question: the difference between milliamperage (mA) and kilovoltage peak (kvp) in radiology?
comment: This is an ELI5 explanation, and is not sufficient for a radiology exam. The kV is the potential across the tube (from anode to cathode) in kilovolts. Voltage controls the maximum energy of the individual x-ray photons. They will be a spectrum of energies less than the peak. The mA is the current through the tube in milliamps. It, along with exposure time determines the overall dose for a given voltage.
passages: Peak kilovoltage (kVp) refers to the maximum high voltage applied across an X-ray tube during the creation of x-rays within it. During x-ray generation, surface electrons are released from a heated cathode by thermionic emission. The applied voltage (kV) accelerates these electrons toward an anode target, ultimately producing x-rays when the electrons are stopped in the anode. Thus, the kVp corresponds to the highest kinetic energy of the electrons striking the target, and is proportional to the maximum energy of the resulting X-ray emission spectrum. In early and basic x-ray equipment, the applied voltage varies cyclically, with one, two, or more pulses per mains AC power cycle. One standard way to measure pulsating DC is its peak amplitude, hence kVp. Most modern X-ray generators apply a constant potential across the x-ray tube; in such systems, the kVp and the steady-state kV are identical.
   BULLET::::- name of the test performed; i.e.“PFR”
  
  BULLET::::- with optical correction “cc” or without correction “sc”
  
  BULLET::::- distance the test was performed at i.e. far “(6m)” or near “(1/3m)”
  
  BULLET::::- prism power at which the patient ‘breaks’ and ‘recovers’ i.e. the prism power number followed by its measuring unit symbol “Δ”
  
  BULLET::::- Note: Some examiners may choose not to assess and/or record ‘recovery’. If recovery is being recorded, separate the ‘break’ and accompanying ‘recovery’ results with a forward slash i.e. “/”.
   In this case, an epidemiology-based differential diagnostic procedure is used, and its first step is to find candidate conditions that can explain the finding.
  
  Hypercalcemia (usually defined as a calcium level above the reference range) is mostly caused by either primary hyperparathyroidism or malignancy, and therefore, it is reasonable to include these in the differential diagnosis.
   kVp controls the property called "radiographic contrast" of an x-ray image (the ratio of transmitted radiation through regions of different thickness or density). Each body part contains a certain type of cellular composition which requires an x-ray beam with a certain kVp to penetrate it. The body part is said to have "subject contrast" (that is, different cellular make up: some dense, some not so dense tissues all within a specific body part). For example: bone to muscle to air ratios in the abdomen differ from that of the chest area. So the subject contrast is said to be higher in the chest than in the abdomen. In order to image the body so that the maximum information will result, higher subject contrast areas require a higher kVp so as to result in a low radiographic contrast image, and vice versa.
   Conventionally, the energy of diagnostic and therapeutic gamma- and X-rays is expressed in kilovolts or megavolts (kV or MV), whilst the energy of therapeutic electrons is expressed in terms of megaelectronvolts (MeV). In the first case, this voltage is the maximum electric potential used by a linear accelerator to produce the photon beam. The beam is made up of a spectrum of energies: the "maximum" energy is approximately equal to the beam's maximum electric potential times the electron charge. Thus a 1 MV beam will produce photons of no more than about 1 MeV. The "mean" X-ray energy is only about 1/3 of the maximum energy. Beam quality and hardness may be improved by X-ray filters, which improve the homogeneity of the X-ray spectrum.
   This unit is commonly used in underground science to express the extent to which the overburden (usually rock) shields an underground space or laboratory from cosmic rays. The actual thickness of overburden through which cosmic rays must traverse to reach the underground space varies as a function of direction due to the shape of the overburden, which may be a mountain, or a flat plain, or something more complex like a cliff side. To express the depth of an underground space in mwe (or kmwe for deep sites) as a single number, the convention is to use the depth beneath a flat overburden at sea level that gives the same overall cosmic ray muon flux in the underground location.
   Section::::How the qCO is calculated?:Detecting characteristic points of the ICG signal: problems and solutions..
   BULLET::::2. The monitor chamber reads 100 MU when an absorbed dose of is delivered to a point at a given depth in the phantom with the surface of the phantom positioned so that the specified point is at the isocentre of the machine and the field size is 10 cm × 10 cm at the isocentre.
  
  Some linear accelerators are calibrated using source-to-axis distance (SAD) instead of source-to-surface distance (SSD), and calibration (monitor unit definition) may vary depending on hospital custom.
  
  Early radiotherapy was performed using "constant SSD" treatments, and so the definition of monitor unit was adopted to reflect this calibration geometry.
   It was developed by Frank Gotch and John Sargent as a way for measuring the dose of dialysis when they analyzed the data from the National Cooperative Dialysis Study. In hemodialysis the US National Kidney Foundation "Kt"/"V" target is ≥ 1.3, so that one can be sure that the delivered dose is at least 1.2. In peritoneal dialysis the target is ≥ 1.7/week.
  
  Despite the name, "Kt"/"V" is quite different from standardized Kt/V.
  
  Section::::Rationale for "Kt"/"V" as a marker of dialysis adequacy.
   BULLET::::- 1977-1982: Associate Professor of Radiology, Dept. of Radiology, Univ. of Pennsylvania School of Medicine
  
  BULLET::::- 1979-2006: Chief, Division of Nuclear Medicine, Hospital of the University of Pennsylvania
  
  BULLET::::- 1979-1991: Co-Director, Positron Emission Tomography Center, University of Pennsylvania
  
  BULLET::::- 1991-2006: Medical Director, Positron Emission Tomography Center, University of Pennsylvania
  
  BULLET::::- 1982–present: Professor of Radiology, Department of Radiology, University of Pennsylvania School of Medicine
  
  BULLET::::- 1984–present: Associate Director, Center for the Study of Aging, University of Pennsylvania
  
  BULLET::::- 2006–present: Director of Research Education, Department of Radiology, University of Pennsylvania
  
  Section::::PET.
   An ST elevation is considered significant if the vertical distance inside the ECG trace and the baseline at a point 0.04 seconds after the J-point is at least 0.1 mV (usually representing 1 mm or 1 small square) in a limb lead or 0.2 mV (2 mm or 2 small squares) in a precordial lead. The baseline is either the PR interval or the TP interval. This measure has a false positive rate of 15-20% (which is slightly higher in women than men) and a false negative rate of 20-30%.
  
  Section::::Abnormalities.:Myocardial infarction (MI).
   A rem is a large dose of radiation, so the millirem (mrem), which is one thousandth of a rem, is often used for the dosages commonly encountered, such as the amount of radiation received from medical x-rays and background sources.
  
  Section::::Usage.
  
  The rem and millirem are CGS units in widest use among the American public, industry, and government. SI units are the norm outside of the United States, and they are increasingly encountered within the US in academic, scientific, and engineering environments.
   In mechanically ventilated patients, the same process takes place in reverse, due to the positive pressure. Therefore, the normal values of SVV depend on the ventilation mode, and it can be calculated through the SV with the formula: formula_1, by a respiratory cycle or other period of time.
  
  During mechanical ventilation the goal is to maintain SVV between 10-15%, higher values along with a low SV may indicate the need of volume resuscitation.
   Monitor unit
  
  A monitor unit (MU) is a measure of machine output from a clinical accelerator for radiation therapy such as a linear accelerator or an orthovoltage unit. Monitor units are measured by monitor chambers, which are ionization chambers that measure the dose delivered by a beam and are built into the treatment head of radiotherapy linear accelerators.
  
  Section::::Calibration and dose quantities.
  
  Linear accelerators are calibrated to give a particular absorbed dose under particular conditions, although the definition and measurement configuration may vary among medical clinics.
  
  The most common definitions are:
   D-dimers are a fibrin degradation product, and an elevated level can result from plasmin dissolving a clot—or other conditions. Hospitalized patients often have elevated levels for multiple reasons. When individuals are at a high-probability of having DVT, diagnostic imaging is preferred to a D-dimer test. For those with a low or moderate probability of DVT, a D-dimer level might be obtained, which excludes a diagnosis if results are normal. An elevated level requires further investigation with diagnostic imaging to confirm or exclude the diagnosis.
   Although the product of tube current and exposure time, measured in milliampere-seconds (mA·s), is the primary controlling factor of radiographic density, kVp also affects the radiographic density indirectly. As the energy (which is proportional to the peak voltage) of the stream of electrons in the x-ray tube increases, the x-ray photons created from those electrons are more likely to penetrate the cells of the body and reach the image receptor (film or plate), resulting in increased film density (compared to lower energy beams that may be absorbed in the body on their way to the image receptor). However, scattered x-rays also contribute to increased film density: the higher the kVp of the beam, the more scatter will be produced. Scatter adds unwanted density (that is, density that does not bring pertinent information to the image receptor). This is why kVp is not primarily used to control film density – as the density resulting from increasing kVp exceeds what is needed to penetrate a body part, it only adds useless photons to the image.
   Effective doses can range from 6 μSv (0.006 mSv) for a 3 MBq chromium-51 EDTA measurement of glomerular filtration rate to 37 mSv (37,000 μSv) for a 150 MBq thallium-201 non-specific tumour imaging procedure. The common bone scan with 600 MBq of technetium-99m-MDP has an effective dose of approximately 3.5 mSv (3,500 μSv) (1).
   Section::::Interpretation of results.
  
  The CM, SP, and AP are all used in the diagnosis of endolymphatic hydrops and Ménière's disease. In particular, abnormally high SP and a high SP:AP ratio are signs of Ménière's disease. An SP:AP ratio of 0.45 or greater is considered abnormal.
  
  Section::::History.
   BULLET::::- The sievert (Sv) is the SI unit of equivalent dose. Although it has the same units as the gray, J/kg, it measures something different. For a given type and dose of radiation(s) applied to a certain body part(s) of a certain organism, it measures the magnitude of an X-rays or gamma radiation dose applied to the whole body of the organism, such that the probabilities of the two scenarios to induce cancer is the same according to current statistics.
   Innovative Imaging Studies in CT/MRI for the Head and Neck – Galdino Valvassori, M.D. conducted many groundbreaking studies in the use of imaging technologies for diagnosis and treatment. Dr. Valvassori was known as the “Father of ENT Radiology,” and published three seminal texts: Radiographic Atlas of the Temporal Bone, Radiology of the Ear, Nose, and Throat, and the Valvassori Textbook of ENT Radiology. 
   using measurements acquired at central and peripheral positions in the head or body phantoms described above.
  
  Section::::Definitions.:CTDI in helical CT.
  
  In helical CT, the pitch of the machine - a factor of the speed at which the couch travels through the gantry and the tube rotation frequency - also impacts on patient dose. The pitch factor, P, is defined as
  
  formula_11
   BULLET::::- d Horizontal distances between array site j and center site in [km].
  
  BULLET::::- s Slowness vector with absolute value s = 1/ v
  
  BULLET::::- v Apparent velocity vector with the absolute value v = 1/s . v = (v ,v ,v), where v ,v ,v are the single apparent velocity components in [km/s] of the wavefront crossing an array.
  
  BULLET::::- v Absolute value of the horizontal component of the apparent velocity. formula_3
   The most commonly used predictor of acute radiation symptoms is the whole-body absorbed dose. Several related quantities, such as the equivalent dose, effective dose, and committed dose, are used to gauge long-term stochastic biological effects such as cancer incidence, but they are not designed to evaluate acute radiation syndrome. To help avoid confusion between these quantities, absorbed dose is measured in units of grays (in SI, unit symbol Gy) or rads (in CGS), while the others are measured in sieverts (in SI, unit symbol Sv) or rems (in CGS). 1 rad = 0.01 Gy and 1 rem = 0.01 Sv.
   RCD sensitivity is expressed as the rated residual operating current, noted I. Preferred values have been defined by the IEC, thus making it possible to divide RCDs into three groups according to their I value:
  
  BULLET::::- high sensitivity (HS): 5** – 10 – 30 mA (for direct-contact / life injury protection),
  
  BULLET::::- medium sensitivity (MS): 100 – 300 – 500 – 1000 mA (for fire protection),
  
  BULLET::::- low sensitivity (LS): 3 – 10 – 30 A (typically for protection of machine).
  
  The 5 mA sensitivity is typical for GFCI outlets.
  
  Section::::Common features and variations.:Break time (response speed).
   BULLET::::- formula_2 is the mass generation rate of the substance - assumed to be a constant, i.e. not a function of time [mmol/min] or [mol/s]
  
  BULLET::::- C is the concentration at the beginning of dialysis [mmol/L] or [mol/m]
  
  Equation "4" is normalized by the volume of distribution to form equation "5":
  
  Equation "5" is multiplied by an arbitrary constant to form equation "6":
  
  Equation "6" is then defined as standardized Kt/V (std Kt/V):
  
  where
  
  BULLET::::- "const" is 7×24×60×60 seconds, the number of seconds in a week.
  
  Section::::Interpretation of std Kt/V.
  