Radiology References

Imaging atlases, normal values, and reporting templates.

302 references · Page 4 of 11

F

Normal Fetal Lateral Ventricle Diameter Size on Ultrasound
Normal fetal lateral ventricle diameter measures less than 10 mm on coronal ultrasound — a key threshold for detecting ventriculomegaly in obstetric imaging.
Normal Fetal Renal Pelvis Diameter Size on Ultrasound
Normal fetal renal pelvis diameter is <4 mm before 32 weeks and <7 mm after 32 weeks on prenatal ultrasound, guiding hydronephrosis assessment.
Normal Fetal Thorax/Abdomen Circumference Ratio on Ultrasound
Normal fetal thorax-to-abdomen circumference ratio is >0.77 on ultrasound, a key marker for detecting thoracic hypoplasia and lethal skeletal dysplasias.
Normal Fibular Angle Size on Radiography
Normal fibular angle on AP and mortise ankle radiographs ranges from 43° to 63°, a key measurement for assessing fibular length and ankle stability.
Normal Filum Terminale Size on Ultrasound and MRI
Normal filum terminale diameter is less than 2 mm on ultrasound and MRI; values at or above this threshold suggest a thickened filum and possible tethered cord.
Normal First Metatarsal Declination Angle Size on Radiography
The normal first metatarsal declination angle is 21° on lateral radiography, a key measurement for evaluating forefoot biomechanics and deformity.
Normal Fischgold's Bimastoid Line Size on X-ray, CT, MRI
Normal Fischgold's bimastoid line measurement: the odontoid tip should lie less than 10 mm above this craniometric line on X-ray, CT, or MRI.
Normal Fourth Ventricle Size on Ultrasound MRI CT: Neonates
Normal fourth ventricle sagittal diameter measures 4 mm in newborns on ultrasound, MRI, and CT—key reference for neonatal neuroimaging.
Normal Fowler-Philips Angle Size on Radiography
The normal Fowler-Philips angle measures 45–75° on lateral foot radiography, a key parameter for assessing Haglund deformity and heel pathology.

G

Normal Gallbladder Diameter & Size on Ultrasound
Reference values for normal gallbladder diameter and dimensions on ultrasound in adults and children, with clinical thresholds and measurement technique pearls.
Normal Gallbladder Wall Thickness on Ultrasound
Normal gallbladder wall thickness on ultrasound is under 3 mm in adults and varies by age in pediatric patients, aiding detection of cholecystitis and other pathology.
Normal Gastric Band Size on Fluoroscopy & Radiography
Learn the normal gastric band measurements on fluoroscopy and radiography, including the >5 mm threshold that signals clinically significant slippage or obstruction.
Normal Gastric Distension Size on Radiography
Learn the normal and abnormal thresholds for gastric distension on plain radiography, including clinical implications and measurement technique.
Normal Gestational Sac Diameter Size on Ultrasound
Normal gestational sac diameter on ultrasound follows the Age − 30 mm rule in the first trimester, with key thresholds guiding early pregnancy assessment.
Normal Gissane Critical Angle Size on Radiography
Normal Gissane critical angle on lateral radiograph measures 120–145°, a key calcaneal landmark for detecting intra-articular fractures.
Normal Glenohumeral Joint Space Size on Radiography
Normal glenohumeral joint space measures 4–5 mm on AP radiography; values outside this range suggest arthritis, effusion, or instability.

H

Normal Haller Index: CT Measurement for Pectus Excavatum
Normal Haller Index on CT is less than 2.5; values ≥3.25 typically indicate surgical correction for pectus excavatum.
Normal Hallux Valgus Angle Size on Radiography
Learn the normal and abnormal hallux valgus angle on weight-bearing AP radiography, with clinical thresholds and measurement technique pearls.
Normal Harris Line Measurements: Cervical Radiography, CT, MRI
Normal Harris line measurements include basion-odontoid and basion-posterior axial line distances of less than 12 mm on lateral cervical imaging.
Normal Heel Pad Thickness on Radiography
Normal heel pad thickness on lateral radiograph measures less than 23 mm; values above this threshold suggest acromegaly or systemic pathology.
Normal Hibbs Angle Size on Radiography: Foot Reference
The normal Hibbs angle on lateral foot radiography is 130°, a key measurement for assessing forefoot and hindfoot alignment in clinical practice.
Normal Hilgenreiner's Epiphyseal Angle Size on Radiography
Normal Hilgenreiner's epiphyseal angle measures less than 60° on AP pelvis radiography, a key threshold in pediatric hip dysplasia assessment.
Normal Hip Alpha Angle Size on MRI: Reference Guide
The normal hip alpha angle on MRI is less than 55°; values at or above this threshold indicate cam-type femoroacetabular impingement.
Normal Hip Alpha Angle Size on Ultrasound
Learn the normal hip alpha angle threshold on ultrasound, its clinical significance in developmental dysplasia of the hip, and measurement technique pearls.
Normal Hip Neck Shaft Angle Size on Radiography
Normal hip neck shaft angle measures 110–140° on AP radiography, with deviations indicating coxa vara or valga and guiding orthopedic management.
Normal Hip Teardrop Distance Size on Radiography
Normal hip teardrop distance on AP radiography measures 6–11 mm, a key landmark for detecting joint effusion and femoral head migration.
Normal Humeral Angle Size on Radiography
Normal humeral angle on lateral elbow radiography measures 72–95°, a key parameter for detecting distal humeral fractures and malalignment.
Normal Hydronephrosis Grading: CT, MRI & Ultrasound
Learn the standard 0–4 hydronephrosis grading system on CT, MRI, and ultrasound, including key imaging findings and clinical thresholds for each grade.

I

Normal Inferior Vena Cava Diameter on Ultrasound and CT
The normal average inferior vena cava diameter is 20 mm on ultrasound and CT, a key threshold for filter sizing and hemodynamic assessment.
Normal Insall-Salvati Ratio Size on Radiography
Normal Insall-Salvati ratio on lateral knee radiography ranges from 0.8–1.2, with values outside this range indicating patella alta or baja.