Ultrasound in medicine & biology
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Ultrasound Med Biol · Jan 1997
Comparative StudyInsufficient and absent acoustic temporal bone window: potential and limitations of transcranial contrast-enhanced color-coded sonography and contrast-enhanced power-based sonography.
The aim of this study was to investigate the diagnostic potential of contrast-enhanced transcranial color-coded sonography (CE-TCCS) and contrast-enhanced transcranial power-based sonography (CE-TPS) in patients with insufficient or absent acoustic bone windows (IABW). Due to temporal bone thickness, the basal cerebral circulation could not be insonated in 21 of 172 patients using unenhanced transcranial color-coded real-time sonography (TCCS) and transcranial power-based sonography. Additional CE-TCCS and CE-TPS were performed after application of 400 mg/ml galactose microbubble suspension. ⋯ In conclusion, CE-TCCS and CE-TPS appear to be sensitive ultrasonic tools that provide reliable data regarding the basal cerebral circulation in patients with IABW. Furthermore, CE-TPS offers advantages over CE-TSSC in the identification of small-caliber arteries and vessels that run at unfavorable angels to the ultrasound beam. Both methods can overcome hyperostosis of the skull that is a major hindrance in transcranial ultrasonography, and may be helpful in the diagnosis of occlusive diseases of intracranial vessels.
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Interventional ultrasound, i.e., US-guided interventions, are diagnostic or therapeutic minimally invasive procedures guided by real-time ultrasound imaging, preferably using attachable needle steering devices. Guided fine- and coarse-needle biopsies of US-detectable abnormalities provide a firm basis for diagnosis and therapy. Multiple US-guided drainage and catheterization procedures such as nephrostomy, pleuracentesis, cholecystostomy, abscess drainage and central venous catheterization, etc., are rapid and safe alternatives to conventional drainage methods and open surgery. ⋯ Focal treatment of malignant tumours in the liver and prostate, using a variety of US-guided methods, are investigated. Complications of interventional ultrasound are reportedly low with a 0.19% overall complication rate and a 0.04% mortality rate. It is concluded that ultrasound provides a safe and cost-effective dynamic imaging modality for guidance of the increasing range of diagnostic and therapeutic interventional procedures.
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Ultrasound Med Biol · Jan 1995
Monitoring intracranial dynamics by transcranial Doppler--a new Doppler index: trans systolic time.
Since the introduction of transcranial Doppler sonography (TCD) several investigators have described the relationship between raised intracranial pressure (ICP) and Doppler waveform. This waveform has been expressed by several indices, such as the pulsatility index (PI) and the resistance index (RI). These indices are used to demonstrate the presence of raised ICP. ⋯ We present a hydrodynamic model, with its electrical analogue, which shows the effects of raised ICP on the intracranial hemodynamic system. Based on these physical findings we define a new Doppler index, the Trans Systolic Time, reflecting specific changes in the TCD waveform induced by changes in the mean ICP. The applicability of this index, compared with PI and RI, is illustrated by consecutive simultaneous TCD and AFP measurements in three children with hydrocephalus.
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Ultrasound Med Biol · Jan 1995
Computerised transient hyperaemic response test--a method for the assessment of cerebral autoregulation.
A simple bedside test has been developed to assess the state of autoregulation in subarachnoid haemorrhage patients. Transcranial Doppler was used to measure blood flow velocity in the middle cerebral artery after a brief common carotid compression. Acceleration of blood flow postcompression was interpreted as evidence of intact cerebral autoregulation. ⋯ The flow velocity signal from the TCD was recorded, carotid compression and release automatically detected and the test results immediately displayed and stored in a database. The program was verified in 614 tests; 552 of them were analysed off-line using previously recorded data and 62 on-line during the examination. A significant correlation was found between the results of computerised testing and the patient's neurological state.