Introduction
Modern day healthcare practices incorporate significant use of ultrasound. The general application of ultrasound aims to perform diagnosis and is brought into common use in the clinical practice of cardiology. Ultrasound imaging is also often referred to as sonograph and is a technique that is brought into use to acquire images of the body using extremely high-frequency sound waves (Hofer, 1999). Being of an extensively high frequency, the sound waves come as inaudible to the human ear and are generally within the range of 2MHz to 12MHz.
In layman terms, the principles behind the functioning of ultrasound are the same as those behind every functioning of bats and seagoing fishermen. The entire idea revolves around sound waves. Upon striking an object, sound waves tend to bounce back into the direction from where they were emitted. Through careful and accurate analysis of the echo waves returning to the source of the emission, elements on the object’s location can be ascertained.
These elements include those such as the object’s size, consistency, shape and even the form within which the object is in, i.e., solid-liquid or plasma. Ultrasound, therefore, comes in as a highly significant instrument for the measurement of the appearance and the development of human tissue that forms organs and also of vessels in an attempt to detect active or benign tumours. The instrument performing the emission of the sound waves and the recording of their bouncing back is referred to as the transducer and the medical practitioner generally gently presses the transducer against the skin of the subject after having applied a water-based gel to serve as a medium between the transducer and the individual’s body that can be relied upon to force out any air bubbles or pockets (Duck, Baker, & Starritt, 1998).
The recorder in the transducer continues to record even the most minor of alterations in direction and pitch of the echoed high-frequency sound waves as they enter the body and bounce back towards the transducer over tissue, fluids and internal organs.
Ultrasound is brought into use commonly since it does not make use of radiations and therefore is safe for use in cases involving pregnancy and other sensitive medical conditions. Ultrasound is brought into use for the specific purpose of monitoring through imagery, the development of embryos and fetuses.
The use of means other than ionizing radiations is an attribute of Ultrasound that makes it a preferred means of body imagery and it is for the same reason that it has remained active and in prevailing use in the face of developing technology (Duck, Baker, & Starritt, 1998). However, there have been indications that the free radicals of ultrasound may indeed be having implications on the subject being subjected to the ultrasound. The foremost biological implications of ultrasound include effects such as damage to chromosomes caused as a result of interference with DNA.
Studies carried out to observe the implications of ultrasound in the biological perspective indicated that sister chromatid exchanges may undergo a significant increase as a result of being exposed to ultrasounds and other researchers have indicated that there is no implication that exposure to ultrasound waves can have on subjects. The body of literature present on the subject can therefore be surmised to incorporate a high degree of contradiction and uncertainty (Andreassi, 2004).
This paper shall attempt to contribute to this body of literature by performing an elaborative study of the literature and to acquire an understanding of the physics background of ultrasound as well as the mechanisms of interaction that occur in biological tissues. The paper shall also give regard to the applications of ultrasound in medicine and biology before concluding. The paper shall attempt to highlight the productivity that ultrasound provides and shall evaluate the positive and negative characteristics of the implementation of ultrasound on patients.
Physics behind Ultrasound
It is important to note that sound waves brought into use in modern day ultrasound applications are based on highly complex acoustic structures and that this complexity of structure is further increased when the sound waves are propagated to pass through complex tissue structures. In terms of their physics, the spatial resolution of the ultrasound acoustic waves is maintained at a length that spans less than a singular millimetre. The velocity may lie anywhere between 1450m/s to 1600m/s and the wavelength may be present in anywhere between 0.15mm to as far as 0.75mm (Hofer, 1999).
The symmetry of the sound waves transmitted is of the utmost importance in the application of ultrasound and modern day ultrasound machines bring phased arrays into use to ensure symmetry. Also, any discussion on ultrasound, its applications and its implications will be incomplete without an overview of the properties of tissues that make them responsive to ultrasound. Ultrasound images are generally formed as a result of the impedance, scattering, attenuation and absorption of sound waves. Tissues generally tend to emit a plane sound wave as a result of absorption and scattering phenomena.
The process that constitutes the creation, intensification and implosion of cavity bubbles is perhaps the central element because of which biological implications take place as a result of the application of ultrasound. The imploded collapse of the cavity and the high temperature developed causes radical heating and cooling rates to take place. Energy interacts with matter in a unique form in the application of ultrasound and the resulting ultrasonic irradiation is one that causes the generation of a scenario so complex that the resulting consequences incorporate the development of sonochemistry (Duck, Baker, & Starritt, 1998).
It is imperative to note at this point that this process of heating and cooling occurs at extremely fast speeds and the conditions created in the implosion of cavities are nothing less than extraordinary when considered along with the fact that the surrounding conditions are relatively cold.
Not only is ultrasound being brought into use in the administration of drugs, therapy and treatment to patients but is also being brought into use in the development of biomaterials. Ultrasound technology is being brought into use to develop non-aqueous micro-capsules that are fundamentally liquid-filled and are small enough to successfully be administered in the circulatory system. Once administered, these micro-capsules assist in the performance of sonography in the process of drug-delivering.
Mechanisms of interaction with biological tissue and resulting bio-effects
Ultrasound, when subjected to an individual, generally constitutes compression and expansion cycles that continue to deliver a positive/negative expression in alternating combination. As a result, the molecules on which the waves exert a force with attempts to pull the molecules apart and then push them together (Aljarboua, 2008). Therefore, the negative cycle of each pulse introduces a cavity into the molecules. Since the human body fundamentally constitutes pure liquids, the tensile strengths are generally quite high and they attempt to exert a force for the prevention of the creation of cavities.
However, the gases trapped within the body tissues serve to bring about a decrease in the tensile strength and allow the ultrasound waves to create gaps and conjunctions during their subjection. As a result, the gases are eventually channelled out of their pockets and the molecule eventually reaches a size that is no other than critical (Aljarboua, 2008). At a time like this, the subjection of ultrasound in high intensity or the continuous subjection of a low-intensity ultrasound can cause the weakened molecule to implode.
As the process continues, the absorption capacity of the cavity created by the release of the gases begins to rise until it reaches a critical state, shortly after which it implodes. This implosion causes a number of unusual chemical reactions to take place within the proximity of the imploded cavity (Aljarboua, 2008). An exceptionally high temperature can be created as a result of the implosion and the pressure may increase just as extensively during the implosion. Fluid is generally sent at high speeds causing small particles to be propelled at just as high and exceptional speeds.
A common implication as a result of this activity is that changes in cell suspension are observed (Aljarboua, 2008). Research has indicated that a relationship exists between the implosion of cavities as a result of ultrasound and the suspended fluid of the cell in which the implosion took place. The heat produced is usually dissipated in the body’s regular circulation system and can even be brought into productive and therapeutic uses if it is controlled.
It is of the utmost importance to highlight at this point that in functions such as lithotripsy and the like, the application of ultrasound becomes a highly sensitive matter and is applied concerning the degree of sustenance of the patient. In cases where anaesthesia is not an available option because of any reason, the patient cannot be subjected to a high degree of a pulse. If the patient is subjected to a degree of a pulse of the ultrasound waves that is more than the patient’s actual degree of bearing, there may be implications such as the detection of blood in the urine or the sensation of a hard blow being delivered to the region where the intensity of the ultrasound was over-applied.
The effects of ultrasound can be broadly classified to fall into two categories. the primary effects of ultrasound are those that include cavitation, sound pressure and absorption. Small bubbles may form as a result of the ultrasound in the event of the termination of the cohesion forces between intermolecular forces (Kellermayer, 2009). The sound pressure may cause the subjection of directed pressure on the object being subjected to the pressure in a manner such that the pressure experienced by the object is in direct proportionality to the intensity of the ultrasound. A third primary implication that may take place as a result of ultrasound application is absorption in which an increase in temperature is caused as a result of the absorption of energy on the part of the molecule. The rate of absorption in this case relies on the distance travelled and frequency.
The secondary effects are relatively complex and incorporate mechanical, chemical and biological implications. The cleansing and dispersing effect may be observed if the particles begin to resonate exceedingly. If the cleansing effect does not take place, a dispersing effect may occur. The chemical implications of the application of ultrasound include the incidence of reactions such as condensation of iodine or oxidation. The biological implications include more diverse effects such as the development of scenarios incorporating fungicidal, bactericidal and other complex effects.
Applications of Ultrasound in Medicine & Biology
Ultrasound technology is brought into a wide array of uses in medical science and treatment. Abdominal ultrasound is commonly used to detect abdominal irregularities as well as pelvic abnormalities, vaginal ultrasound, pelvic abnormalities and rectal ultrasound.
Equally commonly exercised applications of ultrasound include the use of high-energy pulses of ultrasound to break down gall bladder stones and kidney stones to a size where they can easily pass through the human body during urination. This process is commonly referred to as lithotripsy which is a method that has been in use since the early 1980s (Andreassi, 2004). Using this method, the stone present in the gall bladder or the kidney is subject to ultrasonic pulses at a rate that may reach 120 pulses to the minute in certain cases. The stone is subjected to these pulses until it is reduced to nothing more than a powder form.
Magnetic Resonance Guided Focused Ultrasound is yet another biological application of ultrasound in which it is brought into use with Magnetic Resonance Imaging. The process incorporates the use of ultrasound constituting an extensively high frequency and is used to treat benign tumours. A similar use is in the delivery of chemotherapy to cancer cells in the brain. Acoustic Targeted Drug Delivery is perhaps one of the most incredible uses of ultrasound where ultrasound is brought into use in its high-frequency form to purposely excite the matrix of the tissue in an attempt to increase its level of permeability to drug treatment.
The blood brain barrier is also regulated in certain cases to increase the efficiency of drug delivery. Bone growth is also stimulated by making use of exceptionally low-intensity ultrasound waves. This treatment gives ultrasound a position of drug administration assistance. Other forms of surgery in which ultrasound can assist include liposuction and lipectomy as well as in acoustophoresis which employs low range ultrasound in an attempt to carry out separation and manipulation activities on biological cells and micro-particles.
It can be understood therefore that ultrasound has taken on the role of a position of a biological instrument where it is now used not only as a form of surgery but is also as a supplementing passive role in the administration of drugs.
“Ultrasound has been a late starter in its application to medicine. Even during the period of vigorous growth in applying physics to medical problems which Val Mayneord and his contemporaries experienced following the war, ultrasound still had a somewhat secondary place to the innovations in nuclear medicine, diagnostic radiology and radiotherapy” (Duck, Baker, & Starritt, 1998).
Robotics has now been combined with modern day ultrasound technology to make ultrasound all the more effective and efficient. An ultrasound probe is affixed at the end of a robotic arm which is controlled by a computer operator. The operator manoeuvres the arm to position the probe directly above the patient’s body at any point or location he wishes. The computer continues to take input from the ultrasound imagery which is communicated to the operator who makes decisions regarding the intensity of the ultrasound sound waves and the area to subject to ultrasound imagery.
There are two forms of application through which modern day ultrasound is used. The first is the Doppler ultrasound through which the Doppler Effect is made use. The fundamental working behind the ultrasound as per the Doppler effect is through the understanding that when an object in motion reflects ultrasound, the echo frequency undergoes a change and eventually becomes higher if the object under observation is in movement that is directed towards the receiver (Radiological Society of North America, Inc., 2009). However, the response takes on an inverse property if the object under observation is moving in a direction that is opposite to that of the receiver.
By monitoring the changes in the echo frequency, a clear understanding of the speed of the object can be acquired. The Doppler Effect allows the monitoring of activity inside the human body (Radiological Society of North America, Inc., 2009). Common applications of ultrasound on the principles of the Doppler Effect include those such as the examination of blood speed in the human heart. Different colours can be brought into use to depict different speeds of blood flow. This allows the identification of cardiac diseases.
Another form of ultrasound application brought into use is 3D Ultrasound Imaging. 3D Ultrasound Imaging by combining standard 2D ultrasound technology with advanced computer innovation. The examiner in this case takes consecutive 2D images of the subject which are compiled in the computer in a form such that a computer-generated 3D image is created. This particular technology allows medical practitioners to acquire detailed pictures of the insides of the human body (Radiological Society of North America, Inc., 2009). Cysts and other similar defects come forth clearly in 3D imaging and continuous application of this 3D imaging technology allows the observation of the steady development of internal growths.
The ultrasound technique in itself is noninvasive and is, therefore, one that is generally considered to be quite painless by patients. Considering its ease of use, it comes as no surprise that it has become a less expensive form of diagnostic imaging methods as compared to others such as MRIs and X-Rays. No ionizing radiations are brought into use and the fact that the sound waves are highly sensitive to tissues allows a clear picture of the tissue to be developed. The imaging in the case of Ultrasound in this regard may exceed the result that would have been acquired through an X-Ray in the same circumstance (Kellermayer, 2009).
To date, there have been no negative implications reported for diagnostic ultrasound and it is therefore repeated frequently to acquire an understanding of the development of the patient’s internal condition. Monitoring of the fetus is perhaps the most common use in which ultrasound technology is brought about in this regard. Combined with computer innovation, modern day ultrasound implementation now allows real-time imaging to be carried out. This attribute is not merely used for diagnostic purposes but is also supplemented in its use with needle aspiration and needle biopsies.
Research performed in early 2006 indicated that even though ultrasound is a highly effective and frequently used technique of monitoring the internal dimensions of the human body through imaging, it may still be far more premature than modern day healthcare practices give them credit to be. The research addressed the vast body of literature that has as yet been able to ascertain the authenticity of the neutrality of the implications of ultrasound (Bello, 2006).
According to the research, in almost all the research that has been carried out to validate this hypothesis, there has been a significant degree of reliance placed on the theories relating to the functionality and development of human organs. This comes forth as a highly significant limitation since the in-utero time frames of the tastes are kept significantly small. The research suggested that the performance of these tests should span periods being measured in days if they are to be effectively conducted.
Conclusion
The research carried out in the above paragraphs was one that was aimed at the development of a comprehensive understanding of ultrasound technology, its application in treatment and therapy and its credibility in light of its implications on the human tissue. It was observed that the uses of ultrasound have become extensively diverse and that it is being brought into use in medical facilities around the world. What began as a means of imagining and acquiring a picture of the internal functioning of the body has now become the basis of a highly sophisticated method of carrying out therapy and treatment.
Ultrasound comes forth as a form of therapy that can be subjected to generalized therapy and surgical procedures. Even though there is a body of literature that indicates that the application of ultrasound may be having adverse implications on the subjects, it was observed that no concrete statement has been reached by medical science upon the implications of ultrasound as yet. Ultrasound technology is not merely brought into use for diagnosis but has evolved to a point where it is now a rapidly implemented form of treatment. Lithotripsy comes forth as an undeniably significant alternative to traditional surgery based solutions.
This mere fact places ultrasound technology in a position where even the most modern surgical practices cannot replace ultrasound technology; at least until an alternate can be found. The research identified that patients consider lithotripsy as a preferred mode of treatment as compared to standard surgery.
Ultrasound does not in any manner incorporate the use of hazardous radiations and is comparatively safer than alternate imaging techniques such as X-Ray and the like. In this regard, there remains no doubt in the fact that ultrasound is a highly effective technology that cannot be replaced with any other form of the present technology.
Nevertheless, one cannot deny the fact that the nature of the reaction that occurs in the administration of ultrasound on an individual is centrally destructive if not regulated appropriately. This serves to put ultrasound technology in a position where it still requires research and development to ascertain that there is no possibility that the application of ultrasound technology can have any unintended adverse implications. Ultrasound technology is highly intensive in cases where destructive functions are being derived from its application and when one considers the biological reactions that occur every time ultrasound is carried out for stone disintegration, one cannot help but feel that the slightest misdirection or maladjustment of the ultrasound waves can cause harm to the patient.
It is however recommended as a conclusive statement for this paper that research and development be carried out on ultrasound technology with the consistency that it is being currently subjected to since it comes forth as an ideal instrument for monitoring the growth and development of the fetus in pregnant woman and is perhaps the safest method of performing this monitoring to date. In this regard, ultrasound remains an undeniably significant technique. However, in light of the discussion and the paradox that currently exists concerning the benefits and risks of ultrasound, it would be justified to bring the discussion to a close with the understanding that no harmful implications have been detected as yet for diagnostic ultrasound.
“Even though we do not have a detailed understanding of the mechanism of sound absorption, tissue impedances are known which can be used to predict heat production and to estimate the reflection and transmission of sound at macroscopic tissue interfaces” (Duck, Baker, & Starritt, 1998).
References List
Andreassi, M. G. (2004). The Biological Effects Of Diagnostic Cardiac Imaging On Chronically Exposed Physicians: The Importance Of Being Non-Ionizing. Cardiovascular Ultrasound , 2 (25), 1476-7120-2-25.
Bello, S. O. (2006). How we may be missing some harmful effects of ultrasound – A hypothesis. Medical Hypothesis, 765-767.
Duck, F. A., Baker, A. C., & Starritt, H. C. (1998). Ultrasound in Medicine. New York: CRC Press.
Hofer, M. (1999). Ultrasound Teaching Manual: The Basics Of Performing And Interpreting Ultrasounds Scans. New York: Thieme.
Kellermayer, M. S. (2009). Effects and Medical Applications of Ultrasound. University of Pecs – Faculty of Medicine – Department of Biophysics, 1-4.
Radiological Society of North America, Inc. (2009). General Ultrasound Imaging. Web.