Lub luag haujlwm ntawm diodes hauv cov khoom siv kho mob (CT/MRI) yog dab tsi?

Ib, Lub diode hauv CT khoom: lub hauv paus ntawm lub zog hloov dua siab tshiab thiab teeb liab ntes
1. X-ray tiam thiab rectification: lub "zog hluav taws xob" ntawm siab-voltage diodes
Cov khoom tseem ceeb ntawm CT cov cuab yeej yog X- txoj kab hluav taws xob, uas ua haujlwm los ntawm kev ua kom cov kab hluav taws xob nrawm kom sib tsoo nrog cov khoom siv hlau (xws li tungsten) los ntawm qhov siab -voltage electric teb, tsim X-rays. Thaum lub sijhawm ua haujlwm no, siab -voltage diodes ua lub luag haujlwm ntawm "zog hluav taws xob":

Rectification muaj nuj nqi: CT tube yuav tsum tau kaum ntawm kilovolts siab -voltage direct tam sim no tsav, thaum lub mains fais fab yog alternating tam sim no. High voltage diodes (xws li diodes nyob rau hauv peb -theem kaum ob yoj rectification circuits) hloov alternating tam sim no mus rau pulsating ncaj tam sim no los ntawm unidirectional conduction yam ntxwv, muab ruaj khov siab -voltage hwj chim rau lub raj. Nws cov yam ntxwv qis qis qis qis tuaj yeem txo qis zog thiab txhim kho X-ray ntau lawm efficiency.
Pulse tswj: Nyob rau hauv ceev nruam dynamic CT scanning, diodes yuav tsum tau luv luv - lub sij hawm mem tes siab voltage (xws li 3ms pulse exposure), thiab lawv ceev ceev cov yam ntxwv ua kom ruaj khov ua hauj lwm nyob rau hauv siab - zaus switching, zam cov duab artifacts tshwm sim los ntawm voltage fluctuations.
2. Ntes teeb liab hloov dua siab tshiab: "photoelectric translator" ntawm photodiodes
CT detector yog ib qho tseem ceeb rau kev ntes X-ray signals, nrog rau nws cov tub ntxhais yog photodiode array (xws li amorphous silicon photodiodes). Lub hauv paus ntsiab lus ua haujlwm yog raws li nram no:

Kho qhov muag teeb liab hloov dua siab tshiab: Tom qab X-rays dhau los ntawm tib neeg lub cev, lawv tau hloov mus rau hauv lub teeb pom kev los ntawm scintillators (xws li cesium iodide) nyob rau hauv lub detector. Photodiodes hloov photon zog rau hauv cov teeb liab hluav taws xob, thiab lawv cov lus teb ceev (nanosecond theem) thiab siab rhiab heev kom ntseeg tau tias muaj kev cuam tshuam dawb teeb liab ntes.
Kev txwv tsis pub muaj suab nrov: Cov yam ntxwv tsis tshua muaj qhov tsaus ntuj tam sim no ntawm photodiodes tuaj yeem txo cov suab nrov thermal cuam tshuam, txhim kho teeb liab - rau - suab nrov piv (SNR), thiab muab lub hauv paus rau siab - daws teeb meem duab. Piv txwv li, amsOSRAM's AS5950 ntes nti integrates photodiodes thiab AD converters ntawm ib wafer, nce SNR los ntawm 30% thaum txo hwj chim noj los ntawm 40%.
3. Kev tiv thaiv kev nyab xeeb: "surge protector" ntawm TVS diodes
CT cov cuab yeej yuav tsum tau muaj zog ruaj khov heev, thiab xob laim los yog kab sib chaws hloov pauv yuav ua rau muaj kev hloov pauv siab -voltage pulses, ua rau cov kab hluav taws xob puas tsuaj. TVS (Transient Voltage Suppression) diodes muab kev tiv thaiv los ntawm cov txheej txheem hauv qab no:

Nanosecond teb: Thaum qhov hluav taws xob ntau tshaj qhov hluav taws xob tawg, TVS ua nyob rau hauv 1ns, clamping qhov hluav taws xob nyob rau hauv qhov chaw nyab xeeb (xws li 6.5V) kom tsis txhob muaj kev puas tsuaj rau cov khoom txuas ntxiv (xws li microprocessors).
Muaj peev xwm ua kom muaj peev xwm ua tau ntau yam: TVS zoo tuaj yeem tiv taus ntau pua qhov cuam tshuam, haum rau kev ua haujlwm ntev -cov khoom siv CT.
2, Lub diode hauv MRI cov cuab yeej: "tus neeg saib xyuas tsis pom" ntawm RF tswj thiab kev sib cais kev nyab xeeb
1. RF pulse modulation: "lub teeb liab hloov" ntawm cross diode
MRI tsim cov cim qhia los ntawm kev txaus siab hydrogen nuclei nrog xov tooj cua zaus pulses, thiab nws cov emission thiab txais tos yuav tsum tau tswj lub sij hawm meej. Tus ntoo khaub lig mounted diode array plays lub luag haujlwm tseem ceeb hauv cov txheej txheem no:

Pulse kis tau tus mob: Thaum lub tshuab hluav taws xob RF outputs siab - theem pulses, lub diode array conducts, cia cov pulses kis tau los ntawm tus kav hlau txais xov; Tom qab cov mem tes xaus, lub diode rov qab mus rau lub xeev siab impedance los tiv thaiv cov teeb liab cuam tshuam los ntawm kev cuam tshuam nrog qhov system txais.
Kev tiv thaiv kev rho tawm: Los ntawm kev tsim lub quarter wavelength kis kab, lub diode array ua ib qho luv luv -circuit effect ntawm qhov kawg tau txais los xyuas kom meej tias cov mem tes xa mus tsis nkag mus rau hauv lub receiver thiab tsis txhob ua rau tus kheej -zoo siab oscillation.
2. Superconducting hlau nplaum tiv thaiv: "zog absorber" rau damping diodes
MRI superconducting hlau nplaum khaws lub zog loj (xws li ob peb lub zog megajoules hauv 1.5T hlau nplaum), thiab demagnetization ceev yuav tsum tau kaw thaum muaj xwm txheej ceev kom tsis txhob muaj kev pheej hmoo ntawm cov kua helium vaporization. Damping diodes ua tiav kev nyab xeeb demagnetization los ntawm cov txheej txheem hauv qab no:

Lub zog nqus: Thaum lub sij hawm demagnetization, lub zog ntawm cov hlau nplaum hloov mus rau hauv thermal zog los ntawm lub damping diode. Nws cov yam ntxwv qis qis rau pem hauv ntej kom ntseeg tau tias muaj zog nqus thiab tiv thaiv cov khoom puas tsuaj los ntawm vaporization ntawm cov kua helium.
Kev tswj lub siab: Ua ke nrog lub helium re liquefaction system, damping diodes tuaj yeem ua rau qeeb tus nqi ntawm qhov siab, muab lub sijhawm thaum muaj xwm txheej ceev rau cov neeg ua haujlwm.
3. Kev sib cais hluav taws xob: "kev nyab xeeb barrier" ntawm optocouplers
Hauv cov khoom siv MRI, qhov siab -voltage RF Circuit Court thiab qis-voltage control system yuav tsum tau cais nruj me ntsis kom tsis txhob muaj kev pheej hmoo ntawm hluav taws xob poob siab. Optocouplers ua tiav kev sib cais kev nyab xeeb los ntawm cov hauv qab no:

Optical signal kis tau tus mob: Lub optocoupler muaj lub teeb -emitting diode (LED) thiab photodiode. Cov teeb liab tawm tswv yim tau hloov mus rau hauv lub teeb liab kho qhov muag los ntawm LED, thiab tom qab ntawd rov qab los rau hauv lub teeb liab hluav taws xob los ntawm photodiode, ua tiav kev sib cais hluav taws xob.
Muaj peev xwm tiv thaiv kev cuam tshuam: Optocouplers tuaj yeem cuam tshuam electromagnetic cuam tshuam (EMI), ua kom muaj kev ruaj ntseg ntawm cov ntaub ntawv duab, tshwj xeeb tshaj yog nyob rau hauv kev cuam tshuam loj xws li chav ua haujlwm.