European journal of radiology
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Transcranial color Doppler sonography permits the accurate assessment of intracranial arteries. The latest Doppler units, using the color and power techniques, can show even very small flow volumes (1 x 1 mm). Low frequency (2-2.5 MHz) and very focused transducers are used in transcranial color Doppler. The skull is a very strong barrier for ultrasounds, which requires the use of some acoustic windows like some thin portions of the skull bone or some natural skull foramina. The use of echocontrast agents in color Doppler seems to increase the applications of transcranial studies. ⋯ With reference to internal carotid stenoses, the main applications of transcranial color Doppler are the study of intracranial vessels, of intracranial arterial stenosis, of arteriovenous malformations and of Willis circle aneurysms, as well as the monitoring of blood flow velocity during carotid endarterectomy. Echocontrast agents play an important role in the visualization of intracranial vessels.
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Sonography is well suited for breast studies. Adequate equipment is needed to acquire high quality images because several technical factors influence ultrasound images. Thus, the use of high frequency dynamic scanning probes, the ultrasound beam focusing corrected for the near field, the adjustment of the gain and image contrast may all interfere with ultrasound beam reflection and scattering, determined by the heterogeneity of the gland parenchyma. ⋯ In the last few years, several quality assurance programs have been introduced. Dedicated phantoms are generally used. Recently, computer systems have been also developed.
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Since the assessment of lymph node metastases in head and neck cancer patients remains a major problem, the findings of different imaging methods and the role of these methods in the clinical management are compared. ⋯ CT is superior to low field MRI in depicting small pathologic lymph nodes. Unlike lymph node structure, lymph node size is not a highly reliable criterion for malignancy. The findings must be correlated in relation to the primary disease. Since FNAC under US-guidance offers additional information about enlarged lymph nodes and since it can show malignancy in small lymph nodes not found by other methods, it can be recommended for most head and neck cancer patients irrespective of the use of CT or MRI.