CT Sim and QA MRI

ARRT Specification

SAFTEY

Components and operation

Quality control procedures

Warm Up and Inspection

Interlocks

Safety lights

Emergency switches

Critical machine parameters

Electrical and mechanical hazards

Imaging systems

Evaluation of QA results

Interpretation

Course of action

Documentation

Importance of Simulation

FIrst place in a patients course of tx

Identify exact location of tumor within the body

Identify the tumor's relationship to surrounding anatomy/critical structures

Determine the ideal patient position for tx

Simulation Process

Gather patient information

-Imaging studies

-Special considerations/instructions

Immobilization devices

Prep room

Patient Interaction

-Face photo

-Consent

Time out

Scout

Topogram

Simulation Instructions

Immobilization devices/indexing

Protocols and parameters

Mark isocenter (at tumor or on body)

Slice thickness/spacing

Photographs/set up notes, tattoos

Name 2 or 3 things to check at a time out?

Name, Date of Birth, Tx area, Fractionation, MU, Gantry angles

What are 2 or 3 things to look at in a chart check?

Consultation

Consent

Additional Imaging

Pathology

Simulation Order

BUN and Creatine levels

High Risk Patients

> 50 y/o

Diabetes

Kidney dysfunction

CV diease

What should you look for before giving Barium contrast

Risks such as perforation or ulceration

Adverse Reactions to Contrast

Can occur 30 mins after injection

Medical hx

Contrast reaction kit on hand always

CT Simulation

Produces images of high spatial resolution

Provides electron density information

Allows for smaller, more precise tx fields, unique field and beam arrangements tailored to the patient, better visualization

Increased dose to tumor

Decreased dose to normal tissue

DRRs can be manipulated to enhance tumor visualization

Hounsfield Units

CT number that describes attenuation/density

Gantry

Donut shaped part of CT

Traditional bore=70cm

Large bore=85cm

FOV is the actual width of the scanner's imaging capacity

Critical that the entire anatomy is in the FOV

When are DRRs first created for tx planning purposes?

the dosimetrist creates the DRR in treatment planning to give a clear reference image (from the planning CT)

Sim allows to import additional images for a more accurate tx planning

Daily QA

Tube warm up

Lasers (-/+ 2 mm)

Accuracy of CT #'s (HU) with phantom

Image noise evaluation

Electromechanical Features

Laser alignment

Table position

Gantry tilt position

Scan localization

Safety interlocks

Emergency off

DFOV is ____ than SFOV

Smaller

Average CT #'s in water and standard deviation

Frequency is daily

Phantom

Expected results: near 0

Acceptable range: -3/+3

High and low contrast resolution

Phantom with whole pattern

Frequency

Biannually (2 per year)

CBCT

QA image quality daily

Geometric accuracy

Patient dose (MV and KV)

MR Lin Acc

Imaging/scan time

Treatment

Magnetic field

Positioning lasers

Artifacts/patient selection criteria

Implanted tissue markers (MR safe)

Simultaneous acquisition of MR images

during treatment

May allow reduction of large margins