Radiology
Toshiba tests 256-slice CT

CT scanning technology is taking another giant stride forward with the development of a 256-slice scanner. Middle East Health reports.

CT scanner technology hits another exciting milestone with the testing of Toshiba’s 256-slice CT scanner in Japan in the past year, and now also in the United States following the recent installation of a prototype scanner at Johns Hopkins University School of Medicine.

Johns Hopkins will test the beta system at its Heart Institute in Baltimore for its value in early assessment of critical radiology and cardiac CT protocols. The 256-slice will be tested for a limited period only, to obtain data that will help to further clinical research and product development.

Toshiba’s describes 256- slice system as “the next revolution in CT scanning”, but emphasises that it is a work-in-progress. It is designed to obtain a large amount of data and can cover the brain or heart in a single rotation. It should provide more detailed images with lower radiation dose.

Prototype

The introduction of the 256-slice CT scanner promises to make major contributions to CT instrumentation, Japanese radiologist Dr Kazuhiro Katada, who has been working with a prototype of the system in Japan, was quoted as saying on the Auntminnie.com website.

Dr Katada, who is chairman of the department of radiology at Fujita Health University School of Medicine in Japan, has been involved in CT development since 1975.

He’s been evaluating the 256-slice CT for the past year. He said that a scanner with 256 slices is the logical progression of CT’s development towards ever-more detector rows.

However, the unit presents a big challenge in terms of data transmission and image review applications, because it generates such a large amount of information. A typical 256- slice brain or cardiac study could include up to 5,000 images. A more detailed neuro exam at a higher resolution could generate more than 10,000 images. As a result, new software tools would need to be developed to manage this data for it to be useful in a clinical environment. “The data is there, but how do you extract the information?

“If you cannot see it, you cannot make a diagnosis. Which means the 256-slice CT would not work as a clinical tool,” Dr Katada said.

Toshiba is currently working on image-review applications with a partner company and is developing the hardware needed for such large volumes of data. In his presentation to Stanford University’s International Symposium on Multidetector-Row CT last June, Dr Katada said that one of the biggest benefits of 256- slice system is its potential to move beyond the helical scanning paradigm that has been in place since the first spiral scanners arrived on the market in the late 1980s.

According to AuntMinnie.com, a website focussing on radiology, Dr Katada said: “Even with the growing anatomical coverage possible with 64- slice CT, images from several gantry rotations must be reconstructed and merged to form a 3D image of a single organ, such as the heart. “This can lead to banding artifacts because the ‘strips’ of anatomy in the image weren’t collected in the same gantry rotation.”

He said that with 125 cm of organ coverage, 256-slice CT is able to scan the entire heart in one rotation. This concept will enable clinicians to dispense with slices and will open up a whole new world of scanning. An obvious clinical application is cardiac imaging. In addition to reducing banding artifacts, 256-slice CT can be conducted without the use of ECG gating, which is commonly used in cardiac CT angiography to compensate for the fast cardiac motion. This means that all data, from the top slice to the bottom slice, is collected during the same phase of the heart. Dr Katada’s team has used its 256-slice system to produce 4D images (3D moving images) of the heart.

He said: “Another promising clinical application is brain imaging of patients suspected of stroke. One programmed scan sequence could be used to collect the entire study, from non contrast CT, to contrastenhanced CT for CT angiography (CTA), to the CT perfusion study.

“All these three can be done in a single sequence. Three scans at one time, and that will help reduce the time for the diagnosis.” The 256-slice system has been used recently to image the hearts of two human volunteers. They showed that the system could successfully visualise the coronaries, myocardial contraction and myocardial enhancement during a single imaging exam.

They also found the system’s radiation dose to be approximately 2mSv per second, allowing either very low-dose, single-shot coronary imaging or lowdose dynamic imaging that can visualise the coronaries while concurrently obtaining detailed perfusion information. Toshiba says it will be able to obtain whole organ evaluation and perfusion in a single rotation, which will bring about many new areas of study in functional CT imaging.

Toshiba’s 256-slice scanner is yet to get regulatory approval.

                                  
                                                     Copyright © 2007 MiddleEastHealthMag.com. All Rights Reserved.