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DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER TWO Common Gynecological Anomalies – Part 1 CRT04210 · Ultrasound Imaging START READING NOTES Study Common Gynecological Anomalies – Part 1 using the sections below. Use the topic navigation to continue through Ultrasound Imaging. Contents of This Topic Common Gynaecological Anomalies- Part 1 UTERUS TECHNIQUE CONGENITAL ANOMALIES Septate/arcuate uterus Bicornuate uterus Uterine didelphys Differentiation requires visualization of Less divergence of endometrial stripes SEPTATE UTERUS Endocrine causes Primary amenorrhea 3.Pelvic inflammatory disease (PID) A.Pelvic Inflammatory Disease: US Findings B.Endometritis Indistinct, thickened endometrial stripe, +/- fluid, air C.Pelvic Inflammatory Disease (PID) Hydrosalpinx (Hydrosalpingitis) US Findings :Complex, multicystic, thick walled mass, internal echoes TOA: US Findings Complex, multicystic, thick walled mass, internal echoes 4.Uterine Fibroids Uterine Fibroids Risk factors: the following factors are predisposing Fibroids (Leiomyomas) Types of Fibroids TYPES(LOCATION) OF LEIOMYOMAS (FIBROIDS) Location of Fibroids Fibroids: US Findings Fibroid Pedunculated LEIOMYOMA- Calcifications in Pedunculated subserosal leiomyoma Complications of Fibroids: Benign neoplasm Hormonally responsive 7.Uterine Sarcoma Ectopic endometrium located within the myometrium Adenomyosis Pt presentation: Adenomyosis: US Findings Think adenomyosis: Think leiomyoma (Fibroid): 8.Endometrial Hyperplasia, and Polyps 10.Abnormal bleeding in postmenopausal women 11.Endometrial carcinoma 12.Cervical Mass 12.Abnormal Vagina 12.Intrauterine Device (IUD) Intrauterine Device (IUD) Echogenic, shadowing, linear structure in endometrial cavity Common Gynaecological Anomalies- Part 1 MDU,BMI,ECHO&ECG,DDR UTERUS Outline- Uterine Pathologies Technique Normal anatomy Congenital anomalies Leiomyoma/Fibroids Pelvic Inflamatory Disease Adenomyosis Endometrial Hyperplasia and polyps. Postmenopausal uterus- Endometrial Ca TECHNIQUE Endovaginal improved spatial resolution smaller field of view Transabdominal imaging complementary enlarged uterus congenital anomalies evaluation of the kidneys MRI/HSG may provide more specific information in selected cases Review of normal Anatomy 1.CONGENITAL ANOMALIES CONGENITAL ANOMALIES Incidence 0.1% to 0.5% all women 9% in women with infertility or fetal loss Associated with renal anomalies Defects include: Septate/arcuate uterus Unicornuate uterus Bicornuate uterus Uterine didelphys Septate/arcuate uterus Has a normal external surface but two endometrial cavities Degree of septation varies from a small midline septum to total septate uterus with longitudinal vaginal septum Arcuate has slight midline septum with minimal fundal cavity indentation Unicornuate uterus Bicornuate uterus Uterus in which the fundus is indented (≥1 cm) and the vagina is generally normal. Results from only partial fusion of the müllerian ducts Leads to a variable degree of separation of the uterine horns that can be complete, partial, or minimal. Uterine didelphys “double uterus” duplication is limited to the uterus (didelphys) and cervix (bicollis) although other structures (vagina, bladder, etc may be involved) Differentiation requires visualization of endometrial stripes fundal contour Visualization of fundal contour may require Transabdominal Ultrasound or 3 dimensional ultrasound SEPTATE VS. BICORNUATE UTERUS BICORNUATE UTERUS Divergent endometrial stripes > 1.0 to 1.5 cm cleft between horns BICORNUATE UTERUS Divergent endometrial stripes > 1.0 to 1.5 cm cleft between horns X > 1.5 cm Bicornuate uterus ( Double Endometrium) Less divergence of endometrial stripes Flat, convex, or minimally indented fundal contour (< 1 cm) SEPTATE UTERUS SEPTATE UTERUS SEPTATE UTERUS X < 1.0 – 1.5 cm Endocrine causes Absence, atresia or obstruction of vagina, cervix, or uterus +/- Pelvic mass Role of imaging confirm level of abnormality extent of vagina presence / absence of uterus and cervix 2.Primary amenorrhea Primary amenorrhea Uterine Agenesis Note: No Uterus posterior to UBL Primary amenorrhea Haematocolpos in imperforate Hymen Note: Blood collection in Uterine cavity(HAEMATOMETRA) 3.Pelvic inflammatory disease (PID) Ascending infection that may involve the uterus(endometrium), fallopian tubes, ovaries, and pelvic cavity, and may produce tubo-ovarian abscesses(TOA) Presents with LAP, Fever, PV discharge, Cervical motion tenderness A.Pelvic Inflammatory Disease: US Findings Endometritis (Endometrial fluid) Hydrosalpinx: Dilated fallopian tube Thickened, inflamed fallopian tube +/- internal echoes (pyosalpinx)- Pus fillled Tubo – Ovarian Abscess Fluid in cul-de-sac (Pouch of Douglas) B.Endometritis Sx: fever, leukocytosis, tenderness, foul smelling discharge Occurs post partum, following D&C, PID Indistinct, thickened endometrial stripe, +/- fluid, air post partum findings RPOC Endometritis: US Findings Endometritis (Fluid in Endometrium) C.Pelvic Inflammatory Disease (PID) Fluid in pouch of Douglas Significant Fluid > 1cm deepest pool D.Hydrosalpinx (salpingitis) Hydrosalpinx (Hydrosalpingitis) Infection of fallopian tubes Dilated, tubular, anechoic structure between uterus and ovary E.PYOSALPINX US Findings :Complex, multicystic, thick walled mass, internal echoes F.(Tubo-ovarian cyst)-TOA: TOA: US Findings Often bilateral Ovarian margins may be indistinct ovary relatively spared Complex, multicystic, thick walled mass, internal echoes TOA: US Findings 4.Uterine Fibroids Definition Are benign monoclonal tumors arising from the smooth muscle cells of the myometrium, termed leiomyoma. They contain a large amount of extracellular matrix (collagen, proteoglycan, fibronectin) and are surrounded by a thin pseudocapsule of areolar tissue and compressed muscle fibers. Synonyms: fibroid or fibromyoma. Incidence: The most common gynecological tumors in about 30% of women of reproductive age. 20% of women after 30 years develop uterine fibroid. More prevalent in black African women Uterine Fibroids Etiology: The possible etiology is hyperestrinism (estrogen-dependent tumor). The evidences supporting this include: Associated with exposure to circulating estrogen (arise during adulthood) Shrink following menopause Maximum growth when estrogen secretion is maximal, spurt in growth in the decade before menopause (an ovulatory cycles with unopposed estrogen) Increased growth during pregnancy (caused by estrogen) Estrogen receptors are more in leiomyoma compared to the rest of myometrium N.B. Growth factors may act synergistically with estrogen to induce growth of myoma Risk factors: the following factors are predisposing Age: common between 35 & 45 years. Parity: common in nulliparous or low porous & relatively infertile women. Race: common in black women Family history : +ve. Obesity Early menarche (<10 years old) A longer interval since last birth increases risk Consumption of alcohol, especially beer, appears to increase the risk of developing fibroids however smoking decreases the risk of having fibroids. Significant consumption of beef, ham, or other red meats is associated with an increased relative risk of fibroids Protective factors Early age at first birth decreases risk consumption of green vegetables with a decreased risk Fibroids (Leiomyomas) Fibroids are benign tumors of the uterus arising from the Myometrium Smooth muscle neoplasms Patients Presentation Asymptomatic Abnormal Uterine bleeding- Menorrhagia Pelvic pain Infertility Abortions ( Submucosal and Intramural

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER TWO Biological Effects of Diagnostic Ultrasound CRT04210 · Ultrasound Imaging START READING NOTES Study Biological Effects of Diagnostic Ultrasound using the sections below. Use the topic navigation to continue through Ultrasound Imaging. Contents of This Topic GROUP NO.9 Ultrasound energy, is type of mechanical energy called sound characterized by vibrating or moving particles within a medium. It is true that ultrasound energy can cause adverse effects in human body but diagnostic ultrasound is safe. CAVITATION B.HEAT FORMATION C. FETAL EFFECTS Group Members; GROUP NO.9 ASSIGNMENT Ultrasound energy can cause adverse effects in human body, but diagnostic ultrasound is safe discuss. Ultrasound energy, is type of mechanical energy called sound characterized by vibrating or moving particles within a medium. Diagnostic ultrasound, is the sound of frequency between 1MHz to 20MHz. It is true that ultrasound energy can cause adverse effects in human body but diagnostic ultrasound is safe. The following are the effects of ultrasound energy in the human body,. Cavitation Heat formation Fetal effects CAVITATION any cavity contains fluid or gas. when there is exposure of ultrasound beam there is formation of bubbles within the cavity during compression bubbles burst result in formation of free radical which combine with chemical components in the cavity lead to the formation of chemical compound.E.g toxins which can cause death of body cells. NB. but this phenomena is very rare. B.HEAT FORMATION When ultrasound waves pass through a tissue they tend to heat it up due to the collision of medium particles. This tissue can be easily warmed to 40 degree celsius but in diagnostic ultrasound the rise in temperature is just a small fraction of 1 degree celsius. Although in normal circumstance the heat is usually easily carried away by blood circulation or simply dissipated into surrounding tissues. C. FETAL EFFECTS The ultrasound technology have effects on fetal bodies. Due to frequent scanning of pregnant women, gave birth to lower weight babies, the newborn babies also seems to have delayed speech disorder and most of the babies who were frequently exposed to ultrasound are left handed. Despite of all those above effects, the growth and development of child will proceed as normal. Group Members; 1.SAID RAMADHAN 2.FELIX DEUS 3.FRANCISCO F SUKA ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER TWO Quality Control and Care of Ultrasound Equipment CRT04210 · Ultrasound Imaging START READING NOTES Study Quality Control and Care of Ultrasound Equipment using the sections below. Use the topic navigation to continue through Ultrasound Imaging. Contents of This Topic QUALITY CONTROL AND CARE OF EQUIPMENT THE COMPETENCE OF THE OPERATOR QUALITY ASSURANCE SERVICE TO THE PATIENT QUALITY OF IMAGE PRODUCTION PERFORMANCE TESTING TISSUE EQUIVALENT PHANTOMS TEST PHANTOMS Maintenance and care of equipment QUALITY CONTROL AND CARE OF EQUIPMENT Getting the best from your machine THE COMPETENCE OF THE OPERATOR Because of the difficulty of interpreting ultrasound images, ultrasound examinations should only be performed by trained and competent personnel. It is better not to do an examination at all than to provide incorrect or misleading diagnostic information. Operators should not only be trained according to acceptable international standards, but they should continue to improve their knowledge and skills throughout their working life. People in training should be supervised by trained and experienced personnel. QUALITY ASSURANCE Quality assurance (QA) is the process of ensuring that all aspects of an ultrasound service meet accepted international standards. A quality assurance program should consider: The competence of the operator The quality of service to the patient The quality of the image production The maintenance and care of equipment SERVICE TO THE PATIENT Patient care should consider the following matters: Careful appointment system to guarantee correct patient preparation, and minimal inconvenience. Careful consideration of patient safety, privacy and confidentiality. A well organized system of reporting procedures, including storage and delivery of results. Patient consent should always be obtained for invasive ultrasound procedures QUALITY OF IMAGE PRODUCTION Performance testing of ultrasound equipment is controversial for the following reasons: Ultrasound is considered a safe modality Modern ultrasound machines are considered stable and reliable Ultrasound QA testing is often considered to be rather subjective There are presently no regulations requiring a QA program PERFORMANCE TESTING Although testing of equipment is not essential, there are some applications, such as breast ultrasound, where it is very advisable. There are also some situations, where trained personnel are available to perform the task, and for those situations, there is special testing equipment available. TISSUE EQUIVALENT PHANTOMS The accuracy with which the ultrasound image represents an anatomical area depends on the correct functioning of the many components of the ultrasound machine. Occasional testing can ensure the machine is performing according to acceptable standards, and is accurate and consistent. Special test phantoms are available which enable people to make these checks TEST PHANTOMS Test phantoms are made of materials which are similar to tissue in their acoustic characteristics. They contain various targets and structures designed for testing a number of parameters such as image resolution and measurement accuracy. TEST PHANTOMS Maintenance and care of equipment Great care must be taken to keep an ultrasound machine in good working order and safe from hazards. 1/ The transducer If piezo electric elements are heated they lose their piezo electric properties because they become depolarized. Therefore the transducer should never be heat sterilized. They are also sensitive to mechanical shock and should never be dropped. MAINTENANCE AND CARE OF EQUIPMENT After use, always leave the transducer clean and dry. Wipe it with warm soapy water and dry. Never used oil based coupling gels. They will perish the rubber casing covering the transducer and allow oil to enter the inside which will cause damage. Use good quality, aqueous based gels only. The transducer should occasionally be sterilized by wiping with aqueous chlorhexidine solution or similar. Don’t leave the transducer to soak. MAINTENANCE AND CARE OF EQUIPMENT 2/ The control desk Remove any dirt or coupling gel by wiping with a soft cloth dampened with warm soapy water. NEVER sit liquids, such as cups of coffee on the control desk, or use the surface to hold other items. 3/ The main console Use the ultrasound machine in a cool dust free environment. Keep the air vents on the side of the machine clear of obstruction and clean. Clean any air filters present. Operate the machine with a voltage stabilizer to protect it from damage by voltage surges. MAINTENANCE AND CARE OF EQUIPMENT 4/ Electrical safety Inspect the transducer closely for any cracks or damage to the plastic housing. Inspect cables for any wear or damage to the insulation. Inspect any plugs, adapters or connector assemblies for any electrical dangers. Connect the machine directly to mains power and not to a multi outlet power board. ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER TWO Ultrasound Safety and Biological Effects CRT04210 · Ultrasound Imaging START READING NOTES Study Ultrasound Safety and Biological Effects using the sections below. Use the topic navigation to continue through Ultrasound Imaging. Contents of This Topic ULTRASOUND SAFETY IS ULTRASOUND SAFE? OPERATING MODES AND THEIR RISKS PULSED DOPPLER AND POWER DOPPLER BIOLOGICAL EFFECTS SAFE USE SOME GUIDELINES CONCLUSION ULTRASOUND SAFETY ULTRASOUND SAFETY BASIC RULES AND PRINCIPLES IS ULTRASOUND SAFE? So far ultrasound has not been proven to be unsafe in humans. However, ultrasound is now being very widely used and advances in technology are leading to increasing power levels being used to obtain diagnostic information. This can lead to measurable biological effects The interaction of ultrasound with biological tissue can result in effects which may cause heating, interfere with normal functioning of cells, and cause structural damage. It is important for people using ultrasound to do all they can to minimize the exposure of the patient to ultrasound to reduce these risks. OPERATING MODES AND THEIR RISKS B Mode ultrasound imaging records returning echoes strength as a brightness display on the screen. This is the normal grey scale imaging used for real time ultrasound. This uses the lowest output power and intensities and is generally considered safe in all applications, PULSED DOPPLER AND POWER DOPPLER Pulsed Doppler uses higher intensity of ultrasound than B Mode, and is therefore more likely to cause biological effects, particularly from heating. Pulsed Doppler ultrasound focuses the beam in a small area for longer periods increasing the dose to those tissues. Power Doppler also uses intensities higher than B Mode, but less than pulsed Doppler BIOLOGICAL EFFECTS There are two important effects which can be caused by ultrasound: 1/ Thermal (heating) 2/ Non thermal effects (cavitation) 1/ As the ultrasound beam travels through the tissue some of its energy is lost through absorption. This absorbed energy is converted into heat which causes a temperature rise of the tissues. The heat rise will depend upon: * the attenuation coefficient of the tissue * the operating frequency of the transducer * power/ intensity of the ultrasound beam * the length of operating exposure time BIOLOGICAL EFFECTS 2/ Non thermal effects ( cavitation ) The oscillating pressure wave caused by an ultrasound beam creates areas of compression and rarefaction. This can cause small bubbles to form in tissues. These can grow, oscillate in size, an at high intensity and pressure these can collapse. This causes high pressures and temperatures in the localized area with the potential to cause biological damage. While this risk is very small in general ultrasound, it is wise to be careful in early pregnancy where the tissues are more vulnerable. CAVITATION SAFE USE Changes in power output and increased use of Doppler ultrasound have led to awareness of the need to take every measure to ensure safe practice. The accepted guideline for safe use is known as the ALARA principle ( “As Low As Reasonably Achievable” ) This is a guide to minimizing exposure times and exposure intensity. ALARA SOME GUIDELINES 1/ Examinations should use B mode real-time in the first instance and employ color and spectral Doppler only when and if required. 2/ The overall examination should be kept as short as possible to minimize exposure times. 3/ The transducer should not be held in a fixed position any longer than necessary. 4/ The transducer should never be left resting on the patients body when not in use. 5/ The output power setting should be as low as possible consistent with obtaining a satisfactory image. 6/ Ultrasound examinations should only be performed for a specific medical indication to obtain useful diagnostic information. 7/ Only suitably trained people should be allowed to operate ultrasound machines. CONCLUSION Although harmful effects have not been shown to result from the use of ultrasound at normal diagnostic levels, the potential for harm does exist. More research still needs to be done. For example, we do not know if the effects from ultrasound exposure are cumulative. As in the use of x-rays, a very small risk is justified when the risk is minimal and the benefit high. ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER TWO Ultrasound Artifacts CRT04210 · Ultrasound Imaging START READING NOTES Study Ultrasound Artifacts using the sections below. Use the topic navigation to continue through Ultrasound Imaging. Contents of This Topic ULTRASOUND PHYSICS LECTURE 4 DEFINITION COMMON ARTIFACTS REVERBERATION ACOUSTIC SHADOWING ACOUSTIC ENHANCEMENT EDGE SHADOWING BEAM WIDTH ARTIFACT SLICE THICKNESS ARTIFACT SIDE LOBE ARTIFACT MIRROR IMAGE ARTIFACT DOUBLE IMAGE ARTIFACT EQUIPMENT GENERATED ARTIFACTS ULTRASOUND ARTIFACT ULTRASOUND PHYSICS LECTURE 4 ARTIFACTS DEFINITION In ultrasound imaging, an artifact is an appearance on the image which does not faithfully represent the structures present in the subject being scanned. Therefore the echoes are a false or misleading image which need to be properly understood and interpreted. Artifacts may appear as structures seen in the image which do not exist in the subject, or structures which should be seen in the image but are not. Structures may also be represented in the wrong location in the image ( mis -registration ). Artifacts may be caused by improper function or use of equipment, or they may simply be a characteristic of the physical properties of ultrasound waves and their interaction with tissues. COMMON ARTIFACTS Reverberation Acoustic shadowing Acoustic enhancement Edge shadowing Beam width artifact Slice thickness artifact Side lobe artifacts Mirror image artifacts Double image Equipment generated artifacts REVERBERATION Reverberation is the production of false echoes due to repeated reflections back and forth between the transducer face and a strong reflector in the subject. The first returning echo is displayed correctly, but some of the returning sound bounces off the face of the transducer back into the subject like a weak transmitted pulse. This returning pulse meets the strong reflector again causing another returning echo from the same interface. As the time taken for the second echo to arrive is twice that taken by the first echo, the image will display it at twice the depth. This results in a series of equally spaced false echoes to be displayed on the ultrasound image. REVERBERRATION REVERBERATION The bouncing of the sound back and forth (reverberation) often occurs between the transducer face and the subcutaneous fat / muscle layer. It also commonly occurs when the sound waves reverberate between two anatomic reflecting surfaces in the subject, such as between the near and far surface of an area of gas. In this case the echoes are placed much closer together in the image, and the appearance is termed comet tail. Small gas bubbles create an almost continuous band of reverberation called Ring down FORMATION OF COMET TAIL ARTIFACT COMET TAIL ARTIFACT RING DOWN ARTIFACT ACOUSTIC SHADOWING Acoustic shadowing appears as an area of low level echoes or no echoes at all distal to an interface with a large acoustic mismatch. It is caused by severe attenuation of the beam at the interface. This will occur where the beam passes from soft tissue to gas (99.9 % of the beam is reflected) It also occurs where the beam passes from soft tissue to bone (40% reflection and 60% absorption by the bone) ACOUSTIC SHADOWING GAS OR STONES? ACOUSTIC ENHANCEMENT This artifact appears as an area of increased echo brightness distal to an area of low attenuation. Enhancement is normally seen distal to structures containing fluid such as the urinary bladder, gall bladder, or cyst. Time –gain compensation is applied equally to areas of the subject with minimal attenuation such as a cyst, and to adjacent areas of tissue. Therefore echoes from within the cyst are increased by the TGC unnecessarily resulting in a distal brightness. ACOUSTIC ENHANCEMENT EDGE SHADOWING When the sound beam meets a curved interface both refraction and reflection occur which results in an edge shadowing artifact. As the ultrasound beam meets the curved surface, some is reflected away from its true course and some continues into the second medium, but is refracted or bent from its original course This results in an acoustic shadow distal to the curved edges of the mass. EDGE SHADOWING BEAM WIDTH ARTIFACT The beam width can vary depending upon focusing, divergence etc. Since the width of the beam is not always as small as the objects being imaged, echoes arising from the edge of the beam will be displayed as having arisen from the beam centre. A small reflector will generate an echo for as long as it remains in the beam and so will be represented as a line in the display rather than a dot. Some echoes from outside the assumed plane will be displayed as if from within the plane. We may for example, see some echoes arising from outside the bladder but displayed within the bladder BEAM WIDTH ARTIFACT SLICE THICKNESS ARTIFACT This is similar because it is related to the size of the ultrasound bream, and creates false echoes in areas that should be echo free. The ultrasound machine assumes the echoes received by the transducer are from a very thin slice of tissue. However, an image is actually composed from several slices, and therefore echoes from slices either side of the intended slice may be displayed in the image. This is often seen in transverse views of the urinary bladder. Structures adjacent to the slice through the bladder will be included within the bladder. SLICE THICKNESS ARTIFACT SIDE LOBE ARTIFACT As well as the main beam used to form the ultrasound image, the transducer also produces many smaller and weaker side lobes. These are not normally used to form the primary image, but they can cause artifacts These also cause echoes to be displayed in areas which should be echo free. This is more apparent when there are very strong reflectors , such as gas, adjacent to an echo free area. This can give a false impression of a septation within the urinary bladder or gall bladder. SIDE LOBE ARTIFACT MIRROR IMAGE ARTIFACT Some large smooth reflectors, such as the diaphragm, return such a strong echo to the transducer that they are read by the machine as part

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER TWO Ultrasound Transducers and Scanning Modes CRT04210 · Ultrasound Imaging START READING NOTES Study Ultrasound Transducers and Scanning Modes using the sections below. Use the topic navigation to continue through Ultrasound Imaging. Contents of This Topic THE ULTRASOUND BEAM BEAM SHAPE PULSED ULTRASOUND Beam intensity BEAM WIDTH AND SLICE THICKNESS FOCUSING THE BEAM IMAGE RESOLUTION AXIAL AND LATERAL RESOLUTION AXIAL RESOLUTION SPATIAL PULSE LENGTH LATERAL RESOLUTION Ultrasound Transducers and Scanning Modes FACTORS AFFECTING BEAM WIDTH INTRODUCTION OF USS THE ULTRASOUND BEAM CHARACTERISTICS BEAM SHAPE The path which the ultrasound waves travel from the transducer is called the ultrasound beam. It is divided into two regions. The near field (or Fresnel zone) which is shaped like a cylinder. The far field (or Fraunhofer zone) where it becomes cone shaped. NOTE: Increasing the frequency will give a longer near field and less far field divergence. PULSED ULTRASOUND Instead of a continuous output of waves from the transducer face, most transducers use a series of short pulses of sound energy. These short pulses form the ultrasound beam. This is important, as we will see later, in giving good axial resolution. Beam intensity The intensity of the beam is the power (measured in watts) flowing through a unit area of the ultrasound beam. Increasing the output power to the transducer produces high intensity sound pulses, which make returning echo signals from all reflectors appear brighter. BEAM WIDTH AND SLICE THICKNESS Beam width means the measurements of the beam in the scan plane. This will vary according to distance from the transducer and what focusing is applied to the beam. The width of each pulse of sound will therefore change with depth. The beam width affects the spatial resolution of the image (the ability to differentiate small structures). The narrower the beam width the better the spatial resolution. Slice thickness is the measurement of the beam at 90 degrees to the scan plane FOCUSING THE BEAM The ultrasound beam can be focused to improve image quality. This is mostly done electronically. The depth of the focal zone and the length of the focal zone can be changed by the operator on modern ultrasound machines. IMAGE RESOLUTION Spatial resolution is the ability of an ultrasound system to display two closely spaced reflectors as separate structures. This depends upon the wavelength of the sound used to produce the image. For example, the wavelength of a 5MHz ultrasound beam is about 0.3mm, so it could not resolve (display separately) objects less than 0.3mm apart AXIAL AND LATERAL RESOLUTION Axial resolution is resolution along the axis of the direction of the ultrasound beam. Lateral resolution is resolution at right angles to the direction of the ultrasound beam. Axial resolution depends on the spatial pulse length. Lateral resolution depends on the ultrasound beam width. AXIAL RESOLUTION A short pulse length gives good axial resolution and the best resolution that can be achieved is half the spatial pulse length Therefore if the pulse length is 1mm, then structures along the axis which are less than 0.5 mm will not be resolved. Axial resolution is affected by the frequency of the ultrasound beam and damping applied to the piezoelectric crystal SPATIAL PULSE LENGTH Each ultrasound pulse is about two wavelengths long, and therefore a shorter wavelength will reduce the pulse length. Since wavelength is related to frequency, we can see that a high frequency beam will result in a shorter pulse length and better axial resolution. Pulse length also depends upon the amount of damping applied to the piezoelectric crystal. Increasing the damping shortens the pulse length and improves axial resolution. LATERAL RESOLUTION A narrow ultrasound beam gives best spatial resolution and the best resolution that is achieved is equal to beam width at the focus of the beam. The beam width determines the size of the echoes displayed and the structures must be separated by a distance greater than the beam width for them to be resolved. That is, the beam must fit into the gap between the two structures so that is can return “no echoes” from that position. Ultrasound Transducers and Scanning Modes Reflector separation is less than beam width in fig A and B but greater than beam width in Fig C and D. Fig A The beam first encounters the left reflector, then both reflectors, then the right reflector. Fig B This results in continuous reflection from one or both reflectors. Fig C The beam encounters the left reflector, then fits between both, and then meets the right reflector. Fig D Separate echoes are shown and the reflectors are resolved. FACTORS AFFECTING BEAM WIDTH As the diameter of the piezoelectric crystal increases so does the beam width near the crystal face. Higher frequency beams have a longer near field and less divergent far field. The amount of focusing and the length of the focal zone. Divergence of the beam increases beam width further from the crystal face. The best lateral resolution is at the focal point of the beam. ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES

DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER TWO Formation of the Ultrasound Beam CRT04210 · Ultrasound Imaging START READING NOTES Study Formation of the Ultrasound Beam using the sections below. Use the topic navigation to continue through Ultrasound Imaging. Contents of This Topic ULTRASOUND PHYSICS LECTURE 2 THE PIEZOELECTRIC EFFECT Dipolar Molecules The piezoelectric crystal as a transmitter of sound The piezoelectric crystal as a receiver of sound TRANSDUCERS ELECTRONIC ARRAY TRANSDUCERS CONTROLLING THE ULTRASOUND BEAM ELECTRONIC BEAM STEERING TYPES OF ELECTRONIC ARRAY TRANSDUCER Linear Array: elements are arranged in a straight line allowing for a rectangular field of view ULTRASOUND PHYSICS LECTURE 2 FORMATION OF THE ULTRASOUND BEAM THE PIEZOELECTRIC EFFECT This is the ability of a material to generate an electric charge in response to applied pressure. When a piece of piezoelectric material is compressed a potential difference is generated across opposite faces- the one becomes positive, the other negative. Conversely, if an electric field is applied across the crystal, it changes its shape. This property is natural to certain crystals such as quartz and man made materials such as zirconate titanate. Piezoelectric materials are crystals composed of dipolar molecules, which are positive at one end and negative at the other Dipolar Molecules Normally dipolar molecules have a random arrangement within the material, and they are unable to align themselves with an electric field. However, when heated to a high temperature in the presence of an electric field the molecules align themselves with that field, and will maintain that alignment when they have cooled. The piezoelectric crystal can now be used as an ultrasound transducer to transmit or detect sound. The piezoelectric crystal as a transmitter of sound In this case the crystal is converting electrical energy into mechanical energy. A voltage is applied across the conducting plates causing the molecules to twist in the direction of the electric field, and this causes the crystal to become thicker. If the voltage is reversed, the molecules will twist back in the opposite direction making the crystal thinner. Applying an alternating voltage to the crystal will cause it to expand and contract (oscillate) at the same frequency as the voltage, producing a continuous sound wave of that frequency. The amplitude of the sound wave will depend upon voltage applied and the natural resonant frequency of the crystal. The piezoelectric crystal as a receiver of sound In this case the crystal is converting mechanical energy into electrical energy. When a sound wave makes contact with the piezoelectric crystal the changing pressures cause the crystal to contract and expand. This twists the dipolar molecules, and causes the conducting plates to become charged. These small signals from the conducting plates are used to create a two dimensional image of the returning echoes. The strength of an echo determines the size of the voltage signal produced, which in turn determines the brightness of the echo display on the image TRANSDUCERS Ultrasound transducers act as both a sender and receiver of sound. The essential parts of a transducer assembly are: Piezoelectric element Electrical connections Backing material Acoustic lens Impedence matching layer Physical housing assembly Components of an electronic array transducer ELECTRONIC ARRAY TRANSDUCERS Electronic array transducers consist of a row of rectangular piezoelectric crystals. They all have backing material, to shorten the pulse length, and matching layers on the front surface to improve the sound transmission into the patient. Normally there are between 128 to 256 piezoelectric elements across the face of these transducers. Each element is connected so that small groups of elements can be fired together and in sequence. FIRING ONE GROUP OF ELEMENTS CONTROLLING THE ULTRASOUND BEAM Each single element in an electronic array transducer can produce a small wave front which joins with other small wave fronts to form a larger ultrasound beam. By using time delays, and activating each element in a sequence, the beams shape and direction can be controlled to focus and direct the beam. Focusing the ultrasound beam improves the image quality (resolution) by making the beam thinner within the focal zone. Directing the ultrasound beam ELECTRONIC BEAM STEERING The ultrasound beam can also be steered (directed) using time delays. An image is formed as each group of elements is directed to form a wider wave front, or wide sector field of view. Transducers used today are of three main types: Linear array transducers Curvilinear array ( also called curved linear array or sector) transducers. Phased linear array transducers TYPES OF ELECTRONIC ARRAY TRANSDUCER Linear array transducers transmit parallel scan lines at right angles to the transducer face producing a rectangular field of view. These are high frequency transducers used for superficial structures Curved linear (curvilinear) array is similar but the face of the transducer is curved giving a wider, diverging field of view. These are low frequency transducers used to image deep lying structures. Phased array transducers are similar to linear array with a rectangular, flat face. However, the beam is electronically steered to produce a wide field of view similar to a curved linear array. These have a smaller area of contact with the advantage of a wide field of view, making them suitable for applications with a small acoustic window such as cardiac scans . They also use lower frequencies like the curved array. Linear Array: elements are arranged in a straight line allowing for a rectangular field of view Curvilinear Array: elements are arranged in a curved line resulting in a wider field of view Sector Array: elemnts are arranged in a sector shape, providing a wider field of view at the expense of a smaller footprint NEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? Need a clean, well-formatted PDF copy for offline study, revision or printing? Request the complete notes directly through WhatsApp. GET WELL-FORMATTED PDF NOTES