Free CT software for PCs tracks perfusion

The technique of creating a quantitative map of tissue perfusion from dynamic CT data by means of a color scale was demonstrated some years ago. But it is not generally available because the necessary computer software has not been widely distributed.

A new paper reports on the development of free perfusion CT software for personal computers (Acad Radiol 2002;9(8):922-926).

MRI and ultrasound provide detailed anatomical information, but the spatial resolution is much lower than CT, according to Dr. Yoshito Tsushima of the diagnostic radiology and nuclear medicine department at Gunma University Hospital in Japan. Perfusion CT is a new application yielding high spatial resolution.

It may have the potential to evaluate angiogenesis of malignant tumors, since increased microvessel density within liver nodules leads to increased tissue perfusion, or blood flow per unit volume of tissue.

"In our study, reliable perfusion CT images were created in most cases with our software, which works in standard personal computers," Tsushima said.

Perfusion CT imaging is able to combine quantifiable information about perfusion with detailed anatomical information in one image and can be readily performed with conventional helical CT scanners.

Creating perfusion CT images, however, requires special software, which is usually expensive. One commercial version costs approximately $40,000. As an alternative, Tsushima has developed free software called Basama Perfusion, which is available in both Macintosh and Windows versions at no cost from http://www.basama.net/perfusion/index.htm.

To transfer the dynamic CT images online to a Macintosh computer, Tsushima used DICOM protocol and an available file transfer protocol client software (Fetch 4.0.1, from Fetch Softworks, Hanover, NH). The images were subsequently compressed into a 256 x 256 matrix, from which he created quantitative maps of arterial and portal perfusion using a software development tool called Realbasic 2 (Real Software, Austin, TX).

Portable perfusion images, however, were successfully created only in 38% of examinations. Patient motion during the single-section sequence or slight differences in anatomy among the dynamic CT images because of different breathing levels make it difficult to create reliable portal perfusion CT images, Tsushima said.

The technique cannot be used in patients who unable to hold their breath for about 25 seconds, but the development of multidetector CT addresses this limitation.