Download Value of "large" FOV calcium score as as screening method for

Value of "large" FOV calcium score as as screening method
for detection of extracardiac incidental findings
Poster No.:
C-0997
Congress:
ECR 2012
Type:
Scientific Paper
Authors:
A. S. Ibrahim, W. Tantawy; Cairo/EG
Keywords:
Cardiac, CT-Angiography, CAD, Obstruction / Occlusion
DOI:
10.1594/ecr2012/C-0997
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Page 1 of 16
Purpose
The purpose of this study was to emphasize the value of calcium scoring (Ca score) using
a large field of view ("large FOV") as a screening method for detection of extracardiac
incidental findings
Methods and Materials
Between July 2010 and December 2011, 382 consecutive patients candidate for coronary
MDCT exam were scanned starting by a calcium score exam - using a "large FOV"
- followed by a routine "small FOV" coronary CT angiography examination (CCTA).
Patientswere excluded if they declined to enter this study (n=5) ordid not have an
accessible large intravenous line (n=2). The remaining patients gave their informed
consent and a total of 375 patients, 203 men and 172 women, ranging between 40-80
years (mean, 60 years), were included in study.
Image Acquisition
All MDCTA examinations were performed with a MDCT scanner (Toshiba® Aquilion
64 CT Scanner) at Misrscan center located in east Cairo, Egypt. As a preparatory
phase non-contrast calcium score was preliminary done using a "large FOV" of
32-50 cm, other CT technical parameters included mA: 250-300; kV: 120; and
section thickness, 3mm x 4 detectors. Then arterial enhancementwas provided by IV
administration, in an antecubital vein throughan 18- to 20-gauge IV catheter, of 65-85
mL of nonionic iodinatedcontrast material (Ultravist 370 [iopromide], Bayer HealthCare
[formerly Schering] at an injectionrate of 5-5.5mL/s with a power injector (double syringe
pump), sure start 160, "small FOV": 18-24 cm (Fig 1,2); mA: 300-400; kV: 120; and
section thickness, 0.5 mm x 64 detectors.
CT Reconstruction
®
All images werereviewed on Vitrea Workstation in axial, coronal and sagittal planes as
well as MIP, MPR, 3D volume rendering and curved MPR after evaluation of calcium
score.
Image
Analysis/Interpretation
Page 2 of 16
Two experienced radiologists, in a blind protocol, independently reviewedall cases. The
reviewers surveyedeach calcium score exam using axial source images for evaluation
of extracardiac findings. No specific window level settingswere prescribed for image
analysis. Instead, each reviewer modifiedthese settings to better depict the extracardiac
incidental findings.
Usually all images were reviewed in the axial plane using all of the following settings:
mediastinal windows (width=400, level=40), lung windows (width=1500, level= 500),
vascular (width=700, level=200) and bone windows (width=2000, level=350) and in
general, the window level settingswere quite large, progressing to very wide settings in
the casesof dense calcifications (usually around W2093:L792).
Results were classified into four groups: 1) Emergent findings where therapy is often
needed 2) Intermediate findings where timely workup is often needed 3) Mild findings
where later follow-up is often needed 4) Incidental lesions where follow-up is often not
needed (Figure 4). Afterwards, the two radiologists reviewed the findings together and
reached a consensus about the findings.
Images for this section:
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Fig. 1: MDCT Ca score using a "small FOV"
Page 4 of 16
Fig. 2: MDCT Ca score using "large FOV". Dose calculation and analysis of our cases,
on a 64 MDCT scanner, showed an increase of +/- 1.2-1.9 mSv in dose, comparing ca
score with a "large FOV" technique dose versus that of a "small FOV" technique
Page 5 of 16
Results
375 patients, 203 men and 172 women, 40-80 years old (mean, 60 years), were included
in this study; incidental extracardiac findings were found in 62.4% of scanned patients
(figure 2,3,4). Usage of "large FOV" technique during Ca score acquisition in all our cases
permitted detection of a higher percentage of incidental extracardiac findings.
Among whole incidental extracardiac findings, "significant" extracardiac abnormalities
(emergent and intermediate findings) were detected in 93 out of 375 cases (24.8%), 42
cases (11.2%) out of these 93 cases were detected by using "small FOV" technique, so
51 out of remaining 93 cases (13.6%) would have been missed if only using a "small
FOV" technique (Table 1,2,3). Dose calculation and analysis of our cases, on a 64 MDCT
scanner, showed an increase of +/- 1.2-1.9 mSv in dose, comparing ca score with a "large
FOV" technique dose versus that of a "small FOV" technique.
Images for this section:
Page 6 of 16
Fig. 3: MDCT angiography for coronary assessment using the standard "small FOV"
revealing a left sided bronchogenic carcinoma.
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Fig. 4: MDCT: "Large FOV" Ca score for Fig 3 patient revealing suspicious pulmonary
deposit, that would only have been detected with the "large FOV" technique.
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Fig. 5: MDCT: "Large FOV" Ca score for another patient revealing benign pulmonary
deposit, that would only have been detected with the "large FOV" technique.
Page 9 of 16
Page 10 of 16
Table 1: Distribution of emergent and intermediate significant findings. Extra cardiac
findings detected using "large FOV" compared to "small FOV" technique
Table 2: Distribution of all extracardiac incidental abnormalities
Table 3: Calculation of additional significant extracardiac abnormalities using "Large
FOV" compared to "small FOV".
Table 4: Distribution of all extracardiac incidental abnormalities according to their
anatomical location: extracardiac upper mediastanal findings - from lung apex to level
of carina, and extracardiac peripheral findings representing findings outside the confines
of the pericardium.
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Fig. 6: Distribution of extra cardiac findings detected via "large FOV" Ca score among 375
consecutive patients candidate for coronary MDCT between June 2010 and December
2011. Results were classified into four groups: 1) Emergent findings where therapy
is often needed 2) Intermediate findings where timely workup is often needed 3)
Mild findings where later follow-up is often needed 4) Incidental lesions where followup is often not needed. Among whole incidental extracardiac findings, "significant"
extracardiac abnormalities (emergent and intermediate findings) were detected in 24.8%,
among which 13.6% would have been missed if only using a "small FOV" technique.
Page 12 of 16
Conclusion
Using a "large FOV"; Incidental extracardiac abnormalities were detected in 62.4% of the
scanned patients. Among those incidental extracardiac findings, "significant" extracardiac
abnormalities (emergent and intermediate findings) were detected in 24.8%, among
which 13.6% would have been missed if only using a "small FOV" technique. For ca
scoring with "large FOV" technique; only a small increase in patient dose was needed
(1.2 -1.9 mSv). We would specially recommend with new MDCT including dual, 256 and
320 detectors CT machines -using a sub mSv dose- routine acquisition of "large FOV"
for detection of more extra-cardiac findings including serious significant findings as lung
cancer or metastatic nodules at a very small expense in dose.
We confirmed that the frequency of incidental findings is influenced by the scanning
range. Larger scanning ranges containing more anatomic structures would reveal a
greater number of incidental findings and several serious diagnoses would be missed
with the limited viewing approach. 6.6% of our cases were extracardiac upper mediastinal
findings while 14.9% of our cases were extracardiac peripheral findings
Our results showed that before performing a coronary MSCT angiography with contrast,
carrying out a Ca score with a "large FOV" is important for detection of extracardiac
incidental findings in addition to usage of ca scorring as a risk factor for assessment
of cardiac disease and anticipation of the degree of difficulty in the evaluation of the
coronaries especially in cases where high Ca burden was detected in a single major
artery. Using "large FOV", only a subtle increase in dose was noted in our study estimated
at +/- 1.2-1.9 mSv.
Radiologists should aim at analyzing the non-cardiac findings as meticulously as possible
to ensure that important findings that might be responsible for a patient's symptoms
are not missed and unnecessary follow-up examinations are avoided. A patient with
absolutely normal coronary arteries could have a potentially life-threatening finding in
the thorax accounting for chest pain, such as acute pulmonary embolism, acute aortic
syndrome, or a relatively benign finding such as a large hiatal hernia. Thus, interpreters
of cardiac CTA images should have adequate training and skill in differentiation between
benign and potentially clinically significant lesions so as not to cause undue cost or patient
anxiety and reducing additional work-up.
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Personal Information
Ahmed S. Ibrahim
Radiodiagnosis Department, Ain Shams University, Cairo, Egypt
[email protected]
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