#Digital Radiography# With the fast
development of digital technology, the 21st century is a digital age, based on
the international DR digital radiography technology has been widely used in
clinical, China's "National Health Information Development Plan (2003 to
2010)" indicates, strengthen the hospital information construction achieve
hospital digital information, filmless, strengthen computer networks,
biomedical imaging and other high-tech applications in hospital clinical
aspects of medical imaging will also enter the digital age.
Digital Imaging Technology (Digital
Radiography DR) is the application of digital detectors will pass through the
body of X-rays into electrical signals that can be accepted by the computer,
and then the A / D converted into a real-time image, which is a digital image
detectors and replace the traditional workstation X-ray film systems (plastic /
screen system) and radiography system consisting of digital imaging is a core
component of the digital detector.
Common digital detectors have CCD
(charge-coupled device), CMOS (complementary metal-oxide semiconductor), TFT
(thin film transistor circuits) and line scan detector (multi-wire proportional
chamber detectors, ionization chamber detectors).
Beijing Zhongxing instrumentarija production
LDRD type DR machine is a line scan DDR machine (it has two models
LDRD-01-B-type and LDRD-01-C type), its digital multi-wire proportional chamber
detector detectors (Multi-Wire proportional chamber MWPC) is a high-efficiency,
high sensitivity detectors, LDRD slit-scanning technique, x-ray tube emit
fan-shaped x wiring harness plane through the body to reach the linear array
detector, which detects the direct line information data and stored in the
detector or simultaneously sent to the computer, synchronizing gear and control
structures, control line scan detector and x-ray tube, as constant
synchronization smooth movement, to achieve progressive scan, the computer got
the detector detects after all the data, get a real-time screen digital image
reconstruction software.
Because the human body tissues and organs is
three-dimensional, with different densities, different tissue thicknesses
overlap, again due to the density of low-resolution x-ray, it is difficult to
show the difference of these low-contrast X on a traditional flat sheet.
1 digital imaging technology
Because (1) the use of scanning mode and high
sensitivity detector, it clears the 70% of the scattered radiation, a unit
pixel scanning time is only milliseconds, greatly reducing the radiation dose
of a single pixel; it is only the traditional x-ray exposure dose a few tenths
of machines; (2) the window width and window level, gamma adjustment, a
photography can observe different tissue densities and different thicknesses;
(3) work processes quickly, from technician to patient data via the keyboard
input to the image preview workstation, select the radiography program to
complete the image acquisition requires only tens of seconds. After the image
acquisition is complete, Dicom digital interface for transmission to the
physician diagnosis workstation monitor screen for physicians to make a
diagnosis, print reports, or printed as x-rays, the whole process takes only 3
~ 5min.
2 Clinical Applications
Suitable for all body types of subjects,
obese or skinny person, by adjusting the window width and position can get a
clear contrast and transmittance appropriate multi-level images. Or properly
adjusting the voltage and current density can clearly show the lighter and
low-contrast organizational structure, such as a digitized image of the bone
structure, cartilage, soft tissue display superior conventional X-ray imaging,
another example of the lung periphery texture, heart behind fine texture of
lung tissue between the lungs of chromatin structure, lateral covered by the
scapula, soft tissue structures within the mediastinum, heart and great vessels
can clearly show that these changes are based on the low-contrast scanning
noise, high contrast spatial low Results resolution. Secondly, through the
computer software of the lesion and moderate zoom window width, window level
gray scale adjusted, showing different anatomical structures, measuring image
size, length, angle according to different requirements. Once the image
processing to identify lesions are common X-rays can not be compared, so that
the image quality of X-ray photography has been greatly improved, excellent
piece rate of more than 95%, loo% guarantee the quality of the image, the waste
piece rate is almost zero.
Patients from the scan start to a computer
only a few seconds to display an image, which can be diagnosed within a few
minutes the computer to print the report, save the patient treatment time,
digital video disc storage space savings deposit films ask, easy to find, it
can be transmitted to facilitate remote consultation .
3 DDR的优缺点
3 DDR The pros and cons
3.1 Advantages
Compared with CR 3.1.1 (1) high efficiency,
complete from exposure to the image preview, to judge the success radiography,
to provide diagnostic images to doctors as long as 25 ~ 40s, while the CR to be
hand loaded IP-- exposure - take into IP eleven laser scanner reads the digital
signal --A / D conversion - Preview imaging - diagnostic workstation or laser
print photos. Working procedures are complicated and efficiency comparable with
conventional radiography; better (2) image quality, image DR system free from
optical scattering caused blurred, its clarity major decision by the pixel
size, so DR image quality and spatial resolution , density resolution better
than CR; less (3) the patient suffered the X-ray dose; (4) DR detector life,
you can use the l0 years, and cR the IP life is generally about 5,000 times, but
also in the use of CR We need a variety of IP (8x10,10x12,12x15,14x14,14x17)
about 10 to 40, and once scratched or onto the ground is difficult to read out
on a laser scanner.
3.1.2 Compared with ordinary X-ray machine
(1) One of the main advantages over conventional imaging in digital imaging
technology is its very long exposure time is linear in the characteristic curve
(HD curve), then there are all the recorded signal into an appropriate
intensity range corresponding to its gray, the intensity of these signals can
be imaged, therefore, in addition to the imaging range and available by
conventional film emulsion and appears very dark saturated structure can be
easily digital imaging was seen; (2) may improve post-processing image
information can be identified, ease of accurate and efficient handling of
image; (3) for storage. Saving storage space (film library), to improve the
efficiency of image access can be easily indexed in various ways, in favor of
scientific research; (4) to facilitate the transmission of digital images can
be easily transmitted through the network, remote consultation, full use of
medical resources ; (5) cost savings, reduce material consumption, including
film, syrup, chip bags; (6) chemical liquid can reduce environmental pollution.
3.2 disadvantage of all the spatial
resolution digitized images are lower than conventional X-ray, general x-ray
spatial resolution of 0.25 ~ 0.6mm, CT spatial resolution of 0.4 ~ 0.8mm, while
DR spatial resolution of 0.3 ~ 0.7mm.
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