A technique for providing images of the skull.
X-rays of the skull are usually taken after a head injury to look for a fracture or foreign body, or to evaluate disorders that affect the skull.
X-rays of the skull are usually taken after a head injury to look for a fracture or foreign body, or to evaluate disorders that affect the skull.
Arrangement of the bones In childhood, the bones are independent, gradually fusing together by sutures, and in old age fusing completely so that the cranium forms a solid bony case. At the time of birth the growth of several bones of the infant’s head has not been quite completed, so that six soft spots, or fontanellas, present; here the brain is covered only by skin and membranes, and the pulsations of its blood vessels may be seen. One of these spots, the anterior fontanelle, does not close completely until the child is 18 months to 2••• years old.
Parts of the skull The cranium, enclosing the brain, consists of eight bones, while the face, which forms a bony framework for the eyes, nose and mouth, consists of 14 bones. These two parts can be detached.
Shape of the skull The development of large central hemispheres of the brain in humans has in?uenced the skull shape. Unlike in other mammals, the cranium extends above as well as behind the face which therefore looks forwards. The skull’s proportions change with age: the cranium in children is larger in comparison with the face – one-eighth of the whole head – than is the case in adults, where sizes are about the same. Old age reduces the size of the face because of the loss of teeth and absorption of their bony sockets. Women’s skulls tend to be lighter and smoother with less obvious protuberances than those in men.... skull
The rays are part of the electro-magnetic spectrum; their wavelengths are between 10?9 and 10? 13 metres; in behaviour and energy they are identical to the gamma rays emitted by radioactive isotopes. Diagnostic X-rays are generated in an evacuated tube containing an anode and cathode. Electrons striking the anode cause emission of X-rays of varying energy; the energy is largely dependent on the potential di?erence (kilovoltage) between anode and cathode. The altered tissue penetration at di?erent kilovoltages is used in radiographing di?erent regions, for example in breast radiography (25–40 kV) or chest radiography (120–150 kV). Most diagnostic examinations use kilovoltages between 60 and 120. The energy of X-rays enables them to pass through body tissues unless they make contact with the constituent atoms. Tissue attenuation varies with atomic structure, so that air-containing organs such as the lung o?er little attenuation, while material such as bone, with abundant calcium, will absorb the majority of incident X-rays. This results in an emerging X-ray pattern which corresponds to the structures in the region examined.
Radiography The recording of the resulting images is achieved in several ways, mostly depending on the use of materials which ?uoresce in response to X-rays. CONTRAST X-RAYS Many body organs are not shown by simple X-ray studies. This led to the development of contrast materials which make particular organs or structures wholly or partly opaque to X-rays. Thus, barium-sulphate preparations are largely used for examining the gastrointestinal tract: for example, barium swallow, barium meal, barium follow-through (or enteroclysis) and barium enema. Water-soluble iodine-containing contrast agents that ionise in solution have been developed for a range of other studies.
More recently a series of improved contrast molecules, chie?y non-ionising, has been developed, with fewer side-effects. They can, for example, safely be introduced into the spinal theca for myeloradiculography – contrast X-rays of the spinal cord. Using these agents, it is possible to show many organs and structures mostly by direct introduction, for example via a catheter (see CATHETERS). In urography, however, contrast medium injected intravenously is excreted by the kidneys which are outlined, together with ureters and bladder. A number of other more specialised contrast agents exist: for example, for cholecystography – radiological assessment of the gall-bladder. The use of contrast and the attendant techniques has greatly widened the range of radiology. IMAGE INTENSIFICATION The relative insensitivity of ?uorescent materials when used for observation of moving organs – for example, the oesophagus – has been overcome by the use of image intensi?cation. A faint ?uorographic image produced by X-rays leads to electron emission from a photo-cathode. By applying a high potential di?erence, the electrons are accelerated across an evacuated tube and are focused on to a small ?uorescent screen, giving a bright image. This is viewed by a TV camera and the image shown on a monitor and sometimes recorded on videotape or cine. TOMOGRAPHY X-ray images are two-dimensional representations of three-dimensional objects. Tomography (Greek tomos
– a slice) began with X-ray imaging produced by the linked movement of the X-ray tube and the cassette pivoting about a selected plane in the body: over- and underlying structures are blurred out, giving a more detailed image of a particular plane.
In 1975 Godfrey Houns?eld introduced COMPUTED TOMOGRAPHY (CT). This involves
(i) movement of an X-ray tube around the patient, with a narrow fan beam of X-rays; (ii) the corresponding use of sensitive detectors on the opposite side of the patient; (iii) computer analysis of the detector readings at each point on the rotation, with calculation of relative tissue attenuation at each point in the cross-sectional plant. This invention has enormously increased the ability to discriminate tissue composition, even without the use of contrast.
The tomographic e?ect – imaging of a particular plane – is achieved in many of the newer forms of imaging: ULTRASOUND, magnetic resonance imaging (see MRI) and some forms of nuclear medicine, in particular positron emission tomography (PET SCANNING). An alternative term for the production of images of a given plane is cross-sectional imaging.
While the production of X-ray and other images has been largely the responsibility of radiographers, the interpretation has been principally carried out by specialist doctors called radiologists. In addition they, and interested clinicians, have developed a number of procedures, such as arteriography (see ANGIOGRAPHY), which involve manipulative access for imaging – for example, selective coronary or renal arteriography.
The use of X-rays, ultrasound or computerised tomography to control the direction and position of needles has made possible guided biopsies (see BIOPSY) – for example, of pancreatic, pulmonary or bony lesions – and therapeutic procedures such as drainage of obstructed kidneys (percutaneous nephrostomy), or of abscesses. From these has grown a whole series of therapeutic procedures such as ANGIOPLASTY, STENT insertion and renal-stone track formation. This ?eld of interventional radiology has close a?nities with MINIMALLY INVASIVE SURGERY (MIS).
Radiotherapy, or treatment by X-rays The two chief sources of the ionising radiations used in radiotherapy are the gamma rays of RADIUM and the penetrating X-rays generated by apparatus working at various voltages. For super?cial lesions, energies of around 40 kilovolts are used; but for deep-seated conditions, such as cancer of the internal organs, much higher voltages are required. X-ray machines are now in use which work at two million volts. Even higher voltages are now available through the development of the linear accelerator, which makes use of the frequency magnetron which is the basis of radar. The linear accelerator receives its name from the fact that it accelerates a beam of electrons down a straight tube, 3 metres in length, and in this process a voltage of eight million is attained. The use of these very high voltages has led to the development of a highly specialised technique which has been devised for the treatment of cancer and like diseases.
Protective measures are routinely taken to ensure that the patient’s normal tissue is not damaged during radiotherapy. The operators too have to take special precautions, including limits on the time they can work with the equipment in any one period of time.
The greatest value of radiotherapy is in the treatment of malignant disease. In many patients it can be used for the treatment of malignant growths which are not accessible to surgery, whilst in others it is used in conjunction with surgery and chemotherapy.... x-rays
On exposure to cold, the digits turn white due to lack of blood. As sluggish blood flow returns, the digits become blue; when they are warmed and normal blood flow returns, they turn red. During an attack, there is often tingling, numbness, or a burning feeling in the affected fingers or toes. In rare cases, the artery walls gradually thicken, permanently reducing blood flow. Eventually painful ulceration or even gangrene may develop at the tips of the affected digits.
Diagnosis is made from the patient’s history. Treatment involves keeping the hands and feet as warm as possible. Vasodilator drugs or calcium channel blockers may be helpful in severe cases. (See also Raynaud’s phenomenon.)... raynaud’s disease
Raeann, Raeanna, Raeanne, Rayana, Rayanna, Rayanne, Rayane, Raeane, Raeana, Raiann, Raiane, Raianne, Raianna, Raiana... rayann
Symptoms The condition is most commonly con?ned to the occurrence of ‘dead ?ngers’ – the ?ngers (or the toes, ears, or nose) becoming white, numb, and waxy-looking. This condition may last for some minutes, or may not pass o? for several hours, or even for a day or two.
Treatment People who are subject to these attacks should be careful in winter to protect the feet and hands from cold, and should always use warm water when washing the hands. In addition, the whole body should be kept warm, as spasm of the arterioles in the feet and hands may be induced by chilling of the body. Su?erers should not smoke. VASODILATORS are helpful, especially the calcium antagonists. In all patients who do not respond to such medical treatment, surgery should be considered in the form of sympathectomy: i.e. cutting of the sympathetic nerves to the affected part. This results in dilatation of the arterioles and hence an improved blood supply. This operation is more successful in the case of the feet than in the case of the hands.... raynaud’s disease
Possible causes include arterial diseases, such as atherosclerosis; connective tissue diseases, such as rheumatoid arthritis; and various drugs, such as beta-blocker drugs.
The disorder is an occupational disorder of people who use pneumatic drills, chain saws, or vibrating machinery; it is sometimes seen in typists, pianists, and others whose fingers suffer repeated trauma.
Treatment is the same as for Raynaud’s disease, along with treatment of the underlying disorder.... raynaud’s phenomenon
A fracture without complications usually heals by itself; damage to brain structures often requires neurosurgery.... skull, fracture of
Ultraviolet lamps produce UVR and are used to tan skin but, because of the risk of producing skin cancer (see SKIN, DISEASES OF), the lamps must be used with great caution.... ultraviolet rays (uvr)
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