X-ray or gamma ray systems or devices – Electronic circuit – Object responsive control
Patent
1997-07-03
1999-04-20
Porta, David P.
X-ray or gamma ray systems or devices
Electronic circuit
Object responsive control
378 982, H61B 600
Patent
active
058964398
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the object characterized in the claims, i.e., a process for avoiding radiation injury in diagnostic radiology, as well as a device for implementing this process.
In the case of some modern radiological problems, especially in contrast-enhanced computer tomography, the recording time is to be synchronized with the arrival of the contrast medium bolus in the tissue section in question. This is especially necessary in the case of vasography (CT angiography). At present, the exact transit time of the contrast medium bolus from the injection site to the particular tissue section can be only roughly estimated. Today, the problem that the arrival of the contrast medium bolus in the tissue to be examined can be determined only imprecisely is generally solved by triggering the x-ray source even before this contrast medium bolus arrives. The drawback to this approach consists in the fact that the irradiation lasts longer than absolutely necessary. A solution to this problem is described in German laid-open specification DE 42 18321 A1. The diagnostic system that is indicated there has the drawback that the measurement of the contrast medium bolus is done either by a radioisotope source, which in turn contributes to the radiation exposure of the patient or, on the other hand, by adding an optically detectable dye, which for its part increases the foreign substance burden on the patient.
Therefore, there is still a need for a process that allows synchronization with the contrast medium bolus at the x-ray source, without unnecessarily burdening the patient with foreign substances or additional radiation.
This object is achieved by the process according to the invention and the device for implementing this process.
The process according to the invention consists in the fact that the natural components of the blood stream or lymph tract are measured with the aid of a sensor. When the contrast medium bolus arrives at the tissue to be examined, the natural bodily fluid is displaced (diluted) by the arrival of the contrast medium. The change in the physical properties of the bodily fluids can be measured and produce the necessary signal for triggering the x-ray device. In an advantageous embodiment of the process according to the invention, the concentration of the blood pigment hemoglobin is measured by, for example, transmission or reflection spectroscopy. When the signal drops below an adjustable setpoint value, the x-ray source is triggered.
The process according to the invention has the advantage that the arrival time of the contrast medium bolus in a specific tissue section can be precisely determined without additional radiation or foreign substance burden. In another advantageous embodiment of this process, it is also possible to measure the drainage of contrast medium. As a result, it is possible to limit the irradiation time of the patient to the time during which a sufficient amount of contrast medium is available in the tissue that is to be examined.
Preferred is a process whereby the sensor is a measurement device for determining the concentration of blood components. Especially preferred is a process in which the concentration of hemoglobin is determined by transmission or reflection spectroscopy. For measurement, the light sensor of a device (e.g., Multiscan OS 10 or OS 15) is placed on the skin over a peripheral vein or artery. As a result, the absolute hemoglobin content of the blood can be determined. After a medium, e.g., a contrast medium that is commonly used in CT is injected, the hemoglobin concentration briefly dips, and a signal that can be picked up by a sensor is thus produced. This signal is processed by the setpoint switch. If the signal is adequate, the pulse generator activates the radiation source. After the contrast medium bolus passes through the examination area, the sensor detects the rise in hemoglobin concentration. After a setpoint is exceeded, the radiation source is shut off.
Another embodiment consists in the fact that the sensor is a flow gauge. Since the m
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Holik, Von B., Methode zur Vermeidung der Becken-Bein-Angiographie miy schrittweiser Tischplattenverschiebung, Electromedia, vol. 45, No. 1, pp. 2-6, 1977.
Krause Werner
Kruger Uwe
Muschik Peter
Porta David P.
Schering Aktiengesellschaft
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