Using the Fourth Dimension to Distinguish Between Structures for Anisotropic Diffusion Filtering in 4D CT Perfusion Scans - Longitudinal Registration and Shape Modeling - page 73

Using the Fourth Dimension to Distinguish
Between Structures for Anisotropic Diffusion
Filtering in 4D CT Perfusion Scans

B

Adrienne M. Mendrik 1(

) , Evert-jan Vonken 2 , Theo Witkamp 2 ,
Mathias Prokop 3 , Bram van Ginneken 3 , and Max. A. Viergever 1

1 Image Sciences Institute, University Medical Center Utrecht,
Utrecht, The Netherlands
[e-mail]
2 Radiology Department, University Medical Center Utrecht,
Utrecht, The Netherlands
3 Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands

Abstract. High resolution 4D (3D+time) cerebral CT perfusion (CTP)
scans can be used to create 3D arteriograms (showing only arteries) and
venograms (only veins). However, due to the low X-ray radiation dose
used for acquiring the CTP scans, they are inherently noisy. In this
paper, we propose a time intensity profile similarity (TIPS) anisotropic
diffusion method that uses the 4th dimension to distinguish between
structures, for reducing noise and enhancing arteries and veins in 4D
CTP scans. The method was evaluated on 20 patient CTP scans. An
observer study was performed by two radiologists, assessing the arter-
ies and veins in arteriograms and venograms derived from the filtered
CTP data, compared to those derived from the original data. Results
showed that arteriograms and venograms derived from the filtered CTP
data showed more and better visualized small arteries and veins in the
majority of the 20 evaluated CTP scans. In conclusion, arteries and veins
are separately enhanced and noise is reduced by using the time-intensity
profile similarity (fourth dimension) to distinguish between structures
for anisotropic diffusion filtering in 4D CT perfusion scans.

1 Introduction

Cerebral CT perfusion (CTP) scans are acquired to detect areas of abnormal
perfusion in patients with cerebrovascular diseases [ 1 , 2 ]. They consist of mul-
tiple sequential 3D CT scans over time, acquired after an injection of contrast
material. Besides perfusion maps, vascular information can be derived from high
resolution CTP scans [ 3 - 6 ]. In [ 4 , 5 ] we proposed a method to derive 3D arte-
riograms (showing only the arteries) and venograms (only veins) from 4D CTP
scans. A limitation of CTP scans is, however, the low X-ray radiation dose that
is used to acquire the multitude of sequential 3D CT scans over time. There-
fore these scans are inherently noisy. Reducing the noise in these CTP scans
has the potential to improve the quality of the CTP-derived arteriograms and
c