CT SCANNING AND SAFETY

INR measures

coagulation of blood

INR range

0.8-1.2

high INR is

contraindication for biopsy

oral temp range

97-99

rectal temp range

1 deg higher than oral

axillary temp range

1-2 deg lower than oral

tympanic temp range

0.5-1 higher than oral

systolic BP range

100-199

diastolic BP range

60-79

normal BP

120/80

angio delay

15-30 sec

venous delay

35-90 sec

portal venous delay

60-90 sec

delayed scan delay

3-10 min

routine head indications

stroke, HA, vertigo, seizure

routine head slices

2.5mm in posterior fossa and 5.0 through vertex

routine head gantry tilt

|| to SOML (rh)

routine head contrast use

only for tumors and when MRI contraindicated

routine head standard window

80WW 30WL

bone window

2500WW 600WL

facial bone slice thickness

1.25mm (fb)

facial bone gantry tilt

|| hard palate/floor maxillary sinuses/roof of mouth

facial bone delay w contrast

45 sec

standard window

400WW 40WL

facial bone windows

standard and bone

orbit gantry tilt

|| hard palate/roof of mouth/floor of maxillary sinuses (orb)

orbit delay w contrast

60 sec

orbit slice thickness

1.25mm (orbit)

sinuses slice thickness

1.25 mm (sinus)

how is pt positioned for sinuses?

prone. for A/F lvl and true coronal

sinuses positioning

perp. hard palate

sinuses and t-bones viewed in what window ONLY

bone

t-bone slice thickness

0.625mm (with 0.315 intervals if axial)

t-bone views

cor, ob

CTA HEAD/COW STUDY slice thickness

0.625mm (cow)

CTA HEAD/COW STUDY contrast details

100-150ml @ 4+mL/sec. from inferior to superior. (cow)

CTA HEAD/COW STUDY not used for

stroke.

CTA HEAD AND NECK slice thickness

1.25mm (CTA hn)

CTA HEAD AND NECK contrast details

100-150mL @ 4+mL/sec. inferior to superior, bolus tracking in arch

sft neck slice thickness

2.55 to view but thinner post processing

sft neck contrast details

100mL @ 3mL/sec.

sft neck arterial delay time

20s

sft neck venous delay time

45s

sft neck delay time

90s

c-spine slice thickness

1.25mm (spine)

t/l spine thickness

2.5mm (spine)

spinal stenosis for a spine exam should be

myelo instead

tumor for spine should be

MRI

myelo slice thickness

1.25 (myelo)

myelo contrast info

intrathecal. important to roll pt before scan.

myelo detail windowing

2100WW 700WL

myelo special reformats

axials to individual disc spaces

chest slice thickness

5mm with thinner post processing (ch)

chest contrast info

100mL @ 3mL/sec.

chest venous delay

30s

lung window

1800WW -600WL

CTA CHEST thickness

2.4mm (cta ch)

dissection type a

in ascending

dissection type b

in descending

CTA CHEST contrast info

100-150mL @4mL/sec scanned superior to inferior, track on descending

PE Chest contrast info

100-150mL @4mL/sec, scanned superior to inferior, tracking on pulmonary trunk

HRCT slice thickness

1.25mm (and 10-20mm interval if axial)

renal stone slice thickness

3.75 to view (reformatted with smaller)

what do you typically build for a renal stone?

coronal

kidney/renal mass slice thickness

3.75 to view (renal mass)

kidney/renal mass contrast information

100mL @3mL/sec (renal)

phases of a renal mass exam

1. non con

2. 30s arterial

3. 90s portal venous

4. 4+min delay

what does renal mass arterial look for?

renal arteries and cortex

another name for arterial kidney phase

corticomedullary

another name for 90s portal venous kidney phase

nephrographic

what does the nephrographic phase look at?

nephrons/middle of kidney

what else can a renal mass’s 4 min delay be called?

excretory phase

what do you look at on a kidney during excretory phase?

collection system

renal pelvis

adrenal scan slice thickness

3.75 mm (adrenal)

DFOV for adrenals?

18cm

injection info for adrenal study

100mL @ 3mL/sec (adrenal)

phases of an adrenal scan

1. non corn

2. 60 sec

3. 15 min delay

what HU typically means an adrenal will be scanned with contrast?

>10 HU

what does a 60s adrenal delay visualize?

adenoma

urogram slice thickness

3.75mm for viewing (uro)

what is contraindicated for a urogram?

going potty

injection info for urogram

100mL @ 3mL/sec (uro)

urogram phases

1. non corn

2. 90sec portal venous

3. 4+min delay

what do you visualize on a urogram nephrographic phase?

parenchyma

what is another name for a urogram 4+min delay?

excretory or pylographic phase

what does the pylographic phase visualize on a urogram?

transitional cell tumor, ruptured ureter

MSK prefers what?

MRI for soft tissue.

CT usually scans MSK for

fractures (2mm view and interval)

MSK IVcon is only for

soft tissue if MRI is contraindicated

CTDI is

CT dose index. mGy. average dose to any part of pt in SFOV. compares technique

CTDI head phantom

16cm

CTDI body phantom

32cm

CTDI predicts what kind of effects?

deterministic

DLP

dose linear product. mGY/cm

DLP formula

CTDI x scan length

what compares total radiation exposure?

DLP

DLP predicts what kind of effects?

stochastic

adult head dose

75mGy

ped head dose

35mGy

adult abdomen dose

25mGy