Temat Projektu: Perfusion Monitoring System - Oprogramowanie do wspomagania badań perfuzyjnych wykonywanych technikami rezonansu magnetycznego i tomografii komputerowej

Termin: 2000-2003

Project Description

The goal of the project is to design a radiological imaging system capable of quantitatively monitoring organ flow/perfusion. This information is essential for the improvement of several surgical (including minimal invasive intervention procedures) and pharmacological treatment techniques so that they will be generally less costly and less traumatic to the patient, involving smaller incisions, less pain, and shorter hospital stays. There are several commercial systems available today, offering so called 'perfusion imaging' based on dynamic scanning protocols. They use theoretical background developed in early Fifties for nuclear medicine purposes, slightly modified for rapid sequence tomography. Execution speeds, complicated theoretical background, insufficient robustness and the relative non-quantitative character of the final image mean that perfusion imaging, based on the dynamic scanning procedure, is popular in research applications, and still not accepted by routine clinicians. In order to gain acceptance from clinicians, another approach to the problem is proposed. Instead of starting from a technical consideration of the system and methodology details, a interdisciplinary technical/medical group will be involved, created previously in two successful European TEMPUS projects. The group consists of world known medical and technical experts in the medical imaging area, who can define medical targets and clinical applications, as well as solve technical and research problems such as image registration (Belgian group), parametric imaging (Polish group), cardiac modelling (Austrian group). First, a scanning procedure satisfying physiological and pathological models, for chosen organs will be created by the clinicians, in order to create a cross-centre comparable case database. On this base, perfusion imaging methodology and instrumentation will be designed, leading ultimately to the final commercial imaging/monitoring system. Existing data from Graz (over 200 cases of dynamic CT), and Leuven (over 100 dynamic MRI) will be used in the Definition Phase. Perfusion relevant images called either parametric or functional images can be obtained from X-ray computed tomography (CT), Magnetic Resonance Imaging (MRI), Electron Beam Tomography (EBT) modalities, through a special sequential scanning after injection of a contrast medium. This kind of examination, called a dynamic study, forms an image sequence, that monitors the first pass transit of injected boluses of the contrast agents, through an organ of interest. In order to assess organ perfusion, physicians need a system with repeatable and robustly relate physical organ flow properties (like for example volume flow in ml/(min*g)) with parameters extracted from time stack of images obtained in dynamic scanning procedures. The theoretical basis of the operation was originally introduced by Stewart and proven for intravascular tracers by Meier and Zierler for radioactive tracers in nuclear medicine. Flow is estimated from the registered time stack of images using the Central Volume Principle - theoretical base of the indicator-dilution methods that have become popular for the measurement of flow through an organ or tissue. Both these two-stage procedures (dynamical scanning protocol and based on CVP theory image generation algorithm) affect the quality of the final parametric image. Weisskoff showed that CVP does not hold for MR or CT dynamic data of purely intravascular tracers; moreover, due to measurement noise, a very time consuming, fitting procedure has to applied to the original data.

Technological Development Envisaged

The following main technological developments will be performed:

• Dynamic scanning protocols development for the vascular system, brain, heart, kidney, aorta and peripheral vessels, designed by the world known specialists allowing cross- centre comparison study, as well as quantitative flow/perfusion assessment;
• User interface software to the perfusion monitoring system developed in close collaboration with clinicians more appropriate to their work and their needs;
• Parametric image creation procedures, new flow estimating methods, models and faster, more robust methods than those currently available, dedicated to the data obtained in already described dynamic scanning protocols;
• Implementation of the most time consuming procedures on TMS320C80 multi-DSP processor board. The C80 integrates four programmable DSP processors, a RISC processor, and a sophisticated DMA controller on a single chip. Various parallel processing approaches are supported by this architecture enabling support of a wide range of video, image, and signal processing applications with speed up to 2 billion operations per second.

Market Application and Exploitation

The application focuses on an entirely new development, which uses either real-time MRI or CT as a means of monitoring treatment procedures. This capability would be particularly appealing for use in conjunction with the emerging methods of minimally invasive surgery such as ablative procedures using lasers, cryoprobes, or focused ultrasound. Interventional systems incorporating new technology such as superconducting magnets, that allow physicians to have access to heir patients during a scan are already undergoing trials and are predicted to radically alter the ways surgical procedures will be performed in the 21st century. The prognoses for the intervention radiology market in the year 2000 show an increase of up to 500 million US dollars. This forms a basis for the new developments and products in this area. Moreover, all traditional pharmacological and surgical treatments can be monitored with the new system. This opens up a wide new drugs market. All the developments will be performed in close collaboration with the relevant clinical partners. This will ensure that the developed procedures are needed by the clinicians and have an excellent chance of being successfully marketed.