ECHOCARDIOGRAM USING HIGH FREQUENCY ULTRASOUND Deanna Trinh Physics 89 Honor Seminar ABSTRACTDuring this research we surveyed the inner workings of sound this being the main element usedduring medical imaging with ultrasound. We discovered that sound has limitations mainly in avacuum; however, for purposes of medical imaging this was a non issue because biologicalmolecules have mass. Ultrasound is the more advantageous type of imaging than CT, MRI and X-rays for numerous reasons. There are various ultrasound procedures that mainly focus there imageson the heart, these procedures are known as echocardiography. These days, ultrasound not only canprovide crucial analysis on heart failure/problems, but it can potentially ride oneself certaindiseases. Ongoing developments in ultrasound have allowed for small gas bubble usage to obtainbetter resolution of cardiac imaging. INTRODUCTIONThe purpose of waves is to transmit energy. Sound waves are basically longitudinal waves createdby molecular vibrations. These molecules vibrate and oscillate in the same direction as the wavemotion. Therefore in order for sound to occur it must travel through a medium (a region withmatter). In general, the closer atoms the neighboring atoms are to each other, the easier sound cantravel. From this knowledge we can see that sound travels faster in solid objects than in water or inair this means that the velocity of the wave is always dependent on the medium through which ittravels. So what does this have anything to do with ultrasound one may wonder?Here is why. Ultrasound is Sound!Thus, ultrasound also has properties of longitudinal waves. The molecules oscillate in thedirection of wave motion with a different velocity rate depending on which material the wave ispropagating through.
Velocity of Material Sound (m/s) Air 330 Fat 1450 Water 1480 Soft Tissue 1540 Muscle 1580 speed = distance/ time wave speed = frequency * wavelengthThese waves emit high frequency sounds that can be used to produce images of the organs andstructures of the body.Humans hearing ~ 20 to 20,000 HzHowever, Ultrasound is above 20 kHz.These high frequency waves will reflect off different surfaces. As we shall see later, the transducer,which is a small handheld device that is connected to the ultrasound machine will emit and receivethe waves. So the ray that is emitted is the incident ray while the angle of reflection is the receivingray. The reflecting surfaces would be the organ of interest in which we want to obtain images ofrather than a mirror seen below. This figure illustrates the basic law of reflection, which states that: angle of incidence = angle of reflection i=r
Echocardiogram2.1 BenefitsEchocardiogram is a test that uses ultrasound to create an image of the heart. Echocardiogram ismore advantageous than CT, MRI, and X-rays because it is cheaper. These echo cardiac images aremuch more detailed than X-ray images and involves no radiation exposure.The procedure to get an echocardiography requires a short amount of time. It is noninvasive,painless and harmless.2.2 DiagnosisAn echocardiography is used to help diagnosis a heart disease/problem. Observe heart motions
See if valves are opening and closing properly Determine the size of the heart chambers and major vessels (e.g. examine any narrowing of the vessels cause from blood clots or fat deposits)2.3 Types of EchocardiogramPatients can have numerous types of echocardiogram done on them. The physician will decidewhich is the best approach to use on the patient.A Transthoracic echocardiogram, may include bubble study. Normally a transthoracicechocardiogram is used where the transducer is placed on the chest to obtain cardiac images. Abubble study is sometimes used for better resolution. These gas bubbles, which are smaller thanyour blood cells are injected into your blood vessels where it can help diagnosis if there are anyheart defects on the interior chambers of the heart.A Doppler Echocardiogram can be use to get a better understand of the direction of blood flowdue to the different pitches (change in frequency) as the blood cells move in the blood vessel(Doppler Effect).A Transesophageal echocardiogram uses an endoscope, which an instrument that allows forvisual images in the interior. The endoscope is placed down the esophagus to get a clearer image ofthe heart. Since the esophagus lies in back of the heart, it gives more precise image than thetransthoracic in which the lung may interfere.The Dobutamine stress echocardiogram works by swallowing a chemical called Dobutamine.This chemical stimulates the heart beat faster. The goal is compare the heart a rest vs. the heartwhen it is under strenuous exercise or stress.
In a Bicycle stress echocardiogram there are petals attached to the bed that allow patients to use tostimulate the heart to beat faster. It is also used to compare the heart at rest vs. during stress state.2.4 How the Exam is Done This figure shows a electrocardiogram device with different sizes and shape of the transducer.The examinations take 20 to 30 minutes. First the examiner will put a few electrodes (patches) onthe patient’s chest for a electrocardiographic (EKG) tracing. Then a small amount of clear gel isapplied to the transducer (handheld device) and the skin to unsure there is proper contact. Next thetransducer is placed on the chest for images.Recall, the transducer sends (incident rays) and receives (reflected rays) the sound waves. It isconnected by a cable to the ultrasound machine where the machine then converts these sound wavesinto pictures.
2.5 Fetal EchocardiogramFetal echocardiography is used during pregnancy to evaluate the heart of the unborn baby. In thisprocedure the transducer is now placed on the abdomen instead of on the chest. Discovering theheart disease sooner can allow for faster medical and surgical intervention once the baby is born.Fetal ECG is necessary whenthere is… A family history of congenital heart disease A genetic abnormality discovered in the fetus. Or if the mother has abused alcohol or drugs during pregnancy. Or if a routine prenatal ultrasound has discovered possible heart abnormalities.
2.6 Future OutlookUltrasound is not only used to scan the body, it can cure it as well without need for surgery. Highfrequency waves have been used to crush kidney stones into powder, warm aching muscles and helpstimulate healing. Recently doctors also have been using these high-intensity ultrasound devices tokill tumors. Some therapeutic ultrasound has shown success in treating tumors in the prostate glandand other organs. CONCLUSIONUltrasound is growing really fast in the field of research. Tests such as the bubble study in thetransthoracic echocardiogram are currently going on. Ultrasound is a wonderful way of treatingpatients for it is minimally invasive, very precise and safe (no radiation). In addition, there is a shortrecovery time and hospital stay so it would be extremely economical for the patient and theirfamily. REFERENCES•http://www.massgeneral.org/cardiology/cardiology/ultrasound.html•http://www.americanheart.org/presenter.jhtml?identifier=3005161•http://www.childrenshospital.org/clinicalservices/Site1032/mainpageS1032P0.html•http://www.medicinenet.com/ultrasound/article.htm•http://health.yahoo.com/topic/heart/symptoms/medicaltest/healthwise/hw4480;_ylt=A9htdWP07x9ELB0BKZrkNs4F