CT Scan Protocols PDF

Computed Tomography  COMPUTED TOMOGRAPHY  Ct head protocols  :BY AHMED JASEM ABASS  MSCof Medical Imaging Computed tomography (CT) of the head  uses special x-ray equipment to help assess head injuries, severe headaches, dizziness, and other symptoms of aneurysm, blee...

Computed Tomography  COMPUTED TOMOGRAPHY  Ct head protocols  :BY AHMED JASEM ABASS  MSCof Medical Imaging Computed tomography (CT) of the head  uses special x-ray equipment to help assess head injuries, severe headaches, dizziness, and other symptoms of aneurysm, bleeding, stroke, and brain tumors. It also helps to evaluate your face, sinuses, and skull or to plan radiation therapy for brain cancer. In emergency cases, it can reveal internal injuries and bleeding quickly enough to help save lives. What is CT Scanning of the Head?  Computed tomography, more commonly known as a CT or CAT scan, is a diagnostic medical imaging test. Like traditional x-rays, it produces multiple images or pictures of the inside of the body.  The cross-sectional images generated during a CT scan can be reformatted in multiple planes. They can even generate three-dimensional images. These images can be viewed on a computer monitor, printed on film or by a 3D printer, or transferred to a CD or DVD.  CT images of internal organs, bones, soft tissue and blood vessels provide greater detail than traditional x- rays, particularly of soft tissues and blood vessels.  CT scanning provides more detailed information on head injuries, stroke brain tumors and other brain diseases than regular radiographs (x-rays). Prepration  You should wear comfortable, loose-fitting clothing to your exam. You may need to wear a gown during the procedure.  Metal objects, including jewelry, eyeglasses, dentures and hairpins, may affect the CT images. Leave them at home or remove them prior to your exam. You may also be asked to remove hearing aids and removable dental work. Women will be asked to remove bras containing metal underwire. You may be asked to remove any piercings, if possible. What are some common uses of the procedure?  CT scanning of the head is typically used to detect:  Bleeding, brain injury and skull fractures in patients with head injuries.  Bleeding caused by a ruptured or leaking aneurysm in a patient with a sudden severe headache.  A blood clot or bleeding within the brain shortly after a patient exhibits symptoms of a stroke.  Brain tumors.  Enlarged brain cavities (ventricles) in patients with hydrocephalus.  Diseases or malformations of the skull.  CT scanning is also performed to:  Evaluate the extent of bone and soft tissue damage in patients with facial trauma, and planning surgical reconstruction.  Diagnose diseases of the temporal bone on the side of the skull, which may be causing hearing problems. Determine whether inflammation or other changes are present in the paranasal sinuses.  Plan radiation therapy for cancer of the brain or other tissues.  Guide the passage of a needle used to obtain a tissue sample (biopsy) from the brain.  Assess aneurysms, arteriovenous malformations, and blood vessels through a technique called CT angiography. What are the benefits vs. risks?  Benefits  CT scanning is painless, noninvasive and accurate.  A major advantage of CT is its ability to image bone, soft tissue and blood vessels all at the same time.  Unlike conventional x-rays, CT scanning provides very detailed images of many types of tissue as well as the lungs, bones, and blood vessels.  CT examinations are fast and simple; in emergency cases, they can reveal internal injuries and bleeding quickly enough to help save lives. Benefits  CT has been shown to be a cost-effective imaging tool for a wide range of clinical problems.  CT is less sensitive to patient movement than MRI.  CT can be performed if you have an implanted medical device of any kind, unlike MRI.  A diagnosis determined by CT scanning may eliminate the need for exploratory surgery and surgical biopsy.  No radiation remains in a patient's body after a CT examination.  X-rays used in CT scans should have no immediate side effects. Risks  There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis far outweighs the risk.  The effective radiation dose for this procedure varies. See the Radiation Dose in X-Ray and CT Exams page for more information about radiation dose.  Women should always tell their doctor and x-ray or CT technologist if there is any chance they are pregnant. See the Safety in X-ray, Interventional Radiology and Nuclear Medicine Procedures page for more information about pregnancy and x-rays. Risks  CT scanning is, in general, not recommended for pregnant women unless medically necessary because of potential risk to the baby. This risk is, however, minimal with head CT scanning.  IV contrast manufacturers indicate mothers should not breastfeed their babies for 24-48 hours after contrast material is given. However, the most recent American College of Radiology (ACR) Manual on Contrast Media reports that studies show the amount of contrast absorbed by the infant during breastfeeding is extremely low. For further information please consult the ACR Manual on Contrast Media and its references Risks  The risk of serious allergic reaction to contrast materials that contain iodine is extremely rare, and radiology departments are well-equipped to deal with them.  Because children are more sensitive to radiation, they should have a CT exam only if it is essential for making a diagnosis and should not have repeated CT exams unless absolutely necessary. CT scans in children should always be done with low-dose technique. Rotine Adult Head (BRAIN)  PATIENT POSITIONING:  Patient should be supine, head first into the gantry, with the head in the head-holder whenever possible.  Center the table height such that the external auditory meatus (EAM) is at the center of the gantry.  To reduce or avoid ocular lens exposure, the scan angle should be parallel to a line created by the supraorbital ridge and the inner table of the posterior margin of the foramen magnum. This may be accomplished by either tilting the patient’s chin toward the chest (“tucked” position) or tilting the gantry. While there may be some situations where this is not possible due to scanner or patient positioning limitations, it is considered good practice to perform one or both of these maneuvers whenever possible. PATIENT POSITIONING: CONTRAST:  Oral: None.  Injected: Some indications require injection of intravenous contrast media during imaging of the brain.  Intravenous contrast administration should be performed as directed by the supervising radiologist using appropriate injection protocols and in accordance with the ACR Practice Guideline for the Use of Intravascular Contrast Media. A typical amount would be 100 cc at 300 mg/cc strength, injected at 1 cc/sec. A delay of 4 minutes between contrast injection and the start of scanning is typical. AXIAL VERSUS HELICAL SCAN MODE (both are provided in the following sample protocols):  There are advantages and disadvantages to using either axial or helical scans for routine head CT exams. The decision as to whether to use axial or helical should be influenced by the specific patient indication, scanner capabilities, and image quality requirements. Users of this document should consider the information in the following table and consult with both the manufacturer1 and a medical physicist to assist in determining which mode to use. CT SCAN PROTOCOLS(without and with contrast)  Scan Coverage: Just below foramen magnum through vertex. IF TRAUMA, begin below the anterior C1 arch.  Scan Plane: Stacked axial, parallel to line from orbital roof to external auditory meatus  Scan Slice thickness: 5-3 mm.  Reconstruction Slice Thickness: 1 mm.  kVp, mA, Rotation Time: 120, 250 – 400, 1s.  Non-contrast study; soft tissue algorithm; then repeat with:  Contrast: 50cc Omnipaque 300 IV, Soft tissue algorithm.  Soft Tissue Window: WC : 40, WW : 80  Contrast injection protocol: -  1- Non-contrast performed first.  2- Delayed phase post-contrast acquisition.  - 50 cc hand injection or 1 cc/s via injector.  - Delayed acquisition: >5 minutes post-contrast injection. CT SCAN PROTOCOLS(without and with contrast) Thank You