초음파물리학 Dept. of Radiological Science Hanseo University
초음파장비의정도관리 정도관리 QC (Quality Control) : 품질관리 QA (Quality Assurance) : 품질보증 PM (Preventive Maintenance) : 예방점검 Tissue-mimicking phantom 초음파장비의 QA에사용 미세흑연이섞인 gelatin 용액 음속 : 540 m/s 감쇠계수 : 0.5 / 0.7 db/cm- MHz - 0.5 : 정상상태 - 0.7 : 최악상황고려 지방간 분리된반사체 : 나일론선 거리측정정확도
Performance Measurements Dead Zone Horizontal Distance Accuracy Vertical Distance Accuracy Depth of Penetration Image Uniformity Axial Resolution Lateral Resolution Anechoic Mass Resolution Gray Scale Contrast Resolution
Performance Measurements Dead Zone ( 불응영역 ) 팬텀과탐촉자의경계에서탐촉자의앞면으로부터처음확인할수있는에코까지의거리 (9 개의표적이스캔표면으로부터 2~0 mm 깊이에있음 )
Vertical Distance Accuracy( 종측정 ) : 구조물의크기. 깊이, 부피를정확히표시 ( 표적은 7 개이며, 표적간의거리는.0+0. cm)
Horizontal Distance Accuracy( 횡측정 ) : 구조물의크기, 부피를정확히표시 ( 에코간의거리는 2 cm 이며, 허용오차범위는 2.0 cm+ mm)
Axial / lateral resolution ( 축방향 / 외측해상도 ) : 해상도는근접한두물체를구별할수있는능력을말한다. 각측정점의크기는 mm 이며중앙에있는측정점간의거리는.0 mm 이며점차 2.0 mm, 3.0 mm, 4.0 mm 로거리가멀어져가장자리에있는측정점간의거리는 5.0 mm 이다 ( 종선거리를측정하는영상에서 개의측정점이보여야한다.)
Maximum depth penetration ( 최대가시화깊이 ) : cm 간격으로 6cm 깊이까지배열되어있다. 측정오차범위는 6.0 ±.0 cm Sensitivity ( 민감도 ) : 낭종으로보이는 8 mm, 6 mm, 4 mm, 3 mm, 2 mm 크기의약한에코를구별할수있는깊이 8 과 6 mm 사이의간격은 2 cm 이며나머지는 cm 간격으로 (8 번째측정물체까지보여야함 )
Gray scale contrast resolution ( 회색조대조조해상도 ) : 가장낮은회색조부터최대밝기까지에코신호를조절 표준팬텀을옆으로뉘어서구조물이횡으로배열하게한후 6 개의구조물이한화면에보이고구조물의중앙이화면의중앙이되도록영상을획득한다.
초음파장비의정도관리 기본적인 QA tests transducer choice system sensitivity photography & gray scale hardcopy scan image uniformity distance measurement accuracy others 변환기선택 여러개를가지고규격검사를하는것은부적합 표준이될수있는변환기선택 자주사용하는것 다음검사시주파수크기, 분류번호 (serial No.) 기록
초음파장비의정도관리 시스템감도 감도조정장치 : gain, power 마지막 QA 검사이후감도에변화가있는지확인 원인 - 변환기손실 - 손상된변환기케이블 - 송, 수신부의전기적이상 electronic noise < 그림 8-4>
초음파장비의정도관리 < 그림 8-5, 6> - (5) : 최대가시화깊이 : 5.8 cm (4 MHz) - (6) : 최대가시화깊이 : 6.3 cm (7.5 MHz) - 최대가시화깊이는 gain, power는최대위치에 setting 검사주기 : 6 개월 결과 : cm 이내
초음파장비의정도관리 영상촬영과그레이스케일의하드카피 monitor, printer 대조도 (contrast), 휘도 (brightness) gray bar : 전체화면안에보여야함 < 그림 8-7>
초음파장비의정도관리 탐상된영상의일관성. 수직방향의일관성 < 그림 8-8> 원인 - 변환기내의불량진동자존재 - board 내단자의접촉불량 2. side to-side image compensation - 영상의한면에서다른쪽명의밝기의변화가없어야함 3. pixel data 의부적절한조합확인 - 수직, 수평으로흰줄무늬야기 - < 그림 8-9>
초음파장비의정도관리 거리측정의정확도 수직거리, 수평거리측정검사. 수직거리정확도 (= 깊이조정정확도 ) - < 그림 8-0> - 0cm 간격의두반사체사이 - 오차 : mm or.5% 이내 - top top 2. 수평거리정확도 - < 그림 8-> - 원인 : 빔폭효과, 진단기의부정확도 - 오차 : 3mm or 3% 이내 - center - center
초음파장비의정도관리 기타 공기필터세척 헐거운전기케이블점검 바퀴잠금장치확인 먼지제거 기록 (documentation) 성능검사용지 < 표 8-> 공간분해능검사 진단장치의성능을결정 축방향분해능검사 < 그림 8-2, 3> 측방향분해능검사 < 그림 8-4> 단면두께분해능검사 < 그림 8-5>
초음파장비의정도관리 Doppler testing string test object < 그림 8-8> flow velocity object < 그림 8-9> Doppler flow phantom < 그림 8-20> - tissue-mimicking 물질내부를통과하는빈튜브로구성 - 튜브내로혈액유사물질을흘림
. Routine tests done to determine that an ultrasound scanner is operating at its expected of performance are referred to as: A : Equipment acceptance tests B : General equipment maintenance C : Quality assurance D : Instrument upgrades 2. Which one of the following statements is true regarding quality assurance tests of ultrasound scanners? A : They require expertise of a hospital engineer or physicist B : QA for each scanner takes around 2 hours per week C : Good record keeping is an essential component D : Quantitative results are generally not necessary
3. In-house QA programs usually involve all of the following except: A : Tests using phantoms B : Inspection and cleaning of air filters C : Records and worksheets showing test results D : Voltage measurements at specified test points 4. Material making up the body of a typical QA phantoms is tissuelike in terms of its properties. A : Attenuation and perfusion B : Sound speed and attenuation C : Sound speed and reflector location D : Echogenicity and reflector location
5. The maximum depth of visualization can indicate changes in: A : Vertical distance measurement accuracy B : Axial and lateral resolution C : Slice thinkness D : Sensitivity 6. Maximum depth of visualization tests are done using: A : Minimum receiver gain and maximum transmit power B : Maximum receiver gain and minimum transmit power C : Maximum receiver gain and maximum transmit power D : Minimum receiver gain and minimum transmit power
23. A string phantom is useful for measuring: A : Maximum depth of Doppler signal detection B : Velocity accuracy in spectral Doppler C : Axial resolution in B-mode D : Vertical distance measurement accuracy 24. A string phantom is useful for measuring: A : Its depth from the transducer can be specified precisely B : It present a parabolic velocity profile like blood C : Its velocity can be precisely specified D : It has the same echogenicity as blood
7. Maximum depth of visualization is often limited by: A : Noise at high gain B : Poor axial resolution C : Too low a power setting D : too low a transducer frequency 8. Suppose that the maximum depth of visualization using a 3.5-MHz transducer is 4.2 cm. On the previous two tests 3 months and 6 months earlier it was 4.4 cm and 4. cm, respectively. These variations should be interpreted as: A : Just barely tolerable performance B : Normal variations inherent in the machine C : Excessive variations indicating the machine requires immediate service D : Normal variations inherent in the measurement process
9. A scan is done of a uniform section in a phantom, and a vertical shadow emanates from a position on the image corresponding to the transducer surface. This likely is caused by: A : Poor TGC control B : Poor lateral gain control C : Inadequate gray scale photography D : Loss of signal from one or more transducer elements 0. On the viewing monitor of scanners sonographer counts 6 shades of gray in the gray bar pattern. The hard copy B-mode image displays only the 3 brightest gray bar s. This should be interpreted as: A : Normal performance B : Too low a receiver gain setting C : Inadequate photography and processing that need correction D : Poor contrast and brightness settings on the viewing monitor
. To be used for tests of geometric accuracy, the and in a phantom must be precisely specified. A : Echogenicity and reflector location B : Sound speed and reflector location C : Attenuation and reflector location D : Echogenicity and attenuation 2. A measurement comparing the actual separation between two reflectors placed at different positions along the beam axis with the separation indicated on calipers is a test of: A : Axial resolution B : Ultrasound wavelength C : Vertical distance measurement accuracy D : Horizontal measurement accuracy
3. Where should the digital caliper cursors be placed for the above measurement? A : Top of the higher reflector, bottom of the other B : Top of one and top of the other C : Left side of one and right side of the other D : Bottom of the higher reflector, top of the other 4. If the actual distance between two reflectors in a phantom is 4.0 cm, but the digital caliper readout indicates it is 3.8 cm, the percentage error in the caliper readout is: A : less than % B :.5% C : 5% D : 0%
5. An image of a pointlike reflector results in a short line on the display. Horizontal measurement accuracy is done by placing the calipers to measure the distance between tow such reflectors displaced laterally from each other. Where should the caliper-cursors be placed? A : From the inside of one to the inside of the other B : From the center of one to the center of the other C : From the outer margin of one to the center of the other 6. For which of the following tests would it be okay if the results varied with the transducer frequency? A : Maximum depth of visualization B : axial distance measurement accuracy C : Lateral distance measurement accuracy D : Scan uniformity
8. The size of the displayed echo from a single, tiny reflector, measured along the direction of beam propagation, is related most closely to the: A : Depth measurement accuracy B : Axial resolution C : Lateral resolution D : Monitor distortion
9. Two reflectors are separated along a line perpendicular to the beam axis in the image plane. A measure of the minimum distance between the reflectors that still allows them to be distinguished is called the: A : Lateral resolution B : Axial resolution C : Axial depth of visualization D : Axial distance measurement accuracy 20. The width of the ultrasound beam, measured perpendicular to the scanning plane, determines the: A : Horizontal distance measurement accuracy B : Maximum depth of visualization C : Lateral resolution D : Slice thickness
2. On the slice thickness phantom the slice width is estimated from the of the image of the scattering plane. A : Axial extent B : Lateral margins C : Brightness D : Amount of shadowing 22. Large slice thickness hinders visualization of: A : Small, low-contrast spherical masses B : Nylon fibers oriented perpendicular to the scan plane C : Narrow anechoic tubes oriented perpendicular to the scan plane D : Specular reflectors oriented perpendicular to the beam
25. Doppler flow phantoms are useful for determining: A : Maximum depth of Doppler signal detection B : Vertical distance measurement accuracy C : Acoustical output during color flow imaging D : Horizontal distance measurement accuracy 26. In order to produce echo signals that are of a similar magnitude as blood in the body, what two factors in a Doppler phantom must be comparable to human tissues? A : Phantom material attenuation and mimicking material blood echogenicity B : Phantom material density and mimicking material blood attenuation C : Mimicking material blood viscosity and attenuation D : Mimicking material blood velocity and acceleration