Corrections within processing software such as the Back-Projection Algorithm (for CT or NM/PET) or the Fast Fourier Transform (for MRI) are unable to overcome or remove the century-old Penumbra Effect.
But this effect may be overcome by the following post-processing Computer Aided Detection (CAD) algorithm. The Penumbra Effect (refer to Figure1 (Figure A) for the definition of Penumbra-Spread) causes blurring at the image edge-profile due to the size of the energy-source.
A CAD software based...
Methods and Materials
(I) Phantom-Calibrations - A New York Catphan 500 was examined using Single Slice helical CT using technique factors of 120 kVp,
10mm slice. Penumbra Spread,
and processing time were measured: Coin & Wire Phantom was also used to study the removal of Penumbra Effect at the edges of a Guide Wire. (II) Field-Studies:- (1) MR breast tumor images (3D T1 W Fat suppression with Gadolinium enhancement (T1_3D_FS+GD)) was used for the...
Calibrations – Penumbra spread,
Area/Volume Accuracies- Penumbra spread = 2.4 pixels (or 1.30mm for pixel size = 0.54mm) across using a 1.2mm X-ray tube-spot. Distance – At high-contrast & 1% low-contrast edge,
both accurate to 1/50 th of a pixel in (delta)r (i.e.
(delta)r in (delta)r/r); and, Area/Volume – At high-contrast & 1% low-contrast edge,
accurate to 1/18 th & 1/10 th of a pixel respectively in (delta)r (i.e.
2(pi)r(delta)r/(pi)r 2 or (delta)(area) = 2(pi)r(delta)r...
The penumbra spread effect can not be overcome by current digital enhancement as its true edge position is not located.
But this deconvolution technique permits sensitive and accurate edge-profile detection and enhancement to overcome the century old 'penumbra spread' problem without any trade-off loss. Applications are:- (1) coordinates of edge-profile may be fed into a mathematical model for oncological treatment monitoring &/or advanced physiological research study, and (2) in fracture...
(1) "A De-Convolution Technique used for NDT in X-ray & CT".
K.M.Chui et al.,
Oral/Full paper presentation in 17th World Conference on Non-destructive Testing (17WCNDT),
( NDT.net - The e-Journal & Database of Nondestructive Testing - ISSN 1435-4934). (2) "The line spread function and modulation transfer function of a computed tomographic scanner".
Technical Inquiries – For technical inquiries or slide-set,
please contact Dr.
Kui Ming Chui at E-mail: firstname.lastname@example.org or via www.iet.org.uk .