I
iatrogenic describes a secondary condition arising from treatment of a primary condition.
icon a pictorial representation on a computer screen.
identity bracelet a plastic band attached to either a patient’s wrist or ankle when they are admitted to hospital, usually giving their name and patient number; it should not be removed until a patient leaves hospital.
idiopathic scoliosis characterized by a lateral curvature of the spine together with rotation and associated rib hump or flank recession. The treatment is by spinal brace or traction or internal fixation with accompanying spinal fusion. See also halopelvic traction, Harrington rod, Milwaukee brace.
IHE (Integrated Health Enterprise) a consultation exercise between manufacturers and health professionals to ensure that computerization of the healthcare system achieves what the users require.
ileal conduit a surgical procedure when the ureters are attached to the ileum, part of the ileum then forms a reservoir for urine which drains to the anterior abdominal wall through a fistula.
ileocaecal associated with the ileum and the caecum.
ileocolic associated with the ileum and the colon.
ileorectal associated with the ileum and the rectum.
ileostomy a surgically made fistula between the ileum and the anterior abdominal wall; a type of opening (stoma) discharging liquid faecal matter. Usually permanent when the whole of the large bowel has to be removed, for example, in severe ulcerative colitis.
ileostomy bags special plastic bags used to collect the liquid discharge from an ileostomy.
ileum the lower three-fifths of the small intestine, lying between the jejunum and the caecum. Concerned with the absorption of various nutrients such as vitamin B12.
ileus intestinal obstruction. Usually restricted to paralytic as opposed to mechanical obstruction and characterized by abdominal distension, vomiting and the absence of pain.
iliac associated with the ilium. iliac arteries carry arterial blood to the pelvis and legs.
iliac crest the highest point of the ilium.
iliac region/fossa the abdominal region situated either side of the hypogastrium.
iliac veins drain venous blood from the legs and pelvis.
iliococcygeal associated with the ilium and coccyx.
iliofemoral associated with the ilium and the femur.
iliopectineal associated with the ilium and the pubis.
iliopectineal line bony ridge on the internal surface of the ilium and pubic bones. It is the dividing line between the true and false pelvis.
iliopsoas associated with the ilium and the loin.
ilium the upper part of the innominate (hip) bone; it is a separate bone in the fetus.
Ilizarov frame external fixation device used commonly in the management of fractures of the tibia.
image acquisition the collection of data in order to produce a computed tomography or magnetic resonance image.
image acquisition time the scanning time required to produce a set of images from a measurement sequence in magnetic resonance imaging. For a two-dimensional sequence it is the repetition time, times the number of signal excitations/averages times the number of phase encoded steps. For a fast two-dimensional sequence it is the two-dimensional sequence divided by the echo train length. For three-dimensional volume sequence it is the two-dimensional sequence multiplied by the number of partitions.
image annotation the marking of information on a radiograph to denote the side of the body, the patient position and the exposure factors; digital systems allow preset terms, numbers and letters to be added alongside the patient image.
ImageChecker™ an aid to screening routine mammograms by automatically marking clusters of white areas and dense areas with radiating lines.
image format the manner in which a computed tomography image is stored or displayed such as on screen, computer disk, magnetic tape or film.
image intensifier a means of producing a real time image of a patient. The X-ray beam passes through the patient and onto the image intensifier which converts the image to light, this image is scanned and an electrical signal is sent to a television monitor where the image is viewed.
image manipulation in CT scanning the ability to digitally alter the appearance of the acquired image to enhance depiction of the required anatomy.
image quality the ratio of signal over noise.
image reconstruction the process of producing an image from computer data or a set of unprocessed measurements.
image segmentation in digital imaging, dividing an image into its various parts or taking the image from the background to increase the definition of the object.
imaging plate a re-usable plate coated with barium phosphate that, when exposed to radiation excites the electrons, and then, when scanned by a helium-neon laser, produces an image which can be recorded.
imaging techniques diagnostic techniques used to investigate the condition and functioning of organs and structures. They include radiographic examination, radionuclide scans, ultrasonography, computed tomography, magnetic resonance and positron emission tomography.
imbalance want of balance. Term refers commonly to the upset of acid–base relationship and the electrolytes in body fluids.
immersion foot see trench foot.
immobilization device a method of reducing movement during radiotherapy treatment or diagnostic imaging.
immobilize to keep from moving, splints or plaster of Paris bandages are used to prevent realigned broken bones from becoming displaced.
immune protected against infection by specific or non-specific mechanisms of the immune system. Altered reactivity against an antigen, caused by previous exposure to that antigen.
immune response the response of the immune system to a perceived threat, either from non-self antigens, or from self antigens during a pathological immune response. This may be against microorganisms, malignant cells, and damaged or healthy tissues.
immunity an intrinsic or acquired state of immune responsiveness to an antigen. active immunity is acquired, naturally during an infection or artificially by immunization. It involves the production of antibodies and specific T cells in response to exposure to an antigenic stimulus. The primary response to exposure is followed by a lag phase of 2–3 weeks before enough antibodies are produced, but the secondary response following a subsequent exposure is more intense and has a much reduced lag phase because the memory cells are able to produce antibodies very quickly. This type of immunity tends to be of long duration. cell-mediated immunity T-lymphocyte-dependent responses which cause graft rejection, immunity to some infectious agents and tumour rejection. humoral immunity from immunoglobulins produced by plasma cells derived from B lymphocytes. Immunity can be innate (from inherited qualities), or it can be acquired, actively or passively, naturally or artificially. passive immunity is acquired, naturally when maternal antibody passes to the fetus via the placenta or in colostrum and breast milk, or artificially by administering immunoglobulins (usually human in origin). This type of immunity tends to be short-lived because the immune response is not stimulated to produce specific antibodies.
immunization a process by which resistance to an infectious disease is induced or increased.
immunocompromised patients (immunosuppressed patients) patients with defective immune responses, which can be inherited or acquired. Often produced by treatment with drugs or irradiation. Also occurs in some patients with cancer and other diseases affecting the lymphoid system. Depending on the immune defect, different patterns of infection result. Patients with cellular defects are likely to develop infections with opportunistic organisms such as Candida, Pneumocystis carinii and Cryptococcus neoformans. Patients with antibody defects are more liable to infections with encapsulated bacteria such as pneumococcus.
immunocytochemistry staining cells with specific antibodies for diagnostic purposes.
immunodeficiency the state of having defective immune responses, leading to increased susceptibility to infectious diseases.
immunoglobulins (Igs) (antibodies) high-molecular-weight glycoproteins produced by plasma cells (derived from B lymphocytes) in response to specific antigens. The basic structure of immunoglobulins is Y-shaped, consisting of two identical heavy chains, each linked to two identical light chains. Immunoglobulins are found in the blood and other body fluids where they form part of body defences. Immunoglobulins function in a variety of ways, but all involve combining with the antigen to form an immune complex. There are five classes of immunoglobulins, IgG, IgA, IgD, IgM and IgE, each with different characteristics, functions and locations.
immunohistochemistry staining tissue with specific antibodies for diagnostic purposes.
immunological response see immunity.
immunology the study of the immune system of lymphocytes, inflammatory cells and associated cells and proteins, which affect an individual’s response to antigens.
immunosuppression the administration of agents to significantly interfere with the ability of the immune system to respond to antigenic stimulation by inhibiting cellular and humerol immunity. May be deliberate such as before bone marrow transplants to prevent rejection by the host or incidental such as following chemotherapy for the treatment of cancer.
immunosuppressive that which reduces immunological responsiveness. Describes an agent such as a drug that suppresses immune system function.
immunotherapy the use of knowledge about immunity to prevent and treat disease. Can be used to mean desensitization therapy against specific allergens, for example, insect venom, or can refer to therapeutics which use agonists or antagonists based on immune system components, for example, treatment based on biological modifiers such as interleukin-2.
impacted firmly wedged, abnormal immobility, for example, faeces in the rectum; a fetus in the pelvis; a tooth in its socket or a calculus in a duct.
impacted fracture a break in bone continuity when the ends of the bone overlap, the most common site is just above the wrist joint.
impedance the general opposition of flow of electric current measured in ohms. In ultrasound a measure of the tissue’s resistance to distortion by ultrasound and depends on the tissue density and the velocity of the sound.
imperforate lacking a normal opening.
imperforate anus a congenital absence of an opening into the rectum.
imperforate hymen a fold of mucous membrane at the vaginal entrance which has no natural outlet for the menstrual fluid.
implant any drug, structure or substance inserted surgically into the human body, for example, implants of progestogens for contraception, or implants used in plastic surgery. Those used to augment tissue contour may be of two types: alloplastic synthetic foreign body implants such as those used in breast reconstruction, or autologous implants tissue obtained from the same patient. dental implant artificial structure implanted surgically into the alveolar bone, usually made from titanium.
implantation the insertion of living cells or solid materials into the tissues, for example, accidental implantation of tumour cells in a wound; implantation of radioactive material or solid drugs; implantation of the fertilized ovum into the endometrium.
incidence rate the total number of new cases, of a specific disease, occurring in a given period of time among a given number of people.
incident beam the beam of radiation striking an object.
incident light the light travelling from the light source.
incipient initial, beginning, in its early stages.
incision in surgery, a cut into soft tissue, the act of cutting.
incisional hernia protrusion through the site of a previous abdominal incision.
incisor tooth an anterior tooth with a cutting edge and single root, placed first and second from the midline in both primary and secondary dentition.
incompetence inadequacy to perform a natural function, for example, mitral valve regurgitation.
incomplete abortion a termination of pregnancy or a miscarriage when the products of conception are not fully expelled or removed. See also miscarriage.
incomplete fracture the bone is only cracked or fissured, called greenstick fracture when it occurs in children.
incomplete miscarriage part of the fetus or placenta is retained in the uterus. See also evacuation of retained products of conception.
incontinence inability to control the evacuation of urine or faeces. See also functional incontinence, neurogenic incontinence, stress incontinence.
incubator an apparatus with controlled temperature and oxygen concentration used for preterm or sick babies. A low-temperature oven in which bacteria are cultured.
incus anvil-shaped bone of the middle ear. See also malleus, stapes.
independent variable the variable conditions of an experimental situation, e.g. control or experimental.
indicator a substance used to make visible the completion of a chemical reaction or the achievement of a certain pH.
indicator lamps situated on a control panel to give the status of equipment, for example, if the door of the treatment room is closed, or outside the room to indicate treatment is in progress.
indigenous of a disease, etc., native to a certain locality or country.
indigestion (dyspepsia) a feeling of gastric discomfort, including fullness and gaseous distension, which is not necessarily a manifestation of disease.
indirect cost a cost that cannot be attributed to any one department and its budget. It is shared between various budgets, for example, the cost of heating a building.
indolent slow growing, reluctant to heal.
induction the production of an electromotive force in a conductor when it is moving relative to a magnetic field of changing intensity. The act of bringing on or causing to occur, as applied to anaesthesia and labour.
induration the hardening of tissue, as in hyperaemia, infiltration by tumour, etc.
industrial dermatitis a term used in the National Insurance (Industrial Injuries) Act to cover occupational skin conditions.
industrial disease (occupational disease) a disease contracted by reason of occupational exposure to an industrial agent known to be hazardous, for example, dust, fumes, chemicals, irradiation, etc., the notification of, safety precautions against and compensation for which are controlled by law.
inelastic collisions the mutual attraction of atoms, molecules, etc. when either the energy from one particle is given to the other or only kinetic, excitation or ionization energy is transferred after the collision.
inevitable abortion miscarriage.
inevitable miscarriage loss of the pregnancy cannot be prevented.
in extremis at the point of death.
infant a child of less than 1 year old.
infarct area of tissue affected when the end artery supplying it is occluded by atheroma, thrombosis or embolism, for example, in myocardium or lung.
infarction irreversible premature tissue death. Necrosis (death) of a section of tissue because the blood supply has been cut off. See also myocardial infarction, pulmonary infarction.
infection the successful invasion, establishment and growth of micro-organisms in body tissues. It may be acute or chronic. See also autoinfection, cross infection, hospital-acquired infection, opportunistic infection.
infectious disease a disease caused by a specific, pathogenic microorganism and capable of transmission to another individual by direct or indirect contact.
infective infectious. Disease transmissible from one host to another.
inferential statistics also known as inductive statistics. That which uses the observations of a sample to make a prediction about other samples, i.e. makes generalizations from the sample. See also descriptive statistics.
inferosuperior radiograph a radiograph taken from below to above.
infestation the presence of animal parasites.
infiltration the entry into cells, tissues or organs of abnormal substances or cells, for example, cancer cells, fat. Penetration of the surrounding tissues; the oozing or leaking of fluid into the tissues.
infiltration anaesthesia analgesia produced by infiltrating the tissues with a local anaesthetic.
inflammation local defence mechanism initiated by tissue injury. The injury may be caused by trauma, microorganisms, extremes of temperature and pH, UV radiation, or ionizing radiation. It is characterized by heat, redness, swelling, pain and loss of function. See also calor, dolor, rubor, tumor.
inflammatory bowel disease (IBD) a condition of unknown (idiopathic) intestinal inflammation. Mainly ulcerative colitis and Crohn’s disease. Also lymphocytic and collagenous colitis.
inflammatory response a reaction of the immune system to protect the body against harmful substances or physical agents.
influenza (flu) a viral infection of the respiratory tract.
informatics information management and technology (IM&T). Information is needed to ensure the effective running of any organization. Data are pieces of material which, when compiled effectively, form information. Information is managed in a number of different ways but increasingly it is managed using technological means (information technology, IT). Non-technological means may be more appropriate for the target group/recipient. For example, telephone calls and notice boards are ways in which information might be managed.
informed choice in order to make decisions about their own care and management clients/patients need information from healthcare professionals. This means the provision of accurate, appropriate information about the person’s condition, and about the treatment options available. Healthcare professionals may disagree with the patient/client’s decisions, but the latter takes precedence where an adult patient is deemed to be mentally competent.
informed consent in the UK consent forms must include a signed declaration by the doctor or other healthcare professional that he/she has explained the nature and purpose of the operation or treatment to the patient in non-technical terms. Any questions that the patient may have after signing the form should be referred to the doctor or other health professional who is to carry out the treatment. See also consent.
infundibulum any funnel-shaped passage, for example, the ends of the uterine tubes.
infusion fluid flowing into the body either intravenously or subcutaneously over a long period of time, an aqueous solution containing the active principle of a drug.
infusion cholangiography the radiographic investigation of the biliary tract following the infusion of a radiographic contrast agent into the median cubital vein.
ingestion taking food or drugs into the stomach. The means by which a phagocytic cell takes in material such as microorganisms.
inguinal associated with the groin.
inguinal canal a tubular opening through the lower part of the anterior abdominal wall, parallel to and a little above the inguinal (Poupart’s) ligament. In the male it contains spermatic cord; in the female the uterine round ligaments.
inguinal hernia protrusion through the inguinal canal in the male. See also hernia.
inhalation the breathing in of air, or other vapour, etc. A medicinal substance which is inhaled, such as an inhalation anaesthetic or in the aerosols used for asthma treatment.
inherent filtration the filtration of the beam which is outside the operator control for example, the target material, the glass envelope and the X-ray window of the X-ray tube.
inherent wedge a microprocessor controlled wedge used to attenuate part of the beam in radiotherapy treatment.
inhomogeneities variations within a patient due to the different densities of bone, tissue and organs.
inhomogenicity the slight variation in uniformity of the static magnetic field in parts per million as a fractional deviation from the average value of the field.
initialize at the beginning of computation all variables are given specific values in the program.
injection the act of introducing a fluid (under pressure) into the tissues, a vessel, cavity or hollow organ, air can be injected into a cavity, the substance injected. See also pneumothorax.
inkjet printer a printer which sprays streams of quick-drying ink through very fine jets, building up the characters or images in very fine dots to produce an image on paper. Often a separate cartridge is used for each of the main ink colours, black, red, green and yellow.
inlay in dentistry, a restoration made from cast gold or porcelain to fit a prepared cavity, into which it is then cemented.
innervation the nerve supply to a part.
innocent benign; not malignant.
innominate unnamed. See also hip bone.
inquest in England and Wales, a legal enquiry by a coroner into the cause of sudden or unexpected death.
insecticide an agent which kills insects.
insensible without sensation or consciousness. Too tiny or gradual to be noticed.
insensible perspiration the water lost by evaporation through the skin surface other than by sweating. It is significantly increased in inflamed skin.
insert the part of an X-ray tube which contains the anode, and cathode in a vacuum.
insertion the act of setting or placing in, the attachment of a muscle to the bone it moves.
in situ in the normal position, undisturbed.
inspiration inhalation; breathing in.
instep the arch of the foot on the dorsal surface.
instillation insertion of drops into a cavity, for example, conjunctival sac.
insufflation the blowing of air along a tube (pharyngotympanic, uterine) to establish patency. The blowing of powder into a body cavity.
insulator a substance which has a high resistance to the flow of electricity or heat.
insulin a polypeptide hormone produced by the beta cells of the pancreas. Insulin secretion is regulated by the blood glucose level and it opposes the action of glucagon. It has an effect on the metabolism of carbohydrate, protein and fat by stimulating the transport of glucose into cells. An absolute or relative lack of insulin results in hyperglycaemia, a high blood glucose with decreased utilization of carbohydrate and increased breakdown of fat and protein; a condition known as diabetes mellitus. Three types of insulin are available commercially: bovine insulin, porcine insulin and human insulin, produced using recombinant techniques. Insulin is produced in U100 strength, i.e. 100 units per mL, a standardization replacing the previous 20, 40 and 80 unit strengths.
insulin coma when a diabetic patient loses consciousness due to either an overdose of insulin or fails to eat at the appropriate time.
insulin-dependent diabetes mellitus (IDDM) see diabetes mellitus type 1.
insulinoma pancreatic islet beta cell adenoma.
integral dose the sum total of dose to all elements of irradiated tissue and represents the total absorbed energy.
integument a covering, especially the skin.
intelligent peripheral a keypad linked to a computer that can act as a computer in its own right.
intensifying factor the ratio of the radiation exposure required to produce a density of 1.0 on a radiographic film without screens compared to the exposure required to produce a density of 1.0 with screens and using the same film.
intensity the total energy of a beam of electromagnetic radiation per second at a given point. In ultrasound the intensity of the ultrasound beam is the energy flow rate per unit area in watts per square centimetre.
intensity-modulated radiotherapy (IMRT) the use of a computer system to optimize the beam shape and profile to the target tissues by using multileaf, moving collimators and therefore maximizing the radiation delivery technique by evaluating millions of possible beam arrangements to create a clinically accurate treatment plan.
intensive therapy unit (ITU) (intensive care unit) an area within a hospital with augmented levels of staff and equipment in which highly specialized monitoring, resuscitation and therapeutic techniques are used to support critically ill patients with actual or impending organ failure, particularly those needing artificial ventilation.
interaction cross section the size of the area of the patient that lies in the field of the X-ray beam.
interarticular between joints.
interatrial between the two atria of the heart.
interface the connection from the computer to other hardware, allowing free communication between the two.
interferons (IFNs) protein mediators that enhance cellular resistance to viruses. They are involved in the modulation of the immune response. Interferon has caused regression of some cancers and is used in the management of some types of multiple sclerosis.
interlacing the construction of an image when an electron beam scans a tube phosphor, first the odd lines are scanned and then the even lines.
interleukins (IL) large group of signalling molecules (cytokines). They are non-specific immune chemicals produced by various cells, such as macrophages. Interleukins are also involved with the regulation of haematopoiesis.
interlobular between the lobules.
interlock a safety device, for example, to protect the X-ray unit from overheating, to prevent exposure if the room door is open.
internal conversion the transfer of energy from the nucleus of a heavy atom to an electron in the K shell.
internal ear that part of the ear which comprises the vestibule, semicircular canals and the cochlea.
internal haemorrhage bleeding inside the body, often with no external signs.
internal hydrocephalus excess of cerebrospinal fluid mainly in the ventricles of the brain. A valve (e.g. Spitz–Holter type) is used to drain excess CSF and return it to the bloodstream.
internal respiration (tissue respiration) the reverse of external respiration, involving gaseous exchange between the cells and blood. Oxygen moves from the blood, via the tissue fluid, to the cells, and waste cellular carbon dioxide moves into the blood for onward transport to the lungs. See also respiration.
internal (medial) rotation a limb or body movement where there is rotation towards the vertical axis of the body.
internal secretions those produced by the endocrine glands; hormones.
Internet a network of computers, accessible to anyone throughout the world who has access to a computer and modem, giving access to the World Wide Web and email.
interphalangeal between the phalanges.
interpretive approach a research approach that incorporates the meaning and significance individuals attach to situations and behaviour. May be used in social science research.
interprofessional intense teamwork among practitioners from different healthcare professions focused on a common problem-solving purpose and requiring recognition of the core expertise and core knowledge of each profession and blending of common core skills to enable the team to act as an integrated whole.
interprofessional education (IPE) shared (or common) learning of common (or generic) core skills among students and qualified practitioners of different healthcare professions that fosters respect for each other’s core knowledge and expertise, capitalizes on professional differences, and cultivates integrated teamwork to solve patients’ problems.
interpupillary line line joining the centre of the two orbits and is perpendicular to the median sagittal plane. See also median sagittal plane.
interserosal between serous membrane, as in the pleural, peritoneal and pericardial cavities.
intersexuality the possession of both male and female characteristics.
interspinous between spinous processes, especially those of the vertebrae.
interstitial the space between cells; distributed through the connective structures or the space between organs.
interstitial cell stimulating hormone (ICSH, luteinizing hormone) a hormone released from the anterior lobe of the pituitary gland; causes production of testosterone in the male.
interstitial fluid (tissue fluid) the extracellular fluid situated in the spaces around cells.
interstitial lamellae plates of bone filling the spaces between haversian systems.
interstitial lung disease a wide range of respiratory disorders characterized by inflammation and eventually, fibrosis of the connective tissue of the lungs.
interstitial therapy brachytherapy where the sources are implanted directly into the affected tissue.
intertrochanteric between trochanters such as those on the proximal femur.
interval cancer one that is discovered in the time interval between screening episodes, such as breast cancer detected between mammography examinations.
interval data measurement data with a numerical value, for example, temperature, that has an arbitrary zero. The intervals between successive values are the same, for example, a 1 degree increase from 38 to 39 is exactly the same as one from 39 to 40. See also ratio data.
interval status when the numbers are ordinal and the steps between each number are of equal size.
interventricular between ventricles, as those of the brain or heart.
intervertebral between the vertebrae, as discs and foramina. See also nucleus, prolapse.
intestinal obstruction a blockage that stops the contents of the intestine passing into the lumen of the bowel.
intestine a part of the alimentary canal (extending from the stomach to the anus). Consists of the small and large intestine (bowel).
intima the internal coat of a blood vessel.
intra-abdominal inside the abdomen.
intra-amniotic within or into the amniotic fluid.
intra-aortic within the aorta. intra-aortic balloon pump (IABP) device used to increase cardiac output in ventricular failure or shock.
intra-arterial within an artery.
intra-articular within a joint.
intrabronchial within a bronchus.
intracanalicular within a canaliculus.
intracapillary within a capillary.
intracapsular within a capsule, for example, that of the lens or a joint. See also extracapsular.
intracardiac within the heart.
intracaval within the vena cava.
intracavitary therapy brachytherapy where the sources are arranged in a suitable applicator to irradiate the walls of a body cavity from the inside.
intracellular within cells. intracellular fluid (ICF) that fluid inside the cells. See also extracellular.
intracerebral within the cerebrum, such as a haemorrhage.
intracranial within the skull.
intracranial pressure (ICP) the pressure inside the cranial cavity. It is maintained at a normal level by brain tissue, intracellular and extracellular fluid, cerebrospinal fluid and blood. A change in any of these compartments can increase the pressure, for example, after head injury. See also raised intracranial pressure.
intradural inside the dura mater.
intragastric within the stomach.
intragluteal within the gluteal muscle of the buttock.
intrahepatic within the liver.
intrahepatic cholestasis caused by blockage of the small bile ducts within the liver, such as in hepatitis or cirrhosis.
intralobular within the lobule, for example, vessels draining a hepatic lobule.
intraluminal within the lumen of a hollow tube-like structure.
intralymphatic within a lymphatic node or vessel.
intramedullary within the bone marrow.
intramural within the wall of a hollow tube or organ.
intramuscular within muscle tissue.
intranasal within the nasal cavity.
intranet a small network of computers, for example, within a Hospital Trust to allow limited access and enable the sharing of confidential files within the organization.
intraocular within the globe of the eye.
intraoperative probe a very small footprint, high-frequency ultrasound probe which is inserted into blood vessels to visualize their anatomy, for example, in cardiac work.
intraoperative radiotherapy radiotherapy that takes place during an operative procedure.
intraoral radiograph a radiograph of a tooth when the film is placed inside the mouth. See also periapical film.
intraorbital within the orbit.
intraosseous inside a bone. The intraosseous route has been developed as a way of giving fluids when rapid establishment of systemic access is vital and venous access is impossible. It provides an alternative route for the administration of drugs and fluids until venous access can be achieved.
intraperitoneal within the peritoneal cavity.
intrapharyngeal within the pharynx.
intraplacental within the placenta.
intrapleural within the pleural cavity.
intrapulmonary within the lungs, as intrapulmonary pressure.
intraspinal within the spinal canal.
intrasplenic within the spleen.
intrasynovial within a synovial membrane or cavity.
intrathecal within the meninges; into the subarachnoid space. A route used for the administration of certain drugs, such as antibiotic drugs for meningitis.
intrathoracic within the cavity of the thorax, such as pressures.
intratracheal within the trachea.
intrauterine within the uterus.
intrauterine contraceptive device (IUCD, IUD) a device which is inserted in the cavity of the uterus to prevent conception. Its exact mode of action is not known.
intrauterine fetal death death of a fetus weighing at least 500 grams or after 24 weeks gestational age.
intrauterine growth restriction (IUGR) the impairment of fetal growth rate commonly arising due to placental insufficiency.
intrauterine transfusion of the fetus endangered by Rhesus inco-mpatibility. Red cells are transfused directly into the abdominal cavity of the fetus, on one or more occasions. This enables the induction of labour to be postponed until a time more favourable to fetal welfare.
intravaginal within the vagina.
intravascular within the blood vessels.
intravenous (IV) within or into a vein.
intravenous infusion (IVI) commonly referred to as a ‘drip’: the closed administration of fluids from a containing vessel into a vein for such purposes as hydrating the body, correcting electrolyte imbalance or introducing nutrients.
intravenous injection the introduction of drugs, including anaesthetics, into a vein.
intravenous urography (IVU) demonstration of the urinary tract following an intravenous injection of a contrast agent.
intraventricular within a ventricle, especially a cerebral ventricle.
intrinsic detector efficiency the ability of a detector to produce a signal for each quanta of radiation falling on it.
introitus any opening in the body; an entrance to a cavity, particularly the vagina.
intubation placing of a tube into a hollow organ. tracheal intubation is used during anaesthesia. duodenal intubation a double tube is passed as far as the pyloric antrum under fluoroscopy, the inner tube is then passed along to the duodenojejunal flexure.
intussusception a condition in which one part of the bowel telescopes into another, causing severe colic and intestinal obstruction. It occurs most commonly in infants around the time of weaning.
intussusceptum the invaginated portion of an intussusception.
intussuscipiens the receiving portion of an intussusception.
invagination the act or condition of being ensheathed; a pushing inward, forming a pouch.
invasion the entry of bacteria into the body or the spread of cancer cells.
inverse square law the intensity of radiation from a small isotropic source is inversely proportional to the square of the distance from the source, used in radiography for calculating the dose rate and exposure factors when changing the focus film distance.
inverse piezo-electric effect when an electric current is applied to a material it expands and contracts producing an ultrasound pulse.
inverse treatment planning computer software to determine optimal isodose contours and maximum tumour dose for a given radiotherapy treatment, used in intensity modulated radiotherapy.
inversion turning inside out, as inversion of the uterus.
inversion recovery in magnetic resonance imaging it is the basic pulse sequence which inverts the magnetization and measures the time taken for the nuclei to return to equilibrium. The rate of recovery depends on the relaxation rate (T1).
inversion time (TI) in magnetic resonance imaging it is the time after the middle of a 180° radio frequency inverting pulse and the inversion recovery sequence to the middle of the 90° read pulse, and monitors the amount of longitudinal magnetization.
in vitro in glass, as in a test tube.
in vitro fertilization (IVF) human oocytes are fertilized by spermatozoa in test tubes in laboratories that are specialized in this technique.
involucrum a sheath of new bone, which forms around necrosed bone, in conditions such as osteomyelitis. See also cloaca.
involuntary independent of the will, as muscle of the thoracic and abdominal organs.
iodine (I) an element required for the formation of thyroid hormones (T3, T4). oral iodine may be prescribed preoperatively for patients with hyperthyroidism to control the release of thyroid hormones and reduce vascularity of the gland. radioactive isotopes of iodine, for example, 131I, are used in the diagnosis and treatment of thyroidconditions, such as cancer. Iodine is bactericidal and is used as povidone iodine for skin disinfection prior to invasive procedures. It is used within several proprietary wound dressings.
iodine seeds a source of iodine125 used to treat the pituitary by permanently implanting the seeds and as surface applicators to treat the cornea.
ion when an atom either loses or gains an electron it forms an ion. See also anion, cation.
ion channel water-filled channels in the cell membrane that allow certain ions to pass through as in the transmission of nerve impulses. Some drugs act at the level of the ion channels.
ion-exchange resins substances administered orally to reduce the level of specific ions (calcium and potassium) in the body such as in renal failure.
ionic bond when one or more electrons move from one atom to another and then form ions which are attracted to each other as they have an opposite charge, after the electron exchange the shells in each ion appear to be intact.
ionization the process of removing an electron from an atom, thus forming a positive ion.
ionization chamber a device, containing air for measuring the potential dosage of a beam of radiation by collecting charge on an electrode, thimble ionization chamber a modification to enable the device to be used practically, it is smaller in size and uses an air equivalent medium in the capsule. Used in radiotherapy planning to record the output of the X-ray tube.
ionizing radiation form of radiation that destabilizes an atom, forming an ion. Examples include gamma rays, X-rays and particle radiation. It has the ability to cause tissue damage. See also radiation.
ions when an atom either loses or gains an electron it forms an ion.
IP address (Internet Protocol Address) a unique number given to any computer when it is connected to the internet, it is formed by four blocks of three numbers, the highest being 255.
ipsilateral affecting the same side of the body.
iridium (192Ir) a radioactive element used in brachytherapy to treat cancers in anus, tongue, breast as implanted wires or hair pins. Can also be used as a Selectron source.
iridium wire a source of Iridium192 used in manual afterloading systems and is purchased by specifying the activity per unit length required.
iris the circular pigmented structure forming the anterior one-sixth of the middle coat of the eyeball. It is perforated in the centre by an opening, the pupil. Contraction of its muscle fibres regulates the amount of light entering the eye. iris bombe bulging forward of the iris due to pressure of the aqueous behind, when posterior synechiae are present around the pupil.
iron (Fe) a metallic element needed in the body as a constituent of haemoglobin and several enzymes.
irradiated volume in radiotherapy, the quantity of tissue that receives a radiation dose that is considered to be significant in relation to normal tissue tolerance.
irradiation exposure to any form of radiant energy such as heat light or X-rays. The lateral scattering of light in the emulsion layer of a radiographic film causing unsharpness.
irreducible hernia when the contents of the sac cannot be returned to the appropriate cavity, without surgical intervention.
irregular bones cancellous bones surrounded by a thin layer of compact bone and irregular in shape, for example the vertebrae, facial bones.
irritable capable of being excited to activity; easily stimulated.
irritable bowel syndrome (IBS) functional intestinal symptoms not explained by organic bowel disease. Symptoms include abdominal pain, bloating and change in bowel habit (alternating constipation and diarrhoea).
irritant describes any agent which causes irritation.
ischaemia deficient blood supply to any part of the body. See also angina.
ischaemic heart disease (IHD) see coronary heart disease.
ischiorectal associated with the ischium and the rectum, as an ischiorectal abscess which occurs between these two structures.
ischium the lower part of the innominate bone of the pelvis; the bone on which the body rests when sitting.
ISDN (Integrated Services Digital Network) a set of standards for the transfer of digital information over a telephone wire and other media.
islets of Langerhans collections of special cells scattered throughout the pancreas, mainly concerned with endocrine function. The pancreatic islets contain four types of hormone-secreting cells: alpha cells, which secrete glucagon; beta cells, which secrete insulin; the delta cells, which secrete several substances, including somatostatin or growth hormone inhibiting hormone (GHIH); and others that produce regulatory pancreatic polypeptide.
isobar any nucleus that has the same atomic mass number as another nucleus but with different atomic numbers. A line joining points of equal pressure.
isocentre the point in space at which the central beams from each beam angle intersect. In CT this is the point of greatest accuracy of the reconstructed image, hence its importance when positioning a patient on the table prior to scanning. In radiotherapy, the point where the axis of rotation of the diaphragm, the horizontal axis of rotation of the gantry and the vertical axis of rotation of the couch intersect.
isocentric gantry a C-shaped structure that connects the X-ray tube to the image intensifier so that the central beam from the X-ray tube is always aligned to the centre of the image intensifier.
isocentric reference mark a point marked onto the patient to enable accuracy of repositioning, for example, in radiotherapy.
isodose chart a number of isodose lines to represent the output from a specific source of radiotherapy equipment.
isodose contour a line on an isodose chart that plots doses of equal value.
isodose curve the graphical representation of the distribution of radiation dose within a uniform area.
isodose distribution lines plotting the radiation dose received by the patient throughout the radiotherapy treatment area.
isodose lines the lines that plot the areas of a patient that receive a radiation dose of equal value.
isodose surface the graphical representation of the area of skin surface receiving a radiation dose.
isoelectric point the pH value in which a substance or system is electrically neutral. In a film emulsion it determines some characteristics of the emulsion: the minimum solubility, viscosity, conductivity and swelling and determines how easily products are removed from the emulsion.
isolated limb perfusion a method of introducing cytotoxic drugs into an isolated arterial supply by administering a tourniquet to the limb, under general anaesthetic.
isolation separation of a patient from others for a number of reasons. See also containment isolation, protective isolation, source isolation.
isolator apparatus ranging from what is virtually a large plastic bag in which a patient can be nursed to that in which surgery can be performed. It aims to prevent pathogenic microorganisms either gaining entry or leaving the enclosed space.
isometric transition is the move from an excited state of a nucleus to a stable state.
isotonic equal tension; applied to any solution which has the same osmotic pressure as the fluid with which it is being compared. isotonic saline (normal saline, physiological saline), 0.9% solution of sodium chloride in water.
isotope of an element any nucleus which contains the same number of protons as the element but has a different mass number.
isotopes two or more forms of the same element having identical chemical properties and the same atomic number but different mass numbers. Those isotopes with radioactive properties are used in medicine for research, diagnosis and treatment of disease.
isotropic to emit radiation in all directions.
ISP (Internet Service Provider) a company that enables access to the internet.
isthmus a narrowed part of an organ or tissue such as that connecting the two lobes of the thyroid gland.
iteration to repeatedly execute an instruction in a computer program.
iterative reconstruction algorithm a mathematical method of image reconstruction which involves continually updating and adjusting the image as data are acquired. Back projection methods are more commonly used today.
