Neuroimaging of midbrain structures with different phased-array ultrasound systems

Purpose: Transcranial sonography (TCS) has been recently used to detect alterations in the echo pattern of the basal ganglia in movement disorders. Data about the impact of the TCS equipment on depiction of basal ganglia are not yet available. Aim of the study was to compare the feasibility of two different ultrasound systems to determine the echo pattern of brain parenchyma.

Methods: TCS was performed through the temporal bone window in twenty-four subjects (age: 20–77yrs). Two phased-array ultrasound systems (A – Sonoline Elegra; B – Sonoline Antares) equipped with a 2–2.5MHz transducer (2.5PL20, PX4–1, PH4–1; Siemens, Erlangen, Germany) were used. The bone window and the echo pattern of basal ganglia was assessed in each subject by two investigators. The echogenic size of the substantia nigra (SN) and the width of the third ventricle was measured systematically on axial TCS scans.

Results: Using TCS-system A and B, classification of bone window did not differ (excellent: 54 vs. 58%; moderate 38 vs. 34%, insufficient 8 vs. 8%). The mean third-ventricle width was 3,5±0,9mm (system A) and 3.4±0,9mm (system B) (p=0.49). Echo pattern of midbrain structures was identical using both systems. Examination with system B demonstrated larger area of echogenic SN than measurements with system A (mean area±SE: 15,4±1,4mm² vs.12,4±1,2mm²; p=0.00). Enlargement of echogenic SN area (³20mm²) was found in 5 and 8 subjects using system A and B, respectively. SN size measured by system A and B (Fig.) correlated significantly (Spearman coefficient: 0.72; p=0.00).

Conclusion: SN echogenic size is substantially influenced by the TCS equipment used. The normal range of SN echogenic size should be redefined for each ultrasound system if brain parenchyma sonography will be applied as diagnostic tool.