Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

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Fat suppressed imaging

Fat suppression is commonly used in magnetic resonance (MR) imaging to suppress the signal from adipose tissue or detect adipose tissue 1. It can be applied to both T1 and T2 weighted sequences. Due to short relaxation times, fat has a high signal on magnetic resonance images (MRI). This high ...

Short tau inversion recovery

Short tau inversion recovery (STIR), also known as short TI inversion recovery, is a fat suppression technique with an inversion time TI = ln(2)·T1fat, where the signal of fat is zero. This equates to approximately 140 ms at 1.5 T. To distinguish two tissue components with this technique, their...

Fluid attenuated inversion recovery

Fluid attenuated inversion recovery (FLAIR) is a special inversion recovery sequence with a long inversion time. This removes signal from the cerebrospinal fluid in the resulting images 1. Brain tissue on FLAIR images appears similar to T2 weighted images with grey matter brighter than white mat...

Apparent diffusion coefficient

Apparent diffusion coefficient (ADC) is a measure of the magnitude of diffusion (of water molecules) within tissue, and is commonly clinically calculated using MRI with diffusion-weighted imaging (DWI) 1. Basics Diffusion-weighted imaging (DWI) is widely appreciated as an indispensable tool i...

Ferromagnetism

Ferromagnetic materials generally contain iron, nickel, or cobalt. These materials include magnets, and various objects that might be found in a patient, such as aneurysm clips, parts of pacemakers, shrapnel, etc. These materials have a large positive magnetic susceptibility, i.e. when placed ...

Magnetism

Magnetism is a property of matter that is a result of the orbiting electrons in atoms. The orbiting electrons cause the atoms to have a magnetic moment associated with an intrinsic angular momentum called spin. Magnetic field strengths are measured in tesla (T), a derived SI unit. The equivale...

MRI sequence parameters

Listed in the table below are the most common acquisition parameters for commonly used MRI pulse sequences (in msec). For a general introduction to these sequences please refer to MRI sequences (basic). The specific parameters for any given study varies from one manufacturer to another, and fr...

Contrast resolution

Contrast resolution in radiology refers to the ability of any imaging modality to distinguish between differences in image intensity. The inherent contrast resolution of a digital image is given by the number of possible pixel values, and is defined as the number of bits per pixel value. Imagi...

Hunter's angle

Hunter's angle (HA) is a term coined from a neurosurgeon, C Hunter Shelden, at Huntington Medical Research Institutes. He placed his comb on the spectrum at approximately a 45° angle and connected several of the peaks. If the angle and peaks roughly corresponded to the 45° angle, the curve was c...

Pulsatile portal venous flow

A pulsatile portal venous flow pattern is an abnormal form of portal venous flow and can result from both physiological and pathological causes. In well subjects mild pulsatility, or in rare situations, even marked pulsatility has been described, particularly in thin subjects, with a venous pul...

Echo planar imaging

Echo planar imaging (EPI) is performed using a pulse sequence in which multiple echoes of different phase steps are acquired using rephasing gradients instead of repeated 180-degree radiofrequency pulses following the 90°/180° in a spin echo sequence. This is accomplished by rapidly reversing th...

Pitch (CT)

Pitch (P) is a term used in helical CT. It has two terminologies depending on whether single slice or multislice CT scanners are used 1-3. Single slice CT (SSCT) The term detector pitch is used and is defined as table distance traveled in one 360° gantry rotation divided by beam collimation 2....

Roentgen (unit)

The roentgen (symbol R) or röntgen (in German) is a legacy unit to measure radiation exposure. It was defined as the quantity of x-rays that produce 2.580 × 10-4 coulombs of charge collected per unit mass (kilograms) of air at standard temperature and pressure (STP): 1 R = 0.000258 coulombs per ...

Exposure

The term exposure refers to the concentration, in air, of x-rays at a specific point and is the ionization produced in a specific volume of air: E = Q / m where E is exposure, Q is the quantity of charge on the ions and m is the unit mass of air. Exposure describes the ability of x-ray photons ...

CT dose index

CT dose index (CTDI) (measured in mGy) is a standardized measure of radiation dose output of a CT scanner which allows the user to compare radiation output of different CT scanners. In the past CTDI100 (measured over a 100 mm long ionization chamber) and CTDIw (weighted average of dose across a ...

Magnetic susceptibility artifact

Magnetic susceptibility artifacts (or just susceptibility artifacts) refer to a variety of MRI artifacts that share distortions or local signal change due to local magnetic field inhomogeneities from a variety of compounds. They are especially encountered while imaging near metallic orthopedic...

Zero filling interpolation

Zero filling interpolation (ZIP) is the substitution of zeroes for unmeasured data points in order to increase the matrix size of the new data prior to Fourier transformation of MR data. This results in pixels smaller than the actual resolution of the image. The zero filling occurs in the periph...

Speckle tracking echocardiography

Speckle tracking echocardiography describes the semi-automated analysis of grey scale (B-mode) echocardiographic studies in which the spatial translocation of derived functional units (speckles) allows quantitative analysis of myocardial function. Speckle tracking constitutes a subset of deform...

k-space

k-space is an abstract concept and refers to a data matrix containing the raw MRI data. This data is subjected to mathematical function or formula called a transform to generate the final image. A discrete Fourier or fast Fourier transform 1-3 is generally used though other transforms such as th...

Non contrast enhanced MR angiography

Non contrast enhanced MR angiography is performed in several ways including: time of flight angiography phase contrast angiography three-dimensional (3D) electrocardiograph-triggered half-Fourier fast spin echo Generally, these techniques are time-consuming as compared with contrast enhanced...

MR angiography

Magnetic resonance angiography (usually shortened to MR angiography or MRA) is an alternative to conventional angiography and CT angiography, eliminating the need for ionizing radiation and iodinated contrast media, and sometimes contrast media altogether. It has evolved into several techniques ...

Spoiled gradient echo MRI

Spoiled gradient echo MRI (also known as incoherent gradient echo) is an MRI technique which destroys residual transverse magnetization at the end of each excitation cycle. Vendor-specific examples T1 FFE (Philips) SPGR (GE) FLASH (Siemens)

Gadolinium contrast agents

Gadolinium-based contrast media (GBCM), gadolinium-based contrast agents (GBCAs), or simply gadolinium contrast agents are molecular complexes containing the rare earth metal gadolinium, chelated to a carrier ligand. They are a type of paramagnetic contrast agent, which are the primary class of ...

Gradient echo sequences

Gradient echo sequences (GRE) are an alternative technique to spin-echo sequences, differing from it in two principal points: utilization of gradient fields to generate transverse magnetization flip angles of less than 90° Compared to the spin-echo and inversion recovery sequences, gradient e...

Contrast enhanced MR angiography

Contrast-enhanced MR angiography (MRA) is a technique involving 3D spoiled gradient-echo (GE) sequences, with administration of gadolinium-based contrast agents (GBCA). It can be used to assess vascular structures of almost any part of the body. Its key features are: T1 weighted spoiled gradien...

Time of flight angiography

Time of flight angiography (TOF) is an MRI technique to visualize flow within vessels, without the need to administer contrast. It is based on the phenomenon of flow-related signal hyperintensity of spins entering into an imaging slice. As a result of being unsaturated, these spins give more sig...

CT enteroclysis (protocol)

Computed tomographic (CT) enteroclysis refers to a hybrid technique that combines the methods of fluoroscopic intubation-infusion small bowel examinations with that of abdominal CT. Indications CT enteroclysis is complementary to capsule endoscopy in the elective investigation of small-bowel d...

Pelvic cervical carcinoma protocol (MRI)

A dedicated pelvic MRI protocol is very useful for imaging assessment of cervical carcinoma. Although the FIGO is a clinical staging, the 2009 revised FIGO staging encourages the use of MRI to complement clinical staging. Preparation Imaging is optimally performed after three hours of fasting...

Temporal resolution

Temporal resolution relates to the duration of time for acquisition of a single frame of a dynamic process, i.e., cine imaging. Discussion The concept of temporal resolution is fundamental to cardiac CT and MRI, in which a rapidly beating heart is imaged over the order of milliseconds into mul...

Diffusion-weighted imaging

Diffusion-weighted imaging (DWI) is a form of MR imaging based upon measuring the random Brownian motion of water molecules within a voxel of tissue. In general simplified terms, highly cellular tissues or those with cellular swelling exhibit lower diffusion coefficients. Diffusion is particular...

Cross-excitation artifact (MRI)

Cross-excitation artifact is a type of MRI artifact and refers to the loss of signal within a slice due to pre-excitation from RF pulse meant for an adjacent slice. The frequency profile of the RF pulse is imperfect; this means that during slice selection there is some degree of excitation of t...

MRI artifacts

MRI artifacts are numerous and give an insight into the physics behind each sequence. Some artifacts affect the quality of the MRI exam, while others do not affect the diagnostic quality but may be confused with pathology. When encountering an unfamiliar artifact, it is useful to systematically...

Gibbs and truncation artifacts

Gibbs artifact, also known as truncation artifact or ringing artifact, is a type of MRI artifact. It refers to a series of lines in the MR image parallel to abrupt and intense changes in the object at this location, such as the CSF-spinal cord and the skull-brain interface. The MR image is reco...

Zipper artifact

Zipper artifacts are a type of MRI artifact where one or more spurious bands of electronic noise extends across the image. There are various causes for zipper artifacts in images and no single solution exists. These artifacts can be related to hardware or software problems either of the scann...

Quenching

Quenching refers to rapid expulsion of the liquid cryogen used to maintain the MRI magnet in a superconducting state. Discussion Modern MRI scanners contain superconducting magnets which have very low energy consumption, made possible by maintaining internal subzero temperatures by way of a 'c...

Fourier transform

Fourier transform is a mathematical operation which converts a time domain signal into a frequency domain signal 5. Discussion Fourier transform is integral to all modern imaging, and is particularly important in MRI. The signal received at the detector (receiver coils in MRI, piezoelectric di...

T2* relaxation

T2* decay refers to an exponential decrease in Mxy (i.e. signal strength) following the initial excitation pulse as a function of time constant T2*. A picture of the signal or free induction decay (FID) is shown on the right, occurring immediately after a 90o RF excitation pulse in a liquid pha...

T2 relaxation

T2 relaxation, also known as spin-spin relaxation or transverse relaxation, refers to the progressive dephasing of spinning dipoles resulting in decay in the magnetization in the transverse plane (Mxy). Following a radiofrequency pulse, this form of relaxation occurs with the time constant T2, w...

Free induction decay

Free induction decay (FID) refers to a short-lived sinusoidal electromagnetic signal which appears immediately following the 90° pulse. It is induced in the receiver coil by the rotating component of the magnetization vector in the x-y plane which crosses the coil loops perpendicularly. It does ...

Nuclear magnetic resonance

Nuclear magnetic resonance (NMR) is a powerful technique which allows the study of the magnetic properties of an atom's nucleus 1. It involves placing nuclei within an external magnetic field enabling thus them to undergo precession 2. The 'resonance' part of the names implies the fact that a se...

Electron-positron annihilation

Electron-positron annihilation is the process in which a positron collides with an electron resulting in the annihilation of both particles. Electrons (or β- particles) and positrons (or β+ particles) are of equal mass but opposite charge. Positrons are the antimatter equivalent of an electron,...

Half-life time

The half-life time is the duration it takes for any physical process to reduce the initial amount to fifty percent of its initial value. Physical half-life time (Tp) The time interval required for an amount of certain radioactive nuclei to decay to half of its original value. Tp is always a co...

Production of radioactive nuclei

Naturally occurring radioactive nuclei have a physical half life time of ~108 to 1010 years which makes them unsuitable for use in medical imaging. Thus radioactive nuclei used in medical practice are artificially synthesized. Production of these nuclei involve bombarding stable nuclei with pro...

Aliasing on MRI

Aliasing on MRI, also known as wrap-around, is a frequently encountered MRI artifact that occurs when the field of view (FOV) is smaller than the body part being imaged. The part of the body that lies beyond the edge of the FOV is projected onto the other side of the image 5. This can be correc...

Scintigraphy performed with Tc-99m labeled RBCs

Tc-99m labeled RBCs - with radiolabelling technique in vivo or in vitro of red cells 3 - is one of the technetium radiopharmaceuticals used in the non-invasive assessment of gastrointestinal (GI) bleeding 2, characterized by high sensitivity (93%) and specificity (95%) 4. It is capable, in fact,...

Tc-99m HMPAO labeled WBC

Tc-99m HMPAO (hexamethylpropyleneamine oxime) labeled WBC is one of the technetium radiopharmaceuticals used in WBC imaging. There are three potential radiochemical impurities in the 99mTc-HMPAO: a hydrophilic secondary complex, the free pertechnetate and the reduced 99mTc-hydrolyzate. 1The min...

Thyroid scintigraphy (Tc-99m)

Tc-99m pertechnetate thyroid scintigraphy (thyroid scan) is a functional nuclear medicine study used to assess the thyroid gland. The uptake of the pertechnetate anion - similar in chemical-physical characteristics to the iodide ion (i. e. ionic size and negative charge) - in the thyroid parench...

Tc-99m pertechnetate

Tc-99m pertechnetate (Na+ 99mTc O4-) is one of the technetium radiopharmaceuticals used in imaging of thyroid, colon, bladder and stomach. Technetium (99mTc) has eight oxidation states 6, from -1 to +7; specifically, the oxidation state of technetium in the pertechnetate anion (99mTcO4-) is +7....

Tc-99m MAG3

Tc-99m MAG3 (mercaptoacetyltriglycine) is one of the technetium radiopharmaceuticals used in renal imaging. Due to favorable energy and dosimetric characteristics, MAG3 radiolabeled with technetium has replaced the iodide-131 Hippuran for the study of renal function (tubular secretion physiology...

Modulation transfer function

The modulation transfer function (MTF) describes the ability of a detector to retain the contrast (signal amplitude) of an object. It also measures how much spatial frequency is transferred from the object to an image 8. This is because each detector has its own limiting spatial resolution. Such...

Detective quantum efficiency

Detective quantum efficiency (DQE) is one of the fundamental physical variables related to image quality in radiography and refers to the efficiency of a detector in converting incident x-ray energy into an image signal. The words "quantum efficiency" have a precise meaning, because the DQE mea...

Contrast-enhanced mammography

There are 2 types of contrast-enhanced mammography examination – temporal subtraction and dual-energy. Initial work in the early 2000s used temporal subtraction, but artefacts due to patient movement during prolonged compression limited its diagnostic usefulness. Travieso et al produced a usef...

High-intensity focused ultrasound

High-intensity focussed ultrasound (HIFU), sometimes referred to as focussed ultrasound surgery (FUS), is a promising non-invasive thermal ablation technique. Unlike diagnostic ultrasound, HIFU focuses the ultrasound waves precisely upon a target. In a similar way to how light can be focussed t...

Automated full-field volumetric ultrasound

An automatic full-field volumetric breast ultrasound scanner (AFFBUS) is a developing technology which was initiated to overcome the drawback of dense breast and to get a three-dimensional view of the breast. Components scan station view station Scan station Automatic ultrasound imaging ac...

Maximum intensity projection

Maximum Intensity Projection (MIP) consists of projecting the voxel with the highest attenuation value on every view throughout the volume onto a 2D image 1. Such an algorithm is rather simple: for each XY coordinate, only the pixel with the highest Hounsfield number along the Z-axis is represe...

Minimum intensity projection (MinIP)

Minimum intensity projection (MinIP) is a data visualization method that enables detection of low-density structures in a given volume. The algorithm uses all the data in a volume of interest to generate a single bidimensional image, in other words, it consists of projecting the voxel with the l...

Repetition time

The repetition time (TR) is the time from the application of an excitation pulse to the application of the next pulse. It determines how much longitudinal magnetization recovers between each pulse. It is measured in milliseconds.

Echo time

The echo time (TE) refers to the time between the application of the radiofrequency excitation pulse and the peak of the signal induced in the coil. It is measured in milliseconds. The amount of T2 relaxation is controlled by the TE.

Gyromagnetic ratio

The gyromagnetic ratio, often denoted by the symbol γ (gamma) is the ratio of the magnetic momentum in a particle to its angular momentum. The SI unit is the radian per second per tesla (rad⋅s−1⋅T−1). The gyromagnetic ratio of the proton is 2.675 221 900(18) x 108 s-1⋅T-1. Since a proton wil...

Standard uptake value

The standard uptake value (SUV), also known as standardized uptake value, is a simple way of determining activity in PET imaging, most commonly used in fluorodeoxyglucose (FDG) imaging. It is also known as the dose uptake ratio (DUR). As the name suggests it is a mathematically derived ratio of ...

Bremsstrahlung radiation

X-rays are produced by high-energy electrons bombarding a target, especially targets that have a high proton number (Z). When bombarding electrons penetrate into the target, some electrons travel close to the nucleus due to the attraction of its positive charge and are subsequently influenced by...

Spatial resolution (MRI)

In MRI, spatial resolution is defined by the size of the imaging voxels. Since voxels are three-dimensional rectangular solids, the resolution is frequently different in the three different directions. The size of the voxel and therefore the resolution depends on matrix size, the field-of-view,...

Signal-to-noise ratio (MRI)

Signal-to-noise ratio (SNR) is a generic term which, in radiology, is a measure of true signal (i.e. reflecting actual anatomy) to noise (e.g. random quantum mottle). On MRI the signal-to-noise ratio is measured frequently by calculating the difference in signal intensity between the area of int...

Air gap technique

The air gap technique is a radiographic technique that improves image contrast resolution through reducing the amount of scattered radiation that reaches the image detector. In select situations, this technique can be used instead of an antiscatter grid as the primary scatter reduction method in...

Susceptibility weighted imaging

Susceptibility weighted imaging (SWI) is an MRI sequence that is particularly sensitive to compounds which distort the local magnetic field and as such make it useful in detecting blood products, calcium, etc. Physics SWI is a 3D high-spatial-resolution fully velocity corrected gradient-echo M...

Abnormal ductus venosus waveforms

Abnormal ductus venosus waveforms can arise in a number of conditions ranging from aneuploidy to vascular malformations and fetal tumors. "A wave" reversal can be seen in 5% of euploid fetuses 9. Pathology Abnormal waveforms in fetal ductus venosus flow assessment can occur in a number of situ...

Diffusion-weighted imaging in acute ischemic stroke

Diffusion-weighted imaging (DWI) is a commonly performed MRI sequence for the evaluation of acute ischemic stroke and is very sensitive in the detection of small and early infarcts. Conventional MRI sequences (T1WI, T2WI) may not demonstrate an infarct for 6 hours, and small infarcts may be hard...

Myo-inositol peak

Myo-inositol is one of the compounds images with MR spectroscopy (MRS) at both 1.5 T and 3 T and is seen to resonate at 3.5 ppm chemical shift (right of the choline peak). Myo-inositol is a precursor of both phosphatidylinositol (the major inositol-containing phospholipid) and phosphatidylinos...

Noise

Noise, variability that is not part of a desired signal, is present in all electronic systems, and originates from a number of sources including electronic interference. It appears as an irregular granular pattern in all images and degrades image information. It may be inapparent or render image...

Ontology

Ontology is the study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations. Traditionally listed as a part of the major branch of philosophy known as metaphysics, ontology deals with questions concerning what entities exist or can be ...

RadLex

RadLex is a lexicon of radiological information that has been produced by the Radiological Society of North America (RSNA). It is an ontological system whose principle aim is to develop a useful vocabulary for radiologists. In the words of the RSNA "As images, imaging reports, and medical re...

Thorotrast

Thorotrast is a suspension of radioactive thorium dioxide first produced in Germany in 1928, used as a contrast agent until the 1950s. Its principal use was for cerebral angiography: 90% of the estimated 50,000-100,000 patients treated received it for this purpose. Umbrathor was another thorium ...

Inverse square law

The inverse square law describes the principle of dose reduction as the distance from the source increases. This assumes a point source. If radiation spreads over a spherical area, as the radius increases, the area over which the dose is distributed increases according to A=4πr2 where A is th...

Vicarious contrast media excretion

Vicarious contrast media excretion (VCME) refers to the excretion of intravascularly-administered water-soluble iodinated contrast media in a way other than via normal renal excretion. More rarely it may occur following oral contrast medium administration 6. Epidemiology The most common vicari...

Tc-99m sulfur colloid

Technetium-99m sulfur colloid is one of the technetium radiopharmaceuticals. Characteristics photon energy: 140 keV physical half-life: 6 hours biological half-life: 2 to 3 minutes normal distribution: liver: 85% spleen: 10% bone marrow: 5% excretion: hepatic target organ: liver, splee...

Radiopharmaceuticals

Radiopharmaceuticals are drugs that are bound to radioactive substances. The pharmaceutically active portion determines the activity that will be measured and the radioactive portion emits radiation that can be measured by the scanner. A number of radiopharmaceuticals are used in human imaging...

Functional MRI

Functional magnetic resonance imaging (fMRI) is a technique used to obtain functional information by visualizing cortical activity. fMRI detects subtle alteration in blood flow in response to stimuli or actions. It is used in two broad ways: clinical practice typically in presurgical patients ...

T2 shine through

T2 shine-through refers to high signal on DWI images that is not due to restricted diffusion, but rather to high T2 signal which 'shines through' to the DWI image. T2 shine through occurs because of long T2 decay time in some normal tissue. This is most often seen with subacute infarctions due ...

Comet tail artifact

The comet tail artifact is a grey scale ultrasound finding seen when small calcific / crystalline / highly reflective objects are interrogated and is believed to be a special form of reverberation artifact. It is similar to the color comet tail artifact and is seen in similar situations, althou...

Color comet tail artifact

The color comet tail artifact is an ultrasonographic sign seen in a number of situations when color Doppler scanning is performed. Typically the artifact, which resembles the grey scale comet tail artifact, is seen in a situation when a small highly reflective (usually calcific) object is inter...

Octreotide scintigraphy

Octreotide scintigraphy uses 111In-labeled octreotide, which is a somatostatin analog; it is also known as Octreoscan, a brand name for 111In-labeled pentetreotide. Pentetreotide is a DTPA-conjugated form of octreotide, originally manufactured by Mallinckrodt Nuclear Medicine LLC, which now form...

Rectal cancer protocol (MRI)

MRI protocol for rectal cancer is a group of MRI sequences put together for imaging staging of primary tumors of the rectum and assessment of response following neoadjuvant therapy. Modified versions of the protocol may also be used for the assessment of local recurrence. Note: This article is ...

Attenuation coefficient

The attenuation coefficient is a measure of how easily a material can be penetrated by an incident energy beam (e.g. ultrasound or x-rays). It quantifies how much the beam is weakened by the material it is passing through. In X-rays, there are two types of attenuations 2: linear attenuation co...

X-rays

X-rays (or much more rarely, and usually historically, x-radiation or Roentgen rays) represent a form of ionizing electromagnetic radiation. They are produced by an x-ray tube, using a high voltage to accelerate the electrons produced by its cathode. The produced electrons interact with the anod...

Ultrasound frequencies

Ultrasound frequencies in diagnostic radiology range from 2 MHz to approximately 15 MHz. It is important to remember that higher frequencies of ultrasound have shorter wavelengths and are absorbed/attenuated more easily. Therefore, higher frequencies are not as penetrating. This explains why h...

Physical principles of ultrasound

Medical ultrasound is based on the use of high-frequency sound to aid in the diagnosis and treatment of patients. Ultrasound frequencies range from 2 to approximately 15 MHz, although even higher frequencies may be used in some situations. The ultrasound beam originates from mechanical oscillat...

Piezoelectric effect

The piezoelectric effect converts kinetic or mechanical energy, due to crystal deformation, into electrical energy. This is how ultrasound transducers receive the sound waves. The same effect can be used in reverse – inverse piezoelectric effect – whereby the application of an electric field to...

History of ultrasound in medicine

The first written document dealing with the use of waves in spatial orientation dates back to 1794, when an Italian physicist Lazaro Spallanzani (“Opus coli di fisica”), analyzed the basic mechanisms of the navigation of flying bats in the dark, and rightly deduced that bats employed sound rathe...

Alpha decay

Alpha decay (a.k.a. α decay) is the radioactive process in which an alpha (α) particle (containing two neutrons and two protons) is ejected from the nucleus. An alpha particle is identical to the nucleus of a helium atom. All nuclei with an atomic number (Z) greater than 82, are considered unsta...

Beta decay

Beta particles occur with either negative or positive charge (β- or β+) and are known to be either electrons or positrons, respectively, therefore beta decay represents radioactive decay, in which a beta particle is emitted. The kinetic energy of beta particles has a continuous spectrum. Beta m...

Cathode (x-ray tube)

The cathode is part of an x-ray tube and serves to expel the electrons from the circuit and focus them in a beam on the focal spot of the anode. It is a controlled source of electrons for the generation of x-ray beams. The electrons are produced by heating the filament (Joule heating effect) i.e...

Anode (x-ray tube)

The anode (or anticathode) is the component of the x-ray tube where x-rays are produced. It is a piece of metal, shaped in the form of a bevelled disk with a diameter between 55 and 100 mm, and thickness of 7 mm, connected to the positive side of the electrical circuit. The anode converts the en...

X-ray tube

An x-ray tube functions as a specific energy converter, receiving electrical energy and converting it into two other forms of energy: x-radiation (1%) and heat (99%). Heat is considered the undesirable product of this conversion process; therefore x-radiation is created by taking the energy from...

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