Xray machine introduction — What are your options: CR or DR — http://hv-caps.biz
In my previous article, we discussed the advantages and disadvantages of CR systems as the modality utilized to make the transition to digital imaging. This section will focus on CCD based DR (or DDR) as an imaging modality for digital imaging.
Digital Radiography (DR)
In the medical imaging industry, there are several definitions used for the various modes of digital imaging. For this series, CR was used to describe digital imaging achieved by the use of photo-stimuable plates used in a cassette. The term DR will be used to describe digital imaging in which the image receptor is non-cassette based. This may be DR that is either CCD based or Flat Panel based. In either of these systems, the x-ray exposure is made directly to the image receptor and it is not necessary for the technologists to handle an imaging plate or cassette.
CCD – DR systems utilize a scinctillator (intensifying screen), CCD chip and an optical system to capture the image and convert a light signal to an electrical signal. The details of this conversion process are beyond the scope of this article.
Like CR systems, CCD based DR imaging offer many advantages when compared to conventional analog film/screen (“F/S”) radiography. They may also offer advantages when compared to CR systems. These benefits include but are not limited to:
1. Improved Efficiency: Since imaging plates/cassettes are not utilized with CCD based DR systems, workflow efficiency is improved. This may be particularly useful in high volume situations.
2. Image Display: Typically, images are displayed in 4-10 seconds and the unit is ready for the next image. This compares to a 30-120 second cycle for image display and subsequent erasure of the image plate for CR.
While the above benefits can be important, CCD based DR systems also have disadvantages when compared to CR plate imaging:
1. Cost: In general CCD based systems are more expensive that CR based systems.
2. Resolution: Except for higher priced CCD based systems, the resolution of CCD based systems is at times much less than CR based systems.
3. Utilize Existing Equipment: Although some CCD based receptors may be retrofit into existing equipment, this is not true in all cases. Care must be taken if attempting to retrofit a CCD based system with existing equipment to assure a successful transition. Also, the optics of the CCD system generally requires more space than traditional image receptors. This may cause logistical issues depending on the specific room layout.
4. Positioning Flexibility: In general, CCD based systems are fixed position and do not allow for cross table or table top exposures.
5. Dose: Exams that are done on table top with analog or CR systems are done “bucky” on DR systems. This generally results in a higher dose to both patient and operator.
6. Increased Image Noise: Due to the logistics of the signal transformation, in general, CCD based DR systems exhibit greater image “noise” relative to CR or Flat Panel DR systems.
7. Some CCD based systems save image file in JPEG format. It is desirable to have studies saved in DICOM format to assure integration with other PACS components.
In conclusion, when speed of image acquisition is of major concern, CCD based DR systems are a desirable option for those wishing to transition to digital radiography. While CCD based systems are less expensive than Flat Panel based DR systems, they are more expensive that CR based systems. In addition, CCD based DR systems generally do not demonstrate the resolution of Flat Panel DR systems or CR systems.