programma & abstracts - Nederlandse Vereniging voor Radiologie

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programma abstracts & abstracts
on a 64 detector-row scanner. Diastolic and systolic images
were reconstructed with FBP (high and low-dose) and the
IR algorithm (low-dose only). Hypo- and hyperdense artifact
volumes were determined using two threshold filters (≤-50
HU and ≥175 HU, respectively). Image noise was measured.
Results: Mean image noise was 16.3±1.6 HU (high-dose
FBP), 23.2±2.3 HU (low-dose FBP) and 16.5±1.7 (low-dose
IR). Low-dose IR reconstructions had similar image noise
compared to high-dose FBP (16.5±1.7 vs. 16.3±1.6, mean
± SD). Mean hypo- and hyperdense artifact volumes (mm 3 )
were 1235/5346 (high-dose FBP); 2405/6877 (low-dose FBP)
and 1218/5333 (low-dose IR). For all PHV types, hypodense
and hyperdense artifact volumes were similar for the highdose
scans reconstructed with FBP when compared to lowdose
scans reconstructed with IR.
Conclusion: Iterative reconstruction allows ECG-gated PHV
imaging with similar image noise and PHV artifacts at 50%
less dose compared to FBP in an in vitro pulsatile model.
Figure 1
O3.5
RADIATION DOSE AND ARTIFACTS
ARE REDUCED BY PROSPECTIVE ECG-
TRIGGERING RELATIVE TO RETROSPECTIVE
ECG-GATING FOR IMAGING OF PROSTHETIC
HEART VALVES WITH 256-SLICE CTS
P. Symersky 1 , J. Habets 2 , B.A.J.M. de Mol 1 , M. Prokop 3 ,
R.P.J. Budde 2
1
Academisch Medisch Centrum, Amsterdam
2
Universitair Medisch Centrum, Utrecht
3
Radboud University Nijmegen Medical Center, Nijmegen
Introduction: Multislice CT imaging has complementary
diagnostic value in the evaluation of prosthetic heart valve
(PHV) dysfunction. For PHV imaging, modified coronary protocols
with retrospective ECG-gating have been used at
considerable radiation exposure. We compared image noise,
radiation dose and artifacts with prospective triggering to
retrospective gating for PHV evaluation.
Methods: Two mechanical PHVs (St Jude bileaflet and
Medtronic Hall tilting disc) were scanned using a pulsatile
in vitro model. Image acquisition was performed with a
256-slice scanner with either a retrospectively gated helical
scan (120kV, 600mAs, CTDI vol
39.8mGy) or a prospectively
triggered axial scan (120kV, 200mAs, CTDI vol
13.3mGy), rotation
time 0.27sec. Hypo- and hyperdense artifact volumes
were quantified using thresholds of -45 and 175HU. Image
noise and artifacts were compared between protocols.
Additionally, mean image noise and radiation dose were
compared between 6 patients with mechanical PHVs
scanned with a prospectively triggered protocol and 20
30
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