What Is CT(Computed Tomography) Scan?

 

Computed Tomography, often abbreviated as CT, is a medical imaging technique that uses X-rays and advanced computer processing to create detailed cross-sectional images of the inside of the body. It is also commonly referred to as a CT scan or CAT scan (Computerized Axial Tomography). This non-invasive procedure allows healthcare professionals to visualize internal structures such as bones, organs, blood vessels, and tissues with high clarity and precision. CT scans are widely used for diagnosing a variety of medical conditions, planning surgeries, monitoring ongoing treatments, and providing valuable insights into the body’s anatomy and pathology. The technology’s ability to produce detailed 3D images makes it an invaluable tool in modern medicine, aiding in accurate diagnosis and effective patient care.

 

 

Used Of CT Scan.

1. Bleeding and brain substance injury as well as fracture of skull bones; in a case of head injury.

2. Bleeding caused by a ruptured or leaking aneurysm in a patient with a sudden severe headache.

3. Blood clot or bleeding within the brain shortly after a patient exhibits symptoms of a stroke.

4. Causes of stroke, especially with a new technique called perfusion CT.

5. Brain tumor.

6. Enlarged brain cavities (ventricles) in hydrocephalus.

7. Disease or malformation of the skull.

8. Evaluate the extent of bone and soft tissue damage in patients with facial trauma and help planning surgical reconstruction.

9. Diagnose disease of the temporal bone of skull which may be causing hearing problem.

10. Determine whether inflammation or other changes are present in the paranasal sinuses.

11. Plan radiation therapy for cancer of the brain.

12. C.T. helps to the passage of a needle used to obtain a tissue sample (biopsy) from the brain.

13. Useful to assess aneurysms or arteriovenous malformation through a technique called C.T. angiography.

 

 

PATIENT PREPARATION.

A. Consent

1. The patient is required to provide informed consent before the start of any invasive procedure.

2. Patient consent may be deemed “informed” only when the procedure, including its risks, benefits, and alternatives, are clearly explained in a language the patient fully comprehends.

3. Any patient questions must be adequately answered by qualified personnel before the procedure is begun.

4. The patient or a competent, legal representative must sign a form documenting informed consent for the procedure.

5. A parent or legal guardian must sign the informed consent form for a minor.

6. Implied consent occurs when a patient is in need of immediate medical services but is unconscious or is physically unable to consent to treatment. In this case, services are rendered with the assumption that the patient would consent if able.

 

B. Patient Screening/Education

1. Communication is the key to any successful patient interaction.

2. It should begin during the scheduling/screening process to identify concerns regarding exam tolerance, potential contrast agent contraindications, and so on.

3. Clear and thorough explanation by the technologist at the point-of-care helps make certain that the patient follows the instructions necessary for optimum exam quality.

4. Review breathing instructions when necessary, and include an opportunity for the patient to practice to ensure understanding and compliance.

5. Particularly during contrast studies, the patient should be instructed to empty the bladder before the start of the exam to reduce the possibility of discomfort or interruption.

 

6. Before contrast agent administration, discuss potential physical effects, such as warm sensation and metallic taste so that the patient is not surprised and upset during data acquisition.

7. High-density or metallic items, such as jewelry, hair fasteners, and electronic devices, should be removed when necessary and appropriate.

8. Care must be taken to ensure patient comfort on the CT table. This comfort will result in less patient motion and lead to higher-quality CT examinations.

C. Immobilization

 

1. As with any imaging procedure, patient motion during the CT exam can cause substantial image degradation.

2. CT scan manufacturers routinely include a variety of cushions, straps, and other safety devices that may be carefully used to help the patient hold still during data acquisition. These items are typically nonabrasive and can be utilized in place of medical tape.

3. The breath-hold is another form of patient immobilization required during many CT examinations. Carefully instruct the patient to suspend respiration at the end of inhalation or exhalation, providing a visual example when necessary. Cessation of breathing works to reduce motion and is particularly important during CT imaging of the chest and abdomen.

 

D. Patient History

1. Obtaining an accurate and pertinent patient history is one of the most important responsibilities of the CT technologist.

2. Proper documentation of the patient’s recent procedures, surgeries, symptoms, possible trauma, and specific areas of pain or discomfort can greatly assist the radiologist in the diagnostic process.

E. Patient Monitoring

1. Vital sign assessment is the measurement of basic body functions to monitor critical information regarding the patient’s physical condition.

2. Vital signs are temperature, pulse, blood pressure, and respirations:

a. Normal body temperature is 97°F (36.1°C) to 99°F (37.2°C). Pulse rate for adults ranges from 60 to 100 beats per minute. Pulse rate for children ranges from 70 to 120 beats per minute.

c. Systolic blood pressure indicates the pressure within arteries during cardiac contraction and should be less than 120 mm Hg. Diastolic pressure is measured during relaxation of the heart and should be less than 80 mm Hg.

d. Normal respiration rate for an adult is 12 to 20 breaths per minute, and that for a child is 20 to 30 breaths per minute.

3. A pulse oximeter is an electronic device used to measure pulse and respiratory status. Placed on a patient’s finger, toe, or ear lobe, the pulse oximeter measures blood oxygen levels, which are normally
between 95% and 100%.

4. The cardiac cycle refers to the series of blood flow related events that occur from the beginning of one heartbeat to that of the next.

5. It is the frequency of the cardiac cycle that determines the patient’s heart rate.

6. As related to the cardiac cycle, diastole refers to relaxation of heart muscle, and systole refers to contraction of the heart muscle.

7. An electrocardiogram (ECG or EKG) is a graphic representation of the electrical activity of the heart. It is used particularly during cardiac CT procedures to evaluate the heart rhythm and cycle.

8. Cardiac CT images are typically reconstructed from data acquired during the diastolic phase.

9. Patients with slower heart rates exhibit longer diastolic phases, which yield higher-quality cardiac CT exams.

 

14. Please consult the physician and/or department protocol for further information regarding administration of pharmaceuticals for cardiac CT procedures.

F. Laboratory Values

1. A number of laboratory values are important for the CT technologist to recognize and understand, particularly as they relate to the patient’s capacity to undergo iodinated contrast agent administration

2. Blood urea nitrogen (BUN) and creatinine level are laboratory values used to indicate renal function. These values may be examined individually or in ratio form, as follows:

a. Normal BUN values in adults range from 7 to 25 mg/dL.

b. Normal creatinine levels range from 0.5 to 1.5 mg/dL. Range may also vary with lab reference. An elevated creatinine value (>1.5 mg/dL) may not always indicate renal function compromise, because this value can vary widely with different populations. Recent changes in a patient’s creatinine level are thought to be more informative as a renal function indicator.

 

3. Glomerular filtration rate (GFR) is a more accurate measure of renal function. The normal range of GFR is 70 to 14 mL/min/m2 for men and 60 to 10 mL/min/m2 for women.

 

G. Medications

1. Coumadin is a proprietary name for the generic drug warfarin, an anticoagulant. This drug is used to prevent the formation of blood clots in veins and arteries and may reduce the incidence of heart attack and stroke. Patients undergoing therapy with warfarin or any other anticoagulant are prone to excessive bleeding due to trauma, including intravenous (IV) access for contrast agent administration. The CT professional must take special precautions when providing care to the patient undergoing anticoagulant therapy. Adequate pressure must be applied to the site after IV removal to avoid excessive bleeding and bruising.

2. Metformin, also commonly referred to by the brand name Glucophage, is a drug used to treat type 2 diabetes. Patients are typically instructed not to take a metformin product for up to 2 days following a contrast enhanced CT examination. There is a small risk of renal impairment from iodinated contrast agents, and reduced renal function can cause the potentially harmful retention of metformin within the body. The patient should consult the referring physician for instructions before resuming metformin treatment. A blood test to check renal function may be required.

 

H. CONTRAST MEDIA

Contrast may be indicated for your exam. The contrast media improves the radiologist’s ability to find structures that are abnormal and understand normal anatomy better.

a. Some patients should not have an iodine-based contrast media. If you have problems with your kidney function, please inform your radiologist in advance. We may be able to perform the scan without the contrast media or find an alternate imaging exam.

b. The most common type of CT scan with contrast is the double-contrast study, which will require you to drink a contrast media before your exam begins in addition to the IV contrast. The more contrast you are able to drink, the better the images are for the radiologist to visualize your digestive tract.

 

Advantage of CT Scan

 

1. It is painless, non-invasive and accurate procedure.

2. Able to image bony anatomy, soft tissue, blood vessel all at same time.

3. Provides detail image of many types of tissue as well as lung, bones and blood vessels.

4. The process is fast and simple in emergency cases. Reveal internal injuries and bleeding quickly to save life.

5. Cost – effective imaging technique.

6. Less sensitive to patient movement than MRI.

7. Unlike MRI. CT scan can be done even in patient with metallic implant.

8. CT avoids exploratory laparotomy and surgical biopsy.

9. No radiation remains in body after examination.

10. No side effect.

 

Risks.

 

1. Minimal chances of cancer due to high dose radiation.

2. Womon are advised to tell the radiologist whether she is pregnant.

3. Breast feed is prohibited to baby for 24 – 48 hours if contrast has been given.

4. Serious allergic reaction may occur with iodine containing contrast. Nowadays non-ionic contrast is used.

 

Limitation

 

1. No absolute contraindication.

2. Very large head circumference in relation with Gantry window in conventional CT or over weight patient.

3. Compared to MRI, precise details of soft tissue (Brain) are less visible on CT scan. It is not sensitive in detecting inflammation of meninges.

 

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