welcome to the basic obstetric ultrasound training course for healthcare providers ultrasound plays an important role in identifying pregnancy-related conditions that put the mother or fetus at risk during delivery in most low-income countries there is a shortage of people experienced in performing pregnancy ultrasound this course was created to train healthcare workers to perform basic pregnancy ultrasound in parts of the world where formal training is not available the videos as well as other educational materials are available at tinyurl.com backslash uw ultrasound and are designed to be used in a two-week ultrasound course the hands-on sessions in the trainer's guide are an essential component of this course and must be supervised by an experienced ultrasound practitioner this is not a comprehensive pregnancy ultrasound course and does not result in an official certification or diploma after you finish the course and pass the written and practical tests we strongly recommend you have at least 40 hours of scanning experience with clinical mentoring before you undertake unsupervised scanning my name is dr christina adams waldorf and i will be narrating the second video in our pregnancy ultrasound series this video will teach you how ultrasound works and how to operate the ultrasound machine to healthcare providers taking our basic obstetric ultrasound training course please visit our website for access to all of our video and training materials in this session we will introduce you to the ultrasound machine we'll explain how it works and how to use it the main questions we will answer in this lesson are what produces the image that we see how do we use ultrasound to identify different structures such as fetal organs amniotic fluid and bones how can we use the controls on the machine to improve our image and is ultrasound harmful sound is simply a series of vibrations or waves that travel through the air and can be heard once they reach the ear when these waves are very tight meaning that they vibrate at a high frequency or are far apart vibrating at a low frequency humans cannot hear the sound the process to create an ultrasound image is fairly simple first the transducer produces high frequency sound waves that the human ear cannot hear those sound waves travel through the body and bounce off different tissues in this diagram the transducer is on the left and the patient is on the right the red lines represent the sound waves sent into the body by the transducer the green lines are the reflected sound waves that return to the transducer from the body these reflected waves are called echoes the reflected echoes go back to the transducer and the computer analyzes these waves and builds an image on the left is an image of a midwife learning to perform an ultrasound on a pregnant patient the transducer is in her right hand the cable connecting the transducer to the computer is draped around her neck the image on the right is what is seen on the screen notice the many different shades of gray in the image of the fetus we see black white and shades of gray on ultrasound because the sound waves react differently to different tissues and fluids for example sound waves tend to pass through fluids without reflecting back to the transducer this means that fluid tends to produce no echoes in contrast sound waves cannot penetrate bone or air so they are reflected back strongly and produce strong echoes soft tissues are somewhere in the middle some sound waves pass through and some reflect back this is a second trimester fetus placenta and amniotic fluid sound waves pass through the amniotic fluid without reflecting back so amniotic fluid appears black the skull is white because most of the sound is reflected back the placenta is soft tissue so some of the sound passes through and some reflects back this is why it looks gray the fetal abdomen is also gray because it is soft tissue the term echogenicity refers to the brightness or whiteness of the echoes compared to the echoes that surround it in other words it describes the strength of returning echoes echogenic is a term used to describe any structure with echoes there are four levels of echogenicity or strength of the echo hyper means over or above so hyperechoic means a very strong echo which will appear brighter than surrounding echoes usually white or light gray the prefix and means none anechoic structures appear black because they do not reflect sound waves isoechoic and hypoechoic are shades of gray between the white hyperechoic and the black anechoic we will discuss these terms more in the hands-on sessions in this image the amniotic fluid is anechoic and the skull is hyperechoic what does that tell us about the echoes in these two areas this means that there are no echoes from the fluid and there are strong echoes coming from the bone in the skull bone and air are the most echogenic they are hyperechoic and will appear white fluids including blood amniotic fluid and urine in the bladder are anechoic and will appear black soft tissue will appear either isoechoic or hypoechoic as you will see in the hands-on sessions these are different views of the fetus what color are the hyperechoic structures hyperechoic structures are white in these images they are the skull and femur if something is anechoic what does that mean what color will it look like anechoic means there is no echo so it will appear black in these two images the anechoic structures are the bladder which is fluid filled other structures that should be noted here include the hyperechoic fetal spine on the left and the hypoechoic or gray-colored placenta on the left and the uterus and cervix on the right there is another set of terms we use to describe tissues seen by ultrasound in these images we can clearly see three different types of tissue tissues are described as cystic solid or complex the left image is an ovarian cyst the middle image is a fetal abdomen which appears solid the right image shows complex tissue which is an ovarian cyst that is bleeding or hemorrhagic we will now look at each type of tissue more closely a cystic structure is filled with fluid and its walls are generally smooth because a cyst is fluid it will be anechoic these are both images of ovarian cysts unlike cystic tissue solid tissue has no fluid therefore it will reflect some echoes while cystic tissue will appear black solid tissue will appear gray or white the left image shows the fetal abdomen and the right image shows a placenta both are shades of gray or white please also notice the fetal arms in the image to the right the red lines trace the arms from the shoulder to the hands tissue that is complex has both solid and cystic elements the left image shows an ovarian cyst with bleeding inside that appears complex because there's a mixture of fluid which appears black with clot that appears gray compare this with the anechoic bladder that appears completely black next to it the right image shows a uterus without a pregnancy notice that there is complex tissue behind the uterus that appears mostly gray and white but also contains some black within it the complex tissue collection is outlined here to make it clearer and is not normal this is actually hemorrhage a collection of blood clot and fluid behind the uterus from a ruptured ectopic pregnancy now we will get acquainted with the ultrasound machine please pause the video to distribute the ultrasound machines among participants at this time there are many controls and buttons on the machine that help us change the way images look we will learn how to adjust these controls to get the best images this is why it is important to understand how ultrasound works and to learn where these controls are on the machine that you will use understanding how ultrasound works will help you decide how to make adjustments using these controls to achieve a better image don't feel nervous about seeing so many buttons right now although there are many controls you can use to improve your image there are five key functions you will use in every scan for the ultrasound trainers please face your demo machine towards the participants so they can clearly see these controls please locate each of these controls overall gain time gain compensation or tgc depth zoom and focus now we will learn about each of these controls the first control is the overall gain it is the large round control on the lower left corner of the machine pictured in the video where the gain and other knobs are located often vary between ultrasound machines please locate where the gain button is on your machine as sound waves travel deeper in the body the returning echoes weaken because fewer echoes return the quality of the image decreases the gain control increases the echoes that return to the transducer this makes the structures in the image clearer and easier to see we often need to increase gain when scanning heavier patients or patients who are near term this is a profile view of the fetus we know the gain is properly set in this image because we can clearly see the head face chest abdomen spine placenta and amniotic fluid you will learn all about how these structures appear on ultrasound in this course in this image of a fetus the overall gain is too low which makes the image too dark it is difficult to see the fetal structures here the overall gain is too high which makes the image too bright too much gain can make it hard to see the fetal parts just like when the gain was too low sometimes gain must be adjusted differently at different depths of the body time gain compensation helps improve the quality of the smaller details of an image at different gain levels locate the time gain compensation controls on your ultrasound machine by adjusting these knobs you can more finely control the gain at different levels of the image in this image the shallower structures in the near field are too bright and the deep structures in the far field are poorly seen if you cannot make out the different tissues in the fetus in the near field decrease the time gain compensation for these more superficial levels if you cannot see any structures in the far field increase the time gain compensation for these deeper levels this is an image of the adult liver sometimes the gain is not correct in a band in the center of the image the arrow on the left image points to a dark band that is under gained this can also be corrected with time gain compensation notice how the image has improved on the right the next control is depth please locate the depth control on your ultrasound machine gain controls the strength of echoes returning to the transducer depth controls how deeply you send sound waves into the body next we will show how the depth setting changes the appearance of the image for best quality the target of your scan should be in the middle of the image notice how the fetus is centered in the image in this image the target should be the fetus but there is too much unwanted information because of the extra depth we are sending the waves too far into the pelvis we don't need the image below the fetus we would rather see the fetus centered in the image here the image does not show enough depth to see the entire fetus our waves are not going deep enough into the pelvis we can only see the top half of the fetus and the placenta in this image information is lost because there is not enough depth make sure the entire structure you want to examine is included in the image please notice the placenta fetal spine and fetal stomach in this image even though the target is in the center of the image sometimes it is too small to see well we can use the zoom controls to increase the size of our target the zoom controls are usually near the depth controls please locate the zoom control on your own ultrasound machine this is a view of the bottom of a fetal foot the image on the left shows the foot but it is too small the image on the right shows more detail once it has been zoomed you can even see individual bones in the toes the last of the five key functions is the focus the focus increases resolution of the target resolution is the capability of the sensor to observe or measure the smallest object clearly with distinct boundaries another way to say this is that you can see more detail in the image please locate the focus on your ultrasound machine the focus should be adjusted so that it is at the center or near the posterior border of your target area the circled x on the right shows where the focus is in the ultrasound image in this image the focus is targeting the near field where the placenta is the focus should instead be on the fetus and not the placenta it should be placed in the mid to far field region where the fetus is located the focal zone is now in the far field below the fetus it should be moved up to focus instead on the fetus you will have a chance to learn and practice setting the focus appropriately in our hands-on sessions some patients may ask if ultrasound is harmful to them or to their baby with millions of ob ultrasound scans worldwide there is no evidence that ultrasound is harmful there is an important principle in ultrasound that emphasizes this concern for patient safety this is known as the alera principle which means as low as reasonably achievable this means that ultrasound should be used only as appropriate and not more than is medically indicated the alera principle states that we should scan a fetus only when there is a medical reason and that we limit the ultrasound exposure during those scans we can limit exposure by decreasing the output of the ultrasound machine and decreasing the time spent scanning we will review this in the hands-on sessions excessive exposure can heat the tissues in theory a first trimester fetus would more likely be affected from heat than a second or third trimester fetus to summarize key points from this lesson ultrasound images are produced by sound waves reflected from the body and analyzed by the computer the brightness of the echoes can range from hyperechoic to anechoic brightness in between is called isoechoic or hypoechoic tissues can be characterized as cystic solid or complex there are five major functions on the ultrasound machine to optimize the image overall gain time gain compensation depth zoom and focus ultrasound is not harmful to the mother or fetus always follow the alera principle with every scan questions for review please pause the video now to review these questions and answers what happens to ultrasound waves when they reach air or bone the answer is that they are reflected what does fluid look like on ultrasound the answer is that it looks black what are the three main types of tissue the answer is complex cystic and solid what are the five important buttons on the ultrasound machine that can help you improve the image the answer is the gain time gain compensation depth focus and zoom what is the alera principle the alera principle states that we should scan a fetus only when there is a medical reason and that we limit the ultrasound exposure during those scans thank you for your attention and interest in learning pregnancy ultrasound please pause the video now to ask your instructor any questions about this course we thank the following individuals who played a major role in course development dr robert nathan dr william marks and nicole goldsmith registered sonographer many other individuals contributed valuable time and expertise in the instructional design and materials development including dr christina adams waldorf dr scott barnhart dr michael kauya susan kingston and stacey licit finally we wish to thank dr william marks for the use of images from his book ultrasound a practical approach we also thank jennifer summers and jan haminishi for graphic design and illustrations the university of washington department of radiology has trained healthcare workers in pregnancy ultrasound in many parts of the world if you have questions about this video or course please contact dr robert nathan dr william marks or dr christina adams waldorf this course was collaboratively developed by the university of washington department of radiology obstetrics and gynecology and the international training and education center for health itec it was made possible through a grant from the ge foundation consano also contributed funding we are grateful for the video production sponsored by the university of washington institute for simulation and interprofessional studies and uw video please visit our website at tinyurl.com backslash uw ultrasound to access all of our training materials this material is copyrighted you are permitted to copy distribute and post to websites you are permitted to modify the content to adapt to specific populations and user needs on the condition that you include attribution to the university of washington and retain any copyright notices and citations and attributions included in the original basic obstetric ultrasound training for midwives the material in this video was provided for information purposes only the university of washington institute for simulation and interprofessional studies does not take responsibility for the accuracy of the content in this video