Background and Aims Ultrasonography is noninvasive and commonly used for neuroimaging in premature newborns. Studies on brain measurement techniques and reference values of brain diameters are lacking. This paper aimed at

1. determining average diameters of cerebral ventricles, brain and cerebellum in preterm infants;

2. 2. describing discrepancies between left and right sides, and between type of transducers used;

3. 3. assessing possible relationships between diameters measured and gestational age, head circumference, birth length, birth weight, and gender.

Methods 132 newborn infants were enrolled and each subject had 34 diameters measured and 6 ratios calculated. Area of cavum septum pellucidum (ACSP), ventricular index (VI), ventricular width (VW), brain width (BW), third ventricle width (3VW), frontal horn width (FHW) were assessed in coronal plane. Evans (ER) and Johnson (JR) ratios were calculated. Midbody of lateral ventricle (MLV) and thalamo-occipital distance (TOD) were studied in parasagittal plane. Transverse cerebellar diameter (TCD), 4th ventricle width (4VW) and length (4VL) were assessed via mastoid fontanelle.

Results Sector probe gave significantly smaller measurement results than convex transducer. Left side measurements were significantly greater than right side ones. VI, VW, BW, TCD and 4VW were dependent on birth weight, birth length, head circumference and gestational age. ACSP, FHW, TOD and JR were independent of those factors. No relationships were found between gender and measured diameters or calculated ratios.

Conclusions Reference values for cranial measurements, ER and JR were determined for examined population of premature newborns. Described indices may be useful for everyday clinical practice in neonatal units.