Radiation Sources in Radiotherapy

Slides:



Advertisements
Similar presentations
How is radiotherapy given Radiotherapy can be given in two ways: from outside or inside the body. External radiotherapy is the most common method of treatment.
Advertisements

Advantage: Can often be very successful in treating some kinds of cancer if the cancer cells are based in one small area and can easily be cut out and.
Radiation Protection in Radiotherapy Part 16 Discharge of Patients IAEA Training Material on Radiation Protection in Radiotherapy.
32 P Module Objectives  To understand the physical nature of 32 P.  To understand the 32 P is both and internal and external radiation hazard.  To understand.
Types of Exposure Devices
Security of Radiation Sources
4/2003 Rev 2 II.3.6 – slide 1 of 18 Part IIQuantities and Measurements Module 3Principles of Radiation Detection and Measurement Session 6Photographic.
Overview of Industrial Radiography Sources and Accidents
IAEA International Atomic Energy Agency Responsibility for Radiation Safety Day 8 – Lecture 4.
Brachytherapy Rooms Mr John Saunderson
Basic Physics Concepts Firas Mourtada, Ph.D. D. ABR Associate Professor MD Anderson Cancer Center.
Categorization of Radioactive Sources
Radiation Protection in Radiotherapy
University of Wisconsin
Radiation Protection in Radiotherapy
Benefits of Radiation in Every Day Life. Beneficial Uses of Radiation Medical Diagnoses and Treatment Research Applications Industrial/Manufacturing Applications.
Radiation Protection in Radiotherapy Part 6 Brachytherapy Lecture 2 (cont.): Brachytherapy Techniques IAEA Training Material on Radiation Protection in.
Gauges and well logging
Interaction of Radiation with Matter - 4
Gauges and well logging
Radiation Protection in Radiotherapy
Radiation Protection in Radiotherapy Part 14 Transport Safety IAEA Training Material on Radiation Protection in Radiotherapy.
IAEA International Atomic Energy Agency Regulations Part I: Role and Structure of Regulations Day 8 – Lecture 5(1)
Radioisotopes in Medicine
Introduction to Brachytherapy
Radiotherapy for Kidney cancer
Arif Raza Radiotherapy Department. Introduction Clinical speciality for treatment of cancer Tissue destroying procedure Use of ionizing radiation Single.
Perma Permanent Brachytherapy Medical Events: Experiences of Pennsylvania Frank Costello Organization of Agreement States August 28, 2012 Milwaukee, Wisconsin.
Introduction to Nuclear Medicine
RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY
External Beam Radiotherapy
MRI Guided Radiation Therapy: Brachytherapy
Brachytherapy Medical radiation.
IB Objectives - Radiation in Medicine
Radiation Protection in Radiotherapy Part 15 Security of sources, and disposal of disused sources IAEA Training Material on Radiation Protection in Radiotherapy.
IAEA International Atomic Energy Agency Interventional Radiology Radiation Sources in medicine diagnostic Radiology Day 7 – Lecture 1(3)
IAEA International Atomic Energy Agency Dental Radiology Radiation Sources in medicine diagnostic Radiology Day 7 – Lecture 2(2)
IAEA International Atomic Energy Agency Module 3.2: Other cases (brachytherapy) IAEA Training Course.
Using Radiation in Medicine. There are 3 main uses of radiation in medicine: Treatment Diagnosis Sterilization.
Organization and Implementation of a National Regulatory Program for the Control of Radiation Sources Inspection Part II.
Training Module 3 – Version 1.1 For Internal Use Only ® Radiation Therapy 
VIII.3. Optimization of Protection for Medical Exposures in Nuclear Medicine 1. Design considerations Postgraduate Educational Course in Radiation Protection.
 Radiopharmaceuticals are agents used to diagnose certain medical problems or treat certain diseases. They may be given to the patient in several different.
Permanent Interstitial Implants Ideal strategy to curatively manage small volume gynecologic malignancies Can deliver high cumulative radiation dose to.
Part VIII:Medical Exposures in Radiotherapy Lecture 6: Determination of dose to the patient in Radiotherapy II IAEA Post Graduate Educational Course on.
Half life L.O: explain the decay of radioactive atoms.
Brachytherapy and GYN malignancy
Organization and Implementation of a National Regulatory Program for the Control of Radiation Sources Inspection Part III.
Management System Part II: Inventory of Radiation Sources – Regulatory Authority Information System (RAIS)
Organization and Implementation of a National Regulatory Program for the Control of Radiation Sources Technical Services.
IAEA International Atomic Energy Agency Presenter Name School of Drafting Regulations for Borehole Disposal of DSRS 2016 Vienna, Austria Containment and.
210 Po Polonium 210 Alexander Litvinenko. Nuclear Radiation We will look at three types of nuclear radiation. RadiationSymbolRange alpha beta gamma α.
Technical Services. Objectives To identify the technical services needed within the infrastructure for an effective implementation of regulatory programme.
Organization and Implementation of a National Regulatory Program for the Control of Radiation Sources Need for a Regulatory program.
1 Nicolas Varmenot, PhD - PCR Medical Physicist – ICO René Gauducheau Head of risks prevention and of radioprotection – Cyclotron ARRONAX
Brachytherapy in Nuclear Medicine
5.5 Medical Applications Using Radioactivity
SIMULATION CHECK LIST IMAGING PROTOCOL.
Understanding Radiation Therapy Lecturer Radiological Science
Sustaining Cradle-to-Grave Control of Radioactive Sources (INT-9182) Meeting on the development, revision and implementation of the safety case and safety.
Austrian Research Centers Seibersdorf
Categorization of Radioactive Sources
Safety and Security of Radiation Sources
Radioisotopes in Medicine
核子醫學技術學實驗 Radioactivity measurement, Dose Calibrator
Title of Lecture: Using Ionizing Radiation in Medicine
Phenotyping Facility X-ray Awareness Training
Principles of Radiation Therapy
Presentation transcript:

Radiation Sources in Radiotherapy Brachytherapy Day 7 – Lecture 5

Objective To become familiar with the sealed sources, devices and ancillary equipment used in brachytherapy.

Contents Radioactive sources; Afterloading devices (HDR and LDR); Implants (permanent and temporary); Intravascular brachytherapy (IVB); Other techniques (e.g. eye applicators); Brachytherapy treatment planning.

Introduction Brachytherapy (also referred to as Curie therapy) is defined as a short-distance treatment of malignant disease with radiation emanating from small sealed (encapsulated) sources. The sources are placed directly into the treatment volume or near the treatment volume.

Brachytherapy compared to external beam therapy Advantages of Brachytherapy Improved localized dose delivery to the target Sharp dose fall-off outside the target Better conformal therapy Disadvantages of Brachytherapy Only good for well localized tumors Only good for small lesions Very labor intense

Brachytherapy very flexible radiotherapy delivery; the source position determines the success of the treatment; in principle, it is the ultimate ‘conformal’ radiotherapy; highly individualized; dependent on operator skill and experience. Conformal radiotherapy describes the attempt to conform the treatment volume as closely as possible to the actual target volume thereby sparing the surrounding normal tissue as much as possible. In general, the normal radiation safety considerations will also apply to conformal radiotherapy. The lecturer can cross reference brachytherapy to the modern external beam attempts of conformal RT and even intensity modulated radiotherapy (IMRT). Both of these techniques (conforming the high dose region to the target volume and optimizing the dose distribution in target and normal tissues) have been implemented in brachytherapy well before they were technologically possible in EBT. This has been possible as the brachytherapy oncologist is literally in touch with the tumour region and more recently has acquired the potential for optimization due to stepping source high dose rate brachytherapy.

Brachytherapy Sources γ (MeV) HVL (mm Pb) Forms 222Rn 3.83 d 0.047 - 2.45 (0.83 avg) 8.0 Seeds 60Co 5.26 y 1.17, 1.33 11.0 Tubes, needles, pellets 137Cs 30 y 0.662 5.5 192Ir 74.2 d 0.136 - 1.06 (0.38 avg) 2.5 Wires, ribbon etc. 198Au 2.7 d 0.412 125I 60.2 d 0.028 avg 0.025 103Pd 17 d 0.021 avg 0.008 226Ra 1600 y Tubes, needles 90Sr 28 y 2.25 (beta) Curved applicator

Practical Considerations Brachtherapy Sources are commonly used as sealed sources, usually doubly encapsulated in order to: Provide adequate shielding against alpha and beta radiation produced through source decay Contain radioactive material Prevent leakage of the radioactive material Provides rigidity of the source .

“Ideal” Brachytherapy Source The ideal brachytherapy source would be: a pure gamma emitter with an energy suitable for the intended treatment site; with a high specific activity; and suitable for high dose rate applications. physically small; Lecture notes:The requirements of long half life and high specific activity are working against each other. Instructions for the lecturer/trainer for temporary implants, a long half life; to allow economical re-use of sources for permanent implants, a medium half life.

Types of equipment Brachytherapy Manual brachytherapy; Afterloading devices.

Manual brachytherapy In manual brachytherapy several types of treatments are available, including: interstitial treatment of cancer; intra-cavity treatment of cancer; eye plaque implants; and topical application.

Interstitial Treatments The following sources are routinely used: 137Cs and 60Co as sealed sources in needles and applicator cells; 192Ir as seeds or wires encased in nylon ribbons; 198Au, 125I and 103Pd as sealed sources in seeds. 90Sr as a sealed source in an applicator for the treatment of superficial eye conditions.

Eye plaques The eye plaque consists of a curved, soft plastic insert that has a series of grooves molded into the rear convex surface to hold the radioactive seeds. Because the plaque is placed in the orbit of the eye over the tumor site and sutured to the sclera, this is considered interstitial, not topical / surface treatment.

Topical (surface) treatments The following sources are routinely used: 90Sr as a sealed source in an applicator for treatment of superficial eye conditions. 137Cs and 60Co as sealed sources in needles and applicator cells.

History Surface applicator with irregular distribution of radium on the applicator surface. (Murdoch, Brussels 1933)

Surface Moulds Treatment of superficial lesions with radioactive sources in close contact with the skin. A mould for the back of a hand including shielding designed to protect the patient during treatment.

Surface Moulds (cont) Treatment of superficial lesions with radioactive sources in close contact with the skin. Mould for the treatment of squamous cell carcinoma of the forehead. Catheters for source placement.

Surface Moulds (cont) Advantages Fast dose fall-off in tissues due to the inverse square law. Can conform the activity to any surface.

Brachytherapy Applicators

Source storage Storage for radioactive sources must:- provide protection against environmental conditions be only for radioactive materials provide sufficient shielding be resistant to fire be secure

Source storage (cont) Safe for 137Cs sources Numbered and easily identifiable source drawers with color coding of sources

Source accountability Sources must: be stored securely to prevent unauthorized access; be audited regularly to confirm the source inventory in compliance with the requirements of the Regulatory Body. Source inventory records should identify: the radionuclides and source activities; the location and description of sources; disposal details (including permanent implants in patients). MODIFIED

Afterloading devices (HDR and LDR) HDR – high dose rate / LDR – low dose rate Afterloading techniques are those in which non-radioactive applicators or guide tubes are initially placed in the patient and the radioactive sources are later loaded into these applicators. Depending on the manufacturer and model, remote afterloaders typically employ 192Ir, 60Co or 137Cs sources.

HDR and LDR devices HDR units typically have a single source with activities ranging from ~180 GBq to ~740 GBq. LDR units may have single or multiple sources with activities of ~370 MBq to ~550 MBq. Because of the higher activities involved, the shielding requirements for HDR are greater than LDR units. HDR devices typically step the single source through a series of dwell positions while a LDR device does not reposition its multiple source string. HDR employs shorter irradiation time at higher dose rates than LDR treatment. Lecture notes: ( about 100 words) Instructions for the lecturer/trainer

HDR brachytherapy Treatments are usually fractionated (e.g. 6 fractions of 6 Gy each); Either the patient has a new implant each time or stays in hospital for bi-daily treatments; The time between treatments should be >6 hours to allow normal tissue to undertake some recovery.

Catheters are indexed to avoid mixing them up. HDR brachytherapy (cont) Catheters are indexed to avoid mixing them up. Varian Transfer catheters are locked into place during treatment - green light indicates the catheters that are in use.

HDR brachytherapy (cont) Portable HDR Unit

HDR and LDR radiation levels near patients LDR (137Cs) Cervix insertion 10 pellets each 550 MBq = 5.5 GBq total ~ 0.2 mSv/h at 1 m ~ 5 days for 1 mSv HDR (192Ir) 370 GBq source ~ 47 mSv/h at 1 m ~1.3 minutes for 1 mSv The treatment room door should be interlocked

Intravascular brachytherapy This technology uses radioactive catheters, pellets, and stents to treat coronary and peripheral vascular problems. The radioactive source can be ion implanted, plated, or encapsulated in a sealed source device attached to a guide wire used in the angioplasty procedure. The radioactive device can be either permanently implanted or removed via the guide wire following treatment of the affected vessel wall.

Intravascular brachytherapy (cont) Purpose of treatment After opening of a blocked blood vessel by angioplasty there is a high likelihood (60%+) that the vessel will again block. i.e. restenosis will occur. Radiation is a proven agent to prevent growth of cells and has been shown to be effective in preventing restenosis Gamma sources – 192Ir; Beta sources - 32P, 90Sr/Y, 188Re

Intravascular brachytherapy (cont) Hydraulic delivery Beta sources have a finite range in tissue; have fewer radiation safety issues physically smaller size Source train (90Sr) Delivery catheter Beta-Cath™ System (Novoste)

Intravascular brachytherapy (cont) During treatment 6 Months later Pre-PTCA Post-PTCA

HDR Planning Optimization procedure needs extensive checking. How are dwell times transferred to the treatment unit? Where is the source strength correction applied? How is transfer time modeled?

Dose calculation algorithm Software coding and implementation Typically, there is no user control for these features. However it is essential that the user:- is familiar with the physics algorithm; is aware of its implementation and possible software shortcuts; has tested the algorithm for most possible treatment scenarios.

Tests for brachytherapy sources The following should be done on receipt of sources and documented. Physical / chemical form; Source encapsulation, wipe test; Radionuclide distribution and uniformity: autoradiograph; uniformity of activity amongst seeds; visual inspection of seeds in ribbons.

Tests for brachytherapy sources (cont) Calibration Ideally, the calibration of all sources should be checked on receipt. However, for a large number of short lived sources a sample check (~10%) may be satisfactory. Document results. Suggested calibration tolerances: mean of batch (3%) deviation from mean (5%) Review manufacturer’s documentation for tolerances.

Brachytherapy source calibrators Source calibrators are radioisotope and source design specific and should be calibrated by an organization recognized by the Regulatory Authority, noting:- Precision Scale factors and linearity Ion collection efficiency Geometry and length dependence Energy dependence Dependence on the wall of the source

Brachytherapy source calibrators (cont) Quality Assurance Use a long half-life encapsulated source with:- reliable mechanical integrity well known decay constant a manufacturer’s calibration certificate Consider cross checking with another calibrator

References Johns H E and Cunningham J R 1983 The Physics of Radiology, 4th edition (Springfield: C Thomas). Khan F M 1994 The Physics of Radiation Therapy, 2nd edition (Williams & Wilkins, Baltimore). Williams J R and Thwaites D I 1993 Radiotherapy Physics in Practice (Oxford: Oxford University Press). International Commission on Radiation Units and Measurements. Determination of dose equivalent resulting from external sources, ICRU report 39, Bethesda: ICRU; 1985. International Commission on Radiation Units and Measurements ICRU 55, Bethesda. Prescribing, recording, and reporting interstitial brachytherapy, 1993.