Chretien M., Beaulieu L., Vigneault E and Pouliot J “Early clinical experience with anatomy-based inverse planning dose optimization for HDR boost of the prostate” 43^rd AAPM Annual Meeting, Salt Lake City, Utah, 2001.
   
   
6. Lessard E, Hsu I-C., Fisch B. and Pouliot J., “Inverse planning ability to protect the bulb of the penis in HDR brachytherapy of the prostate” 44^th AAPM Annual Meeting, Montréal, Québec, Canada, 2002.
   
   
7. Pouliot J., and Lessard E., “Anatomical conformal inverse planning dose optimization” 11^th Annual Int. Brachytherapy Conference, Santa Fe, New Mexico, 2002.
   
   
8. Béliveau-Nadeau D., Lachance B., Vigneault E., Lessard E., and Beaulieu L., “Etude comparative de deux algorithmes de planification relative au traitement par haut débit de dose du cancer de la prostat” 70ième Congrès de l’ACFAS, Québec, Canada, 2002.
   
   
9. Pouliot J., Lessard E., Charra-Brunaud C., Kim Y., Speight J. and Hsu I-C., “Inverse planning for HDR-Brachytherapy: Clinical implementation” 23^rd ABS Annual Meeting, Orlando, Florida, 2002.
   
   
10. Hsu I-C., Lessard E., Weinberg V., and Pouliot J., “Comparison of inverse planning and geometrical optimization for prostate HDR-brachytherapy” 23^rd ABS Annual Meeting, Orlando, Florida, 2002.
    
    
11. Pouliot J., Taschereau R., Lessard E., Kim Y., and Hsu I-C., “Biological Effectiveness Improvement of High Dose Rate Prostate Brachytherapy” Joint Breast & Prostate Cancer Retreat, South San Francisco, California, 2002.
    
    
12. Beaulieu L., Tremblay C., Lessard E., Pouliot J., Lachance B., and Vigneault E., “Is there a preferred number of catheters in prostate HDR brachytherapy?” CARO Annual Meeting, Montréal, Québec, Canada, 2003.
    
    
13. Chuang C, Hsu I-C., Lessard E. and Pouliot J.”The Feasibility of CT-Based Inverse Planning for Breast HDR Brachytherapy” 45^th AAPM Annual Meeting, San Diego, California, 2003.
    
    
14. L’optimisation inverse en curiethérapie interstielle, Radiothérapie Conformationnelle avec modulation d’intensité et curiethérapie des cancers ORL et des cancers de la prostate, Nancy, France, Dec. 4-5, 2003.
    
    
15. Pouliot J., Kim Y., Lessard E., Hsu I-C., and Kurhanewicz J. “Magnetic-Resonance Spectroscopy Targeting for Inverse Planned HDR Prostate Brachytherapy” 45^th AAPM Annual Meeting, San Diego, California, 2003.
    
    
16. Pouliot J., Lessard E., and Hsu I-C.,”Inverse planning for HDR and PDR brachytherapy” 3^ième Séminaire Francophone de Curiethérapie, Avignon, France, 2003.
    
    
17. Pouliot J., Lessard E., and Hsu I-C., “Use of inverse planning optimization for HDR Brachytherapy” 7^th Int. Symposium on 3D conformal RT and IMRT, San Francisco, California, 2003.
    
    
18. Pouliot J., Lessard E., and Hsu I-C., “Inverse Planning for HDR and LDR Prostate Brachytherapy” Wescan annual meeting, Winnipeg, Canada, 2003.
    
    
19. Pouliot J., Lessard E., and Hsu I-C., “Toward Image-Based Inverse Planning for IO-HDR Brachytherapy, Therapy using Mobile Systems” 1^st Int. Workshop on Intra-Operative Rad. Sydney, Australia, 2003.
    
    
20. Ménard C., Citrin D., Susil R.C., Choyke P., Ning H., Miller R.W., Ullman K.L., Guion P., Pouliot J., Lessard E., Capala J., Coleman C.N., Camphausen K. "High dose rate brachytherapy for prostate cancer using interventional MRI at 1.5T” 5^th interventional MRI Symposium, Boston, 2004.
    
    
21. Huang K., Pouliot J., Lessard E., Weinberg V., Speight J., Chen L-M., and Hsu I-C., “Initial Clinical Results of Inverse Planned High Dose Rate Interstitial Implants for Cervical Cancer” Joint Brachytherapy Meeting GEC-ESTRO-ABS-GLAC , Barcelona, Spain, 2004.
    
    
22. Lessard E., Vigneault E, Lachance B, Chrétien M., Letourneau A., Beaulieu L., Hsu I-C., Speight J., Ménard C., Ning H., Pouliot J., “Algorithme de planification inversé pour les traitements de cancers par curiethérapie de haut débit de dose” 72ième Congrès de l’ACFAS, Montréal, Canada, 2004.
    
    
23. Speight J., Lessard E., and Pouliot J., “Lower D70% and D50% doses are delivered to penile bulb with IPSA HDR” American Radium Society 86^th Annual Meeting, San Francisco, California, 2004.
    
    
24. Alterovitz R., Lessard E., Pouliot J., Hsu I-C., O’Brien J.F., and Goldberg K., "High-dose-rate Brachytherapy Dose Optimization for Prostate Cancer Using Linear Programming," Institute for Operations Research and the Management Sciences (INFORMS) Annual Meeting, San Francisco, California, 2005.
    
    
25. Lessard E., Kwa S., Pickett B., Roach III M., and J. Pouliot, “Class solution for inversely planned permanent prostate implants to mimic an experienced dosimetrist for pre and live treatment planning” GEC-ESTRO meeting, Budapest, Hungary, 2005.
    
    
26. Vigneault E., Martin A.G., Pouliot J., Beaulieu., Lessard E., Harel F., Lachance B., “Clinical outcome based on two years biopsy for HDR prostate boost using inverse planning: the Quebec Experience” GEC-ESTRO meeting, Budapest, Hungary, 2005.
    
    
27. Hsu I-C.,  Lessard E., and Pouliot J., “High dose rate Brachytherapy for prostate cancer”  The Mid-Atlantic Society of Radiation Oncology Fall Meeting, Helen F. Graham Cancer Center, Newark, Delaware, 2005.
    
    
28. Pouliot, J., IPSA, optimization in Brachythetrapy, Basis and Principles, 4ième séminaire francophone de curiethérapie, Arcachon, France, June 15th, 2006.
    
    
29. Pouliot, J., Clinical experience with IPSA for prostate cancer treatment in HDR Brachytherapy, 4ième séminaire francophone de curiethérapie, Arcachon, France, June 15, 2006.
    
    
30. Lessard E., Hsu I-C., and Pouliot J., “Clinical Benefits of Inverse Planning for HDR Prostate Brachytherapy”  World Congress on Medical Physics and Biomedical Engineering, Seoul, Korea, 2006.
    
    
31. Martin A-G., Beaulieu L., Lessard E., Pouliot P., Vigneault E., “Boost within boost in permanent seed implant : A toxicity Analysis” ESTRO meeting, Leipzig, 2006.

 

Poster presentations AT SCIENTIFIC MEETINGS

1. Lessard E., and Pouliot J., “Anatomy-based dose optimization for HDR brachytherapy of the prostate using fast simulated annealing algorithm” 42nd AAPM Annual Meeting, Chicago, 2000.
   
   
2. Lessard E., Hsu I-C., and Pouliot J., “Planning dose optimization of interstitial GYN-template high dose rate brachytherapy boost” 43^rd ASTRO Annual Meeting, San Francisco, California, 2001.
   
   
3. Lessard E., Hsu I-C., Lachance B., Vigneault E. and Pouliot J. “Inverse Planning Anatomy-based dose optimization for HDR-brachytherapy of the prostate” 22^nd ABS Annual Meeting, Vancouver, British Colombia, Canada, 2001.
   
   
4. Lachance B.,  Nadeau D., Lessard E., Vigneault E., Beaulieu L., Pouliot J. and Chretien M. “Early clinical experience with anatomy based inverse planning dose optimization for HDR boost of the prostate” 22^nd ABS Annual Meeting, Vancouver, British Colombia, Canada, 2001.
   
   
5. Lessard E, Hsu I-C., Fisch B. and Pouliot J., “Inverse planning ability to protect the bulb of the penis and other organs at risk in HDR-Brachytherapy of the prostate” 44^th ASTRO Annual Meeting, New Orleans, Louisiana, 2002.
   
   
6. Lessard E., Ho L., Hsu I-C., Lee N., and Pouliot J., “Clinical benefit of inverse planning for Rotterdam nasopharyngeal applicator” 44^th AAPM Annual Meeting, Montréal, Québec, Canada, 2002.
   
   
7. Béliveau-Nadeau D., Lachance B., Beaulieu L., Lessard E., Pouliot J. et Vigneault E. “Evaluation of the point-source approximation accuracy for Ir-192 used in inverse planned optimizated prostate HDR treatment” 44^th AAPM Annual Meeting, Montréal, Québec, Canada, 2002.
   
   
8. Pouliot J., Lessard E., and Hsu I-C., “Inverse planning for HDR-Brachytherapy: clinical implementation” 44^th ASTRO Annual Meeting, New Orleans, Louisiana, 2002.
   
   
9. Lessard E, Hsu I-C., and Pouliot J., “Planning dose optimization of interstitial GYN-template high dose rate brachytherapy boost” 11^th Annual Int. Brachytherapy Conference, Santa Fe, New Mexico, 2002.
   
   
10. Lessard E., Hsu I-C., and Pouliot J., “Anatomy Conformal Dose Optimization for HDR-Brachytherapy of the prostate” Joint Breast & Prostate Cancer Retreat, South San Francisco, California, 2002.
    
    
11. DeWitt K., Hsu I-C., Weinberg V., Lessard E., Pouliot J., “Comparison of anatomy-based inverse planning dose optimization with conventional dose prescription methods for high-dose-rate treatment of the cervix” 45^th ASTRO Annual Meeting, Salt Lake City, Utah, 2003.
    
    
12. DeWitt K, Hsu I-C., Weinberg V., Lessard E., Pouliot J., “Comparison of anatomy-based inverse planning dose optimization with conventional dose prescription methods for high-dose-rate treatment of the cervix” 24^th ABS Annual Meeting, New York, New York, 2003.
    
    
13. Beaulieu L. Varfalvy N., Aubin N. Lessard E. Pouliot J. Clinical Validation of a new inverse planning algorithm for permanent prostate implant, ESTRO meeting, Amsterdam, The Netherlands, 2004.
    
    
14. Lessard E., and Hsu I-C., Speight J., Vigneault E., Lachance B., Chrétien M., Letourneau A., Beaulieu L., Ménard C., Ning H. and Pouliot J., “Clinical benefits of a class solution for inversely planned HDR prostate brachytherapy” Joint Brachytherapy Meeting GEC-ESTRO-ABS-GLAC , Barcelona, Spain, 2004.
    
    
15. Speight J., Lessard E., and Pouliot J., “Lower D70% and D50% doses are delivered to penile bulb with IPSA HDR” Joint Brachytherapy Meeting GEC-ESTRO-ABS-GLAC, Barcelona, Spain, 2004.
    
    
16. Pouliot J., Lessard E., and Hsu I-C., “Number of catheters in prostate High Dose Rate Brachytherapy: the role of inverse planning” Joint Brachytherapy Meeting GEC-ESTRO-ABS-GLAC , Barcelona, Spain, 2004.
    
    
17. Pouliot J., Kim Y., Lessard E., Hsu I-C., and Kurhanewicz J. “Targeting dominant intraprostatic lesion using functional imaging with MR spectroscopy and HDR brachytherapy ” Joint Brachytherapy Meeting GEC-ESTRO-ABS-GLAC , Barcelona, Spain, 2004.
    
    
18. Ménard C., Susil R.C., Choyke P., Gustafson G.S., Kammerer W., Ning H., Miller R.W., Ullman K.L., Crouse N.S., Smith S., Lessard E., Pouliot J., Wright V., McVeigh E., Coleman C. N., Camphausen K., "MRI-guided HDR prostate brachytherapy in a standard 1.5T scanner" Joint Brachytherapy Meeting GEC-ESTRO-ABS-GLAC , Barcelona, Spain, 2004.
    
    
19. Hsu I-C., Lessard E., Speight J., Pouliot J., Vigneault E., Lachance B., Beaulieu L., Ménard C., Ning H., “Inverse Planning for HDR Brachytherapy: Report of Clinical Implementation from Three Centers” American Radium Society 86^th Annual Meeting, San Francisco, California, 2004.
    
    
20. Lessard E., Beaulieu B., Hsu I-C., and Pouliot J., “Inversely planned catheter position for high dose rate brachytherapy of the prostate” AAPM meeting, Seattle, 2005.
    
    
21. Kwa S.L.S., Lessard E., Moerland M.A., Pouliot J., “Objective comparison of rapid strand and free selectSeeds loading for permanent prostate implants using an inverse planning approach” AAPM meeting, Seattle, 2005.
    
    
22. Lessard E., Kwa S., Pickett B., Roach III M., and J. Pouliot, “Class solution for inversely planned permanent prostate implants to mimic an experienced dosimetrist for pre and live treatment planning” ABS meeting, San Francisco, 2005.
    
    
23. Vigneault E.,  Beaulieu L., Harel F., Lachance B., Lessard E., Pouliot P., Martin A-G., “Early Clinical Outcome with Biopsy Results of HDR Prostate Boost using Inverse Planning: The Quebec Experience” ABS meeting, San Francisco, 2005.
    
    
24. Kwa S.L.S., Lessard E., Moerland M.A., Pouliot J., “Objective comparison of rapid strand and free selectSeeds loading for permanent prostate implants using an inverse planning approach” GEC-ESTRO meeting, Budapest, Hungary, 2005.
    
    
25. Lessard E., Hsu I-C., and Pouliot J., “Clinical benefits of a class solution for inversely planned high dose rate prostate brachytherapy” 27^th ABS annual meeting, Philadelphia, 2006.
    
    
26. Lessard E., Hsu I-C., and Pouliot J., “Multiobjective inverse planning optimization: adjustment of dose homogeneity and urethra protection in HDR-Brachytherapy of the prostate” AAPM annual meeting, Orlando, Florida, 2006
    
    
27. Lessard E., and Pouliot J., “Clinical Benefits of Inverse Planning for Permanent Prostate Implant” World Congress on Medical Physics and Biomedical Engineering, Seoul, Korea, 2006.