Hepatic US is performed with standard curvilinear and high-resolution linear probes.
The curvilinear probe (2–6 MHz) allows acoustic penetration of deeper parenchyma while a high-resolution probe (7–12 MHz) may be used to depict greater surface detail.
Optimization of the gain, time-gain compensation, and tissue harmonics by an experienced sonologist, and second-look sonography by informed radiologists are requisites for achieving diagnostic examinations.
Normal liver parenchyma has a homogeneous echotexture, the assessment is subjective but the liver should not appear granular or coarsened if speckle reduction and compound imaging parameters are optimized.
Hepatic echogenicity is subjectively compared with that of adjacent solid viscera such as the kidneys and spleen; normal hepatic echogenicity is marginally higher than that of the kidney but less than that of the spleen.
The spleen provides a more reliable comparison because numerous intrinsic kidney diseases can alter their echogenicity.
Normal hepatic vessels have smooth walls and anechoic lumens.
Intrahepatic arteries are difficult to resolve on gray scale alone, but parallel the portal veins.
Normal spectral Doppler interrogation shows a low-resistance waveform with continuously hepatopetal diastolic flow.
Normal portal veins have thin echogenic walls and monophasic waveforms with mild respiratory variation.
Alterations of portal mural echogenicity should be considered abnormal.
Normal hepatic veins and the inferior vena cava (IVC) lack discernible walls.
The normal hepatic venous waveform is triphasic, owing to 2 hepatofugal peaks and 1 hepatopetal peak reflecting primarily right atrial pressure.
The normal common bile duct measures up to 6 mm in normal individuals, but radiology dogma suggest that the diameter of the duct can increase with age.
The central intrahepatic ducts should normally measure 3 mm or less.
The diameter of the common bile duct may vary following cholecystectomy.
The normal perihepatic spaces should contain a variable amount of homogeneous fat; any ascites, fluid collection, or soft-tissue lesion should be considered abnormal.
The most common benign nasopharyngeal tumour. It is probably hamartomatous in origin. Although benign it can grow to an enormous size and invade local structures.
It is seen virtually exclusively in males, usually in teenagers.
It is a highly vascular tumour which can present with severe epistaxis. Biopsy is extremely hazardous due to the risk of haemorrhage. Part of the radiological work up should assess the extent of the lesion and its vascularity. Some require embolisation prior to surgery to reduce the blood supply.
MR is better at showing the soft tissue extent of the tumour. Subtle bone destruction requires CT.
Characteristically the tumour is of low to intermediate signal intensity on both T1 and T2 weighted sequences. Discrete punctate areas of hypointensity are seen due to flow void channels in highly vascular stroma.