XRay and CT Prof Alberto Aureli Radiography and

X-Ray and CT Prof. Alberto Aureli

• Radiography and radiology: involves exposing a part of the body to a small dose of radiation to produce an image of internal organs. • Organs with high density such as the ribs and spine are radiopaque , meaning they absorb radiation , and appear white or light grey on the image. • Lung tissue is radiolucent- doesn’t absorb radiation -and appears dark on the image. • Before some types of X-rays are given a liquid called a contrast medium , such as barium or iodine , which is a radiopaque and allows the organ or tissue it fills to be examined. The contrast medium may be swallowed , introduce through the anus as an enema , or given as injection. • Radiology : is the use radiation in the diagnosis and treatment of disease such as cancer.

X- ray examination • The chest X-ray is the commonest diagnostic X-ray examination. Normally a frontal (anteroposterior ) view is obtained. The patient stands facing the photographic plate with the chest pressed to the plate, with hands on hips and elbows pushed out in front. • The radiographer , the technician who takes the X-ray, asks the patient not to move , then to breathe in deeply and not to breath out. This makes a blurred, unclear X-ray image less likely and improves the quality of the image , as it is easier to see abnormalities in air -filled (inflated) lungs than in deflated lungs.

Keep still. Now, take a deep breath and hold your breath. For a side , or lateral view , the patient is asked to stand sideways to the photographic plate with arms raised. A chest X -ray may be repeated at intervals to track for any changes. These repeated examinations are called serial chest X- rays.

Computed Tomography Here is an extract from a hospital’s press release

(CT) Scanner • The Western General has installed a new GE Light. Speed 16 Computed Tomography (CT) Scanner. Ct uses an X-ray source which rotates around the body to produce cross-sectional images. • The new scanner takes up to 16 simultaneous cross- sectional images (slices) and transmits more data in less time ever before. Each slice can be less than one millimeter thick , making it possible to find very small abnormalities

The scanner will be used for: • diagnosis muscle and bone disorders • locating tumors , infections and clots • monitoring the progress of malignant diseases and the response to therapy (treatment) • providing accurate guidance for interventional procedures such as biopsies , and drainage removing fluid from the site of an injury or infection.

Explain to a patient what an xray is and ct scanners does

Magnetic Resonance Imaging (MRI) • MRI is safer than X-ray because it does not use radiation. It provides more information than Computed Tomography about some head , neck and spinal disorders because the images are more detailed and have more contrast , meaning the differences between dark and light areas are stronger. Unlike CT , the images can be taken on any plane -any surface of the body seen from an angle. It is now used for imaging -taking images of - the brain and heart , and in oncology.

…MRI • Contraindications , cases in which it should not be used, include patients with metallic foreign bodies in the orbits , and patients with pacemakers electronic devices surgically implanted to regulate heartbeat. MRI is also not approved during the firs trimester of pregnancy .

Ultrasound • Ultrasound examination uses high-frequency sound waves to view organs and structures inside the body. The waves are generated and received by a hand -held device called a transducer. The reflected waves are processed by a computer which produces detailed images for a display on a monitor . Ultrasound is safe as it does not employ ionizing radiation like X-rays. It is cheap , quick and non invasive investigation -with no surgical procedure for a wide range of referrals , although results can be unsatisfactory in obese ( overweight ) patients.

Preparing for medical imaging (Preparing for an MRI scan ) • You will need to have completed a safety questionnaire and have it with you. It is important that there is no metal on you clothing or person . Prior to the scan you can eat and drink normally. Your details and safety questionnaire will be checked with you by the radiographer, who will explain the procedure and answer any questions you may have. You will be asked to remove any metallic objects (as well as credit cards ).

…. Preparing for an MRI scan • You will be asked to lie on the MRI scanner table and make yourself comfortable. . The radiographer will position the part to be scanned carefully in the scanner. During the MRI scan you will not feel anything but you will be required to stay still to achieve the best possible images. The whole examination process takes approximately 45 minutes. Depending on the site , you may require an injection. Only the part of your body requested by your doctor or source of referral will be scanned.

Compare and contrast MRI, CT Scan and Ultrasound CT MRI: Ultrasound Expensive Most expensive Cheapest 10 -45 mins Longest Shortest Most big hospitals can do it So expensive that it only available in specialised units Most widely available Yes No No Least available Most available t agents Nephrotoxic contrast agents, and adverse reactions to the iodinated contrast agents The usual contrast agent [gadolinium chelates] has a good safety profile None used ast and n images State-of-the-art spiral CT gives very detailed images - but not as good as MRI has better detection and descriptive powers than does CT. It provides excellent contrast that can reveal subtle variations in tissues of differing histology. Detailed images are not obtained in Ultrasound of the quality of the other two - but we do get pretty good ones nowadays - see 3 -d imaging! ense time ability o waiting ts) sing efore easing bility of ncer loping bility trained tors as l as pment The scan be done in any direction, not just axially like CT scans. her erations dications Pregnancy - can't have ionising radiation scan if Can't be used if patient has implanted metal like: pacemakers, aneurysm clips, heart valves, vascular stents

Magnetic Resonance Imaging demo Syllabus Extract - MR Scanner: Basic principles of MR scanner; cross-section of patient scanned using magnetic fields: hydrogen nuclei excited during the scan emit radio frequency (RF) signals as they de-excite: RF signals detected and processed by a computer to produce a visual image. Candidates will not be asked about the magnetic fields used in an MR scanner, or about de-excitation relaxation times. Magnetic Resonance Imaging (MRI) works by measuring the way that hydrogen atoms absorb and then relax and re-emit electromagnetic energy. Most of the human body is made up of water molecules, which consist of only hydrogen and oxygen atoms and fat, which also contains hydrogen atoms. You are made up of about 60% hydrogen atoms! The nucleus of a hydrogen atom is a proton, and protons are very sensitive to magnetic fields. When the proton spins it generates a manetic field, therefore the nucleus of a hydrogen atom is like a tiny magnet. When your body is in a strong magnetic field all of your hydrogen nuclei line - just like a row of compass needles lining up with a magnetic field.

MRI scanners use powerful magnets. When the powerful magnets that are used in magnetic resonance imaging (MRI) are switched on, all the protons in your body are pulled so that they spin in the same direction, in the same way that a magnet can pull the needle of a compass. The scanner contains several electric coils. This produces variations in the strength of the magnetic field at different points in your body. This variation means that each hydrogen nucleus experiences a slightly different magnetic field strength. This is important for detecting the position of a particular hydrogen nucleus. The frequency of these waves depends on the strength of the magnetic field where each nucleus is and this means that the scanner can work out the location of each nucleus. The MRI scanner sends a pulse of radio signals to certain areas of the body which ‘snaps’ the protons out of position. The pulse gives enough energy to the hydrogen nuclei in that area to change direction. When the pulse of energy ends the nuclei snap back to their original orientation and each nucleus gives off energy in the form of a radio wave. When this happens, each proton transmits a radio signal that provides information about its exact location in the body. On its own, a single proton will not provide much useful information, in the same way that a single pixel on a computer screen is essentially just a coloured dot. However, just as millions of pixels can create images, so the radio signals of millions of protons can be collected together and combined to create a detailed image of the inside of the body and also allow the scanner to work out what type of body tissue the hydrogen nuclei are part of.

https: //www. youtube. com/watch? v=ctw. XQ 5 x. K 4 PU&feature=player_em bedded video MRI imaging in medicine Demo

(ex. n. 3) Make word combinations using a word from each box. Then use some of the world combinations to complete the sentences. breathe anaesthetic excise your breath experience area foreign disease tissue hold discomfort informed in introduce bodies local consent recovery the endoscope

• breath in • excise diseased tissue • experience discomfort • foreign bodies • hold your breath • informed consent • introduce the endoscope • recovery area • local anesthetic