最新X-ray Grids教学讲义ppt课件.ppt

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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义务教育课程标准实验教科书数学（西师版）二年级下三位数的加法重庆市江津双槐树小学卞小娟10枝10枝10枝10枝10枝10枝钢笔铅笔钢笔100枝100枝10枝10枝100枝100枝10枝10枝10枝10枝10枝10枝铅

6、笔丰收小学男生（人）433女生（人）418合计（人）851小阳家小明家小红家小月家520m380m410m368m小明家小月家,要行多少米?经()家经过小红家到小月家的距离:小阳家小红家小月家520m380m410m368m小明家经过小阳家到小月家的距离:368+520=888(米)410+380=790(米)368+520888410+380790教学设计：卞小娟张健指导教师：张健课件制作：卞小娟