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Adv Imaging Unit 4

radiation therapy

QuestionAnswer
Cancer Disease process that involves unregulated, uncontrolled replication of cells
Radiotherapy treatment of cancer tumors/lesions by ionizing radiation; to control or kill malignant cells. May be used as adjunct therapy after sx to remove malignant tumor.
What % of diagnosed cancer pts are treated with radiation 75%
Radiation Oncology is usually combined with what else? Sx or chemotherapy or BOTH
What are the radiation therapists (Personnel) in charge of? 1. localization films, 2. plan & administer treatment, 3. keep records, 4. monitor pts.
radiation oncologists specialized physician who prescribed quantity of ionizing radiation (megavoltage xrays or radionuclides) in treatment of cancer
surgical oncologist surgical physician management of cancer
medical oncologist physician who specializes in medical methods to treat cancer
goal of treatments: planning phases 1. definitive treatment/ therapy -treatment plan design to potentially cure cancer using interventions 2. palliative therapy -prevent/relieve symptoms; improve quality of life cannot cure 3. adjunct to sx -additional treatment ( radiation therapy)
cancer treatment requires: 1. locate tumor 2. biopsy 3. if prescribed (radiation therapy) after sx
doses are fractioned
staging of cancer (describes progression of cancer) stage 0 - carcinoma in situ stage 1 - localized stage 2 - early locally advanced stage 3 - late locally advanced stage 4 - metastasized (incurable)
Stage 0 earliest stage - Occult lesion; no evidence clinically - also called “carcinoma in situ” Carcinoma = cancer that starts in epithelial tissue in situ = original position or place
stage 1 small lesion confined to organ or origin no evidence of vascular and lymphatic spread or metastasis earliest and most-treatable cancer stages
stage 2 tumor < 5 cm invading surrounding tissue and first-station lymph nodes but no evidence of metastasis
stage 3 extensive lesion >5 cm with fixation to deeper structure and with bone and lymph invasion but no evidence of metastasis
stage 4 more extensive lesion than above or with distant metastasis
TNM Cancer staging system that describes “extent” of cancer. Tumor, Node, Metastasis T = size of primary tumor - whether it has invaded nearby tissue, N = nearby (regional) lymph nodes involved, M = distant metastasis (spread of cancer from one part of body to another)
Effectiveness on malignant tumor depends on: 1. Extent of disease at diagnosis 2. Histologic type of tumor 3. General well being of patient 4. Location of tumor 5. Whether tumor is radio-curable
Types of Therapy 1. External Beam Treatment (EBT): Teletherapy 2. Brachytherapy
External Beam Treatment (EBT): Teletherapy Delivers HIGH-ENERGY X-Ray beams to tumor. Beams are generated outside patient (e.g. linear accelerator) and are targeted at the tumor site. high energy x-rays can deposit dose to the area of the tumor to destroy the cancer cells with careful treatment planning, spare the surrounding normal tissues.
Brachytherapy Radioactive material implanted inside patient Delivers low intensity radiation over an extended period to a small volume of tissue. This can be accomplished by mold technique. intracavitary implant, interstitial implant.
mold technique Placement of radioactive source on or close to lesion - e.g. Iridium for skin cancer
intracavitary implant Placement of radioactive source inside cavity E.G. Cesium 137: uterine canal or vagina
interstitial implant Sarcomas arise from connective tissues Placement of source directly into tumor and adjacent tissue E.g. Iridium 192 (sarcoma in a muscle) Permanent implants with iodine 125 seeds may be used and are left in patient forever (e.g. for early stage prostate cancer)
Steps for treatment in Radiation Oncology Step 1. Simulation (to design a treatment area) Step 2. Dosimetry 3. Radiotherapy Treatment (placement of beam)
Step 1. Simulation (to design a treatment area) Outlines treatment field and positioning marks are placed on patient’s skin surface Immobilization masks can be used to prevent movement
Step 2. Dosimetry Performed by Dosimetrist who designs and monitors technique for PRECISE application of ionizing radiation doses to tumor w/o irreparably damaging normal tissue. Shows how radiation is distributed or attenuated throughout the patient’s body.
Radiotherapy Treatment (placement of beam) Radiation therapists position patient and align field with marks. Verification images (Port Films) are taken weekly to ensure accuracy.
tolerance dose to radiation testes - 500 sGy ovary - 500 cGy lung - 1800 cGy spinal cord - 4500 cGy
Types of / Direction of Treatment Fields (part1) 1. Single field: one treatment port or field (e.g. for skin cancer) 2. Opposing ports: two fields of treatment to protect a non involved structure. 3. Multifield: three or more fields to deliver tumor dose
Types of / Direction of Treatment Fields (part2) 4. Rotational field tumor located at axis of rotation of treatment. Centrally located lesions cancer of the prostate 5. Wedge field used to alter primary beam (e.g. for head and neck) 6. Shaped field Lead alloy blocks are shaped for specific field.
Created by: Kgossio