1. Digital Radiology

2. 2 Aim : To become familiar with the digital imaging techniques in projection radiography and fluoroscopy.Aim : To become familiar with the digital imaging techniques in projection radiography and fluoroscopy.

3. 3 Transition from conventional to digital radiology  Digital images can be numerically processed  Digital images can be easily transmitted through networks and archived  Attention should be paid to the potential increase of patient doses due to tendency of :  producing more images than needed  producing higher image quality not necessarily required for the clinical purpose

4. 4 What is “dynamic range”? ^Wide dose range to the detector, allows a “reasonable” image quality to be obtained ^Flat panel detectors (discussed later) have a dynamic range of 10 4 (from 1 to 10,000) while a screen-film system has approximately 10 1.5

5. 5 Characteristic curve of CR system HR-III CEA Film-Fuji Mammofine CR response Air Kerma (mGy) 0.001 0.01 0.1 1 3.5 3 2.5 2 1.5 1 0.5 0 Density

6. 6 Analogue versus digital Digital: A given parameter can only have discrete values Analogue: A given parameter can have continuous values

7. 7 What is digital radiology?  In conventional radiographic images, spatial position and blackening are analogue values  Digital radiology uses a matrix to represent image  A matrix is a square or rectangular area divided into rows and columns. The smallest element of a matrix is called ”pixel”  Each pixel of the matrix is used to store the individual grey levels of an image, which are represented by positive integer numbers  The location of each pixel in a matrix is encoded by its row and column number (x,y)

8. 8 Digital radiology process  Image acquisition  Image processing  Image display  Importance of viewing conditions  Image archiving (PACS)  Image retrieving  Importance of time allocated to retrieve images

9. 9 Digitizing conventional films iConventional radiographic images can be converted into digital information by a “digitizer”, and electronically stored iSuch a conversion also allows some numerical post-processing iSuch a technique cannot be considered as a “ digital radiology” technique.

10. 10 Different number of pixels per image: original was 3732 x 3062 pixels x 256 grey levels (21.8 Mbytes). Here, resized at 1024 x 840 (1.6 MB).

11. Scintillation-based DR Gadolinium Oxy-sulphide Detector

12. 12 Digital Radiography Systems  Phosphor photostimulable plates (PSP). –So called CR (computed radiography) –Conventional X-ray systems can be used  Direct digital registration of image at the detector (flat panel detectors). –Direct conversion (selenium) –Indirect conversion (scintillation)

13. 13 Computed Radiography (CR)  CR utilises the principle of photostimulable phosphor luminescence  Image plate made of a suitable phosphor material are exposed to X-rays in the same way as a conventional screen-film combination  The CR image plate retains most of the absorbed X-ray energy, in energy traps, forming a latent image

14. 14  A scanning laser is then used to release the stored energy producing luminescence.  The emitted light, which is linearly proportional to the locally incident X-ray intensity is detected by a photo multiplier/ADC configuration and converted to a digital image  The resultant images have a digital specification of 2,370 x 1,770 pixels (for mammograms) with 1,024 grey levels (10 bits) and a pixel size of 100 mm corresponding to a 24 x 18 cm field size Computed Radiography (CR)

15. 15 The principle of PSP ExcitationStorageEmission CB Trap ADC PMT

16. Add module code number and lesson title 16 كــريــستــال هــالـيــد فــلــوريــد بــاريــم فــعــال شــده بـا يــوروپــيــوم (Europium Activated Barium FluoroHalide) BaFX:Eu, (X= Cl, Br, or I)

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18. 18 (Images courtesy of AFGA) PSP digitizer Casette and PSP Workstation

19. 19 DR Detecting Systems

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21. 21 Direct vs indirect conversion detectorsDirect vs indirect conversion detectors

22. 22 CCD Based Detection System

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25. 25 Digital detector

26. 26 Amorphous Selenium Detector

27. 27 Digital fluoroscopy aDigital fluoroscopic systems are mainly based on the use of image intensifiers (I.I.) aIn conventional systems the output screen of the I.I. is projected onto a video camera system or a CCD camera aThe output signals of the camera are converted into a digital image matrix (1024 x 1024 pixel in most systems). aSome new systems start to use flat panel detectors instead of image intensifier.

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30. 30 Tendency to increase dose ?  For digital detectors, higher doses result in a better image quality (less “noisy” images)  When increasing dose, the signal to noise ratio is improved  Thus, a certain tendency to increase doses could happen specially in those examinations where automatic exposure control is not usually available.

31. 31 The digital radiology department  In addition to the X-ray rooms and imaging systems, a digital radiology department has two other components: lA Radiology Information management System (RIS) that can be a subset of the hospital information system (HIS) lA Picture Archiving and Communication System (PACS).

32. 32 HIS Broker RIS Voice Rec. Server TranscriptionPool Radiologist WorkStation Results To Webserver DICOM Images Verified HL7 E-gateHL7 HL7 Modality Worklist InformationModality Worklist Information

33. 33 Data management We write a report! Link both PACS and RIS. Report compares Orders on RIS with Images on PACS. Report highlights RIS orders with No images! PACS RIS

34. 34 DICOM DICOM (Digital Imaging and Communications in Medicine) is the industry standard for transferal of radiological images and other medical information between different systems All recently introduced medical products should therefore be in compliance with the DICOM standard However, due to the rapid development of new technologies and methods, the compatibility and connectivity of systems from different vendors is still a great challenge

35. 35 DICOM format images:  Radiology images in DICOM format contain in addition to the image, a header, with an important set of additional data related with:  the X ray system used to obtain the image  the identification of the patient  the radiographic technique, dosimetric details, etc.