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1、X-rayGridsWhyhaveagrid?ScatterradiationisinevitablyproducedwhenprimaryradiationpassesthroughsubjectWithoutagridradiographicfogisproducedonthefilmwhichdegradesthediagnosticqualityWhatisaGrid?ActsasafiltertoremovescatterradiationbeforeithitthefilmFocalRangeDistancefromtubetofilm(SID)I
2、dealtomatchgridtoSIDLowerratiogrids=widerfocalrange(typically8:1truefocalrangeis100cmbutcanbeused86-112cm)Higherratiogridseg.12:1,range92-102cmShort,medium,longtermsoftenusedtodescribefocalrangeFocussedGridLeadstripsaretiltedprogressivelyastheymoveawayfromcentreGridfocuswhereperfect
3、alignmentofprimarybeamwithleadstripsParallelGridGenerallynotmadewithgridratio>6.0LeadstripsparalleltoeachotherStripsareneveralignedwithprimarybeamsinceallarevertical(exceptforstripsdirectlyundercentralrayCutoffonbothsidesoffilmwheneverusedCrossGrid(crosshatch)2gridsontopofeachotherw
4、ithleadstripsofoneperpendiculartootherGridUseMostcommonisfocussedgridReadlabeltodeterminefocussingdistanceEstablishtubesideUsehighratioifusedasstationarygridtolessenobviousgridlinesEnsureCRisperpendiculartogridtopreventgridcutoffAnytubeangulationisalonglinesofgridIncreasemAsby6steps
5、(4x)whencomparedtonongridtechniquePositioningLatitudeGridratioCleanupPositioninglatitude12:1ExcellentVeryslight10:1VerygoodSlight8:1GoodSlight6:1ModerateGood5:1ModerateExtreme義務(wù)教育課程標準實驗教科書數(shù)學（西師版）二年級下三位數(shù)的加法重慶市江津雙槐樹小學卞小娟10枝10枝10枝10枝10枝10枝鋼筆鉛筆鋼筆100枝100枝10枝10枝100枝100枝10枝10枝10枝10枝10枝10枝鉛
6、筆豐收小學男生（人）433 女生（人）418合計（人）851小陽家小明家小紅家小月家520m380m410m368m小明家小月家,要行多少米?經(jīng)()家經(jīng)過小紅家到小月家的距離:小陽家小紅家小月家520m380m410m368m小明家經(jīng)過小陽家到小月家的距離:368+520=888(米)410+380=790(米)368 +520 888410 +380 790教學設(shè)計：卞小娟張健指導教師：張健課件制作：卞小娟
