Morphological Angiography

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Project members

Prof. Hans Knutsson	Project manager, Supervisor	IMT, LiU
Mats Andersson	Expert	IMT, LiU
Torbjörn Kronander	CEO	SECTRA-Imtec
Magnus Hemmendorff	PhD student	IMT, LiU, and SECTRA-Imtec

Introduction

Angiography means depiction of blood vessels using X-ray. To increase the contrast of the blood vessels a contrast media is injected. The development of the contrast media is recorded in a sequence of images. To remove the static background e.g. bones a mask image is constructed from the initial frames and subtracted from the following frames (Digital Subtraction Angiography, DSA). If the patient moves during the image acquisition motion artifacts are introduced. The traditional method to reduce motion artifacts is for the physician to do a manual pixel shift of the affected images. This is tedious work and a global pixel shift can only compensate for pure translations.

DSA and pixelshift originate from ancient photographic methods. In spite of the fact that today angiography sequences are recorded digitally and advanced image processing methods offer more powerful signal processing DSA and pixelshift still dominate the clinical work.This project is carried out in cooperation with with SECTRA-Imtec and is supported by the Swedish National Board for Industrial and Technical Development, NUTEK.

Motion Artifacts

Motion artifact i an angiography image of a knee. The patient has rotated his/her leg during the image acquisition. The magnitude and direction of the artifact vary with the position in the image and cannot be compensated for by traditional pixelshift methods.

Time to Arrival

Computation of time to arrival of contrast pulse for the above sequence. The color scale red-green-blue indicate the time to arrival of the contrast pulse. The arrival time is obtained from the phase of a quadrature filter in the temporal direction. Digital image processing offer a huge variety of methods for presentation, color coding and time to arrival is one of many possibilities.

Synthetic pulse Sequence

An alternative method is shrink the duration of the pulse syntetically. A short color coded pulse improve visualization of the flow dynamics. View MPEG sequence.

 

Movies

The following movies are digital versions of our video tapes. The format is multiframe GIF.

• Motion Compensated Digital Subtraction Angiography (5 Mb)
• Estimation of multiple transparent motions and separation of layers. 20 frames (1.5 Mb)
• Estimation of multiple transparent motions and separation of layers. 50 frames (3.5 Mb)

Pressklipp

Dagens Medicin, 12 Maj 1998 Svår matematik kompenserar direkt för rörelse vid angiografi (336k)