MR

FLUOROSCOPY

A.Shajitha

B.Sc Radio Diagnosis Technology

Madras Medical College

FLUROSCOPY

Fluoroscopy is a method of obtaining real

time images that is especially useful for

guiding a variety of diagnostic and

interventional procedures.

The ability of fluoroscopy to display motion

is provided by a continuous series of

images.

Types of fluoroscopy

Conventional fluoroscopy

CT fluoroscopy

MR fluoroscopy

MR FLUOROSCOPY

Magnetic resonance fluoroscopy is a

method for high speed MR image

acquisition.

Short acquisition time per image(500

msec or less).

High image rate ( 10 or more per sec ).

High speed image reconstruction (150

msec 0r less).

MR fluoroscopic image were acquired with a

limited flip angle pulse sequence with reduced

repetition times(TRs) and fewer phase encodings

used per image.

The sequence is applied continuously.

Images are formed by updating one set of data

with data from the most recently taken.

Artifacts from the motion become less evident on

images as progressively shorter acquisition time

is used.

In the MR fluoroscopy, high rate imaging,

reconstruction and display are performed

sequentially, periodically for a slice of a

subject.

Real time images of the slice are displayed.

The image reconstructing time for a

slice is substantially adjusted to the

imaging time for the slice.

So that images if slice can be

displayed in real time.

The acquisition is a modification of the basic

sequence FLASH.

But with a restricted number of phase encodings.

The encodings are applied continuously.

Images are formed by sliding a window of width

encodings along the acquired data and

reconstructing an image for each position of the

window

MR fluoroscopy offers guidance and monitoring

advantages that enable one to perform biopsy

and cross-sectional imaging in near real time.

The advent of MR fluoroscopy has made it

possible to obtain images at a rate that can be

considered real time in terms of effectiveness

Image rates can be as low as 1 second,

which is fast enough to facilitate MR

imaging guidance of biopsy procedures.

Such procedures include the localization of

biopsy needles within a tumor and the

localization of surgical tools for

administering therapeutic drugs

The advantages of MR fluoroscopy are

near-real-time imaging and the absence of

radiation hazards.

A potential disadvantage of MR fluoroscopy

is that the image feedback with this system

is not as immediate as that with US, CT

fluoroscopy, or x-ray fluoroscopy.

With CT imaging, it is possible to identify fissures, focal

areas of emphysema and thereby avoid these areas

during biopsy.

MR imaging does not offer this advantage.

MR imaging is not routinely used for evaluation of the

lungs, mediastinum, or pleura in practice, but it is an

established tool for evaluation of the thoracic vasculature

and chest wall.

And is used as an alternative to CT for evaluation of the

mediastinum in patients who are allergic to intravenous

contrast agents.

Contrast-enhanced coronal T1-weighted image shows a left temporal abscess and

infection of the temporal bone (A). Image of the drainage seen during MR

fluoroscopy image (B).

Contrast-enhanced coronal image demonstrates a subdural emphysema

in occipital localization (A). The needle has ruptured the capsule and is

seen in the abscess cavity (B). The interhemispheric fissure is seen very

close to tip of the needle, but it is intact. After the drainage, no pus is

seen in the abscess localization (C).