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Computed Radiography & Direct/Indirect Digital Radiography

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목 차 <ul><li>DR(Digital Radiography) 의 개요 </li></ul><ul><li>CR(Computed Radiography) </li></ul><ul><li>Direct/Indirect Digital Radiography </li></ul><ul><li> DR Detectors </li></ul><ul><li> DR Image Preprocessing </li></ul>

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Digital radiograpy 의 개요 <ul><li>단순촬영장치의 Digital 화 </li></ul><ul><li> TFT(Thin Film Transistor) 와 F P D(Flat Panel Detector) 이용한 단순 촬영장치 </li></ul>좁은 의미 Digital Image 를 얻는 영상장치  MRI, CT, Ultrasound, Fluoroscopy 등 기계장치 넓은 의미

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Digital & Analog 구 분 Digital 방식 기존 film 방식 저장성 피폭량 재촬영 여부 환경문제 특 징 획득시간 네트워크 Digital Storage Media(HD, CD,) 5~6m 뢴트겐 컴퓨터 처리 및 실시간 판독 가능 필름불필요 ( 환경 친화적 ) 재현성 , 영상통신 및 원격진료 수 초 이내 PACS 및 DICOM 연동 30m 뢴트겐 필름 저장공간 과다소요 재촬영 및 실시간 처리 불가 필름현상에 화공약품 사용 재현성 낮고 , 영상통신 불가능 수 분 네트워크 연동 불가

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X-ray Imaging Technologies Imaging Plate Conventional Film/Screen System C R I.I.- DR I.I.-CCD CRT X-ray Film FPD （ Flat Panel Detector) View Box View Box (CR : Computed Radiography) ＦＰＤ CRT Wet Processor Wet Processor Image Processing Unit Ｄｉｒｅｃｔ Shot Indirect Shot Image Processing Unit Image Processing Unit

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Computed Radiography ▶ Conventional Screen/Film System 촬영법을 대신하여 , PSL 현상을 일으키는 IP 에 영상정보가 축적 ▶ IP 에 축적된 X-ray 영상정보는 CR Reader 내부의 LASER Beam 과 PM Tube 에 의해 DSP 에 필요한 Analog 형태의 영상정보로 변환

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Reading ► X-ray 영상정보가 축적된 IP 에 LASER Beam 을 주사 ► IP 의 X-ray 영상정보는 Light Photon 의 형태로 변환 ► 신호정보는 Fiber Optical Light Guide 를 통해 PM Tube 로 전달 ► Light Signal 을 Electrical Signal 로 변환 ► Amplifier 에서 증폭 ► A/D Converter 에서 Digital Signal 변환 Amplifier 1100110010101110010110101100110 A/D Converter PM Tube Light Guide LASER Beam Imaging Plate Optical Scanner

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Recording/Reading/Erasing Cycle Unexposed Imaging Plate X-ray Tube Scanning Erasing Light Recording Reading Erasing

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Image Plate (IP) Image Plate 구조 <ul><li>Photo Stimulable Luminescence(PSL) 물질이 Doping 된 1mm 이하의 얇고 유연한 Flat Panel 이다 . </li></ul><ul><li>Structure </li></ul><ul><li>1.Protective Layer( 보호체 ) </li></ul><ul><li>2.Phosphor Layer( 형광체 ) </li></ul><ul><li>3.Support Layer( 지지체 ) </li></ul><ul><li>4.Backing Layer( 후면보호 ) </li></ul><ul><li>5.Bar Code Layer( 환자정보 ) </li></ul>

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IP 화학기전 <ul><li>1. 방사선 또는 자외선에 노출되면 Eu ++ 이 Eu +++ 로 변환 , 전자 방출 </li></ul><ul><li>2. 자유전자들이 Fluoride Center(F + ) 에 포획 </li></ul><ul><li>3. 포획된 전자들이 Subsequent Exposure 뒤에 형광체의 특성방사선 보다 긴 파장의 가시광선으로 방출 </li></ul><ul><li>4. 방출된 전자들이 Eu ++ 분자로 되돌아 오고 390nm 의 </li></ul><ul><li>형광을 방출하고 분자들을 Eu ++ 로 되돌려 변환 </li></ul><ul><li>5.Phosphor 에서의 특성방사선 방출은 7  sec Light Exposure 안에서 </li></ul><ul><li>이루어진다 </li></ul>

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Digital Fluoroscopy Image Intensifier Tube Tube Application(DR/DF) Digital Subtraction Angiography (DSA) Digital Video Angiography (DVA) Digital Video Subtraction Angiography (DVAS) Computerized Fluoroscopy (CF)

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CCD Technologies Optical Lens CCD Tiled Fiber Optic CCD Slit scanning X-ray Photons Light Scintillator Optics Mirrors CCD sensor CCD Array Translation Scintillator/CCD/ Fiber Optic Array Tube Collimation Mechanism Photons Scintillator Light Fiber Optic Taper Electrons CCD

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Selenium Technology Photons Selenium Amorphous Silicon Panel (TFT Semiconductor) Digital Data Electrons Read Out Electronics

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Image Quality Parameters  Dynamic Range & Contrast  Limiting Spatial Resolution ( LSR )  Signal to Noise Ratio ( SNR )  Modulation Transfer Function ( MTF )  Detective Quantum Efficiency ( DQE )

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Contrast / Dynamic Range Low Contrast High Contrast Film-Screen Detector

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Limiting Spatial Resolution (LSR) Resolution Line pair resolution pattern Radio paque bar and open space constitute a line pair.

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Signal to Noise Ratio (SNR) Decreasing Noise Increasing Contrast High SNR Low SNR Noise Signal Contrast Ratio

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Impact of Noise <ul><li>Quantum and electronic noise are unavoidable in a digital imaging chain. The effect, often expressed as signal-to-noise ratio (SNR), can vary widely from system to system. Signal Useful Image Formation ---------- = -------------------------------------- Noise Erratic Information </li></ul>1:1 SNR 2:1 SNR 5:1 SNR Quantum and electronic noise are unavoidable in a digital imaging chain. The effect, often expressed as signal-to-noise ratio (SNR), can vary widely from system to system. Signal Useful image formation ---------- = ----------------------- Noise Erratic Information Quantum and electronic noise are unavoidable in a digital imaging chain. The effect, often expressed as signal-to-noise ratio (SNR), can vary widely from system to system. Signal Useful image formation ---------- = ----------------------- Noise Erratic Information 1:1 SNR 2:1 SNR 5:1 SNR 1:1 SNR 2:1 SNR 5:1 SNR Signal-to-noise ratio. As noise decreases in a digital x-ray system, object detectability increases very rapidly.

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Modulation Transfer Function (MTF) Input Output Transfer MTF Spatial Frequency 1.0 1.0 1 0.5 0 0.5 -1 1 0.5 0 0.5 -1 1 0.5 0 0.5 -1 1 0.5 0 0.5 -1 1 0.5 0 0.5 -1 1 0.5 0 0.5 -1

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Digital Detector Outperforms ... Area X-ray Absorption DQE @ 0 lp/mm @ 5 lp/mm Dynamic Range Equivalent Noise Panel Readout Time Image Display Time FFDM 19 x 23 85% 0.7 0.3 4096:1 15µR 0.3s 5s Film 18 x 24 50% 0.2 0.15 100:1 100µR ? ? *FFDM : Full-Field Digital Mammography

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DR Data Processing <ul><li>► Penetration X-ray Photon Data 는 FPD 에서 Electrical Analog Signal 로 변환 </li></ul><ul><li>► A/D Conversion Processing 과정 </li></ul><ul><li>► Pixel Data(Gray Scale) 값 획득 </li></ul><ul><li>► DSP 과정 (Noise 제거 ) </li></ul>

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Quality Assurance Plan <ul><li>Image Quality Signature Test (IQST) Phantom </li></ul><ul><li>Automated, Pass / Fail Test Procedure </li></ul><ul><li>Run by Technologist </li></ul><ul><li>Insite Interactive </li></ul><ul><li>Not a Calibration </li></ul><ul><li>Tracks IQ Over Time </li></ul><ul><li>Spatial Resolution </li></ul><ul><li>Small Signal Contrast </li></ul><ul><li>Dynamic Range </li></ul><ul><li>Resolution Uniformity </li></ul><ul><li>Distortion </li></ul>

23.
FDA Standard Parameters at Digital Radiography System <ul><li>Requirements : at DN-5 Condition </li></ul><ul><li>1) Horizontal MTF data sheets / Comparing Internet data </li></ul><ul><li>2) Vertical MTF data sheets / Comparing Internet data </li></ul><ul><li>3) DQE data sheets / Comparing Internet data </li></ul><ul><li>4) Low no of dead pixels </li></ul><ul><li>5) High resolution Monitor > 2k * 2k </li></ul>

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Digital Mammography HIS/ RIS 30 sec/ worklist 75 sec/ exam 75 sec/ exam 75 sec/ exam 2.5 min/ exam 2.5 min/ exam 45 sec / CD Review CD-R (option) Mass Archive (option) Laser Camera (Option) PACS Acquisition 50-60 patients/day DR 적용 사례

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Digital Mammography - Productivity Estimated > 60% Reduction In Exam Times DR 적용 사례 First Film Out of Processor Patient in Room First Exposure Last Exposure Last Film Out of Processor QC Release Patient Conventional Exam With Film 12:10 min 1:30 4:45 2:15 :10 :05 :30 8% Repeat Rate Exam Using Digital Detector Patient in Room First Exposure & QC Last Exposure & QC Release Patient / Send Study To WS 1:30 1:45 :45 4:00 min Minimal Repeats

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T HANK YOU!! U