The Penumbra-Effect describes blurring at the margins of an image-profile due to the finite size of the energy-source.
A CAD based on the De-Convolution Technique can be used to pinpoint true-edge positions to sub-pixel accuracy and remove the Penumbra-Effect via sub-pixel transfers without trade-off losses (Ref.
Derived from this,
a definitive method of accurate measurement may have been found.
Enhanced edge-profiles may be used for clearer diagnosis and accurate measurements.
62 scan slices of 4 field samples were used to demonstrate the merits of...
Methods and Materials
Composite phantom and New York Catphan-500 and 62 scan slices of four CT and MR field examples were used.
(1) Phantom calibrations:
(i) Penumbra-Spread = 2.4 pixels (1.30mm) using a 1.2mm X-ray tube focal-spot.
(ii) Measurements: Distance & area/volume - At 1% low-contrast,
accurate to less than 1/10th of a pixel.
Guide-wire thickness: (manufacturer's specification) = 0.89mm; measured by a software ruler = 0.91mm,
error = 2.25% (Figure 1).
(iii) High Contrast Resolution - Modulation Transfer Function (MTF) (measured by Judy Method (Ref.
2)) - Improved from 3.38 to 9.61 lp/cm at 50% normalized modulation after 7x magnification and enhancement.
(iv) Processing Time...
(1) As illustrated in Figures 1-4,
that sharper images were obtained by the CAD enhancement for the diagnostic and measurement uses,
(2) With the exception of one point out of the total of 60 points,
the smoothness of the graph-plot profiles in Figure 5 of Average Width and Y-Axis Width versus Slice Positions over the successive year period did indicate the good accuracy in measurements of the methodology.
(3) The critical diameter width measurements of the aneurysm may be used to determine if...
(1) "A De-Convolution Technique used for NDT in X-ray & CT",
by Kui M.
& David B.
Oral/Full paper presentation in 17th World Conference on Non-destructive Testing (17WCNDT),
(www.NDT.net - The e-Journal & Database of Non-Destructive Testing - ISSN 1435-4934).
(2) "The line spread function and modulation transfer function of a computed tomography scanner",
by Judy P.F.,
(3)"The long-term prognosis in untreated cerebral aneurysms: A...
(1) Acknowledgment: - The authors wish to thank Mr.
BSc MS FRCS of Oxford John Radcliffe Hospital for his permission to use image data of CT Angiograms.
(2) Technical Inquiries:- Please contact Dr.
Kui Ming Chui at:-
E-mails: email@example.com or firstname.lastname@example.org or via
(3) Free Power-Point slide-set:- Please contact Dr.
Kui Ming Chui,
(4) Research Collaboration:- Collaborations are very welcomed,
please contact Dr.
Kui Ming Chui for further details.