Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Intro to Medical Dosimetry > Hand Calc > Flashcards

Hand Calc Flashcards

(62 cards)

Start Studying
1
Q

How does MU change when TMR change

A

as TMR decreases, MU increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How does TMR change when calc point depth changes

A

as depth increases, TMR decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Whole brain irradiation- patient selection

A

metastatic diseases: frequent breast, lungs, melanoma, sarcoma, CNS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Goal of treatment (whole brain)

A

palliation of symptoms
quality of life
prolonging survival
could be prophylactically (PCI)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what us treating prophylactically

A

PCI given to small cell lung cancer a head of time because patients have brain cancer frequently. when treating prophylactically, we treat the areas that we think will develop cancer later on, so we treat in advance with lower dose (24 Gy in 12 fx)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

whole brain immobilization

A

supine, exact bar, reg.h. “B”, pad on table, mask, arms across chest holding A-bar, knee wedge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

where is the isocenter placed for whole brain

A

mid- separation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

why is isocenter placed at mid separation

A

for homogeneous dose distribution, if the isocenter is off, we will have a hot and cold plan

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Conventional Whole brain sim

A
  1. Fluoroscopic x-ray will be taken of treatment field
  2. Doctor draw field (wax pencil in scan or digitally)
  3. Blocking created (cerrobend or MLC)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Virtual whole brain sim (more realistic)

A
  1. Pt receives CT scan
  2. Axial slices imported into treatment planning computer
  3. Dr draws field on TPS
  4. MLCs for blocking
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Whole Brain Fields gantry angles

A

Opposed laterals

tilted anterior

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

why do we set beam angles tilted anterior and opposed laterals (obliged) for whole brain

A

TO LIMIT DIVERGENCES TO THE LENSES

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How to change gantry angles to limit divergence for whole brain

A

ex: if beam 1 is at 278 (270+8), beam 2 will be at 82 (90-8)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

where is interior border usually placed for whole brain

A

below C1, or could be below C2 as well but rare

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

why is the interior border always placed at C1 or C2

A

patients are usually here for metastatic cancer, chances are they will come back for more treatment. When that happens, we want to know where we stopped at the previous irradiation so that we can avoid overlapping and overtreating that area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Superior and lateral borders incorporate flash for whole brain, why?

A

patient’s set up can be different each day. flash ensures we have the whole skull covered every treatment. Also, if the field borders are against the head, we do not have adequate dmax to tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

critical structures to consider when treating whole brain

A

face

lenses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what happens if we dont consider face and lenses for whole brain irradiation

A

radiation induced cataract that can develop in 20 years

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

block position for whole brain

A

“one thumb length” away from target

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Whole brain palliative prescription

A

30 Gy for 10 fx

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Whole Brain PCI fractionation

A

24 Gy in 12 fx

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

whole brain calculation

A

heterogeneous calculation if imported into TPS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is the normalization of whole brain

A

100% to iso, no further optimization needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what happens when you normalize down

A

plan gets hotter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
what happens when you normalize up
plan gets cooler
26
what do you do when you want to increase coverage
normalize down (hotter)
27
what is MDACC normalization percentage allowed
95-105% | whole number or 0.5
28
no simulation?
- pt could be seen on weekend by physician - therapist turns collimator to block critical structures or hand block - homogeneous calculation done - calc verified by dosimetrist/physics on monday
29
MU tolerance
3% or 2 MUs
30
what does homogeneous calculation mean
not considering different materials, treating as if were treating water
31
heterogeneous
considering different kinds of materials such as tissues bones, etc...
32
purpose of wedge
wedges are designed for breasts they compensate for missing tissue/ manipulate the iso line to make it look like it pushes dose heel to toe (they dont actually push dose)
33
why do we have MLC on superior part of field border
to make the superior border nondivergent, if not, the border would diverse out
34
what is displacement
how far the calc point is from central axis in y-direction
35
why should electron be at 90 degree (appositional) to skin surface in breast
if at an oblique angle, can have hot spots and cold spots
36
4 calc point rules
1. inside the field 2. at least 2 cm from jaw edge 3. must be tissue equivalent material 4. cannot be in build up region (really close to surface)
37
why does the calc point have to be inside the field
if not, TPS will push MU to that point
38
why does calc point have to be at least 2cm from jaw edge
oe else, we dont have full buildup, dose is not accurately reflected
39
why must calc point be in tissue equivalent material
cant be in bone or air, or else we dont have adequate buildup
40
why cant calc point be in buildup region
cant have dmax | pinnacle doesnt model the buildup region well
41
4 rad onc emergencies
1. spinal cord compression 2. uncontrolled bleeding 3. extreme cases of pain due to bone mets 4. Superior vena cava syndrome (if tumor compressses on SVC, pt can die)
42
Palliative Spine irradiation goal of treatment
- palliation of symptoms - quality of life - could be one of the rad onc emerg
43
Palliative Spine irradiation patient selection
metastatic diseases (breast, lung, melanoma, CNS)
44
when would a patient receive no sim for palliative spine treatment
if they come on the weekend
45
can you use MLCs without sim
yes, you can digitize in Mosaiq
46
Vertebral column anatomy
C1-C7 T1-T12 L1-L5 S1-S5
47
where is T12
floating rib
48
palliative spine single PA field benefits
reproducible efficient to calc, set up, and treat cost efficient for palliative care
49
palliative spine single PA field negatives
high surface dose | not optimized dose distribution
50
palliative spine AP/PA fields benefits
reproducible efficient to calc, set up, and treat cost efficient for palliative care
51
palliative spine AP/PA field negatives
not fully optimized dose distribution | possible excessive dose from entrance from AP beam
52
palliative spine AP/PA field energy choice
AP/Pa- both 6X AP/PA- both 18X PA-6X and AP-18X- very prevalent
53
why is PA-6X and AP-18X the optimal energy choice for AP/PA spine treatment
higher energy, higher penetration
54
palliative spine Rt and Lt Laterals benefits
reproducible | efficient to calc, set up, and treat
55
palliative spine Rt and Lt Laterals negatives
suboptimal dose distribution | possibly added complication and cost of wedges
56
where in the body would you treat the spine with opposed laterals instead of AP/PA
cervical spine- spare mandible
57
palliative spine wedge pair benefits
reproducible efficient to calc, set up, and treat slightly optimized dose distribution
58
palliative spine wedge pair negatives
added complications of wedges in calc and treatment | added cost of wedges
59
Palliative Spine prescription
usually 30 Gy in 10 fx
60
Palliative spine that deliver one large dose to a bone met that is causing extreme pain (8 Gy or 12 Gy)
"rapid" or "one shot"
61
what is the difference between heterogeneous and homogeneous calc
heterogeneous: looks at effective depth homogeneous: looks at reference depth (physical/ geometric depth)
62
Palliative Spin optimization
based on doctor reference

Intro to Medical Dosimetry (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions