CT Scans

Computed tomography, also called CT, is an X-ray procedure that produces detailed images of the body and head, providing information about the internal organs, bones, and soft tissues. The procedure is painless and noninvasive, though it may be used to guide minimally invasive procedures. Formerly referred to as computed axial tomography, or CAT scans, CT scans require a patient lie still for only a few minutes. During this exam, the patient lies on a movable table that slides into a large, round shaped scanner. Often it is necessary to use contrast media in order to better visualize organs and diseases. Contrast media may be given by mouth, as well as through an IV in a vein. The exam type will determine the need for these.

CT scan images are obtained using x-rays and a computer. The x-ray tube rotates around the part of the body to be examined and thin "pictures" are taken. As the pictures are being taken, the table moves through the cylinder. A brief medical history will be taken and the procedure explained. Depending on the procedure, the patient may be asked to drink a barium solution prior to their procedure or at the time of the procedure. This helps to identify certain structures such as the stomach and intestines. The majority of procedures involve an intravenous injection of a special contrast. This is used to identify certain structures such as the liver, spleen, pancreas or kidneys. During the injection, the patient may experience a warm sensation throughout the body. Depending on the procedure, many only take 5 minutes to complete while others are 30 minutes. CT scan procedures are fast, safe, and produce important medical information.

MRI

Magnetic resonance imaging uses magnetic fields and radiowaves to produce detailed internal images of the body. This procedure does not utilize X-rays (radiation), common to most other radiology procedures. MRI procedures are safe and painless, however, patients are asked to complete a questionnaire concerning their compatibility within a magnetic field. The MRI is a sensitive examination used to diagnose disorders of the brain, spine, bones and joints. It also may be a test used to study organs including the heart, gallbladder, pancreas, liver and spleen.

High Resolution MRI

This technique is an extension of clinical Magnetic Resonance Imaging (MRI), but uses greater magnetic field strengths to induce the hydrogen nuclei in biological tissue to absorb and emit radio waves in order to produce an image. The image contrast is determined mainly by the relative abundance and chemical position of hydrogen protons in the tissues. Also referred to as ‘spins’. The proton data used to create the image is collected by exciting the hydrogen spins with a sequence of radio-frequency pulses. After the excitation has ceased, the spins begin to relax and yield a signal known as the echo that provides information on the location and concentration of the protons. Since proton chemistry differs between tissue types, different soft tissues with sufficient hydrogen can be identified. Those tissues with very little hydrogen, like bone, appear as signal voids (empty space) in the image. This technology allows us to see internal structures by making what appear to be ‘slices’ through tissues without disturbing the actual specimen.

Ultrasound

Ultrasound is acoustic energy with frequency above the audible range (e.g. 3.25 MHz). It will penetrate into the human body, for instance to a depth of 14 cm as in the image. The image is obtained by repeated transmissions of sound pulses from a probe. The sound is reflected from the structures in the body and then received by the probe. The signal is then processed and interpreted with respect to depth and direction, and displayed as an image on a screen. The image represents a cut through the body. This image shows a view through the left ventricle, i.e. the chamber that does most of the work in pumping the blood. The image update rate is important for cardiac imaging since the heart is moving through the cardiac cycle. The normal frame rate is 20-50 times per second.

The electric signal from the heart, the ECG signal, is also shown with the image (the light blue curve). The heart contracts for each peak in this signal. The ECG signal and the ultrasound image are combined by the interpreter and together they give information on leaks or stenosis of the cardiac valves, reduced movement of the heart wall (infarction) etc.

Ultrasound examinations are performed with the use of a probe (also called a transducer) that emits sound waves, listens to their reflection, and makes an image from that reflection. This procedure is non-invasive and painless. Diagnostic ultrasound is performed for a wide variety of indications, including obstetrical evaluation, identifying gallstones, and evaluating aneurysms. In addition, Doppler technology, similar to that used by weather stations, can be incorporated into the procedure. The Doppler technology is especially useful in evaluating blood flow.