Download Patient Preparation and Coronary CTA Techniques

Patient preparation and
coronary CTA techniques
Gregory Kicska, M.D. Ph.D.
University of Washington, Thoracic Imaging
Overview
1. Patient preparation
2. Scanning techniques
Patient preparation
Preparation related to any contrast CT examination
Preparation specific to coronary CTA
Exclude contraindications
Patient safety
Study quality
Contraindications: patient saftey
Contrast
renal insufficiency
allergy (anaphylaxis)
Radiation
pregnancy
radiation dose/age
Claustrophobia
Medically unstable
Contraindications: patient saftey
Contrast
ast media
employ a
tection of
rotoxicity.
nction can
ne report.
high-risk
te (GFR).
nt due to
creatinine
f Diet in
on is an
creatinine
renal insufficiency
Table 5 Risk of contrast induced nephrotoxicity based on estimated
glomerular filtration rate (GFR)
GFR (ml/
min/1.73 m2)
Risk of contrast induced
nephrotoxicity
Intravenous iodinated
contrast media
60
30–60
Negligible
Moderate
<30
High
Safe
Use only if clinically
essential prophylaxis
required
Contraindicated
Administration of contrast media to pregnant patients and
Contraindications: patient saftey
214
creatinine measurement before intravenous contrast media
injection are summarized in Table 4. Most centers employ a
serum creatinine threshold of 1.5 mg/dl for detection of
patients at high risk for contrast-induced nephrotoxicity.
However, considerable derangement of renal function can
be masked by a normal appearing serum creatinine report.
Hence, the current recommendation is to screen high-risk
patients with estimated glomerular filtration rate (GFR).
Derangement of GFR can occur in a patient due to
undetected chronic renal disease though the creatinine
measurements are normal. The Modification of Diet in
Renal Disease (MDRD) study group equation is an
accurate method for GFR estimation from serum creatinine
[27]:
Table 5 Risk of contrast induced nephrotoxicity based on estimated
glomerular filtration rate (GFR)
GFR ¼186 " ðserum creatinineÞ
When given in usual clinical doses, iodinated contrast
media cross the human placenta and enter the fetus [3]. No
adequate and well-controlled teratogenic studies of the
effects of these agents in pregnant women have been
performed. While it is not possible to conclude that
iodinated contrast media present a definite risk to the fetus,
there is insufficient evidence to conclude that they pose no
risk. The ACR recommends that iodinated contrast media
may be given to pregnant patients only when [3]:
Contrast
renal insufficiency
% 1:154 " ðageÞ % 0:203 " k
For women, k=0.742; for men, k=1
Multiply by 1.210 if African-American
The risk of contrast-induced nephrotoxicity based on
estimated GFR is summarized in Table 5. Recently, some
vendors are investigating rapid strip-test-based methods for
quick measurement of serum creatinine when patients arrive
for contrast-enhanced radiological studies [28]. Such methods
to estimate serum creatinine can enable efficient detection of
patients at risk for contrast-induced nephrotoxicity.
GFR (ml/
min/1.73 m2)
Risk of contrast induced
nephrotoxicity
Intravenous iodinated
contrast media
60
30–60
Negligible
Moderate
<30
High
Safe
Use only if clinically
essential prophylaxis
required
Contraindicated
Administration of contrast media to pregnant patients and
nursing mothers
–
–
the diagnostic information requested using contrastenhanced study cannot be obtained via other means
(such as ultrasound)
the information needed affects the care of the patient
and fetus during the pregnancy
Contraindications: patient saftey
Radiation
pregnancy
radiation dose/age
Contraindications: patient saftey
Claustrophobia
Diazapam 5 mg oral*
Medically unstable
*Dose adjustment needed specific conditions
Contraindications: study quality
Motion
Breath hold
Gating
Artifact
Inability to raise arms
Metal
Obesity
Contraindications: study quality
Motion
Breath hold (7-12 sec @ 64 slice)
270 ms acquisition dual source
Contraindications: study quality
Motion
Gating
atrial fibrillation or frequent PVCs
Contraindications: study quality
Artifact
Inability to raise arms
Metal
Obesity
The ideal patient
HR < 65, sinus
Calm
Thin
Large veins
Pearl diver (able to hold breath)
Able to follow commands
Preparation: 24-1 hr pre-exam
No caffeine (24 hrs)
No viagra (24 hrs)
No “energy supplement” (24 hrs)
No food (4 hrs)
No liquid (1 hr)
Preparation: 24-1 hr pre-exam
Cardiac medications should not be
suspended!
Preparation: 24-1 hr pre-exam
Non-anaphylactic contrast reaction
• 50 mg prednisone @ 13,7,1 hrs before exam
• oral Benadryl 1 hour before exam
Preparation: 1 hr pre-exam
•IV access
•18 - 20 gauge needle
•Right arm
Preparation: 1 hr pre-exam
Satisfactory IV access
Contraindications excluded / mitigated
Proceed to HR control
Preparation: 1 hr pre-exam
Satisfactory IV access
Contraindications excluded / mitigated
Proceed to HR control
Preparation: 1 hr pre-exam
Oral metoprolol (50 mg tabs)
50-100 mg
Wait 90 minutes, check BP/HR
Consider additional 50 mg
IV metoprolol (5 mg)
Give 5 mg IVP
Wait 20 minutes, check BP/HR
Consider additional 5 mg x 2
Contraindications
Metoprolol allergy
Bronchospastic disease (asthma)
Aortic valve disease
Worsening heart failure
Heart block
Preparation: 1 hr pre-exam
Preparation: 1 hr pre-exam
Beta blocker contraindication?
Consider oral Verapamil
Preparation: 1 hr pre-exam
HR < 65 bpm
Proceed to Ca++ score
Examination: patient positioning
Center heart in scanner
Examination: patient positioning
Center heart in scanner
= Lowest noise
Examination: patient positioning
Center heart in scanner
= Lowest noise
Examination: Ca++ score
Ca++ score coverage
Examination: Ca++ score
Voxels are 3 x 1.3 x 1.3 mm
non-overlapping
Threshold of 130 H.U.
Agatston
volume
mass score
Examination: Ca++ score
= 0 - CAD unlikely
> 400-1000 - high risk of stenosis
Predicting Stenosis
Ca++ Score
Sensitivity
Specificity
>1
92%
75%
>100
73%
90%
>1000
30%
98%
Low false negative
No false positive
Low sensitivity on CTA
Examination: Ca++ score
0 < Agatston score < 400-1000
Proceed to CTA planning
Examination: gating
Retrospective
no modulation
Retrospective
with modulation
Prospective
Retrospective
no modulation
Retrospective
with modulation
Prospective
Rate < 70
no function
no calcium
Age < 40
Rate > 70
function
calcium
Age > 40
A-fib
Prospective
Retrospective
Modulation
Retrospective
No modulation
Examination: CTA coverage
Coronary CTA coverage (retrospective)
Ca++ score coverage
Top slice
with CA
Bottom slice
with CA
Examination: CTA coverage
Coronary CTA coverage (prospective)
Ca++ score coverage
Top slice
with CA
Bottom slice
with CA
Examination: dose
Set kVp and MAS.
Automatic exposure control
set desired held soon in its standard deviation
set upper and lower limits to avoid spikes in
current due to hardware
Weight table
Examination: dose
Examination: dose
Participate in dose related QA
Examination: contrast
80 ml
5 ml/s
40 ml
4 ml/s
50 ml
4 ml/s
40%
100%
100%
60%
Examination: nitroglycerin
Contraindications
Head trauma/bleed
Systolic BP < 100
Nitrate Allergy
Phosphodiesterase inhibitors
Adverse
Headaches - 50%
Examination: nitroglycerin
4 minutes
Examination: nitroglycerin
4 minutes elapsed
Proceed to CTA scanning
Examination: scanning
Examination: reconstruction
Main reconstruction for 3D station
Thin section (0.625 mm) axial
cardiac kernal
< 32cm FOV
50% overlap
Examination: reconstruction
Additional reconstruction for 2D station
•Axial 2.5 mm, lung kernel, lung FOV
•Axial 2.5 mm, body kernel, body FOV
•Coronal/sagittal, body kernel
Conclusions
• Exclude contraindications related to patient safety or exam quality
• ensure proper patient preparation for contrast exam
• control heart rate with beta blocker
• calcium scoring is used to plan CTA or terminate exam
• scanner gating is one of the most effective ways to reduce dose
• utilize automatic exposure control when possible
Thank you