[1] UNIV HELSINKI,CENT HOSP,CHILDRENS HOSP,DEPT RADIOL,FIN-00290 HELSINKI,FINLAND
[2] UNIV HELSINKI,CENT HOSP,CHILDRENS HOSP,DEPT OBSTET & GYNAECOL,FIN-00290 HELSINKI,FINLAND
[3] UNIV HELSINKI,CENT HOSP,CHILDRENS HOSP,DEPT PAEDIAT,FIN-00290 HELSINKI,FINLAND
[4] UNIV UPPSALA,DEPT DIAGNOST RADIOL,S-75105 UPPSALA,SWEDEN