MECHANICAL INDEX (MI) AND THERMAL INDEX(TI)

Mechanical Index (MI) and Thermal Index (TI)



Mechanical Index (MI) and Thermal Index (TI)

Introduction

The paper discusses the ultrasonic matrices known as mechanical and thermal index. It also highlights the safety guidelines of the use of these indices and the significance of scanners to set the values.

Mechanical Index (MI) and Thermal Index (TI)

The terms refer to the matrices to measure the increase in temperature while reprocess of ultrasound in going on. An automated index refers to an estimate of the maximum amplitude of the pressure pulse in the tissue; it is the indicator of the mechanical bio effects. The MI of the ultrasound is the amount of the negative acoustic pressure within the field of ultrasonic waves. The MI should be up to 1.9 for all the applications except from ophthalmic that is 0.23 (Kerry. 2001.51).

On the oath hand, thermal index is the ratio of the acoustic power to the required raising a maximum temperature increase of 1°C. The rise of temperature is dependent on the tissue type and on the presence of bone. During the diagnostic ultrasound, to obtain images of internal body structure, the device uses high frequency sound waves. A small device called a transducer, the sound waves, are sent into the tissue, and then mapped on the basis of signals generated image of the internal organs (Ziskin. Lewin. 2009.79). Thus, a value of 1.0 corresponds to the IT potential of raising the temperature by 1 °C; however, the recommendations say that exposure to a temperature rise of less than 1.5 ° C above normal physiological levels can be implemented without risks (Wells. 2007.89). During the last decade, procedural devices have increased the amount of mW / cm 2applied, so that potential adverse effects may be greater. Against this, standard have been established, which appear on the screen of the devices in real time and provide information about potential increases in temperature (IT) or mechanical injury (LM). While the implementation, of this standard has increased the responsibility of the end users of ultrasound devices in relation to patient safety, the utility of these acoustic indices are associated with the familiarity of their meaning by such professionals. Ultrasound diagnosis is widely recognized as safe. Indeed, as yet there have been no reports of damage done to diagnose patients with ultrasound (Kremkau. 2004.92)

(Kremkau. 2004.92). One cannot categorically state that ultrasound is safe at 100%. Studies have shown that very high intensity ultrasound is harmful to body tissues.

Over the past few years, ultrasound has taken a significant step forward (Timor.Platt .2002.575). This rapid development of the device and values, when constantly introducing new diagnostic techniques has sparked fears about the possible risk of adverse biological effects. Studies have shown that the human body has an impact factor of two different ultrasonic radiations (Barnett, 20063, 65):

The mechanical effect of ultrasound when the pressure exceeds a certain limit, and there is an effect of cavitations (the formation of micro cavities);

Thermal effects due to absorption by tissues of the body ...