ate ▁determ ination ▁of ▁either ▁is chem ia ▁or ▁inf ar ction . ▁ ▁By ▁ 1 9 6 3 , ▁Dr . ▁William ▁Bruce , ▁aware ▁of ▁the ▁t endency ▁of ▁people ▁with ▁coron ary ▁ar tery ▁disease ▁to ▁experience ▁ang ina ▁( card iac ▁ch est ▁dis com fort ) ▁during ▁exercise , ▁developed ▁the ▁first ▁standard ized ▁method ▁of ▁" str ess ing " ▁the ▁heart , ▁where ▁serial ▁measurements ▁of ▁changes ▁in ▁blood ▁pressure , ▁heart ▁rate ▁and ▁electro card i ographic ▁( E CG / E K G ) ▁changes ▁could ▁be ▁measured ▁under ▁" str ess - str ess " ▁conditions . ▁ ▁By ▁ 1 9 6 5 ▁Dr . ▁William ▁Love ▁demonstrated ▁that ▁the ▁cum bers ome ▁cloud ▁chamber ▁could ▁be ▁replaced ▁by ▁a ▁Ge iger ▁counter , ▁which ▁was ▁more ▁practical ▁to ▁use . ▁However , ▁Love ▁had ▁expressed ▁the ▁same ▁concern ▁as ▁many ▁of ▁his ▁colle agues , ▁namely ▁that ▁there ▁were ▁no ▁suitable ▁radio is ot op es ▁available ▁for ▁human ▁use ▁in ▁the ▁clin ical ▁setting . ▁ ▁Use ▁of ▁th al li um - 2 0 1 ▁By ▁the ▁mid ▁ 1 9 7 0 s , ▁scient ists ▁and ▁clin icians ▁al ike ▁began ▁using ▁th al li um - 2 0 1 ▁ ▁as ▁the ▁radio is ot ope ▁of ▁choice ▁for ▁human ▁studies . ▁ ▁Ind ividual s ▁could ▁be ▁placed ▁on ▁a ▁t read mill ▁and ▁be ▁" str essed " ▁by ▁the ▁" B ru