Aims and objectives
Extended field of view (EFOV) algorithms to estimate the projection data outside the SFOV have been reported1).
EFOV is capable of reconstructing images of wider FOV than SFOV (Fig. 1),
but EFOV algorithms cause image distortion and CT value reduction2)(Fig. 2).
We reported that bolus improves eFOV distortion and CT value decrease at ECR 2017,
2018.
HD FOV Pro is SIEMENS's new eFOV algorithm.
However Siemens' new eFOV algorithm,
HD FOV Pro was announced.
The purpose of this study was to compare distortionand CT value...
Methods and materials
CT scanning
A whole-body phantom and two arm phantoms were scanned on a SOMATOM Definition AS+ (eFOV) and Biograph mCT(HD FOV Pro)(Siemens Medical Solutions.
Germany).
The scan parameters were set at 120 kV,
50 mAs,
1.0 s/rotation,
128 × 0.6 mm detector configuration(eFOV),
40 × 0.6 mm detector configuration (HD FOV Pro) and a pitch of 1.0.
Images were reconstructed at B40s kernel,
3mm slice thickness,
and 650mm display FOV.
Using the point where the limbic region around the upper arm of the phantom meets...
Results
CT Value of eFOV
When eFOV was Without Bolus,
the CT value decreased from offset 1 cm or more.
The CT value was the lowest at offset 4 cm.
With Bolus,
the CT value decreased from offset 2 cm or more.
In Offset 4 cm,
the CT value was not improved by Bolus,
and the CT value was reduced to -400 HU.
There was no large CT value difference between Bolus 0.5 cm and Bolus 1 cm.
The CT value improved by 61% at the...
Conclusion
HD FOV Pro had lower CT value and distortion than eFOV.
The eFOV significantly decreased CT value at offset 4 cm.
The algorithm used for eFOV is extrapolation.
Offset 4 cm was not properly extrapolated because sinogram was truncated because of bone at the boundary between FOV and Extended FOV.
However,
HD FOV Pro was presumed to be able to appropriately extrapolate even if sinogram was truncated due to the change of the extrapolation method.
The distortion by HD HOV Pro improved by up to...
Personal information
Toru Esaki
Jichi Medical School Hospital,
Department of Radiology
E-mail:
[email protected]
References
1)Hsieh J,
Chao E,
Thibault J,
et al.
A novel reconstruction algorithm to extend the CT scan field-of-view.
Med Phys.
2004 Sep;31(9):2385-91.
2)Beeksma B,
Truant D,
Holloway L,
et al.
An assessment of image distortion and CT number accuracy within a wide-bore CT extended field of view.
Australas Phys Eng Sci Med.
2015 Jun;38(2):255-61.