Exam: CT

About CT scanning

CT scanning (Computer Assisted Tomography, CAT Scan) is a radiological technique that has been in use since the late 1970's. It uses x-rays to acquire anatomic information about the body that is presented in "cross-sectional" format, allowing physicians the capability to see more details than conventional x-rays. The procedure uses x-ray technology to produce a three-dimensional image of a cross-section of your body. A conventional x-ray produces a two-dimensional image of an entire body area, such as an arm, leg, torso or breast. x-rays are predominantly used to image bones, whereas the cross-sectional nature of CT scanning allows it to image soft tissues such as organs.

Please refer to each anatomic location for more detailed information on the use of CT according to anatomy.

At Nutley we use an absolute state-of-the-art 64 detector Toshiba Acquilion CT scanner. It is currently the most advanced CT scanner available. Its 64 detectors mean a much faster exam...scanning is so fast that it allows us to perform studies of the Coronary Arteries. It is used, however, also as a general purpose CT scanner for any part of the body.

At all offices, our CT images are forwarded to a 3D workstation, a Vital Images Vitrea workstation, where we perform sophisticated multi-planar manipulations and 3D reformations to extract the most information out of each exam

At West Caldwell, we have a Toshiba Acquilion 32 detector scanner, and at Park St. a 16 detector scanner. The spatial resolution is identical to the 64 detector scanner we have in Nutley, though the scan times are slightly less. For the purposes of all applications except Coronary Artery Imaging, which we currently do not perform at West Caldwell or Park St., the scanners are identical.

At all offices, our CT images are forwarded to a 3D workstation, a Vital Images Vitrea workstation, where we perform sophisticated multi-planar manipulations and 3D reformations to extract the most information out of each exam. Most of the images on this website are post-processed on a Vital Images Vitrea workstation.

What to expect

CT scanners are open machines, not tubes like some MRI machines. They look like a doughnut. As a patient, you will simply have to lie on the CT table as it goes in and out of the doughnut. For some exams you will be asked to hold your breath in order to stop breathing motion (CT exams of the Chest and Abdomen). Some exams require an IV injection of CT IV contrast material, which is performed as the scan is being acquired. Whenever IV contrast is required, then a period of fasting is required before the exam. In addition, some abdominal exams (but not all) also require patients to drink before the exam (Oral contrast).

The entire exam lasts no more than 30 minutes, but most of this is preparation for the exam, ie, putting you on the table, putting in an IV line (if IV contrast is needed), and positioning you. The actual exam time itself is no more than 20 seconds. During this time, you will be moved into the doughnut (the CT gantry), and the technologist will give exact, easy to follow instructions (ie, when to hold our breath, if necessary). For most exams, all you have to do as the patient is relax and be sure to be still (motion will degrade the quality of the images, and may make a repeat of the exam necessary). During the exam you will hear the apparatus of the CT scanner moving, but you will not feel a thing.

As soon as the scanning is finished, the images are almost immediately available to one of the CT specialized radiologists at Montclair Radiology who will analyze them and make a detailed report immediately to your doctor.

CT IV Contrast Material

Some CT exams require an IV injection of iodinated contrast material. This is an aqueous solution containing Iodine. It is injected through an IV catheter, and is distributed through your bloodstream. It is picked up by all organs, and renders organs more easily seen on CT scans. Its main use is to allow radiologists to visualize pathologic tissues more easily. Imagine an inflamed tissue...that tissue usually has a bigger blood supply than a non-inflammed organ, and it therefore gets more contrast material delivered to it...it is therefore brighter on the CT scan images. Without the contrast material, many inflammed tissues cannot easily be distinguished from normal tissue. The same is true of malignant (cancerous) tissue...they usually have a more exuberant blood supply than normal tissue, and IV contrast material enables the radiologist to detect them more easily. In fact, some malignancies, if small enough, would be not detectable without IV contrast material.

Iodinated contrast is very safe. It is distributed in your blood, and is excreted by your kidneys, within minutes of the injection. There are two instances when it should not be used:

1) Patients with kidney failure. Since it is excreted by the kidneys, if your kidney function is not good, you should not have IV contrast. We have guidelines when it is safe to use IV contrast, and that is why you may have been asked to have a blood-test before the exam, in order for us to assess your kidney function. Rest assured, if you are going to have an IV injection of CT contrast, we would not do this without having checked your kidney function. Young, non-diabetic patients without a history of kidney disease need not have kidney function checked.

2) Patients with a history of an allergic reaction to iodinated contrast. There is a small population of people who will have a contrast reaction to iodinated contrast. The reaction is usually mild (itchiness and hives), but may be more severe (breathing problems). We routinely screen patients for a history of allergies before approving an exam with iodinated contrast. We also use modern "non-ionic" contrast materials, which are well tolerated, even by people with a history of contrast reactions.

For people with a history of contrast reactions, "pre-medication" with oral steroids (prednisone) is an effective way to avoid reactions. Your doctor can prescribe you a short course of prednisone (usually 3 pills during the day before the exam).

During the injection of iodinated contrast, you may feel flushed, or mildly nauseated. This is normal, and is not a reaction. This sensation will last only a few seconds. The injection usually lasts about 20 seconds. There is a diuretic effect of iodinated contrast, and you will almost certainly have to urinate shortly after the exam.

If you have any questions about CT iodinated contast please feel free to talk to one of our radiologists or nurses.

CT Oral Contrast Material

Most CT exams of the abdomen and pelvis will require you to drink oral contrast before the exam. This contrast contains either iodinated fluid or a dilute suspension of barium. Its purpose is to make your GI tract bright, and allow the radiologist to see it clearly. Without it, it is often difficult to distinguish loops of bowel from possible pathologic entities, such as masses or fluid within the abdomen.

There are no risks. It is not absorbed, and you will pass it right out. For barium oral contrast, it is recommended that you drink a few cups of water after the exam and during the day, to dilute it further. Contrast reactions only occur with IV iodinated contrast, and not with oral barium. In addition, your kidney function is only important in determining whether IV contrast is suitable, and not oral contrast.

Oral contrast and IV contrast are frequently both administered for abdominal and pelvic exams...this is normal, and they do not replace one another. Oral contrast makes the bowel brighter, and IV contrast makes the vessels and organs brighter.