Radiation Science Project



Radiation Science Project

CT vs MRI (The Spine)

Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) are the most common modalities after general x-ray and Ultrasound. They are being used most of the time nowadays to detect abnormalities. Those modalities are being used when it is difficult to diagnosis and see abnormalities on plain x-ray films. Both CT and MRI give us clear pictures of the internal body parts with a very high spatial resolution. They both use computer to form the image of the internal body parts. CT is used most to look at bones, hard tissues and abdomen’s organ, while MRI is preferred more to see the soft tissues because they show more clearly in MRI than they do in CT. Radiation is used in CT while magnet field is used in MRI.

In my project I am going to discuss the difference between MRI and CT and there advantages and disadvantages in imaging the spine.

← Spine Tumors:

Spine tumors can also be called spine cancer. It can arise from the vertebra of the spine. Also tumor can arise at the spinal cord tissues and in this case it calls the spinal cord cancer and this kind of tumor is rare. The common symptom of the spine and the spinal cord cancer is back pain at the site of the tumor. Therefore, usually when a patient complains of a back pain the doctor will request an MRI scan for the patient spine after having plain x-ray film of the spine. MRI is used because it gives us better details of the tumor’s size. And it can provide us with three-dimensional image of the tumor and that will help the specialist to know how the tumor looks like and how big it is. MRI gives us the exact location of the tumor without the use of ionizing radiation. Therefore, that will help the specialist during operation or during chemotherapy to know the tumor site and it size. In addition, using MRI will prevent the patient from getting radiation dose, which might harm the patient because as it was mentioned before we are using magnetic field and that means that there is no radiation involvement. Moreover, MRI reduces the risk of contrast reaction because it gives us a clear image of the tumor and in case contrast is needed Magnevist contrast will be used, which is safer than Iodine Based Contrast, which is being used in CT. So if the patient is allergic to contrast MRI will be used instead of CT, which requires from us to inject the patient with a contrast media and the patient might get allergic to contrast (ADAM; 2003).

MRI will be done to see the spinal cord tumor and the spine bone tumor to see the bone marrow. However, for further diagnosis CT might be done to see the bony bit of the spine and how the tumor affected it.

MRI will not be used if the case was urgent because usually MRI takes a long time to perform the images. Also it requires the patient to keep still without moving because if the patient moved the scan should be repeated all again. Usually in emergency cases the patient can not be still for a long period of time. So as alternative CT scan will be used. Although the tumor in CT will not be as clear as the tumor in MRI, it will give us some information about tumors. MRI is better in tumor detection because it has the ability to differentiate the tissues. Also we can take several sequences with MRI, which will give us more details because we can take 2D sagittal and coronal images, so we can have an over view of the whole tumor from all direction. Also in the new CT we can get 2D images, but in MRI there is no radiation involvement, while in CT there is. In CT we will need to inject the patient with a contrast media to see the tumor and the blood vessels surrounding it and that can be done by using CT angiography. And that will keep the patient in risk if he was allergic to contrast. Also we will be using radiation, which will increase patient dose and that might cause some health problems for the patient in the future. But, one of the biggest advantages is that CT doesn’t need long time to perform the image as MRI need. Therefore, it is preferred to use CT in emergency cases.

The only time that MRI might be used in emergency cases is when the patient suffers from bowel or bladder incontinence or from progressive weakness in the leg due to nerve damage. This will help in early diagnosis of the problem, so the patient can be treated in a short period of time. Because if the patient did not diagnosis the problem early it might get worst, as we know diseases that are not treated earlier might developed to a serious case. Therefore, MRI is being done to see the nerves and the disks as they occur more clearly in MRI that they do in CT.

Nowadays Spinal navigation technology is being used by surgeon before performing a surgery. This new technology gives us a 3 dimensional image of the spine, so the doctor can plan the surgery before hand by measuring the spine and the size of the tumor and the way they remove it and what size materials they need to perform operation. Moreover, another new imaging technique has been introduced by doctors at Mount Vemon Hospital in London. This technique allow specialist to combine two images one is a CT image and the other is an MRI image by using special computer software. And that will help them to know the exact location of the tumor, it size and shape for radiotherapy. Therefore, less damage will be caused to the healthy tissue surrounding the tumor (World Health; 2003).

← Spine Trauma:

Spine trauma is any injury or damage of the spine, the spinal cord and the tissue surrounding them, which might be caused by car accident, sport injuries, falls and others. Usually as a start for diagnosis a plain x-ray film will be taken as a first step. But the doctor will ask for CT if it was a serious injury case and if the doctor is querying any bone fracture. CT will give us cross-sectional imaging of the patient spine, which then can be reconstructed into 3-dimensional image and that will show us any bone injury. Also small fractures is easy to detect by using CT. CT has a good resolution in detecting bone abnormalities more than MRI. Added to that, fresh bleeding is very clear on CT, so if there was any bleeding an area of hyperdense will be clear on a CT images. After CT and after patient stability MRI might be requested to make sure that there are no damages happened to the spinal cord, ligament and discs because MRI will show them more clearly than CT does. One of the disadvantage of using CT is the patient dose, but if the problem was mainly bone fracture mAs can be reduced and that will reduce the patient dose (Amersham Health; 2003).

MRI will only be requested if the patient is stable because if it was an emergency case the patient will not be able to keep still for a long time, which will require from us to repeat the scan again. And if the patient was unconscious MRI will not be done because the patient might have metals such as pacemaker, aneurysm clip and other metals things, which might be pulled to the magnet and cause farther damage to the patient.

Nowadays portable CT is being used for emergency cases. This allows the scanning to be done in the ward rather than brining the patient to the department, and the images have the same resolution as the normal CT images.

← Disk Herniation:

A condition in which part or all of the soft, gelatinous central portion of an intervertebral disk is forced through a weakened part of the disk, resulting in back pain and leg pain caused by nerve root irritation is called disk herniation (ADAM; 2003).

It usually affects the lumber region of the spine because it carries most of the body weight. MRI and CT are used to detect this abnormality, but MRI is preferable more because it can show us the nerves and the disks clearly without contrast. In MRI the herniated disk looks black comparing it to the normal disks because it became dry as it lost the fluid from it and it slip to the back and press on the nerves as it show in the picture below.

MRI-Compatible Spinal Compression Harness device is use nowadays to give us a clearer images of the spine and the intervertable disks. It works by applying force on the spine during the examination. It made of non-metallic footplate connected to shoulder pads by adjustable elastic cords and it applies force and this force make the spine image more detailed than the normal images (Zyn System; 2003).

In spine MRI the patient lies with his back on the bed on a special coil, which is usually called spine coil. This coil acts as a detector, which receives the signals. Then the patient is being entered to the machine with his head first. Different images sequences is being taken some images might be axial and some might be sagittal depending on what the doctor request. T1 and T2 will be used to see the changes. Finally, the image can be printed or saved in CD for further diagnosis.

← Conclusion:

CT and MRI are developing day after day. The newest CT and MRI have been introduced lately to most of the hospitals, which are made by GE Medical System. The new MRI has the ability not only to take the routine images such as spine and brain, but also it has the ability to perform vascular, cardiac and spectroscopy. Also this system is very fast for example if the scan used to take 20 minutes now we will be able to take 3 minutes only. What is more, we will be able to see stroke within minutes of the onset. It usually takes many hours or days before one can see stroke with CT, but in the near future stroke will be shown very quickly. Added to that, it was very difficult to see the heart by using MRI before. However, nowadays this is done very easy by using MRI, as it will give us a clear image of the heart anatomy, function and the blood vessels surrounding it in a real time mode without any trouble and this is done by using ECG gating (Scripps, 2003; SouthernUtah, 2003).

Also CT has developed, now the scan time has been reduced from 3 minutes to 20 seconds, which mean the time has been eliminated. Moreover, the image quality is still the same. To sum up, images can be taken fast, so diagnosis can be done fast and that will save our valuable time.

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MRI

Spine Tumor

MRI

Disk Herination

CT

Spine Fracture

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