▁contribute ▁to ▁over use ▁include ▁" self - refer ral , ▁patient ▁wishes , ▁in app ropri ate ▁finan cially ▁motiv ated ▁factors , ▁health ▁system ▁factors , ▁industry , ▁media , ▁lack ▁of ▁aw aren ess " ▁and ▁def ensive ▁medicine . ▁Res pected ▁organizations — such ▁as ▁the ▁American ▁College ▁of ▁Rad i ology ▁( AC R ), ▁Royal ▁College ▁of ▁Rad i olog ists ▁( RC R ) ▁and ▁the ▁World ▁Health ▁Organ ization ▁( W HO ) — have ▁developed ▁" app ropri aten ess ▁criteria ". ▁The ▁Canadian ▁Association ▁of ▁Rad i olog ists ▁estimated ▁in ▁ 2 0 0 9 ▁that ▁ 3 0 % ▁of ▁imag ing ▁was ▁unnecessary ▁in ▁the ▁Canadian ▁health ▁care ▁system . ▁ 2 0 0 8 ▁Medic are ▁claims ▁showed ▁over use ▁with ▁ch est ▁CT ' s . ▁Fin an cial ▁in cent ives ▁have ▁also ▁been ▁shown ▁to ▁have ▁a ▁significant ▁impact ▁on ▁dent al ▁X - ray ▁use ▁with ▁dent ists ▁who ▁are ▁paid ▁a ▁separate ▁fee ▁for ▁each ▁X - ray ▁providing ▁more ▁X - ray s . ▁ ▁Over use ▁of ▁imag ing ▁can ▁lead ▁to ▁a ▁diagn osis ▁of ▁a ▁condition ▁that ▁would ▁have ▁otherwise ▁remained ▁irrelevant ▁( over di agn osis ). ▁ ▁Phys ician ▁self - refer ral ▁ ▁One ▁type ▁of ▁over use ▁can ▁be ▁phys ician ▁self - refer ral . ▁Multiple ▁studies ▁have ▁rep licated ▁the ▁finding ▁that ▁when ▁non - rad i olog ists ▁have ▁an ▁ownership ▁interest ▁in