Conseils d’achat Mammography Unit

  1. Mammography screening equipment must meet the minimum MQSA requirements for tube outputs, compression performance, position controls, and reproducibility.
  2. Facilities should base their Mammography unit screening purchase decision on life-cycle cost, local service support, discount rates and non-price-related benefits offered by the supplier, and standardization with existing equipment.
  3. Suppliers offer service contracts or service on a time-and-materials basis. This may also be available from a third-party organization. Facilities should carefully consider whether to purchase such a service.
  4. When purchasing a Mammography screening equipment unit, performance and reliability are important factors.
  5. A Mammographic unit high-frequency x-ray generator will help ensure higher efficiency of operation with a minimum of output ripple. It will also need less space than a conventional generator.
  6. Mammography involves a narrow range of tissue thickness, and therefore 1 kV increments and a range of approximately 22 to 35 kV are necessary.
  7. The system should offer at least 500 mAs and an exposure time of 0.1 second or shorter to avoid unnecessary long exposures.
  8. A rotating anode, which has a higher heat capacity than a stationary anode, should be available on the Mammography unit to promote longer x-ray tube life and provide a more consistent x-ray output.
  9. AEC provides the appropriate image optical density and x-ray exposure for breast composition and thickness.
  10. Focal spot sizes should be approximately 0.1-0.3 mm to ensure that micro calcifications as small as 200 µm can be detected.
  11. To clearly image the smallest micro calcifications, an SID of at least 66 cm is needed.
  12. The complexity of the automatic exposure control is the main difference between systems. Some systems control only the exposure time, while more advanced ones control the x-ray spectrum, including the kVp, anode, and filtration. Such systems improve the image quality, especially in larger and denser breasts.
  13. Some manufacturers of Mammography units have developed advanced grids, which are expensive to manufacture but improve the image quality.
  14. Facilities considering the purchase of a stereo tactic biopsy system should consider the number of procedures to be performed and the compatibility with existing Mammographic equipment.
  15. Film-based Mammographic units are not recommended because they do not allow real-time guidance. Instead, both dedicated and add-on systems are equipped with small digital detectors.
  16. Add-on systems may be harder to use because they have more limited motions compared to dedicated mammographic systems. Consequently, most of the differences are a matter of user preference rather than clinical efficacy.
  17. In digital detector performance, detective quantum efficiency is an important factor. DQE is directly related to the signal-to-noise ratio that results between detector input and output. The noise generated by the detector and the spatial resolution contributes to the DQE of the system. To reduce DQE, SNR must be reduced; a recommended DQE is less than 20% at 5 lp/mm.
  18. Another important factor when considering a purchase of a Mammography unit is modulation transfer function. MTF refers to the loss of contrast relative to an x-rayed object. As spatial frequencies in a given image increase, MTF decreases, creating loss of visualization. A 50% MTF at 5 line pairs per millimeter is recommended.
Guide d'achat de matériel médical
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