Test 2 Flashcards
Written procedures posted at every machine
Required by some state regulatory agencies
Know where emergency offs and circuits are
Emergency procedures
Where machine is controlled
Monitor and control linac
Audio and visual
Control console
4 states of operational status
Stand-by
Preparatory
Ready
Beam on
Machine in “napping” state
Has time delay before it turns on
Keeps electronics warm
Stand-by
Shows programmable operational status; record and verify
Preparatory
Confirmed program information
Ready
Turn key and hear “chirping” sound
Beam on
Displayed before or during treatment
Designed to protect patient, employees, and equipment
Interlocks
____ Gy (_____ cGy) can be given in 0.3 seconds at 4000 Gy/min if machine set for wrong beam energy
2 Gy (200 cGy)
8 examples of interlocks
Beam energy Beam symmetry, flatness Dose rate, typical dose Mechanical hazards Carousel rotation for different treatment Bending magnet not steering correctly (BMAG) Foil fault Dose/MU 1.2
11 new technologies
Conformal therapy Multileaf collimation (MLC) Dynamic wedge collimator Electronic portal imaging (EPID) On board imagers (OBIs) Stereotactic radiation therapy IMRT Tomotherapy Image guided radiation therapy (IGRT) Electronic arcs Flattening-field free (FFF)
Took place of cerrobend blocks; 52-160 leaves made of tungsten
Usually rounded on edges so they don’t break if they hit leading to penumbra at end/tip of leaf
Multileaf collimation (MLC)
Older; gets more conformal to tumor volume because peripheral dose decreases, tightens everything up to tumor volume
More angles = les dose per field; more beams
Field shape and beam angle change while gantry moves around patient
Allowed by IGRT
“Forward planning” process
Conformal therapy/3D-CRT
Flat panel MV receptor across from gantry that gives image; demonstrate poor image quality/contrast
Electronic portal imaging (EPID)
kV images on lateral sides of machine, correlates with interaction
Can recreate cone beam CT every 1 degree
Flat panel detector
Offers better detailed image
On board imagers (OBIs)
High dose per fraction for hard to reach areas (brain); long prep time, precise
External 3D frame halo: bolts drilled into head and fastened to apparatus that prevents head movement
Planning can take 3-8 hours
Fiducials track movement
Brain tumors, anterior or venous malformations (AVM), etc.
Stereotactic radiation therapy
Beam arrangements are tested by trial and error until satisfactory dose distribution is produced
“Forward planning” process
IMRT develops treatment plans using this treatment planning; radiation oncologist selects dose parameters for normal tissues and the target volume and computer “back calculates” the desired dose distribution and beam arrangements
“Inverse treatment planning”
How much dose is being received within lines
Isodose lines
Beams in different planes
Non-coplanar
Smaller MLC’s used for SBRT/SRS to conform the dose to very small treatment volumes receiving larger or single fraction doses
Micro-/mini-MLCs
Curved to match beam divergence; took place of cerrobend blocks
Dynamic wedge collimator
3 major components of the linac
Drivestand
Gantry
Couch
Collimation: bimodal (open or shut), static
Similar to CT but 6 MV
Very conformal but limited
Tomotherapy
Similar to tomo arcing around
More arcs = more time, patient has to stay still the whole time
Electronic/rapid arcs
2 types of IGRT
Exac trac
CT overlay
Uses infrared tracking to see reference position
Exac trac
Makes sure patient is perfectly aligned and if there are any shifts to be made
CT overlay
Changing planning right there
Adapted planning
Real-time MRI with Co-60
Viewray
Computers used to assist therapist in the verification of treatment parameters allow incorrect setup parameters to be corrected before machine is turned on
Computer-assisted setup and recording of patient data reduces erros
Patient information comes from treatment planning computer to machine
Record and verify
2 classes of hazards defined by the FDA
Class I
Class II
Accident causes death or injury
Class I
Accident if risk of serious injury low (operator error, linac error, etc.)
Class II
Dmax depth for superficial and orthovoltage
0.0 cm
Dmax depth for Cesium 137 and Radium 226
0.1 cm
Dmax depth for Cobalt 60
0.5 cm
Dmax depth for 4 MV
1.0 cm
Dmax depth for 6 MV
1.5 cm
Dmax depth for 10 MV
2.5 cm
Dmax depth for 15 MV
3.0 cm
Dmax depth for 18 MV
3-3.5 cm
Dmax depth for 20 MV
3.5 cm
Dmax depth for 25 MV
5.0 cm
Traditional and SI unit of Cobalt 60
Traditional: Ci
SI: Bq
Most sources have an activity of ____-____ Ci
750-9000 Ci
To compensate for the reduction in beam output of Co-60 each month (1%), a correction factor of about ___% per month must be applied to the output
1%
Electronic equilibrium
Dmax
Shielding for Co-60
Cerrobend melts at a much lower point than lead and is therefore easier and safer to use (cadmium)
5 methods to expose the Co-60 source
Air pressure (piston) Rotating wheel Mercury reservoir Chain driven Moving jaws
Number of HVLs formula
(1/2)^n = percent transmitted
Ratio of cerrobend to lead
12:1
2 advisory agencies that don’t set regulations for radiation safety procedures
International Commission on Radiological Protection (ICRP)
National Council on Radiation Protection and Measurements (NCRP)
Agency that sets regulations for radiation safety procedures
Nuclear Regulatory Commission (NRC)
States that enter into agreement with NRC to assume responsibility of enforcing regulations for ionizing radiation
Agreement states
3 times full calibration must be done
Sources replaced
5% deviation during QA or spot check
Any major repairs that require removal or restoration of major components
5 things full calibration includes
Radiation field-light coincidence
Timer accuracy
Distance measuring devices (ODIs, etc.)
Uniformity of radiation field and dependence based on useful beam
Exposure and dose rate for +/-3% accuracy for multiple field sizes
Average leakage and leakage for 1 reading at 1 m
Average = 2 or less mR/hr at 1 m
1 reading at 1 m = 10 or less mR/hr
Max permissible leakage in “on” position
0.1% or less of useful beam 1 m from source
Filter paper wiped on collimator edges twice a year with long forceps should read less than 0.005 microcurie
Wipe test
18-24 in bar to push source back into machine; first 7 in red = pretty safe, 2nd 7 in yellow = source back in housing
T-bar
Why dose Co-60 have very high penumbra?
Large source size
Increasing energy _______ penumbra; by over 10 MV penumbra _______ again because of Compton
Increases
Occurs with straight blocks because of divergence
Transmission penumbra
Transmission + geometric penumbra
Physical penumbra
Penumbra formula
P = S(SSD+d-SDD)/SDD
Increasing SSD and distance from source ______ penumbra; increasing SDD _______ penumbra
Increases, decreases
Who insures radiation therapists?
Hospital
Discipline dealing with what’s good and bad, moral duty and obligation
Set of moral principles or values
Theory or system of moral values
Principles of conduct governing an individual or group
Foundation of law
Ethics
Fidelity to conscience; person’s concept of right or wrong as it relates to conscience
Morality
Loyalty, faithfulness
Fidelity
Sum of rules and regulations by which society is governed in any formal and legally binding manner
Legal concepts
Foundation of which is ethics, primarily concerned with the good of a society as a functioning unit; exist so we can all live and coexist in formal and legal binding manner we’re governed by
Doesn’t consider the professional and patient to be on equal terms; greater legal burden/duties are imposed on the healthcare provider
Laws
Application of ethics to the bioethical sciences, medicine, nursing, and healthcare
Bioethics
7 principles of bioethics
Autonomy Beneficence Confidentiality Justice Nonmaleficence Role fidelity Veracity
Patients are independent actors whose freedom to control themselves is to be respected without interference from others
Autonomy
Healthcare professionals act in the best interest of patients, even when it might be inconvenient or sacrifices must be made
Beneficence
Principle that relates to the knowledge that information received by a patient to a healthcare provider or learned in the course of a healthcare provider performing their duty, is private and should be held in confidence
Confidentiality
Fairness and equity maintained among individuals
Justice
Directs professionals to avoid harmful acts to patients
Nonmaleficence
Principle that reminds professionals that they must be faithful to their role in healthcare environment
Role fidelity
Truthfulness specific within healthcare aspect
Veracity
3 groups of ethical theories
Teleology/consequentialism
Deontology/nonconsequentialism
Virtue ethics
2 forms of teleology/consequentialism
Egoism
Utilitarianism
Evaluate good versus bad way person can provide greatest good for most people; ends justify the means
Teleology/consequentialism
Best long-term interests of an individual are promoted; in evaluating an act/action for its moral value, it must produce a greater ratio of good over bad for the individual
Egoism
Ethical behaviors should be geared toward performing acts that produce the greatest ratio of good to bad
Utilitarianism
Uses formal rules for right and wrong for solving problems; duty and right actions to be taken
Deontology/nonconsequentialism
Practical wisdom for emotional and intellectual problem solving; practical reasoning and consideration of consequences
Virtue ethics
Ways of viewing relationship with patient; use all of these to build a relationship with patient
Models for ethical decision making
5 models for ethical decision making
Engineering/analytical Priestly Collegial Contractual Covenant
Dehumanizing approach identifies caregivers as scientist dealing only in facts and doesn’t consider the human aspect of the patient/disease
Engineering/analytical model
Provides caregiver with godlike attitude forcing patient to do whatever caregiver says regardless of pain
Priestly model