Projectional Radiography
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Projectional radiography, also known as conventional radiography, is a form of
radiography Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeuti ...
and medical imaging that produces two-dimensional images by
x-ray radiation X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ''X ...
. The image acquisition is generally performed by radiographers, and the images are often examined by radiologists. Both the procedure and any resultant images are often simply called "X-ray". Plain radiography or roentgenography generally refers to projectional radiography (without the use of more advanced techniques such as
computed tomography A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers ...
that can generate 3D-images). ''Plain radiography'' can also refer to
radiography Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeuti ...
without a radiocontrast agent or radiography that generates single static images, as contrasted to fluoroscopy, which are technically also projectional.


Equipment


X-ray generator

Projectional radiographs generally use X-rays created by X-ray generators, which generate X-rays from
X-ray tube An X-ray tube is a vacuum tube that converts electrical input power into X-rays. The availability of this controllable source of X-rays created the field of radiography, the imaging of partly opaque objects with penetrating radiation. In contrast ...
s.


Grid

An anti-scatter grid may be placed between the patient and the detector to reduce the quantity of scattered x-rays that reach the detector. This improves the contrast resolution of the image, but also increases radiation exposure for the patient.


Detector

Detectors can be divided into two major categories: imaging detectors (such as
photographic plate Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thi ...
s and X-ray film ( photographic film), now mostly replaced by various
digitizing DigitizationTech Target. (2011, April). Definition: digitization. ''WhatIs.com''. Retrieved December 15, 2021, from https://whatis.techtarget.com/definition/digitization is the process of converting information into a digital (i.e. computer-r ...
devices like image plates or flat panel detectors) and dose measurement devices (such as ionization chambers, Geiger counters, and dosimeters used to measure the local radiation exposure,
dose Dose or Dosage may refer to: Music * ''Dose'' (Gov't Mule album), 1998 * ''Dose'' (Latin Playboys album) * ''Dosage'' (album), by the band Collective Soul * "Dose" (song), a 2018 song by Ciara * "Dose", song by Filter from the album '' Short ...
, and/or dose rate, for example, for verifying that
radiation protection Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Expos ...
equipment and procedures are effective on an ongoing basis).


Shielding

Lead Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...
is the main material used by radiography personnel for shielding against scattered X-rays.


Image properties

Projectional radiography relies on the characteristics of x-ray radiation (''quantity'' and ''quality'' of the beam) and knowledge of how it interacts with human tissue to create diagnostic images. X-rays are a form of ionizing radiation, meaning it has sufficient energy to potentially remove electrons from an atom, thus giving it a charge and making it an ion.


X-ray attenuation

When an exposure is made, x-ray radiation exits the tube as what is known as the ''primary beam''. When the primary beam passes through the body, some of the radiation is absorbed in a process known as attenuation. Anatomy that is denser has a higher rate of attenuation than anatomy that is less dense, so bone will absorb more x-rays than soft tissue. What remains of the primary beam after attenuation is known as the ''remnant beam''. The remnant beam is responsible for exposing the image receptor. Areas on the image receptor that receive the most radiation (portions of the remnant beam experiencing the least attenuation) will be more heavily exposed, and therefore will be processed as being darker. Conversely, areas on the image receptor that receive the least radiation (portions of the remnant beam experience the most attenuation) will be less exposed and will be processed as being lighter. This is why bone, which is very dense, process as being ‘white’ on radio graphs, and the lungs, which contain mostly air and is the least dense, shows up as ‘black’.


Density

Radiographic density is the measure of overall darkening of the image. Density is a logarithmic unit that describes the ratio between light hitting the film and light being transmitted through the film. A higher radiographic density represents more opaque areas of the film, and lower density more transparent areas of the film. With digital imaging, however, density may be referred to as ''brightness.'' The brightness of the radiograph in digital imaging is determined by computer software and the monitor on which the image is being viewed.


Contrast

Contrast is defined as the difference in radiographic density between adjacent portions of the image. The range between black and white on the final radiograph. High contrast, or short-scale contrast, means there is little gray on the radiograph, and there are fewer gray shades between black and white. Low contrast, or long-scale contrast, means there is much gray on the radiograph, and there are many gray shades between black and white. Closely related to radiographic contrast is the concept of exposure latitude. Exposure latitude is the range of exposures over which the recording medium (image receptor) will respond with a diagnostically useful density; in other words, this is the "flexibility" or "leeway" that a radiographer has when setting his/her exposure factors. Images having a short-scale of contrast will have narrow exposure latitude. Images having long-scale contrast will have a wide exposure latitude; that is, the radiographer will be able to utilize a broader range of technical factors to produce a diagnostic-quality image. Contrast is determined by the kilovoltage (kV; energy/quality/penetrability) of the x-ray beam and the tissue composition of the body part being radiographed. Selection of look-up tables (LUT) in digital imaging also affects contrast. Generally speaking, high contrast is necessary for body parts in which bony anatomy is of clinical interest (extremities, bony thorax, etc.). When soft tissue is of interest (ex. abdomen or chest), lower contrast is preferable in order to accurately demonstrate all of the soft tissue tones in these areas.


Geometric magnification

Geometric magnification results from the detector being farther away from the X-ray source than the object. In this regard, the ''source-detector distance'' or SDD is a measurement of the distance between the generator and the detector. Alternative names are ''source''/''focus'' to ''detector''/''image-receptor''/''film'' (latter used when using X-ray film) distance (SID, FID or FRD). The ''estimated radiographic magnification factor'' (''ERMF'') is the ratio of the ''source-detector distance'' (SDD) over the ''source-object distance'' (SOD). The size of the object is given as:
Size_ = \frac,
where Sizeprojection is the size of the projection that the object forms on the detector. On lumbar and chest radiographs, it is anticipated that ERMF is between 1.05 and 1.40. Because of the uncertainty of the true size of objects seen on projectional radiography, their sizes are often compared to other structures within the body, such as dimensions of the
vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characterist ...
e, or empirically by clinical experience. The ''source-detector distance'' (SDD) is roughly related to the ''source-object distance'' (SOD) and the ''object-detector distance'' (ODD) by the equation SOD + ODD = SDD.


Geometric unsharpness

Geometric unsharpness is caused by the X-ray generator not creating X-rays from a single point but rather from an area, as can be measured as the ''focal spot size''. Geometric unsharpness increases proportionally to the focal spot size, as well as the ''estimated radiographic magnification factor'' (''ERMF'').


Geometric distortion

Organs will have different relative distances to the detector depending on which direction the X-rays come from. For example, chest radiographs are preferably taken with X-rays coming from behind (called a "posteroanterior" or "PA" radiograph). However, in case the patient cannot stand, the radiograph often needs to be taken with the patient lying in a
supine position The supine position ( or ) means lying horizontally with the face and torso facing up, as opposed to the prone position, which is face down. When used in surgical procedures, it grants access to the peritoneal, thoracic and pericardial region ...
(called a "bedside" radiograph) with the X-rays coming from above ("anteroposterior" or "AP"), and geometric magnification will then cause for example the heart to appear larger than it actually is because it is further away from the detector.


Scatter

In addition to using an anti-scatter grid, increasing the ODD alone can improve image contrast by decreasing the amount of
scattered Scattered may refer to: Music * ''Scattered'' (album), a 2010 album by The Handsome Family * "Scattered" (The Kinks song), 1993 * "Scattered", a song by Ace Young * "Scattered", a song by Lauren Jauregui * "Scattered", a song by Green Day from ' ...
radiation that reaches the receptor. However, this needs to be weighted against increased geometric unsharpness if the SDD is not also proportionally increased.


Imaging variations by target tissue

Projection radiography uses
X-rays X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ' ...
in different amounts and strengths depending on what body part is being imaged: *Hard tissues such as
bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, an ...
require a relatively high energy photon source, and typically a
tungsten Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isol ...
anode is used with a high voltage (50-150 kVp) on a 3-phase or high-frequency machine to generate bremsstrahlung or
braking radiation ''Bremsstrahlung'' (), from "to brake" and "radiation"; i.e., "braking radiation" or "deceleration radiation", is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typica ...
. Bony tissue and metals are denser than the surrounding tissue, and thus by absorbing more of the X-ray photons they prevent the film from getting exposed as much. Wherever dense tissue absorbs or stops the X-rays, the resulting X-ray film is unexposed, and appears translucent blue, whereas the black parts of the film represent lower-density tissues such as fat, skin, and internal organs, which could not stop the X-rays. This is usually used to see bony fractures, foreign objects (such as ingested coins), and used for finding bony pathology such as
osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone which affects 1 in 7 adults in the United States. It is believed to be the fourth leading cause of disability in the ...
, infection (
osteomyelitis Osteomyelitis (OM) is an infection of bone. Symptoms may include pain in a specific bone with overlying redness, fever, and weakness. The long bones of the arms and legs are most commonly involved in children e.g. the femur and humerus, while the ...
), cancer ( osteosarcoma), as well as growth studies (leg length, achondroplasia,
scoliosis Scoliosis is a condition in which a person's spine has a sideways curve. The curve is usually "S"- or "C"-shaped over three dimensions. In some, the degree of curve is stable, while in others, it increases over time. Mild scoliosis does not t ...
, etc.). * Soft tissues are seen with the same machine as for hard tissues, but a "softer" or less-penetrating X-ray beam is used. Tissues commonly imaged include the lungs and heart shadow in a chest X-ray, the air pattern of the bowel in abdominal X-rays, the soft tissues of the neck, the orbits by a skull X-ray before an MRI to check for radiopaque foreign bodies (especially metal), and of course the soft tissue shadows in X-rays of bony injuries are looked at by the radiologist for signs of hidden trauma (for example, the famous "fat pad" sign on a fractured elbow).


Projectional radiography terminology

NOTE: The simplified word 'view' is often used to describe a radiographic projection. Plain radiography generally refers to projectional radiography (without the use of more advanced techniques such as
computed tomography A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers ...
). Plain radiography can also refer to
radiography Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeuti ...
without a radiocontrast agent or radiography that generates single static images, as contrasted to fluoroscopy. *AP - Antero-Posterior *PA - Postero-Anterior *DP - Dorsal-Plantar *Lateral - Projection taken with the central ray perpendicular to the midsagittal plane *Oblique - Projection taken with the central ray at an angle to any of the body planes. Described by the angle of obliquity and the portion of the body the X-ray beam exits; right or left and posterior or anterior. For example, a 45 degree Right Anterior Oblique of the Cervical Spine. *Flexion - Joint is radiographed while in flexion *Extension - Joint is radiographed while in extension *Stress Views - Typically taken of joints with external force applied in a direction that is different from main movement of the joint. Test of stability. *Weight-bearing - Generally with the subject standing up *HBL, HRL, HCR or CTL - Horizontal Beam Lateral, Horizontal Ray Lateral, Horizontal Central Ray, or Cross Table Lateral. Used to obtain a lateral projection usually when patients are unable to move. *Prone - Patient lies on their front *Supine - Patient lies on the back *Decubitus - Patient lying down. Further described by the downside body surface: dorsal (backside down), ventral (frontside down), or lateral (left or right side down). *OM - occipito-mental, an imaginary positioning line extending from the menti (chin) to the occiput (particularly the external occiputal protuberance) *Cranial or Cephalad - Tube angulation towards the head *Caudal - Tube angulation towards the feet


By target organ or structure


Breasts

Projectional radiography of the breasts is called
mammography Mammography (also called mastography) is the process of using low-energy X-rays (usually around 30 kVp) to examine the human breast for diagnosis and screening. The goal of mammography is the early detection of breast cancer, typically through d ...
. This has been used mostly on women to screen for
breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or ...
, but is also used to view male breasts, and used in conjunction with a radiologist or a surgeon to localise suspicious tissues before a
biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a d ...
or a lumpectomy. Breast implants designed to enlarge the breasts reduce the viewing ability of mammography, and require more time for imaging as more views need to be taken. This is because the material used in the implant is very dense compared to breast tissue, and looks white (clear) on the film. The radiation used for mammography tends to be softer (has a lower
photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are Massless particle, massless ...
energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...
) than that used for the harder tissues. Often a tube with a
molybdenum Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with le ...
anode An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemoni ...
is used with about 30 000 volts (30 kV), giving a range of X-ray energies of about 15-30 keV. Many of these photons are "characteristic radiation" of a specific energy determined by the atomic structure of the target material (Mo-K radiation).


Chest

Chest radiographs are used to diagnose many conditions involving the chest wall, including its bones, and also structures contained within the thoracic cavity including the lungs,
heart The heart is a muscular organ found in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon diox ...
, and great vessels. Conditions commonly identified by chest radiography include
pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severi ...
,
pneumothorax A pneumothorax is an abnormal collection of air in the pleural space between the lung and the chest wall. Symptoms typically include sudden onset of sharp, one-sided chest pain and shortness of breath. In a minority of cases, a one-way valve ...
, interstitial lung disease,
heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, ...
, bone fracture and
hiatal hernia A hiatal hernia or hiatus hernia is a type of hernia in which abdominal organs (typically the stomach) slip through the diaphragm into the middle compartment of the chest. This may result in gastroesophageal reflux disease (GERD) or lary ...
. Typically an erect postero-anterior (PA) projection is the preferred projection. Chest radiographs are also used to screen for job-related lung disease in industries such as mining where workers are exposed to dust. For some conditions of the chest, radiography is good for screening but poor for diagnosis. When a condition is suspected based on chest radiography, additional imaging of the chest can be obtained to definitively diagnose the condition or to provide evidence in favor of the diagnosis suggested by initial chest radiography. Unless a fractured rib is suspected of being displaced, and therefore likely to cause damage to the lungs and other tissue structures, x-ray of the chest is not necessary as it will not alter patient management.


Abdomen

In children, abdominal radiography is indicated in the acute setting in suspected
bowel obstruction Bowel obstruction, also known as intestinal obstruction, is a mechanical or functional obstruction of the intestines which prevents the normal movement of the products of digestion. Either the small bowel or large bowel may be affected. Signs ...
,
gastrointestinal perforation Gastrointestinal perforation, also known as ruptured bowel, is a hole in the wall of part of the gastrointestinal tract. The gastrointestinal tract includes the esophagus, stomach, small intestine, and large intestine. Symptoms include severe ab ...
, foreign body in the alimentary tract, suspected abdominal mass and
intussusception Intussusception may refer to: * Intussusception (medical disorder) Intussusception is a medical condition in which a part of the intestine folds into the section immediately ahead of it. It typically involves the small bowel and less commonly t ...
(latter as part of the differential diagnosis). Yet,
CT scan A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers ...
is the best alternative for diagnosing intra-abdominal injury in children. For
acute abdominal pain An acute abdomen refers to a sudden, severe abdominal pain. It is in many cases a medical emergency, requiring urgent and specific diagnosis. Several causes need immediate surgical treatment. Differential diagnosis The differential diagnosis o ...
in adults, an abdominal x-ray has a low
sensitivity Sensitivity may refer to: Science and technology Natural sciences * Sensitivity (physiology), the ability of an organism or organ to respond to external stimuli ** Sensory processing sensitivity in humans * Sensitivity and specificity, statisti ...
and
accuracy Accuracy and precision are two measures of '' observational error''. ''Accuracy'' is how close a given set of measurements (observations or readings) are to their '' true value'', while ''precision'' is how close the measurements are to each ot ...
in general. Computed tomography provides an overall better surgical strategy planning, and possibly less unnecessary laparotomies. Abdominal x-ray is therefore not recommended for adults presenting in the emergency department with acute abdominal pain. The standard abdominal X-ray protocol is usually a single anteroposterior projection in
supine position The supine position ( or ) means lying horizontally with the face and torso facing up, as opposed to the prone position, which is face down. When used in surgical procedures, it grants access to the peritoneal, thoracic and pericardial region ...
. A ''Kidneys, Ureters, and Bladder'' projection (KUB) is an anteroposterior abdominal projection that covers the levels of the urinary system, but does not necessarily include the diaphragm.


Axial skeleton


Head

* Cerebral angiography allows visualization of blood vessels in and around the brain. A contrast agent is injected prior to the radiographs of the head, * Orbital radiography, imaging both left and right eye sockets, generally including the frontal and maxillary sinuses. * Dental radiography uses a small radiation dose with high penetration to view teeth, which are relatively dense. A
dentist A dentist, also known as a dental surgeon, is a health care professional who specializes in dentistry (the diagnosis, prevention, management, and treatment of diseases and conditions of the oral cavity and other aspects of the craniofacial co ...
may examine a painful tooth and
gum Gum may refer to: Types of gum * Adhesive * Bubble gum * Chewing gum * Gum (botany), sap or other resinous material associated with certain species of the plant kingdom ** Gum arabic, made from the sap of ''Acacia senegal'', an Old World tree s ...
using X-ray equipment. The machines used are typically single-phase pulsating DC, the oldest and simplest sort. Dental technicians or the dentist may run these machines; radiographers are not required by law to be present. A derivative technique from projectional radiography used in dental radiography is
orthopantomography A panoramic radiograph is a panoramic scanning dental X-ray of the upper and lower jaw. It shows a two-dimensional view of a half-circle from ear to ear. Panoramic radiography is a form of focal plane tomography; thus, images of multiple pl ...
. This is a panoramic imaging technique of the upper and lower jaw using focal plane tomography, where the X-ray generator and X-ray detector are simultaneously moved so as to keep a consistent exposure of only the plane of interest during image acquisition. *Sinus - The standard protocol in the UK is ''OM with open mouth''. *Facial Bones - The standard protocol in the UK is ''OM and OM 30°''. In case of trauma, the standard UK protocol is to have a
CT scan A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers ...
of the skull instead of projectional radiography. A skeletal survey including the skull can be indicated in for example multiple myeloma.


Other axial skeleton

*The spine (that is, the
vertebral column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordate ...
. A projectional radiograph of the spine confers an effective dose of approximately 1.5 mSv, comparable to a
background radiation equivalent time Background radiation equivalent time (BRET) or background equivalent radiation time (BERT) is a unit of measurement of ionizing radiation dosage amounting to one day worth of average human exposure to background radiation. BRET units are used as a ...
of 6 months. :* Cervical spine: The standard projections in the UK ''AP and Lateral. Peg projection with trauma only. Obliques and Flexion and Extension on special request''. In the US, five or six projections are common; a Lateral, two 45 degree obliques, an AP axial (Cephalad), an AP "Open Mouth" for C1-C2, and Cervicothoracic Lateral (Swimmer's) to better visualize C7-T1 if necessary. Special projections include a Lateral with Flexion and Extension of the cervical spine, an Axial for C1-C2 (Fuchs or Judd method), and an AP Axial (Caudad) for articular pillars. :*Thoracic Spine - ''AP and Lateral'' in the UK. In the US, an AP and Lateral are basic projections. Obliques 20 degrees from lateral may be ordered to better visualize the zygapophysial joint. :*Lumbar Spine - ''AP and Lateral +/- L5/S1 view in the UK, with obliques and Flexion and Extension requests being rare''. In the US, basic projections include an AP, two Obliques, a Lateral, and a Lateral L5-S1 spot to better visualize the L5-S1 interspace. Special projections are AP Right and Left bending, and Laterals with Flexion and Extension. :*Pelvis - ''AP only in the UK, with SIJ projections (prone) on special request''. ::*Sacrum and Coccyx: In the US, if both bones are to be examined separate cephalad and caudad AP axial projections are obtained for the sacrum and coccyx respectively as well as a single Lateral of both bones. * Ribs: In the US, common rib projections are based on the location of the area of interest. These are obtained with shorter wavelengths/higher frequencies/higher levels of radiation than a standard CXR. :*Anterior area of interest - a PA chest X-ray, a PA projection of the ribs, and a 45 degree Anterior Oblique with the non-interest side closest to the image receptor. :*Posterior area of interest - a PA chest X-ray, an AP projection of the ribs, and a 45 degree Posterior Oblique with the side of interest closest to the image receptor. *Sternum. The standard projections in the UK are ''PA chest and lateral sternum''. In the US, the two basic projections are a 15 to 20 degree Right Anterior Oblique and a Lateral. :*Sternoclavicular Joints - Are usually ordered as a single PA and a Right and Left 15 degree Right Anterior Obliques in the US.


Shoulders

These include: ;AP-projection 40° posterior oblique after Grashey The body has to be rotated about 30 to 45 degrees towards the shoulder to be imaged, and the standing or sitting patient lets the arm hang. This method reveals the joint gap and the vertical alignment towards the socket. ;Transaxillary projection The arm should be abducted 80 to 100 degrees. This method reveals: * The horizontal alignment of the humerus head in respect to the socket, and the lateral clavicle in respect to the acromion. * Lesions of the anterior and posterior socket border or of the tuberculum minus. * The eventual non-closure of the acromial apophysis. * The coraco-humeral interval ;Y-projection The lateral contour of the shoulder should be positioned in front of the film in a way that the longitudinal axis of the scapula continues parallel to the path of the rays. This method reveals: * The horizontal centralization of the humerus head and socket. * The osseous margins of the coraco-acromial arch and hence the supraspinatus outlet canal. * The shape of the acromion This projection has a low tolerance for errors and accordingly needs proper execution. The Y-projection can be traced back to Wijnblath’s 1933 published cavitas-en-face projection. In the UK, the standard projections of the shoulder are AP and Lateral Scapula or Axillary Projection. Transaxillary CR shoulder.jpg, alt=A Transaxillary conventional radiography, Transaxillary Y CR shoulder.jpg, alt=A Y-projection conventional radiography, Y-projection


Extremities

A projectional radiograph of an extremity confers an effective dose of approximately 0.001 mSv, comparable to a
background radiation equivalent time Background radiation equivalent time (BRET) or background equivalent radiation time (BERT) is a unit of measurement of ionizing radiation dosage amounting to one day worth of average human exposure to background radiation. BRET units are used as a ...
of 3 hours. The standard projection protocols in the UK are: *Clavicle - ''AP and AP Cranial'' *Humerus - ''AP and Lateral'' *Elbow - ''AP and Lateral. Radial head projections available on request'' File:X-ray of normal elbow by lateral projection.jpg, Lateral projection File:X-ray of normal elbow by anteroposterior projection.jpg, Anteroposterior projection File:X-ray of normal elbow by 30 degrees internal oblique projection.jpg, Left elbow by 30 degrees internal oblique projection File:X-ray of normal elbow by 30 degrees external oblique projection.jpg, Left elbow by 30 degrees external oblique projection *Radius and Ulna - ''AP and Lateral'' *Wrist - ''DP and Lateral'' File:X-ray of normal wrist by dorsoplantar projection (crop).jpg, Left wrist by dorsoplantar projection File:X-ray of normal wrist by lateral projection (crop).jpg, Lateral projection *Scaphoid - ''DP with Ulna deviation, Lateral, Oblique and DP with 30° angulation'' * Hip joint: ''AP and Lateral''. :*The ''Lauenstein projection'' a form of examination of the hip joint emphasizing the relationship of the
femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...
to the
acetabulum The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint. Structure There are three bones of the ''os coxae'' (hip bone) tha ...
. The knee of the affected leg is flexed, and the thigh is drawn up to nearly a right angle. This is also called the frog-leg position. File:Hueftgelenk-gesund.jpg, AP view of normal hip File:X-ray of the pelvis of a 22 months old male - Lauenstein.jpg, Lauenstein projection of normal hips :Applications include X-ray of hip dysplasia. *Hand - ''DP and Oblique'' File:X-ray of normal hand by dorsoplantar projection.jpg, Left hand by dorsoplantar projection File:X-ray of normal hand by lateral projection.jpg, Lateral projection File:X-ray of normal hand by oblique projection.jpg, Oblique projection *Fingers - ''DP and Lateral'' *Thumb - ''AP and Lateral'' *Femur - ''AP and Lateral'' *Knee - ''AP and Lateral. Intra Condular projections on request'' *Patella - ' File:X-ray of a normal knee by anteroposterior projection.jpg, Right knee, anteroposterior File:X-ray of a normal knee by lateral projection.jpg, Right knee, lateral File:X-ray of a normal patella.jpg, Patella, (slightly skew) skyline *Tibia and Fibula - ''AP and Lateral'' *Ankle - ''AP/Mortice and Lateral'' File:X-ray of normal ankle - frontal.jpg, Ankle - frontal File:X-ray of normal ankle - 15 degrees internal rotation.jpg, 15 degrees internal rotation File:X-ray of normal ankle - lateral.jpg, Lateral (this one a bit suboptimal by not seeing straight through the ankle joint) File:X-ray of normal ankle - lateral oblique.jpg, Lateral oblique (to visualize the posterior border of the tibia) *Calcaneum - ''Axial and Lateral'' *Foot / Toes - ''Dorsoplantar, Oblique and Lateral''. File:X-ray of normal right foot by dorsoplantar projection.jpg, Normal right foot by dorsoplantar projection File:X-ray of normal right foot by oblique projection.jpg, Oblique projection File:X-ray of normal right foot by lateral projection.jpg, Lateral projection Certain suspected conditions require specific projections. For example, skeletal signs of rickets are seen predominantly at sites of rapid growth, including the proximal humerus, distal radius, distal femur and both the proximal and the distal tibia. Therefore, a skeletal survey for rickets can be accomplished with anteroposterior radiographs of the knees, wrists, and ankles.


General disease mimics

Radiological disease mimics are visual artifacts, normal anatomic structures or harmless
variants Variant may refer to: In arts and entertainment * ''Variant'' (magazine), a former British cultural magazine * Variant cover, an issue of comic books with varying cover art * ''Variant'' (novel), a novel by Robison Wells * "The Variant", 2021 e ...
that may simulate diseases or abnormalities. In projectional radiography, general disease mimics include jewelry, clothes and skin folds. In general medicine a disease mimic shows symptoms and/or signs like those of another. File:Skin folds close to a hip fracture (with arrows).jpg, A hip fracture (black arrow) next to a skin fold (white arrow). File:Bed sheets artifact on lateral chest radiograph.jpg, Bed sheets looking like lung opacities on a chest radiograph


See also

*
Medical imaging in pregnancy Medical imaging in pregnancy may be indicated because of pregnancy complications, intercurrent diseases or routine prenatal care. Options Options for medical imaging in pregnancy include the following: *Magnetic resonance imaging (MRI) without ...
, including projectional radiography *
Radiography Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeuti ...
* Medical imaging *
X-ray X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ' ...
* X-ray generator * X-ray detector * Radiographer * Digital radiography * Tomography *
Anatomical terms of location Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position ...


References


External links


Online Radiography Positioning ManualNice GuidelinesRADIOGRAPHY WIKI
A fledgling radiography specific wiki {{Medical imaging