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50-401: In humans, the patella is the largest sesamoid bone (i.e., embedded within a tendon or a muscle) in the body. Babies are born with a patella of soft cartilage which begins to ossify into bone at about four years of age. The patella is a sesamoid bone roughly triangular in shape, with the apex of the patella facing downwards. The apex is the most inferior (lowest) part of the patella. It

100-399: A radiocontrast agent or radiography that generates single static images, as contrasted to fluoroscopy , which are technically also projectional. Projectional radiographs generally use X-rays created by X-ray generators , which generate X-rays from X-ray tubes . An anti-scatter grid may be placed between the patient and the detector to reduce the quantity of scattered x-rays that reach

150-447: A sesamoid bone ( / ˈ s ɛ s əm ɔɪ d / ) is a bone embedded within a tendon or a muscle . Its name is derived from the Greek word for ' sesame seed', indicating the small size of most sesamoids. Often, these bones form in response to strain, or can be present as a normal variant . The patella is the largest sesamoid bone in the body. Sesamoids act like pulleys , providing

200-399: 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. 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

250-485: 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

300-530: 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

350-428: A smooth surface for tendons to slide over, increasing the tendon's ability to transmit muscular forces . Sesamoid bones can be found on joints throughout the human body, including: In equine anatomy , the term sesamoid bone usually refers to the two sesamoid bones found at the back of the fetlock or metacarpophalangeal and metatarsophalangeal joints in both hindlimbs and forelimbs . Strictly these should be termed

400-535: A specific energy determined by the atomic structure of the target material (Mo-K radiation). 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 , and great vessels . Conditions commonly identified by chest radiography include pneumonia , pneumothorax , interstitial lung disease , heart failure , bone fracture and hiatal hernia . Typically an erect postero-anterior (PA) projection

450-553: Is a form of radiography and medical imaging that produces two-dimensional images by X-ray radiation . 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 that can generate 3D-images). Plain radiography can also refer to radiography without

500-428: 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 vertebrae , 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

550-440: 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 energy ) than that used for the harder tissues. Often a tube with a molybdenum anode 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

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600-444: Is being imaged: 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 ). Plain radiography can also refer to radiography without a radiocontrast agent or radiography that generates single static images, as contrasted to fluoroscopy . Projectional radiography of

650-442: 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

700-449: 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 results from the detector being farther away from the X-ray source than the object. In this regard,

750-464: Is pointed in shape, and gives attachment to the patellar ligament . The front and back surfaces are joined by a thin margin and towards centre by a thicker margin. The tendon of the quadriceps femoris muscle attaches to the base of the patella., with the vastus intermedius muscle attaching to the base itself, and the vastus lateralis and vastus medialis are attached to outer lateral and medial borders of patella respectively. The upper third of

800-406: Is still unknown; however, it may be to assist in grasping small objects and thin branches. Elephants have similarly enlarged sesamoid bones in both their forelimbs and hindlimbs, referred to as the prepollex and prehallux, respectively. These sesamoids function as "sixth toes", helping to distribute the animals' weight. In contrast to other sesamoids in elephants, which ossify at 3–7 years of age,

850-440: 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

900-425: 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 . 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. In case of trauma,

950-436: The knee . The patella is stabilized by the insertion of the horizontal fibres of vastus medialis and by the prominence of the lateral femoral condyle , which discourages lateral dislocation during flexion. The retinacular fibres of the patella also stabilize it during exercise. Patellar dislocations occur with significant regularity, particularly in young female athletes. It involves the patella sliding out of its position on

1000-444: The proximal sesamoid bones whereas the navicular bone should be referred to as the distal sesamoid bone. The patella is also a form of sesamoid bone in the horse. Although many carnivores have radial sesamoid bones, the giant panda and red panda independently evolved to have an enlarged radial sesamoid bone. This evolution has caused the two species to diverge from other carnivores. The red panda likely originally evolved

1050-429: 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

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1100-401: The "pseudo-thumb" in order to assist in arboreal locomotion. When the red panda later evolved to consume a bamboo diet, the enlarged bone underwent exaptation to assist in grasping bamboo. The giant panda, however, evolved the enlarged radial sesamoid bone around the same time as it evolved a bamboo diet. In the giant panda, the bone allows for a pincer-like motion and is used in grasping

1150-528: The UK, the standard projections of the shoulder are AP and Lateral Scapula or Axillary Projection. A projectional radiograph of an extremity confers an effective dose of approximately 0.001 mSv , comparable to a background radiation equivalent time of 3 hours. The standard projection protocols in the UK are: Certain suspected conditions require specific projections. For example, skeletal signs of rickets are seen predominantly at sites of rapid growth, including

1200-483: 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 (called a "bedside" radiograph) with the X-rays coming from above ("anteroposterior" or "AP"), and geometric magnification will then cause for example

1250-454: The alimentary tract , suspected abdominal mass and intussusception (latter as part of the differential diagnosis ). Yet, CT scan is the best alternative for diagnosing intra-abdominal injury in children. For acute abdominal pain in adults, an abdominal X-ray has a low sensitivity and accuracy in general. Computed tomography provides an overall better surgical strategy planning, and possibly less unnecessary laparotomies. Abdominal X-ray

1300-410: The articular cartilage of the patella is among the thickest in the human body. The lower part of the posterior surface has vascular canaliculi filled and is filled by fatty tissue, the infrapatellar fat pad . Emarginations (i.e. patella emarginata , a "missing piece") are common laterally on the proximal edge. Bipartite patellas are the result of an ossification of a second cartilaginous layer at

1350-403: The bamboo. In these two panda species, DYNC2H1 gene and PCNT gene have been identified as possible causes for the pseudo-thumb development. Recently, the enlarged radial sesamoid bone of cotton rats has been studied. Their enlarged radial sesamoid bone and that of the giant panda have a similar morphology and size relative to the rest of the hand. The reason for this evolutionary change

1400-429: The breasts is called mammography . This has been used mostly on women to screen for breast cancer , 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 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

1450-409: The cause of chronic pain when formed on the patella. The patella is found in placental mammals and birds ; most marsupials have only rudimentary, non-ossified patellae although a few species possess a bony patella. A patella is also present in the living monotremes , the platypus and the echidna . In other tetrapods, including living amphibians and most reptiles (except some lepidosaurs ),

1500-473: The detector. This improves the contrast resolution of the image, but also increases radiation exposure for the patient. Detectors can be divided into two major categories: imaging detectors (such as photographic plates and X-ray film ( photographic film ), now mostly replaced by various digitizing devices like image plates or flat panel detectors ) and dose measurement devices (such as ionization chambers , Geiger counters , and dosimeters used to measure

1550-424: 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, an X-ray of the chest is not necessary as it will not alter patient management. In children, abdominal radiography is indicated in the acute setting in suspected bowel obstruction , gastrointestinal perforation , foreign body in

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1600-433: The equation SOD + ODD = SDD. 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 ). Organs will have different relative distances to the detector depending on which direction

1650-399: The femur and is subdivided into a medial and a lateral facet by a vertical ledge which varies in shape. In the adult the articular surface is about 12 cm (1.9 sq in) and covered by cartilage , which can reach a maximal thickness of 6 mm (0.24 in) in the centre at about 30 years of age. Owing to the great stress on the patellofemoral joint during resisted knee flexion,

1700-405: The front of the patella is coarse, flattened, and rough, and serves for the attachment of the tendon of the quadriceps and often has exostoses . The middle third has numerous vascular canaliculi . The lower third culminates in the apex which serves as the origin of the patellar ligament . The posterior surface is divided into two parts. The upper three-quarters of the patella articulates with

1750-590: The heart to appear larger than it actually is because it is further away from the detector. In addition to using an anti-scatter grid , increasing the ODD alone can improve image contrast by decreasing the amount of scattered radiation that reaches the receptor. However, this needs to be weighted against increased geometric unsharpness if the SDD is not also proportionally increased. Projection radiography uses X-rays in different amounts and strengths depending on what body part

1800-403: 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'. Radiographic density is the measure of overall darkening of

1850-436: 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

1900-443: The joint. A patella baja is a low-riding patella. A long-standing patella baja may result in extensor dysfunction. The Insall-Salvati ratio helps to indicate patella baja on lateral X-rays , and is calculated as the patellar tendon length divided by the patellar bone length. An Insall-Salvati ratio of < 0.8 indicates patella baja. The kneecap is prone to injury because of its particularly exposed location, and fractures of

1950-402: The knee, most often laterally, and may be associated with extremely intense pain and swelling. The patella can be tracked back into the groove with an extension of the knee, and therefore sometimes returns into the proper position on its own. A patella alta is a high-riding (superiorly aligned) patella. An attenuated patella alta is an unusually small patella that develops out of and above

2000-482: The local radiation exposure , dose , and/or dose rate, for example, for verifying that radiation protection equipment and procedures are effective on an ongoing basis). Lead is the main material used by radiography personnel for shielding against scattered X-rays. 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

2050-497: The location of an emargination. Previously, bipartite patellas were explained as the failure of several ossification centres to fuse, but this idea has been rejected. Partite patellas occur almost exclusively in men. Tripartite and even multipartite patellas occur. The upper three-quarters of the patella articulates with the femur and is subdivided into a medial and a lateral facet by a vertical ledge which varies in shape. Four main types of articular surface can be distinguished: In

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2100-403: The monitor on which the image is being viewed. 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

2150-534: The muscle tendons from the upper leg are attached directly to the tibia , and a patella is not present. In 2017 it was discovered that frogs have kneecaps, contrary to what was thought. This raises the possibility that the kneecap arose 350 million years ago when tetrapods first appeared, but that it disappeared in some animals. The word patella originated in the late 17th century from the diminutive form of Latin patina or patena or paten , meaning shallow dish. Sesamoid bone In anatomy ,

2200-423: The object is given as: S i z e o b j e c t = S i z e p r o j e c t i o n E R M F {\displaystyle Size_{object}={\frac {Size_{projection}}{ERMF}}} , where Size projection is the size of the projection that the object forms on the detector. On lumbar and chest radiographs , it

2250-554: The ossification of the prepollex and prehallux is delayed and is known to not have yet occurred in animals in excess of 20 years of age. The prehallux is further divided into two elements; the more proximal of these is fixed, whilst the more distal is mobile. Evidence of these "predigits" has also been found in certain fossil proboscideans . The forepaws of moles also possess a prepollex consisting of an enlarged, sickle-shaped sesamoid. Projectional radiography Projectional radiography , also known as conventional radiography ,

2300-467: The patella an ossification centre develops at the age of 3–6 years. The patella originates from two centres of ossification which unite when fully formed. The primary functional role of the patella is knee extension. The patella increases the leverage that the quadriceps tendon can exert on the femur by increasing the angle at which it acts. The patella is attached to the tendon of the quadriceps femoris muscle , which contracts to extend/straighten

2350-450: The patella commonly occur as a consequence of direct trauma onto the knee. These fractures usually cause swelling and pain in the region, bleeding into the joint ( hemarthrosis ), and an inability to extend the knee. Patella fractures are usually treated with surgery, unless the damage is minimal and the extensor mechanism is intact. An exostosis is the formation of new bone onto a bone, as a result of excess calcium formation. This can be

2400-488: 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. Radiological disease mimics are visual artifacts , normal anatomic structures or harmless variants that may simulate diseases or abnormalities. In projectional radiography, general disease mimics include jewelry, clothes and skin folds . In general medicine

2450-469: The socket. The arm should be abducted 80 to 100 degrees. This method reveals: 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: 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

2500-418: The standard UK protocol is to have a CT scan of the skull instead of projectional radiography. A skeletal survey including the skull can be indicated in for example multiple myeloma. These include: 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

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