Chapter 8 - Treatment Procedures

Positioning the isocenter

-3-point setup - once established, the machine will rotate around it and patient does not move. -Isocenter located relative to three set up coordinates on the patient's surface or on equipment fixed relative to their anatomy is referred to as triangulation. X (left to right) Y (superior to inferior or in/out) Z (depth in patient or up/down) Test

Patient Transfers

-Ambulatory = patient can walk by himself and needs little assistance to get onto table -Wheelchair transfers - assist with stand and pivot; always lock wheels before you get patient on or off the table! -Stretcher - patient may be able to slide over, otherwise use sheet transfer or slider board; lock wheels! -Oxygen, IVs, chemo packs, catheters, chest tubes -need to work around and careful not to pull out -Proper body mechanics will protect back

Treatment Delivery

-Beam on either with key, switch, or both -Audio and visual must both be operating -"Radiation on" lights over door and in room

Treatment Preparation

-Clean linen on table -Positioning aids and immobilization devices -Treatment accessories (blocks, wedges, etc) -Set parameters on machine or with R & V system. -Treatment field or portal. Dimensions are stated width by length in centimeters (12X10)

Dose Prescription

-Completed and signed by physician only - must be done before treatments initiated -Includes anatomic site, total dose, fractionation and protraction schedule, treatment technique (number and orientation of fields, beam energy) -Must be checked by therapist everyday for changes -Each field assigned an identifier and number, ex. AP/PA lung are fields 1 & 2

Components of RT chart

-Consultation notes -Test results, including pathology report -Consent form -Weekly assessment (side effects, vitals, weight) -Treatment setup page -Photo of patient -Prescription -Treatment plan and calculation -Daily treatment record

Compensators (Beam modifiers)

-Custom made or generic -To make up for an irregular surface while maintaining skin sparing -Copper, brass, lead, lucite Absorbs part of the beam

Daily treatment record

-Documents delivery of each treatment - never filled out ahead of time -Daily and cumulative doses -Portal films taken -Treatment number and elapsed days -Implementation of changes -Most common errors are addition and transposition of numbers - corrections must be done appropriately -Increasing complexity of treatment delivery is necessitating the use of R & V systems -Paperless and filmless departments are in the immediate future

Treatment Plan

-Done by dosimetrist and approved by physician -Calculations must be done by at least two people -Therapist must review plan and simulation notes before treatment for setup reproducibility

The Patient

-Identify patient with two different methods - photo, restate full name, wristband, DOB, etc -Patient may receive anywhere between 1 and 45 treatments (fractions (fx)) -Must have a good rapport, protect modesty and privacy -Explain aspects of treatment and equipment -Directions for maintaining marks, skin care, nutrition, or referral if necessary

EMR-Electronic Medical Record

-Information is stored in a centralized database. Comprehensive EMR includes all medical and administrative aspects of the patient's experience. -Electronic imaging -Computed radiography (CR) uses phosphor plates similar to film and electronic portal imaging devices (EPID) mounted opposite of the gantry head or kilovolt x-ray source mounted to the gantry, convert x-ray information to digital information and displayed on a monitor -Display the beam's eye view (BEV) of area to be irradiated. The tx field shape and orientation as the beam passes through the patient.

The Linear Accelerator (Linac)

-Mounted in reference to the isocenter - a fixed point where the axes of rotation of the gantry, collimator, and couch all intersect -Lasers intersect there as well to aid in positioning the patient

Patient position

-Must be comfortable and reproducible for an accurate treatment -Must exactly match simulation guidelines -Variety of positioning aids and immobilization devices available to achieve this -Position the isocenter with the x, y, z system

Verification imaging

-Must verify that what was planned during simulation is what is being treated -Usually do on first day of treatment and then once per week during treatment -Can be done with film, electronic portal imaging, CBCT, or ultrasound

Locating the treatment field

-Need reference marks in order to set patient up correctly each day -Bony landmarks -Tattoos -Permanent fiducial markers -Semipermanent marking -Carfusion www.pamf.org

Common treatment techniques

-Parallel-opposed -4-field box -Tangential fields -3D conformal therapy

The Chart

-RT chart is separate from hospital chart and stays in the RT department -Legal document of patient's RT treatment -Common element in QA programs - goal is to assure accuracy in delivery of treatment -check charts weekly - paper or electronic

Wedges (Beam modifiers)

-Used when multiple beams overlap to get rid of "hotspots" -Evens out the dose distribution -15, 30, 45, and 60 degrees -All beam modifiers must be at least 15 cm from skin surface to eliminate electron contamination.

Verify and Record

-V&R, R&V, RV systems -Provide validated parameters from the treatment plan for treatment machine setup and delivery. -V&R and EMR changes the medium or how a task is accomplished but not the requirement or end result.

4-field box

90 degrees from each other Pelvis is most common Less side effects important structures vs. parallel opposed

Beam modifiers

Bolus -Mimics tissue -Wax, wet gauze, water, superflab -To minimize skin sparing (ie. Bring dose closer to skin surface) -Can also be used as a tissue compensator -Placed over entire tx area, or just the scar or node

Assessment and acceptance of treatment parameters

Control console -Most are computer controlled -Many interlocks to protect patients -Any problems must be reported --NRC for misadministration --FDA for equipment malfunction

SRS

Cyberknife Unit

Tangential fields

Flashing off of a curved surface, such as the breast

Electron beam therapy

For superficial treatments, such as skin or lymph nodes Use cones that come close to skin surface Cerrobend cutouts Often use bolus as well

Total Body Irradiation (TBI)

In preparation for bone marrow transplant Total skin with electrons for superficial lesions

Beam shaping

Linac only produces a square or rectangle shape, so either blocks or multileaf collimation (MLC) needed. test

3D conformal therapy

Multiple fields and shapes

Intensity modulated radiation therapy (IMRT)

Similar to 3D conformal, but the amount of radiation at each field can also be varied Tomotherapy CT image guided IMRT

Stereotactic radiosurgery

Small diameter cones arc over the patients head Can be linear accelerator, gamma knife, or cyberknife

Parallel-opposed

two fields 180 degrees apart AP-PA RT and LT lateral Obliques