Computed tomography: the reasons for the appointment and procedure
Computed tomography (CT) is considered the main method of diagnosis of internal diseases not requiring surgery. For examination of the authorities used X-rays.
But unlike a standard x-ray device, a computer unit of the imager converts images to high-quality three-dimensional image. This allows the doctor details, different angles to consider which organ is affected.
CT can layer by layer to explore the whole body: bones, joints, soft tissues, tendons, blood vascular. The thickness of the layers is 1 mm. But the CT scan clearly visible structure, which will not show normal x-rays. Experts also say the increased safety of the method. Radiation exposure from CT scan is much lower than in other types of x-ray.
Indications for imaging
The method is used for diagnosing a number of pathological processes:
- Vascular disorders (aneurysm, hemorrhage, atherosclerosis);
- Injuries and penetrating wounds of the internal organs;
- Diseases of the heart and blood vascular;
- Detection of obstruction of the urinary tract, presence of stones in the kidneys and bladder;
- Damage to the eyeball;
- Pathology of the paranasal sinuses, the ear canal;
- Diseases, injuries and fractures of the joints, bone tissue;
- Trauma to the spinal column;
- Anomalies of development of organs;
- The nature, localization, stage of growth of various tumors.
Brain damage, headaches, unclear nature of speech disorders. In these cases, can be assigned to computed tomography of the cervical spine.
Scanning is also performed for routine diagnosis and monitoring of treatment. In addition, using CT to verify the accuracy of medical procedures (biopsy, abscess drainage).
Contraindications for CT scan
- Pregnancy. X-rays adversely affect dividing tissue;
- Body weight more than 150 kg;
- Mental disorder, inadequate behaviour of the patient;
- The poor condition of the patient.
Patients often ask how often you can do a cat scan. The time interval between routine examinations is 6-12 months. The consequences of more frequent exposure is the risk of cancer. In urgent cases, CT is performed without consideration of time.
For more clear pictures of the body using special coloring solutions — radiopaque amplifiers:
- Barium, or barium sulfate. Them traditionally performed CT of the abdomen withcontrast agent.
- Gastrografin, urografin.
- Nonionic iodine: omnipak, Universal, Ultravist.
The body enhancers are introduced in three ways: oral, intravenous and rectal. Rarely practiced inhalation method involving the inhalation of xenon. Inhaled gas used to make detailed pictures of the brain or lungs.
Intravenous injection is carried out manually or using an automatic injector. New generation drugs (Ultravist and equivalents) non-toxic, are excreted from the body within a few hours.
Indications for contrast
Particularly precise and detailed images required for the following conditions:
- Vascular disease — embolism, thrombosis, narrowing of the lumen of the artery, damage to the vascular wall. Computed tomography of the head provides for the mandatory introduction of amplifiers;
- Malignant neoplasms of any localization. For example, if you suspect kidney cancer pathology: no contrast it is difficult to distinguish a cyst from a cancerous tumor;
- Lung disease. Using coloring preparations clearly distinguished pathology of blood vascular, bronchi, mediastinum;
- Abscesses, cysts, inflammatory processes of internal organs;
- Direct contraindications to increased;
- Thrombophlebitis of the vein into which the drug is introduced;
- Acute renal failure, preventing the removal of the dye from the body;
- Multiple myeloma;
- Diabetes mellitus;
- Allergy to contrast solutions.
After the CT scan, with amplifiers it is recommended to drink more fluids to accelerate excretion of contrast media.
Preparing the patient for scanning
When scanning of the head and neck should remove jewelry, glasses, hairpins, hearing AIDS, dentures, braces. The fact that under the x-ray beam, the metal becomes very hot and may cause burns. Clothing should be loose and comfortable. In some cases, the radiologist suggests for the patient to change into disposable underwear.
6-8 hours before the procedure is prohibited to eat solid food. Clear liquids you can drink, but in the most limited quantities. The ban stems from the fact that the amplifiers taken on an empty stomach will provide a good quality pictures. In addition, the introduction of contrast with a full stomach may cause nausea.
The procedure scan is painless but some discomfort can deliver the injection or drink radiopaque solutions. They taste bitter, and intravenous injections may receive sensation of heat,a metallic taste on the tongue.
Sometimes during the scan, the person experiences nausea, headache. This should immediately tell a technician on the loudspeaker.
Please tell us about your nervousness, tendency to claustrophobia, possible panic attack. In this case, the patient is administered a sedative medication.
You must also notify the radiologist if you have any implanted electronic devices or metal parts (ligature and surgical staples).
How is the procedure
The MRI scanner is a big machine with short inner tunnel. Inside the housing is mounted a movable ring with an electron-ray tube and sensors. The ring rotates according to the trajectory set by the computer. Unit is connected to the scan table.
To protect medical staff from x-ray tomograph installed in a separate room.
The patient is placed on the table in the desired position — on the stomach, back or side. If necessary, record the correct position of the body using a belt. This helps the patient to hold the specified position, reduces the risk of inadvertent displacement.
X-ray computed tomography is usually conducted by a technician-technologist. Analysis of the finished shots makes the doctor-the radiologist, it gives the conclusion.
Radiology technician degree, handcuffing the patient and giving him some advice, goes into another room, where the computer unit of the device, the monitors and equipment that monitor the patient's condition. Premises are connected with the window through which the technician observes the patient, hears him and talks with him on a two-way speakerphone.
How to do self-scanning? When activated, the machine table moves into the zone of the tunnel. The radiologist monitors the movement of the table, defining the scanning area and a start point. The patient on the cycle time of the transmission are asked to hold their breath to ensure a complete immobility of the body.
Any movement dramatically affects the information content of images — the image will appear blurred, and the procedure must be repeated again. The total duration of the survey does not exceed 30-40 minutes.
Single-photon imaging for each scanning cycle (one full revolution of the ring displays a single layer of a given thickness. Table advances to the next stops, the scanning is performed again.
After each turn the emitter on the computer screen there is a picture of the cross-section. So, step by step, going full information about the diseased organ. How many layers you want to explore, so many times isthe translucence of the body.
Spiral imaging is different because ray tube rotates continuously around the inspected area, making layered shots. The table at this time is constantly moving in one direction, whereby the trajectory of the emitter adopts a spiral form.
Express rotation beam cutting and continuous movement of the table reduce the procedure time. The specified object is scanned completely during one-time breath hold.
This means that patients spend less time under the influence of harmful radiation. Also facilitates diagnosis in patients who are not able long to hold my breath and long to be inside of the imager (the elderly, the infirm, small children, victims with injuries and wounds).
Multislice computed tomography
Another new technology is multislice scanning (MSCT). Its difference is that the scanner built two ray tube and several rows of sensors. The procedure is performed within seconds. The scope of CT:
- Emergency cases when the doctor must make a quick decision on further action (penetrating wounds, ruptures of internal organs).
- The study is small and moving structures.
- Revision of coronary arteries after operations on heart vascular, bypass surgery, stenting), and evaluation of narrowing of the lumen of the artery.
When scanning creates a highly accurate projection of the examined organs. The introduction of contrast dye is necessary. Multislice computed tomography has no other contraindications except severe reaction to iodine. The radiation load on the body, compared with SKT, reduced by 30%.
Features scanning different areas of the body
Computed tomography of the abdomen performed on an empty stomach. Bloating and full stomach would be a serious obstacle for CT.
A few days before the procedure ought to go for products that do not cause flatulence and other problems with a chair.
Prior to imaging is recommended to take sorbents. This is usually activated carbon, Smectite, Polifepan.
If there are any problems in the digestive tract, specialist pre-inspection will prescribe antispasmodics, laxatives or an enema.
Computed tomography of brain is carried out without special training. During scanning, the radiologist can lock the head straps to the random motion did not worsen the image quality. Intravenous contrast agents are introduced below in the images wassee the small defect of the vessel.
CT scan of the spine performed to diagnose these conditions:
- Intervertebral hernia;
- Compression fracture of the spine due to osteoporosis;
- Narrowing of the spinal canal;
- Tumors of the spine.
Computed tomography of the lumbar spine may reveal hemorrhage in the spinal cord, vertebral instability, the growth of osteophytes.
The imaging of children
The child's body is much more susceptible to radiation exposure than an adult, so CT children designate in the case of urgent need. Diagnosis is carried out on a conventional scanner. To reduce the intensity of radiation is not always possible: in children a high percentage of water in soft tissue, making them hard to see.
Preparing for the scan is no different from that for adults. 4-5 hours before the CT scan can not eat or drink. Parents should tell the child how the scanning and why it is needed. Unprepared children are often frightened when they are placed on a hard table and fasten the straps.
Recommended together with the baby to practice holding the breath.
The parent is allowed to stay with your baby in the office where scanning. For protection from radiation, he offered to wear a lead apron. Children wear headphones so that they are not afraid of the noise of the MRI scanner.
Kids from 0 to 6 years, as well as hyperactive children who can not long to lie without movements, shows the introduction of sedatives or General anesthesia. A necessary condition for anesthesia — free nasal breathing.
Interpretation of CT data
Decoding of information takes 30-40 minutes, and then conclude with the disc, and images regarding the patient. The result of the tomographic scan is not a diagnosis but only a description of the problem changes body. If there is a serious pathology, the radiologist will call the patient and recommend to consult the correct specialist.
Ionizing radiation MRI is contraindicated in a number of States. But since the survey is still need to carry out, apply other methods of diagnostics:
- Doppler. The method is applied to study the circulatory system. The ultrasonic waves emitted by the transmitter, reflect from the red blood cells and are captured by the device.
- Ultrasound (sonography). Used in obstetrics and gynecology to monitor fetus with the pathology of the thyroid gland and abdominal organs. Ultrasonic wave harmless tobody.
- Magnetic resonance imaging. The technology is based on the influence of a powerful magnetic field, perpendicular to which the device sends electrical impulses. The hydrogen atoms in the body to resonate in response. Device picks up these signals and making them three-dimensional images of organs.
Patients wonder which is better — a CT or MRI? The principle of operation of the devices is radically different, so the choice of diagnosis is dependent on each specific case. The decision is made by the attending physician.
In conclusion. The benefits of CT are obvious: accuracy, informativeness, fast results, safe, painless. High-quality images allow the doctor to put a correct diagnosis and to develop effective tactics of therapy.