Radiology department diagnoses many diseases with the help of various medical devices. Devices used in radiology department;

A.DEVICES THAT USES X-RAY (MAY BE HAZARDOUS IN PREGNANCY)

• 1- X-Ray
• 2- Mammography
• 3- Bone Densitometry
• 4- Computerized Tomography (CT),
• 5- Angiography = DSA = Digital subtraction angiography = Catheter angiography

B.DEVICES THAT USE SOUND WAVES

• Ultrasound
• Color Doppler Ultrasound

C.DEVICES THAT USES RADIOFREQUENCY WAVES

• MRI (Magnetic Resonance Imaging)

COMPUTERIZED TOMOGRAPHY (CT) AND TECHNICAL DATA

Computerized tomography is a radiological diagnostic method that provides cross-sectional (anterior to posterior = coronal; superior to inferior = axial; right to left = sagittal) images of the intended part of the body using x-rays. While images are acquired, patient lies immobile on the table of computerized tomography device. The table is inserted into an empty space, called “gantry", either manually or with a remote control. The device is connected to a computer. While the X-ray source rotates around the patient by 360 degrees, detectors placed in the hole or the “gantry" identify the part of X-ray beam which passes through the body, and the resultant data is processed by a computer. Ultimately, successive cross-sectional images of tissues are created. Created images can be displayed on the monitor of a computer. Moreover, images can be printed on films or stored in the optic disc in order to re-display on the monitor of a computer, if or whenever necessary. Computerized tomography has several advantages over other X-ray imaging systems. Shape and location of organs, soft tissues and bones are especially visualized very clearly. Moreover, computerized tomography scan helps doctors make differential diagnosis of a simple cyst (a formation filled in by fluid or semi-liquid substance and surrounded by a wall) and solid tumor (a lump caused by abnormally quick division of cells) and thus, diseases are better evaluated. More importantly, computerized tomography assists staging of the cancer by creating much more detailed images relative to direct roentgenogram. Information about the stage of cancer assists the doctors when deciding the treatment for cancer, such as chemotherapy, radiotherapy, surgical intervention or combinations thereof. Thus, healthy tissues are protected against unnecessary adverse effects of this treatment, which have substantially beneficial effects in combination with serious side effects. Computerized tomography can image many body parts, such as brain, that cannot be visualized with direct roentgenograms. Moreover, this method enables earlier and accurate diagnosis of the disease comparing to other imaging modalities. Since diseases are better treated when they are diagnosed early, computerized tomography with such superior features help doctors save many lives.

DOES THIS SCAN CAUSE DISCOMFORT? IS THERE ANY HAZARD?

The scan itself is completely pain-free. While images are acquired, patient is asked to lie constantly immobile on the table of computerized tomography device. Depending on the type of examination, either the contrast agent is injected into a vein of arm or taken by the patient by mouth. This part of examination may be somewhat annoying for the patient. Since contrast agents contain iodine, they may lead to allergic reactions in some patients. The patient should notify the technician or radiologist in advance the past history of allergic reaction to such substances or any other substance. The patient might have been given contrast agent in a previous CT, a renal examination called IVP or a catheterization, also called angiography of heart and vessels. CT devices use X-rays. It is designed to maximize safety of patients and it is manufactured to minimize the dose of radiation exposed in the scan. Since X-rays may damage the fetus in the intrauterine life, the patients with proven or potential damage should notify the doctor or technician before preparations for the examination are started.

WHAT HAPPENS IN THE SCAN?

Technician guides the patient to the examination room and makes the patient lie supine or prone depending on the examination. It is very important to make patient feel comfortable, as the patient should not move throughout the scan. Ct scans may vary depending on medical problems of patients and the body parts to be imaged. Radiologist will decide how the scan will be performed to diagnose the disease. For example, the lower part of chest to upper part of pelvis is scanned if CT of abdomen is scanned. In this examination, you will be asked to hold your breath at certain intervals to avoid blurred images. The machine will strange some sounds throughout the scan. The table, where the patient lies on, will slightly move, after each image is acquired. Moreover, technical or machine will send a signal to the patient to instruct breath holding. For certain examinations, the doctor or technician may inject a contrast agent before or during the scan. This will help the radiologist review images better. If the patient feels something unusual during or after the injection, the technician or doctor should be notified. All CT personnel are educated to render the best service for patient and they have necessary certificates in this field.

HOW LONG DOES COMPUTERIZED TOMOGRAPHY LAST?

Examinations are planned separately for each patient by taking into consideration the clinical signs. Therefore, patients should not get anxious, if the current CT scan differs from the previous CT scan or it is necessary to acquire extra images. The entire scan lasts 15 minutes in average.

COMMON INTENDED USES OF CT

CT imaging for Otolaryngologic Conditions: As is the case with other departments, CT is commonly requested by otolaryngologists. The most common conditions are as follows: Diseases of Paranasal Sinuses, Nose and Nasal Cavity: Computerized tomography is the most useful imaging modality for any and all sinus diseases, especially chronic sinusitis, and hypertrophic nasal turbinate as well as tumors. Paranasal sinuses have a complex structure and physical examination provides an insight to a certain extent. However, CT demonstrates anatomic structure of all paranasal sinuses, their orifices draining into the nasal cavity, hypertrohic nasal turbinate and tumors in a very detailed manner. When CT is scanned to examine sinusitis, it is not necessary to use contrast agents or media, but they might be required for tumors.Diseases of Middle and Inner Ear: It provides information about the spread of chronic inflammation in the middle ear, the loss of bone in ossicles of middle ear and other middle ear structures. CT scan will be useful especially if a surgery is considered for chronic middle ear inflammations. Certain types of hearing loss suggest tumors or similar diseases in the middle ear. In such cases, magnetic resonance imaging is scanned, but CT is, sometimes, required, if it is more useful for the patient.Mass lesions in neck: Identification or definitive diagnosis of lumps or growths in neck is one of the most significant challenges faced by otolaryngologists. CT provides very important information about such conditions or even, it might, sometimes, help the diagnosis.Tumors or Other Diseases of Pharynx, Esophagus and Larynx: Since CT creates cross-sectional images, details about spread of tumors or other diseases in these anatomic structures are obtained and the surgery is planned accordingly.

TYPES OF DOPPLER

The blood flow in vessels can be in two configurations in the sonogram. In the first one, vessels are color coded on the ordinary ultrasound image (Color Doppler); and in the second one, the flow is displayed in a graphic form other than the usual sonogram (Spectral Doppler). These graphics are called flow curves and they have unique characteristics for each vessel. In the Color Doppler Mode, the flows towards and against the probe are displayed in red and blue colors on the screen. After the image is acquired and relevant vessel is identified, Spectral Doppler is concomitantly run by focusing on this vessels and mathematical measurements are made for the velocities of blood flow and resistance against the flow in the blood vessel. Since ultrasound scanners with Doppler feature are extremely expensive relative to conventional devices, they are not available in all centers and therefore, Doppler examinations are often made by a doctor other than the doctor who supervises the pregnancy.Detailed ultrasound scan that is incorrectly called “color ultrasound" in colloquial term and requires specialized education and experience differs from Doppler scan.

DIFFERENCES BETWEEN MRI AND CT

In comparison to CT, MRI is superior in following conditions:

• 1. MRI shows healthy and diseases tissues more clearly. Moreover, it uses magnetic signals rather than radiation (X-ray) that is used in CT in order to demonstrate density differences between tissues.
• 2. MRI allows a cross-sectional investigation and accordingly three-dimensional demonstration of anatomic structures. On the other hand, CT images are limited to horizontal slices.
• 3. In MRI, neither patients nor practitioners are exposed to ionizing radiation.
• 4. MRI can image blood vessels without a need for contrast agent through the signals derived from the circulating blood. Accordingly, risks and problems arising out of iodine contrast agent, as is the case with CT, are not experienced.
• 5. MRI allows establish unique tissue diagnosis in the clinical practice that is based on analysis of metabolic processes on viable tissue. It is also necessary to emphasize that comparing to CT, MRI is more influenced by experiences and knowledge of the practitioner. Practitioners need to investigate best physical parameters over the time to study the case.