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  • SAMIR LAOUI, PH.D 08/15/2016

  • DEFINITION

    Taken from the Greek word brachys, meaning

    near, Brachytherapy (brak-e-THER-uh-pee) is

    a procedure that involves placing radioactive

    material inside your body

  • . there is no reason why

    a tiny fragment of radium

    sealed up in a glass tube

    should not be inserted into

    the very heart of the cancer;

    thus acting directly upon the

    diseased material.

    Alexander Graham Bell Letter to Science, 1903

  • IN 1903 GYNECOLOGICAL BRACHYTHERAPY

    WAS FIRST INTRODUCED BY.

    On 15 September 1903, she treated an

    inoperable cancer of the cervix uteri with 700

    milligrams of radium bromide sealed

    in a glass tube.

    Margaret Abigail Cleaves

    Two applications of 10 minutes each were made with an interval of 3 days between.

    O'Brien, F. w. (1947): Amer. J. Roentgenol., 57, 281.

  • 1920S : RADIUM SURFACE THERAPY

    Radium surface brachytherapy

    treatment of skin cancer at the

    Institut Curie, Paris, 1922

  • 1920S : USE OF SEEDS

    Implantation of radon seeds

    for a carcinoma of the rectum,

    1929, at London Hospital

  • INTRODUCTION

    ICRU 38 classification

    Low dose rate (LDR): 0.4 2 Gy/hr

    Medium dose rate (MDR): 1-12 Gy/hr

    High dose rate (HDR): > 12 Gy/hr

    Intracavitary brachytherapy

    Intraluminal brachytherapy

    Interstitial brachytherapy

  • BRACHYTHERAPY SOURCE STRENGTH

    Milligram radium equivalent

    The air Kerma strength is defined as the air

    kerma rate (Gy/hr) at a specified distance (1m)

    Unit of uGym2/hr

  • CALIBRATION OF BRACHYTHERAPY SOURCE

    Air kerma strength

    22)( lXlKS

    e

    W

    lk

    air kerma rate at

    distance l U

    -12hGym

    -1Gyh

    Distance l

    2m

    air kerma strength.

    -1mRh

    Exposure rate

  • AIR KERMA STRENGTH

    Sk(U) = air Kerma source strength (U)

    Conversion factors from mCi:

    Ir-192 1 mCi : 0.238 U

    I-125 1 mCi : 0.787 U

    Pd-103 1 mCi : 0.773 U

    U-12

    hGym

  • TRACEABILITY

    The AAPM Task Group No. 40 had

    recommended traceability of brachytherapy

    sources in 1994

    Direct traceability

    Secondary traceability

    Secondary traceability by statistical inference

  • TRACEABILITY

    The NIST standard

    ADCLs standards

    A customers source is calibrated at an ADCL or

    NIST by placing it in the well chamber

    A customers well chamber is calibrated at an

    ADCL or NIST against a national standard at an

    ADCL or NIST.

  • TRACEABILITY

  • SOURCE DOSIMETRY: ICWG

    Current standard is to follow the dose

    calculation formalism of ICWG and TG-43

    Specification of dose at a point is given by

    Interstitial Collaborative Working Group

  • GOAL OF QA PROGRAM

    The QA program consists of a set of mandated

    redundant performance checks, physical

    measurements, documentation standards,

    training and experience standards, and

    guidelines

  • GOAL OF QA PROGRAM

    QA program endpoints

    Safety of the patient, the public, and the institution

    Positional accuracy +/-2mm is reasonable (+/-

    1mm, NRC)

    Temporal accuracy 2%

    Source calibration +/-3%, relative to existing air

    kerma strength standards seems reasonable.

    dose calculation +/-2%

  • PHYSICISTS ROLE

    Applicator insertion process

    Implant design and evaluation process

    Treatment delivery process

  • PERFORMANCE OF BRACHYTHERAPY

    PROCEDURE

    The physicianphysicist interaction is a critical

    link in promoting safe and accurate

    Brachytherapy practices

    Ordering sources (RML)

    Receiving sources

    Treatment planning goal, according to

    prescription

  • TREATMENT QA

    It is recommended that standard patterns of

    dwell times for similar applications be used

    whenever possible

    Physicist should check the applicator position

    and the connections between applicator and

    afterloader head before treatment to be sure

    that they agree with the treatment plan.

  • DOSE SPECIFICATION AND REPORTING

    Lack of universal system for dose specification and reporting

    Many quantities have been used to quantify, prescribe, and to constrain intracavitary therapy at gynecologic malignancies

    Dose to point A

    Vaginal surface dose

    Treatment time

    Curie seconds

  • DOSE SPECIFICATION AND REPORTING:

    INTRACAVITARY BRACHYTHERAPY

    ICRU attempted to address this issue in report N 38

    In addition to reporting source strengths, treatment time, and standard isodose contours

    the dimensions of the 60-Gy isodose (EBT + HDR)

    the dose at a bladder point

    Rectal dose

    Doses at points representing lower para-aortic

    Dose at points representing distal parametrium and lymph nodes

  • BACKGROUND

    Prompted by:

    A death related to personnel errors in HDR

    Greater use of HDR brachytherapy units

    NRC proposal to rewrite 10 CFR 35

    The need for education on comprehensive HDR

    safe-treatment-delivery procedures

    None of old reports addresses the details and

    issues related to the safe delivery of HDR

    treatments.

  • EGREGIOUS INCIDENT

    Death related to personnel errors

    Source left in the patient

    Radiation alarm ignored

    Survey meter was not used

  • OVERVIEW

    To examine the current high dose-rate (HDR)

    treatment delivery practices and to prepare a

    document to assure safe delivery of HDR

    treatments

    The document provides an extensive quality

    assurance (QA) check list

  • HDR PROS

    Dose optimization capability

    Outpatient treatment

    More stable positioning

    Smaller applicators

    Sources do not need to be shipped

    Better documentation

    Reduced exposure to personnel

  • HDR CONS

    More complex

    Errors can lead to severe consequences

    Radiobiological disadvantages (normal tissue

    toxicity)

    Need for accurate dosimetry

    Potential of very high dose to patient and

    personnel if source fails to retract

  • DESIGN OF AN HDR BRACHYTHERAPY

    PROGRAM

    HDR brachytherapy is prone to errors

    The physicists role is to define the organization

    and responsibilities of the treatment delivery

    team members

  • PRINCIPLES OF GOOD HDR PROGRAM DESIGN

    Use written documentation whenever possible

    Develop a formal procedure for each type of expected case Roles, applicators, emergency situation, QA list

    Exploit redundancy Independent verification

    Exploit quality improvement techniques: Comprehensive QA program

  • DOCUMENTATION AND CHECKLIST

    I. Written prescription and daily treatment

    record

    II. Treatment day remote afterloader QA protocol

    III. QA procedure flow checkoff list

    IV. Physicists treatment plan/documentation

    review

    V. Implant geometry, Dwell time calculations

    VI. Dose verification

  • STAFFING AND TRAINING

    Physicians, department heads, and

    administrators must realize that development and

    maintenance of a safe and effective HDR program

    requires a significant time commitment for all

    staff involved, especially the medical physicist on

    whom the burden of acceptance testing the

    equipment, developing procedures, and training

    other staff falls

  • STAFFING AND TRAINING

    For an average load of 10 fractions per week,

    including periodic QA, staff training and

    treatment record audits, 1 FTE of a qualified

    medical physicist should be allocated

  • TREATMENT SPECIFIC QA - DAILY

  • DAILY QA

  • PRESCRIPTION

  • TREATMENT SPECIFIC QA

    Applicator preparation & insertion

    Reviewed for correct operation and configuration

    Implant localization and simulation

    A correctly labeled sketch of implant should be drawn

    Make use of template forms which help describe implant geometry

  • DOSE DISTRIBUTION

  • DOSE DOCUMENTATION

  • DOSE DOCUMENTATION

  • DOSE INDEPENDENT VERIFICATION

  • Final Treatment

    checklist

  • TREATMENT SPECIFIC QA

    Whenever treatment is interrupted, it is essential to

    check the area monitor to confirm that the source has

    been retracted

    Again, after treatment is complete, it is again essential

    check the area monitor to confirm that the source has

    been retracted

  • EMERGENCY PROCEDURES

    The best strategy is to be prepared for all scenarios by

    developing emergency procedures for the following

    categories:

    Physical emergencies (fire, earthquake, floods, etc.)

    Minor emergencies (loose source guide tube, vault

    door not closing completely)

    Major emergencies

    Failure of source to retract, patient medical emergency,

    computer failure etc.

  • Dose rates at the periphery of the volume of tissue irradiated by

    a static 10 Ci source. The dose rat

Recommended

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