Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
RadThera
Brachytherapy
| Question | Answer |
|---|---|
| Type of Radiation Treatment in which radioactive sources are arranged in such a fashion that radiation is delivered to the tumor at a short distance by interstitial, intracavitary or surface application. | Brachytherapy |
| ____ _____ _____ is achieved by implanting radioactive material directly into the tumor or very close to it. - Sometimes called ___ ____ ___. | Internal radiation treatment : internal radiation therapy(IRT) |
| - Prefix “brachy” – from Greek for “____ ____” - Implanting radioactive sources directly into a tumor was a strategy first suggested by ____ _____ ____ soon after the turn of the century. | short range : Alexander Graham Bell |
| DIFFERENCE - Brachytherapy works "from the ____ , ____" - External beam radiotherapy (EBRT) works "from the ____, ___" | inside, out outside, in |
| Clinical Advantages 1. High ___ Efficacy 2. Rapid ___ fall-off 3. High tolerance 4. Tolerable ___ intense reaction 5. Decreased risk of tumor __ 6. High ___ rate 7. Better ___ 8. Minimal Radiation ___ 9. ___ ____ procedure | Biological dose acute population control cosmesis Morbidity Day Care |
| LIMITATIONS & DISADVANTAGES - Difficult for ___ regions - Limited for ___ tumors - ___ procedure (requires gen anesthesia) | inaccessible small Invasive |
| LIMITATIONS & DISADVANTAGES - Higher dose ___ - Greater ___ – small errors in placement of sources lead to extreme changes from the intended dose distribution - ___ hazards - Costly | inhomogeneity conformation Radioactive |
| SELECTION CRITERIA - Easily ___ Lesions - _______ diseases (Ideal implant < 5 cm) - ___________ tumor to the organ of origin - No nodal or distant ____ - No local ___ or ___ - Favorable ___ - _____/____ lesions preferred | Accessible Early-stage Well-localized metastases infections or inflammation Histology Proliferative/ulcerative |
| BRACHYTHERAPY SOURCES - Emit gamma rays through gamma decay and possibly characteristic X-rays through electron capture and internal conversion. - Examples: Co-60, Cs-137, Ir-192, I-125, Pd-103 | Photon sources |
| BRACHYTHERAPY SOURCES - Emit electrons following beta source decay. - Example: Sr-90/Y-90 | Beta sources |
| BRACHYTHERAPY SOURCES - Emit neutrons from spontaneous nuclear fission. - Example: Cf-252 | Neutron Source |
| DOSE RATES • Low Dose Rate (LDR) ? • Medium Dose Rate (MDR) ? • High Dose Rate (HDR) ? • Ultra Low Dose Rate ? • Roughly - LDR? - MDR? - HDR? | 0.4 – 2 Gy/hr 2 – 12 Gy/hr > 12 Gy/hr 0.01 – 0.3 Gy/hr LDR – 10 Gy/day MDR – 10 Gy/hr HDR – 10 Gy/min |
| WHICH DOSE RATE - Predictable clinical effects - Superior radiobiological role - Less morbidity, control is best - Well practiced since - Minimum intersession variability in dose distribution | Low Dose Rate |
| WHICH DOSE RATE • Short Time - Geometry well maintained - Better patient compliance/comfort - Day care procedure • Optimization • No Radiation Hazards • Small Applicator (Less Trauma & Better packing) | High Dose Rate |
| AFTERLOADING TECHNIQUE - Avoids Radiation Protection issues of preloading - Better Applicator Placement - Verification before source placement - Min. Radiation Hazard | Manual Afterloading |
| AFTERLOADING TECHNIQUE - No radiation Hazard - Accurate placement - Geometry maintained - Better dose distribution - Highly precise - Short Time - Day Care procedure - Mainly used for HDR | Remote Afterloading |
| TYPES OF BRACHYTHERAPY IMPLANTS - Sources are placed into a body cavity? - Sources are implanted into the tumor volume? | Intracavitary Interstitial |
| TYPES OF BRACHYTHERAPY IMPLANTS - Sources are loaded into the plaque, which is brought into contact with the skin surface lesion? - Sources are inserted into a lumen? | Surface plaque Intraluminal |
| TYPES OF BRACHYTHERAPY IMPLANTS - Sources are brought surgically into or near the tumor volume? - Sources are brought intravascularly into a lesion or near a lesion? | Intraoperative Intravascular |
| BRACHYTHERAPY CLASSIFICATION WITH RESPECT TO TREATMENT DURATION - Dose is delivered over a period of time short in comparison with the half-life of the sources. - Sources are removed when the prescribed dose has been reached. | Temporary implants |
| BRACHYTHERAPY CLASSIFICATION WITH RESPECT TO TREATMENT DURATION - Dose is delivered over the lifetime of the sources. - The sources undergo complete radioactive decay. | Permanent Implants |
| - Sealed radioactive sources are directly geometrically implanted into the tumor. - First suggested by Alexander Graham Bell. | Interstitial Brachytherapy |
| Clinical Applications (Interstitial Brachytherapy) | Head & Neck Tumors (Early-stage oropharyngeal cancers) Breast Cancer Prostate Cancer Soft Tissue Sarcoma Gynecologic Malignancies Anal Canal and Rectum Lung and Pancreatic Cancer |
| Radioactive sources are placed in an existing cavity, usually inside a predefined applicator with special geometry. - Uses: | Intracavitary brachytherapy : cervix, endometrium, vagina, maxilla, & nasopharynx |
| - Refers to the science by which radiation dose is determined by measurement, calculation, or a combination of both. - The technical name for radiation dose is “____ ____.” | Dosimetry : absorbed dose |
| - It is the amount of radiation energy deposited in tissue divided by the mass of the tissue. - It is the most important physical factor influencing the response of tumors and normal tissues to radiation. | Absorbed dose |
| WHAT SYSTEM OF DOSIMETRY - Single application of Radium for 120 hours (5–6 days). - Almost equal amounts of Radium used in uterus and vagina. - Designed to deliver a dose over 5 days (45R/hr; 7000–8000 mg·hrs; ~5500 mg/hr). | Paris system |
| MANCHESTER SYSTEM (POINT A) • Point A corresponds to the _____ _____ at the medial edge of the broad ligament where uterine vessels cross the ureter | paracervical triangle |
| MANCHESTER SYSTEM (POINT A) • Orig. definition: Draw a line connecting superior aspects of ___ ______, measure 2 cm superior along tandem, then 2 cm perpendicular (weakness: poor localization on radiographs). | vaginal ovoids |
| MANCHESTER SYSTEM (POINT A) • Revised definition #1: 2 cm ___ external cervical os and 2 cm ___ to midline. • Revised definition #2 (1953, Tod & Meredith): 2 cm above ____ end of lowest source in tandem and 2 cm _____ to tandem. | above : lateral : distal : lateral Common variation: Use flange at cervical os. |
| MANCHESTER SYSTEM (POINT B) - Defined as __ cm lateral from midline at same level as Point A. - Applicators: ____ ______ +____ ______ ____ (diameters 2, 2.5, 3 cm). | 5 : Rubber tandem and two ellipsoid “ovoids” |
| MANCHESTER SYSTEM (POINT B) - No ___ in ovoids → required generous packing anteriorly and posteriorly. - Used Radium: ____ mg (small), __ mg (medium), _____ mg (large ovoids). | shielding : 17.5 : 20 : 22.5 |
| (Application of Intracavitary Brachytherapy) - Patient informed about procedure; _____ ______ obtained. - Detailed _______ _______ performed: vagina dimensions, uterus size/position, tumor localization/extension. | informed consent : gynecological exam |
| Application of Intracavitary Brachytherapy - Requires cervical ___ → anesthesia (general, spinal, paracervical block/systemic sedation); outpatient procedure: px with open __ ___, ___rectum, ____ surgical condi; px positioned _____ on gynecological table. | dilatation : IV line, empty, sterile : lithotomy |
| BRACHYTHERAPY APPLICATORS - Derived from Manchester System. - Added internal shielding in colpostats. - Afterloading capability. | Fletcher Applicator |
| BRACHYTHERAPY APPLICATORS - This was made up of the thin rubber (to prevent excessive dilatation of the cervical canal) - These tubes were available in three separate lengths: 2cm, 4cm, & 6cm | Intrauterine Tube |
| BRACHYTHERAPY APPLICATORS - To accommodate one, two, or three ___ tubes (2 cm long), I.U. tubes were closed at one end and had a ___ at the other end, ensuring that when packed into position, the uterine tube did not slip out during treatment. | Radium : flange (stopper) |
| BRACHYTHERAPY APPLICATORS - Used in pairs, one in each lateral fornix - The shape of ovoids mimics the shape of isodose curves around a Radium tube having "active length" of 1.5 cm. | Ovoids |
| BRACHYTHERAPY APPLICATORS - The ovoids were designed to be adaptable to the different vaginal capacity, with diameter of __ cm, ___ cm, & __ cm - The largest ovoid are placed in the ________ vagina in order to achieve the best lateral dose throw off | 2 , 2.5, 3 : roomiest |
| BRACHYTHERAPY APPLICATORS - Manchester applicators do not incorporate rectal shielding. - Hence gauze is packed firmly and carefully | Packing |
| PACKING • ___ the ovoids, • anteriorly b/w the ovoids and the base of the ___ , and around the applicator tubes down to the level of the ___ | behind : bladder : introitus |
| ___ helps to keep the applicators in position and to reduce dose to bladder and anterior rectal wall. | Packing |
| Radiation delivered by arranging sources over tumor surface. Sometimes radiation is placed on the skin surface. Doctors arrange radiation sources on a mold that fits the tumor shape. Types? | Surface moulds : Planar (circular, square, rectangular), Line source, Cylinder |
| Indications of Surface Moulds | Superficial/accessible tumors Skin cancer Post-mastectomy recurrence Oral tumors Hard palate, alveolus Penile carcinoma |
| - The radioactive source passed through tube into hollow lumen. - Sites: esophagus, bronchus (bronchogenic carcinoma), biliary duct | Intraluminal Brachytherapy |
| MECHANICAL CHARACTERISTICS OF BRACHYTHERAPY SOURCES (Forms) • Needles • Tubes • Pellets • Seeds • Wires | Needles (Cesium-137) Tubes (Cesium-137) Pellets (Co-60, Cs-137) Seeds (I-125, Pd-103, Ir-192, Au-198) Wires (Ir-192) |
| ____ sources, doubly encapsulated to: - Shield against alpha/beta radiation - Contain radioactive material - Prevent leakage - Provide rigidity | Sealed |
| Common radionuclides in remote afterloading machines: | Co-60, Cs-137, Ir-192 |
| - Based on tables of total dose delivered as a function of area/volume. - Common systems: Patterson-Parker (Manchester), Quimby (Memorial), Paris System | Pre-planning dosimetry system |
Created by:
yulyae