Application Specific Safety Topics; Axial And Helical Scanning; Cardiac Imaging - GE Revolution CT User Manual

14 Application Specific Safety Topics

14.1 Axial and Helical Scanning

14.2 Cardiac Imaging

Chapter 3 Safety
WARNING
HELICAL SCANNING HAS THE INHERENT ABILITY TO PRODUCE
ARTIFACTS WHEN SCANNING HIGHLY SLOPED ANATOMY (E.G.
PEDIATRIC OR ADULT HEADS). FACTORS WHICH WORSEN THIS EFFECT
ARE: FASTER TABLE SPEEDS AND THICKER IMAGE THICKNESS. IN SOME
CASES THESE ARTIFACTS COULD BE MISTAKEN FOR A HEMORRHAGE
NEAR THE CRANIUM, OR A THICKENING OF THE SKULL.
TO REDUCE THE OCCURRENCE OF THESE ARTIFACTS, YOU MAY
PRESCRIBE SLOWER TABLE SPEEDS AND/OR THINNER SLICES (SUCH AS
2.5 MM) DURING HELICAL SCANS NEAR THE VERTEX OF A PEDIATRIC OR
ADULT HEAD.
WARNING
IT HAS BEEN DOCUMENTED IN RADIOLOGY LITERATURE THAT AN
ARTIFACT MAY OCCUR IN THE CHEST THAT BEARS THE DOUBLE
MARGIN OF THE GREAT VESSELS, WHICH EMULATES A DISSECTION OF
THE VESSEL DURING 0.28 - 1.0 SECOND SCANS. THIS CAN OCCUR IN
AXIAL OR HELICAL SCANS. IF YOU HAVE SCANNED AXIALLY WITH A 0.28 –
1.0 SECOND ROTATION TIME AND OBSERVE THIS PHENOMENON, RE-
SCAN THE AREA WITH A GATED SCAN, IF AVAILABLE ON YOUR SYSTEM,
OR USE ANOTHER DIAGNOSTIC MEANS TO DISTINGUISH BETWEEN
POTENTIAL ARTIFACT OR PATIENT PATHOLOGY.
CAUTION
A patient with any of the conditions list below may require additional attention. If
patients are scanned with these conditions, the software may not be able to
detect the R-Peaks and the images therefore may be produced as ungated
segment images: - Patient with multiple pre-contractions or extra systole (e.g.
PVC,PAC) - Patients with persistent or extreme arrhythmia - Patients with bi-
ventricular lead (dual chamber) pacemakers
CAUTION
ECG signal clarity and integrity must be confirmed prior to performing ECG-gated
acquisitions. Items which may require adjustments of equipment settings or
positioning, or patient set-up include: -External Interference - Atypical Patient
ECG (e.g. elevated T-Waves, low ECG amplitude or signal strength) -
Suboptimal Patient Connection ECG lead placement should follow recommended
guidelines to optimize results. If the ECG lead becomes disconnected during the
scan, or the heart rate drops below 30 BPM, the images will be reconstructed as
non-gated segment images. This is done to avoid inaccuracy of the z-location of
images where necessary.
Revolution CT User Manual
Direction 5480385-1EN, Revision 1
83