Problems in the Clinic Day one FCs

what is the purpose of dose coefficients

tracks the daily dose administered from each field

what does a 1 in the column imply

100% of the dose entered into mosaiq for that field is tracked

what is a QS field

quantity sufficient field drawn by dosimetrist

smaller field used to give additional dose/day

given at the same time as the primary field

You are actually giving x cGy (with the QS field) but your doctor wants to track y cGy (the standard of care)

smaller QS field has a DC of 1- 100% of the dose to QS field is tracked

the standard of care coefficient is manipulated (higher dose)

so that the total from both fields is equal to the standard of care Rx

why would you want to track dose less than 100% of the dose to a field

so that a QS field can be added but the total dose is still equal to the primary standard of care Rx

black

green

blue

historical (already treated)

green (go, treat today)

blue, treat in the future

coefficient formula

cGy/MU

ODI tolerances

some areas such as the breast are harder to treat, so there is a larger tolerance (more variability is allowed)

SBRT, small tolerance, only small variability allowed

closer to tolerance ODI procedure 5

Therapist notes ODI difference and alerts dosimetry

close to tolerance

allows treatment but request ODI verification and port films, take separation

verify and record ODI for 3 consecutive days

If ODI still off, alert doctor: recalc/resim or no recalc if port films are reasonable

document

extremely off from expected value ODI procedure3

therapist notes ODI difference and alerts dosimetry

Extremely off from expected value

alert doctor who will make decision concerining treatmnet

Recalc Process with ODI difference

New RadCalc with new SSD

same SIM

if you have a recalc with a New SSD, but no new sim which depth to the calc pt do you know

reference pt depth (do not know all the heterogeneities)

ODI recalc with New SSD formula to calculate the new MUs to use for treatment

New Homogenous Rad Calc to isocenter (ref depth)/Old homogenous rad calc to isocenter (ref depth)

new ssd/old ssd

x plan MU

variances rules

state the facts

state that physician was notified

follow up

Pendulum operation

know how to operate the lights

vertebrae

C1-C7

T1-T12

L1-L5

S1-S5

T12= last floating rib

significance of C1:

the inferior border of WBI is draw just below C1

Tps vs Port Film

Port Film: overexposed to show other structures

Rapid

single dose greater than or equal to 400 cGy

one shot

one shot of radiation dose for a rad onc emergency or for palliation

SOT

someone (Physician, Physicist, CMD) might come to the machine to see the patient on the table

see on table

carriage fault

one or more of the MLC leaves is travelling more than 14.5 cms from the block edge

mlcs are supposed to stop at 14.5

carriage fault correction

shaper script checks for carriage faults

positive/challenging aspects (4)

time constraint

student

physicians

coworkers

what do you think happens to dose at mid-depth if a block is left out

the dose increase (block absorbs RT dose)