Skip to main content

Take 7: Image Intensifier vs Flat Panel Detector

As mentioned before in "Take 4," the Image Intensifier (II) and Flat Panel Detector (FPD) are important fluoroscopic components that function similarly yet are different.  Since we know that the purpose of each component is to brighten the image without increasing dose, here is a brief comparison of the difference of both the II and FPD.

Here is what's different about the II:
  • Consists of input phosphor, photocathode, electrostatic focusing lenses, anode, output phosphor, and glass envelope
    • Input phosphor: absorb and convert x-rays to light photons
    • Photocathode: absorbs the light created by input phosphor and then emits photo(light)electrons
    • Electrostatic focusing lenses: guides and directs photoelectrons to output phosphor
    • Anode: these photoelectrons then pass through the anode
    • Output Phosphor: converts the photoelectrons that exited the anode to light photons


Here is what's different about the FPD:
  • "All flat panel detectors used in radiology convert a flux of x-rays into an electrical charge.  This electrical charge is digitized in the detector's readout matrix" (ASRT, 2010).
    • Composed of amorphous silicon thin- film transistor (TFT)
    • TFT is an arrangement of rows and columns
      • Rows: formed by gate lines that operate the TFT (ASRT, 2010)
      • Columns: linked by drain lines that are connected to the TFT output (ASRT, 2010)
      • Drain lines: connect to charge amplifiers
      • Charge amplifiers: receive the charge from detector elements
  • Two different methods to convert x-rays to electrical charge:
    • Indirect Conversion
      • A phosphor (scintillator)interacts with incoming x-rays to produce light photons
      • A photoconductor such as a Charge-Coupled Device (CCD)then converts light to electrical charge
    • Direct Conversion
      • "An x-ray photoconductor directly converts the x-ray photons into an electrical charge" (ASRT, 2010).



Comments

Post a Comment

Popular posts from this blog

Take 4: Components of Fluoroscopy

The fluoroscope unit is similar to that of a general x-ray unit; however there is one key difference-- it's flipped flopped.  On a regular x-ray unit, the tube is positioned above the patient table and the image receptor is underneath the patient.  On the other hand, the fluoro x-ray tube is located underneath the patient table and the image receptor above.  Here is a simple description of each of the components of the fluoroscopy unit:   1.   Generator : This is important for converting the alternating current (AC) to direct current (DC) which then allows for the adjustment of mAs and kVp as well as to select pulsed fluoroscopy (ASRT, 2010). 2.   X-Ray Tube :  This is contained within a glass or metal tube to help prevent leakage and scatter radiation.  DC will flow from cathode to anode; and once the electrons reach the anode, x-rays are produced.   3.   Collimator: Blades that allow for modification of shape/size of x-ray field, reduction of scatter radiation thus resulting
Post a Comment
Read more

Take 9: Dose Limits & Exposure Patterns

For the protection and safety of radiation workers ands staff, it is very important to limit the amount of dose as much as possible.   It is our responsibility as radiation workers to keep radiation exposure ALARA- As Low As Reasonably Achievable!  In addition to the three keys (time, distance, and shielding) of radiation safety and protection, there are other ways to manage dose.  For example, the number of image taken and repeated.  During fluoroscopy, setting the number of frames per second is one way the radiologist can limit patient dose.  The more frames (or pictures) taken per second, the more radiation being exposed to the patient and surrounding people (ASRT, 2010).  In order to effectively protect workers and patients, dose limits have been established.  Check out the table below!... sorry for the poor quality screenshot.  Note: Dose equivalent is measured in Sieverts and/ or rems. (1 rem= .01 Sv)  Statkiewicz-Sherer, Mary Alice, Paula J. Visconti, E. Russell Ritenour, an
Post a Comment
Read more