JPH01166750A - Nuclear magnetic resonance image diagnostic apparatus for angiography - Google Patents

Abstract

PURPOSE:To enhance resolving power, by dividing the thickness of a slice into a plurality of thicknesses to calculate the angiograms of respective slices and adding said images to obtain a final angiogram of a angiographic range. CONSTITUTION:With respect to a region desired to be imaged, especially, to a thickness direction, the thickness of each of slices and the number of the slices are set to perform imaging in the same way as a multistylus. Angiograms at every slices are obtained by the 'Subfraction' between images. As a method for adding the obtained angiograms at every slices, a method (A) for simply adding said images and a method (B) for adding the same at every regions carrying angiogram at every slices are used. Especially, in the method (B), no division is performed with respect to a Y-axis and the images are partially added with respect to an X-axis. Since a thickness direction is divided, the signal data in the thickness direction is reduced in partial volume effect by the reduction quantity of the slice thickness and the signal data of the angiograms can be effectively reflected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a nuclear magnetic resonance imaging diagnostic apparatus, and particularly to imaging and image configuration suitable for drawing blood vessels.

[Conventional technology]

For blood vessel drawing using nuclear magnetic resonance imaging equipment, please refer to
Similar to line angiography, the slice thickness of the blood vessel depiction range is often set to 30 to 100I.As the slice thickness becomes thicker, the partial volume effect causes the image resolution (especially the resolution in the depth direction) to increase. ) decreases.

This is a disadvantage in diagnosing blood vessel morphology.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into account the partial volume effect in terms of slice thickness, and there is a problem in that the resolution decreases when depicting blood vessels.

An object of the present invention is to prevent resolution degradation due to this partial volume effect.

[Means for solving problems]

The above purpose is to measure the thickness direction (slice thickness) of the blood vessel visualization range.
Divide the image into multiple parts, and use the same method as multi-slice to add the blood vessel images obtained based on each divided image to finally construct a blood vessel drawing with a thickness that covers the blood vessel drawing range. Can be done.

[Effect]

The course of blood vessels is not simple, therefore, 5 mm.

Since it cannot be covered completely within a single slice plane of 10 mm, a thick slice plane of 30 to 100 mm is used. Generally, a 256×256 matrix is used to form an image of the - plane (slice plane), so the size of one pixel is about 1 mm, which means that it has a considerable resolution. However, if the slice thickness direction is 3o~100mm, then 30~100mm of the plane
The value is doubled, and the resolution is reduced to 1/30 to 1/100. If we compare this with the slice thickness of 10 mm for general radiography, it will be reduced to 173 to 1/10.
If you take three images of 0mm and combine the three images to create a 30mm thick image, then
The resolution can be improved three times compared to the one that takes 30mm images.

Furthermore, signal information for drawing blood vessels also has the effect of reducing the partial volume effect.

〔Example〕

FIG. 5 shows the configuration of a nuclear magnetic resonance imaging diagnostic apparatus used in the present invention. As you can see from the figure, it has a standard configuration.

An embodiment of the present invention will be described below with reference to FIGS. 1, 2, 3, and 4. First, set the slice thickness and number of slices for the area you want to photograph, especially in the thickness direction, and photograph in the same way as multi-slice. The pulse sequence is generally S R (Saturation
Recovery method is used.

Furthermore, the imaging timing is synchronized with the rising edge of the R wave of an ECG (electrocardiogram), and the diastolic signal of the first slice is captured. (Gate delay 1). Then, the systolic signal of the first slice is acquired with a delay of 100 to 200 m5ec from the R wave (Gate delay 2). Furthermore, diastolic and systolic signals are similarly captured for the second slice plane. The diastolic and systolic signals of each slice obtained as described above are captured for 256 projections to form an image.

The diastolic and systolic images for each slice obtained in this way are separated by 5 ubfra between images, as shown in Figure 2.
By setting it as ction, a blood vessel drawing for each slice can be obtained. As shown in Fig. 4, there are two methods for adding together the blood vessel drawings for each slice obtained in this way: a simple addition method (A), and a method for adding each region in which blood vessels are drawn for each slice. Method (B) is used.

In particular, method (B), as shown in FIG. 4, does not divide the Y-axis, but adds parts of the X-axis. In the example in Figure 4, the first slice plane is 1 to 10 on the X axis.
The figure shows how 90 to 190 matrices are added on the second slice plane, and 180 to 256 matrices are added on the third slice plane up to 0 matrix.

As you can see above, since it is divided in the thickness direction, the partial volume effect is reduced as the slice thickness is reduced, and the signal information in the blood vessel drawing can be effectively reflected in the signal information in the thickness direction. .

For example, when the thickness of a blood vessel is 3 mm and the slice thickness is 30 mm, the effectiveness of signal information for blood vessel drawing for three 10 mm slices can be evaluated as follows.

In the case of imaging with 30 mm slices (assuming that the signal information for blood vessel drawing in systole and diastole is 0.9° and 0.1, respectively,
Assuming that the signal information of muscles etc. is 0.5, the contraction period (3X0.9) / ((3X0.9) + (27
+0.5)) =0.167 diastole (3XO,1) /
((3xo,t)+(27+0.5)) =0.02
2 The difference between systole and diastole is 0.167-0.022=0
．． It becomes 145. On the other hand, in the case of three 10 mm slices, the systolic period (3X0.9) / ((3X0.9) + (7
+0.5)) =0.435 diastole (3X0.1) /
((3X0.1)+(7+0.5)) =0.079
The difference between systole and diastole is 0.435-0.079 =
It becomes 0.356.

Comparing one 30 mm slice and three 10 mm slices, 0.35610.145=2.46 That is, it can be seen that the present invention is superior as signal information for drawing blood vessels.

In addition to the method shown in the example (ECG synchronized subtraction method, i.e., subtraction between images when blood flow is fast and slow), blood vessel drawings can be performed using a phase-insensitive pulse sequence and a phase-sensitive method. There are also subtraction methods between images with pulse sequences. The present invention can be applied to either method.

〔Effect of the invention〕

According to the present invention, the slice is divided in the thickness direction.

Since each blood vessel drawing is created and combined to obtain the original blood vessel drawing, the partial volume effect can be reduced, which has the effect of effectively reflecting the blood vessel drawing information. For example, if the thickness of the blood vessel is 3 mm, the slice thickness is 3 mm.
Blood vessel drawing information with three 10mm sheets is approximately 2 for 0mm.
．． Improved by 4 times.

[Brief explanation of the drawing]

FIG. 1 is an imaging pulse sequence diagram of an embodiment of the present invention.
Figure 2 is a diagram showing the image obtained by the pulse sequence in Figure 1 and a method of synthesizing blood vessel drawing from that image.
The figure shows the great saphenous vein and the imaging site, FIG. 4 shows a method of compositing divided images, and FIG. 5 shows the configuration of MRI. 1... Great saphenous vein of the right lower leg, 2... Imaging site and slice position, 3... Static magnetic field, 4... Gradient magnetic field coil,
5... RF irradiation coil, 6... RF receiving coil, 7
...For patients 10 Atsushi Figure 4

Claims (1)

[Claims] 1. A nuclear magnetic resonance imaging diagnostic apparatus comprising a static magnetic field, a gradient magnetic field (for X, Y, and Z axes), an RF transmitting/receiving coil, an image processing unit, an operation console, and a patient table,
When capturing a blood vessel depiction image, the slice thickness is divided into multiple slices, a blood vessel depiction image of each slice is obtained, and these blood vessel depiction images are added together to finally obtain a blood vessel image of the blood vessel depiction range. Features: Nuclear magnetic resonance imaging system for drawing blood vessels. 2. Nuclear magnetism for blood vessel drawing according to claim 1, characterized in that, as a method for adding blood vessel drawing images of each slice, a portion where a blood vessel is drawn on each slice plane is selected and added. Resonance imaging diagnostic equipment.