X-ray or gamma ray systems or devices – Auxiliary data acquisition or recording
Patent
1998-08-19
2000-07-04
Porta, David P.
X-ray or gamma ray systems or devices
Auxiliary data acquisition or recording
378163, 378165, H05G 128
Patent
active
06084941&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device comprising a body with known dimensions so designed that, through a simple, visual comparison between the body and a measurement object you can get a good appreciation of the body dimensions. (This should be valid irrespective of whether the object can be regarded directly or via a chain of information transformations, finally resulting in a picture of the object.) The invention has its primary application at the measurement of dimensions of objects that are difficult to reach, e.g. organs and foreign bodies within humans and animals.
The invention is founded on the fact that the human eye, badly equipped for absolute size estimation, gives strikingly good accuracy when comparing similar objects placed near each other. As an exception the comparative measurement may be accomplished at direct watching the measurement object, but as a rule a reproduction of the measurement object is watched. The picture is normally an X-ray picture but may, alternatively be produced with other electromagnetic radiation, such as infrared or visible light (in connection to endoscopic activity) or with ultrasonics. It can be directly analogue, as on a photographic film or digital and presented at a display.
A common way to measure the size of reproduced objects is to introduce a graded scale, e.g. a ruler. The dimensions of the object can then be measured at the picture and the measurement results transferred to the scale at the picture, where the real measure can be read. This implies, however, an active measurement with ruler or compasses or the like by means of which the measurement value can be transferred.
In modern X-ray installations the picture is digital and visible at a viewing screen. This is covered with a protecting glass. This glass prevents the compasses from reaching the very picture. If you try to measure you will get measurement errors or uncertainties because of parallax as well as due to perspective related scale distortion. Additionally, the scale normally is different for the reproduction in the digital picture of the object and the ruler. The reason is that the object and the ruler are not situated in the same plane. Modern zoom technology adds another scale factor. This does not facilitate the establishment of the correct product of all more or less known scale factors. Extensive additional work in the form of checking, retakings and recalculations is required. This takes long time, implies in itself a source of error and may further increase the X-ray exposure of the patient and the radiologist.
One has tried to avoid these disadvantages by replacing the ruler by a scale introduced in the very blood-vessel as part of a catheter, a so-called measurement catheter. Said part is provided with a row of marks of radioopaque material aligned in the longitudinal direction of the catheter. Like the measurement object they are visible at the X-ray picture. One example of embodiment of a measurement catheter is given in the patent letter DE 42 15 119 A1. Instead of distances between scale marks determined lengths of X-ray transparent material are here used as longitudinal length measure.
The french patent letter FR 8804892 presents another variant of measurement catheter the image of which, to the extent it can be measured, provides a possibility to create an opinion of the scale of the reproduction. The catheter image also provides a possibility to calculate to which extent the direction of the catheter in the human body deviates from being perpendicular to the X-rays. The deviation can be calculated from the geometry of the catheter image.
Measurement catheters are all intended to be introduced percutaneously in the human body. Their use therefore involves a risk of infection and wastes considerably the expensive time of the doctor and of his assistants. They are also very expensive.
Measurement catheters allow fairly the reading of the longitudinal size of observed organs to the extent that the measurement catheter can enter the domain the length of which is of interest
REFERENCES:
patent: 4873707 (1989-10-01), Robertson
patent: 5149965 (1992-09-01), Marks
Calluna Ide AB
Hobden Pamela R.
Porta David P.
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