الصوت عبارة عن موجات أو اهتزازات تسير في الهواء بسرعة تبلغ 340 متراً في الثانيةتقريباً، ولكل صوت من الأصوات هناك تردد معين، ويتراوح المجال المسموع للإنسان من 20 ذبذبة في الثانية إلى 20000 ذبذبة في الثانية .وتنتشر هذه الأمواج في الهواء ثم تتلقّاها الأذن، ثم تنتقل عبر الأذن حيث تتحول إلى إشارات كهربائية وتسير عبرالعصب السمعي باتجاه اللحاء السمعي في الدماغ، وتتجاوب الخلايا معها ومن ثم تنتقل إلى مختلف مناطق الدماغ وخصوصاً المنطقة الأمامية منه، وتعمل هذه المناطق معاً على التجاوب مع الإشارات وتترجمها إلى لغة مفهومة للإنسان. وهكذا يقوم الدماغ بتحليل الإشارات ويعطي أوامره إلى مختلف أجزاء الجسم ليستجيب لهذه الإشارات.
الصوت عبارة عن اهتزازات ميكانيكية تصل إلى الأذن ثم تتحول عبر الأذن إلى اهتزازات تصل إلى خلايا الدماغ حيث تتجاوب معها بل وتغير من اهتزازات خلايا الدماغ،
الصوت هو تردد آلي، أو موجة قادرة على التحرك في عدة أوساط مادية مثل الأجسام الصلبة، السوائل، و الغازات، ولاتنتشر في الفراغ , وباستطاعة الكائن الحي تحسسه عن طريق عضو خا ص يسمى الأذن.
من منظور علم الأحياء فالصوت هو إشارة تحتوي على نغمة أو عدة نغمات تصدر من الكائن الحي الذي يملك العضو الباعث للصوت، تستعمل كوسيلة اتصال بينه وبين كائن آخر من جنسه أو من جنس آخر، يعبر من خلالها عما يريد قوله أو فعله بوعي أو بغير وعي مسبق، ويسمى الأحساس الذي تسببه تلك الذبذبات بحاسة السمع
وتقدر سرعة الصوت في وسط هوائي عادي ب 340 متر في الثانية او 1026 كم في الساعة. تتعلق سرعة الصوت بعامل الصلابة وكثافة المادة التي يتحرك فيها الصوت.
الصوت هو اهتزاز ميكانيكي للوسط ، الصوت ليس موجة بل الموجة هي إحدى الاشكال (نماذج الانتشار) التي يبرز و يتميزبها الصوت و كمثال على نماذج اخرى: التيارات الصوتية و التدفق الصوتي
هنالك عوامل اخرى تؤثر على انتشار الصوت وسرعته كطبيعة المادة (اللزوجة، تأثرها بالمجال المغناطيسي)
تستطيع الأذن البشرية سماع الاصوات التي تتراوح تردداتها بين 20 هرتز و 20 كيلوهرتز بوضوح بينما تتوهن جميع الاصوات التي تقل عن 20 هرتز أو تزيد عن 20 كيلوهرتز (20.000 هرتز). لهذا السبب يقوم مصمموا السمعيات بوضع ما يسمى مرشح إلكتروني لتمرير الترددات السمعية فقط كما هو الحال في بطاقات الصوت الخاصة بالحواسيب مثلا.
السماع عند الحيوانات
تختلف درجة السماع في الحيوانات من فصيلة لأخرى. الخفاش : يقوم بتوليد موجات فوق صوتية تصل إلى 100 كيلوهرتز ثم الاستماع إليها لتكوين صورة للاجسام المحيطة به. الكلب: يستطيع سماع الاصوات الأعلى ترددا من السمع البشري. الأسماك: بعض الاسماك تستمع إلى اصوات بترددات تصل إلى 180 كيلوهرتز والبعض الاخر إلى 4 كيلوهرتز فقط
Diagnostic Ultrasound Introduction to Ultrasound and Its Use The human ear can hear sound waves that have a frequency of 20-20,000 hertz.2 Ultrasound refers to waves that have a frequency higher than 20,000 Hz and are therefore outside our hearing range. Sound waves cannot travel in a vacuum like light waves; they must have a medium to travel through. In any homogeneous material, sound Will travel at a constant rate. The rate will differ with different media. Carefully read the following table. 2. Hz is the symbol for “hertz”, the internationally accepted unit for measuring cycles. 1 Hz = 1 cycle per second. MHz is the symbol for megahertz. 1 MHz = 1,000,000 Hz.
Velocity of Sound in Different Media
media feet/second media meters/second
air 1,100 air 331
water 4,800 water 1540
body tissue 1540
Notice that the table uses both the metric unit meter and the English unit feet. Also notice that the approximate speed of sound in water and soft body tissue is the same.1 Why do you think that is so? The reason is that body tissue contains such a large proportion of water that sound travels through it at approximately the same rate it travels through water.
ultrasound basic part 4
ultrasound basic part 5
Before beginning to study the ultrasound medical imaging process, there are two situations I’d like to consider. First, suppose you are standing on an open plane and shout, “HELLO!”. What would happen? Your voice would go forth and disappear. Next suppose you were in a canyon and yell, “HELLO!”. Now what would happen? Sure, you’d hear an echo. How is an echo produced? It is produced from the sound of your voice going forth and bumping into the side of the canyon wall then being reflected back to you.
If you stand in the canyon and yell, “HELLO!”, and in 0.1 seconds an echo comes back to you, how far is it across the canyon? Using the data in this table and the distance formula you can solve that. Distance = Rate x Time d = r x t d = 1,100 ft/s x 0.1 s d = 110 ft Since the sound had to travel 110 ft across the canyon and back, one way, the distance across the canyon, would be half that or 55 ft. Answer: 55 feet
Using the same information, if you see lightning flash 15 seconds before you heard the rumble of thunder, how far away would the lightning be? Answer should be to the nearest mile. We’ll get back to this problem in the section on math. Meanwhile, if you are going to try it, remember that 5280 feet = 1 mile.
1. During this unit when reference is made to body tissue it means soft body tissue like liver or kidney rather than hard tissue like bone.
Basic Ultrasound physics
د.كمال سيد Admin
عدد المساهمات : 2690نقاط : 4494السٌّمعَة : 9الجنس : علم بلدك : تاريخ الميلاد : 03/04/1950تاريخ التسجيل : 30/07/2012العمر : 74 الموقع : السودان - سنارالعمل/الترفيه : طبيب عمومى وموجات صوتيةالساعة الان : دعائي :
basics - contd You are on a sailing vessel out at sea and you want to know the depth of the water. Your ultrasound instrument sends out sound waves that hit the bottom and return in 4 seconds (go return time). How deep is the water? d = r x t d = 4,800 ft/s x 4 s d = 19,200 ft Since the sound wave had to travel 19,200 ft round trip, one way, the depth of the water at that point, would be half that or 9,600 ft. If it took 3 seconds to return, how deep would it be? If the water were 15 feet deep, how long would it take for the sound wave to return? These questions will be answered in the section on math. sound Sound is a mechanical wave Sound is a longitudinal wave Sound is a type of pressure wave Sound is a form of energy Sound is able to converge and diverge Sound is able to reflect Sound is a form of radiant energy Sound is NOT ionizing radiation Sound is NOT a transverse wave Sound is NOT an electromagnetic wave Ultrasound Physics and Instrumentation
SOUND WAVES What is sound? What is a wave? There are many different but similar definitions for these words. I have chosen the following because, in my opinion, they are the most suitable for our purposes. A wave may be defined as a disturbance or variation that transfers energy progressively from point to point in a medium and that may take the form of an elastic deformation or of a variation of pressure, electric or magnetic intensity, electric potential, or temperature. The key words in this description for understanding the behaviour of sound waves is "disturbance", "transfer of energy...from point to point in a medium", and "variation of temperature". A wave may be described by certain parameters or variables which change over space and time. These parameters will help us understand how sound works and how it behaves under various conditions. Wave variables include such things as amplitude, frequency and period. Sound may be defined as mechanical radiant energy that is transmitted by longitudinal pressure waves in air and other matter. To human beings and animals, sound is the sensation perceived by the sense of hearing. The human auditory apparatus is only capable of hearing sounds within a certain frequency range and intensity level. Certain animals like bats and porpoises can hear sounds humans cannot. You've all heard the expression "as blind as a bat". Bats are indeed blind, yet they have an incredible ability to see. How? They have a sophisticated pulsed sound-echo apparatus with which to navigate. This navigational apparatus is indeed very similar in fundamental design to the method we use in diagnostic ultrasound imaging.
Only certain sound frequencies are audible to the human ear. Typically, the audible range is 20 to 20,000 hertz (one hertz is equal to one cycle per second). Sound frequencies below the range of human hearing are known as infrasound. Sound frequencies above the human audible range is known as ultrasound.
Ultrasound Physics 1 - Sound as Waves
Ultrasound Physics 2 - Interactions with Tissue
عدل سابقا من قبل د.كمال سيد في الأربعاء يونيو 26, 2024 6:41 pm عدل 1 مرات
د.كمال سيد Admin
عدد المساهمات : 2690نقاط : 4494السٌّمعَة : 9الجنس : علم بلدك : تاريخ الميلاد : 03/04/1950تاريخ التسجيل : 30/07/2012العمر : 74 الموقع : السودان - سنارالعمل/الترفيه : طبيب عمومى وموجات صوتيةالساعة الان : دعائي :
In general, frequency is the numberof certain events that occur in a specific period of time. For example, what is the frequency of a full moon? Thirteen times per year, or once per twenty-eight days
With respect to sound, frequency is the number of cycles of an acoustic variable that occur in one second.
Units of frequency: cycles per second cycles/second per second
-1 hertz
Frequency is expressed most popularly in the clinical setting in hertz. For testing purposes it would be a good idea to know the other units as well. If you understand the definition of frequency, you should not have any problems remembering the units except perhaps hertz which you'll simply have to memorize initially.
The abbreviation for hertz is Hz.
One hertz is one cycle per second: 1 Hz = 1 cycle/second
Ten hertz is ten cycles per second: 10 Hz = 10 cycles/second
One hundred hertz is one hundred cycles per second: 100 Hz = 100 cycles/second
One thousand hertz is one thousand cycles per second: 1,000 Hz = 1,000 cycles/second = 1 kilohertz = 1 KHz
One million hertz is one million cycles per second: 1,000,000 = 1,000,000 cycles/second = 1 megahertz = 1 MHz
Because diagnostic ultrasound imaging uses very high transducer frequencies, the unit megahertz is usually the unit of choice to express sound frequency. The prefix mega means million. One million hertz is one megahertz. Megahertz is abbreviated MHz.
سرعة الصوت
تختلف سرعة الصوت حسب نوع الوسط الذي تنتشر فيه الموجات الصوتية و درجة الحرارة فتكون أعلى في المواد الصلبة وأقل في السوائل وأقل بكثير في الغازات. وبالنسبة لانتشار الصوت في الهواء فيعتمد على الضغط ، أي أن سرعة الصوت تقل بالارتفاع عن سطح الأرض. فمثلا سرعة الصوت في الهواء عند درجة الصفر المئوي هي 331.1 م/ث وتزداد هذه السرعة بارتفاع درجة الحرارة. تقدر سرعة الصوت في الماء بـ1450 م/ث عند الدرجة القياسية (15 درجة مئوية). وتتراوح هذه السرعة في المواد الصلبة بين 3000 و 6000 متر/ثانية فهي مثلا 5100 م/ث للحديد والألمنيوم و3560 م/ث للنحاس وتبلغ 5200 متر في الثانية في الزجاج.
الاذن البشرية
تستطيع الأذن البشرية سماع الاصوات التي تتراوح تردداتها بين 20 هرتز و 20 كيلوهرتز بوضوح بينما تتوهن جميع الاصوات التي تقل عن 20 هرتز أو تزيد عن 20 كيلوهرتز (20.000 هرتز). لهذا السبب يقوم مصمموا السمعيات بوضع ما يسمى مرشح إلكتروني لتمرير الترددات السمعية فقط كما هو الحال في بطاقات الصوت الخاصة بالحواسيب مثلا. السماع عند الحيوانات تختلف درجة السماع في الحيوانات من فصيلة لأخرى. الخفاش : يقوم بتوليد موجات فوق صوتية تصل إلى 100 كيلوهرتز ثم الاستماع إليها لتكوين صورة للاجسام المحيطة به. الكلب: يستطيع سماع الاصوات الأعلى ترددا من السمع البشري. الأسماك: بعض الاسماك تستمع إلى اصوات بترددات تصل إلى 180 كيلوهرتز والبعض الاخر إلى 4 كيلوهرتز فقط
د.كمال سيد Admin
عدد المساهمات : 2690نقاط : 4494السٌّمعَة : 9الجنس : علم بلدك : تاريخ الميلاد : 03/04/1950تاريخ التسجيل : 30/07/2012العمر : 74 الموقع : السودان - سنارالعمل/الترفيه : طبيب عمومى وموجات صوتيةالساعة الان : دعائي :
Audible sound sound frequencies between 20 Hz and 20 kHz
Ultrasound is sound frequencies above 20 kHz and it is not audible Audible sound is the range of sound frequencies heard by the human ear. Different sound frequencies are perceived as a different pitch of sound. Different sound intensities are heard as sound with a different volume or loudness.
Vibrations with a frequency below 20 Hz are called infrasound. Humans cannot hear infrasound, but they can feel the vibrations if there is sufficient amplitude. Many modern stereo systems contain “subwoofers” which generate low frequency sound that adds a visceral dimension to the listening experience. You “feel” the sound as well as hear it! Frequencies above 20kHz are called ultrasound and are also inaudible to humans. However, certain animals, for example, porpoises, dogs and bats are able to hear frequencies outside the audible human range. Most of you are probably aware of dog whistles. Dog trainers often use these ultrasonic whistles to control their dogs. The dogs hear and respond to the sound produced by the whistle, whereas the sound is inaudible to the trainer.
تصنيف الصوت تبعا للتردد
بحسب التردد يصنف الصوت إلى الأنواع : • تحت الصوتية ، وهي أقل من 16 هرتز وهي غير مسموعة للأذن البشرية حيث التردد منخفض جدا ، • نطاق السمع , وهو يمتد من 16 هرتز إلى نحو 20.000 هرتز ، وهي أصوات مسموعة للبشر ، • فوق صوتية ، بين 20.000 هرتز إلى 6و1 جيجا هرتز (6و1 مليار ذبذبة في • الثانية) ، وهي غير مسموعة للبشر ، حيث ترددها عالي (ويمكن ان يكون هذا اجابة للسؤال : ما معنى الموجات فوق الصوتية ؟). • تصواتي أو فوق صوتي (بالإنكليزية: Ultrasonic or Ultrasound) مصطلح يطلق على الترددات الصوتية التي تفوق 20 كيلوهرتز. القيمة 20 كيلوهرتز هي قيمة تقريبية وتختلف من أذن بشرية لأخرى. • • صوتية فائقة ، موجات صوتية ترددها أكبر من 1 مليار هرتز (1 مليار ذبذبة/ثانية) ، وهذة قد لا تنتشر
تصواتي أو فوق صوتي (بالإنكليزية: Ultrasonic or Ultrasound) مصطلح يطلق على الترددات الصوتية التي تفوق 20 كيلوهرتز. القيمة
تصنيفات الموجات الصوتية
تصنف الموجات الصوتية طبقا لتردداتها كما يلي:
الموجات المسموعة AUDIBLE WAVES
هي تلك الموجات التي تقع تردداتها بين 20 هرتز و 20.000 هرتز ، وتمثل الصوت المسموع بواسطة الأذن البشرية العادية. حيث أن الحد الأدنى لتردد الصوت التي تحس بها الأذن البشرية الطبيعية هو 20 هيرتز تقريبا بينما الحد الأعلى هو 20 الف هرتز ، وينخفض هذا المدى عند كبار السن إلى حوالي 12.000 هرتز. وأقصى درجات الاحساس بالصوت لأذن بشرية عادية يقع في المدى بين 5000 هيرتز و8000 هيرتز والذي يشمل ذبذبات الحروف الهجائية. وكما هو معروف يمكن أحداث الموجات السمعية عن طريق الاحبال الصوتية في الإنسان والآلات الموسيقية سواء الوترية أو النحاسية أو الأنبوبية وغيرها من الآلات الأخرى.
الموجات الفوق سمعية ULTRASOUND WAVES
هي الموجات التي تزيد تردداتها على 20 الف هيرتز والتي تقع خارج نطاق حاسة الاذن البشرية. وهذا النوع من الموجات ما زال موضع بحث واهتمام مكثف نظرا للتطبيقات المهمة التي تمس مجالات عديدة في الصناعة والطب وغيرهما. وقد أصبح بالإمكان إنتاج موجات فوق صوتية تزيد تردداتها على 1000000 هيرتز ولاتختلف هذه الموجات من حيث الخواص عن الموجات الصوتية الاخــرى إلا أنه نظرا لقصر طول موجاتها فإنه بالإمكان تنتقل على هيئة أشعة دقيقة عالية الطاقة.
الموجات تحت السمعية INFRASOUND
هي الموجات الصوتية التي يقل ترددها عن 20 هيرتز ولاتستطيع الاذن البشرية الاحساس بها واهم مصدر لها هو الحركة الاهتزازية والانزلاقية لطبقات القشرة الأرضية وما ينتج عنها من زلازل وبراكين وعليه انها مهمة جدا في رصد الزلازل وتتبع نشاط البراكين. وتستطيع بعض الحيونات الاحساس بالزلازل قبل حدوثها بسببها
تطبيقات الترددات التصواتية (فوق الصوتية)
يمكن تصميم مولدات فوق صوتية وأجهزة تحسس فوق صوتية لاستخدامها في الكثير من التطبيقات الصناعية والطبية مثل: • السونار (رادار فوق صوتي بنطاق عريض يسمح بتصوير ثلاثي البعد) • الاشعة التلفزيونية الثنائية والثلاثية البعد. • قتل بعض أنواع البكتيريا • المنظفات فوق الصوتية
موجات طولية وموجات عرضيةا
عدد من موجات جيبية ذات ترددات مختلفة ; الموجات السفلى لها تردد أعلى من الموجات العليا في الشكل. المحور الأفقي يمثل الزمن. ينتشر الصوت في الغازات والبلازما وفي السوائل على هيئة موجات طولية ، وتسمى عند الفيزيائيين موجات ضغطية. أما في المواد الصلبة فينتشر الصوت فيها كموجات طولية وأيضا موجات عرضية. وتتكون موجات الصوت الطولية من تتابع لطبقات يعلو فيها الضغط وطبقات يقل فيها الضغط عن الضغط المتوازن المعتاد متتابعة. أما الموجات العرضية في المواد الصلبة فهي موجات متتابعة من إجهاد جزي عرضي ، يكون عموديا على اتجاه انتشار الصوت. وفي موجات الصوت تنزاح جزيئات الوسط دوريا وتهتز ، ولكنها لا تنتقل مع الصوت. وتنتقل الطاقة المحمولة مع الصوت كطاقة حركة لاهتزازات الوسط.
التعريف الفيزيائي للصوت
من وجهة نظر الفيزياء فالصوت هو موجة. وتكون الموجة في السوائل والغازات موجة طولية وهي كذلك أيض في الهواء. أما في المواد الصلبة فينتشر الصوت في موجات عرضية. وتحرك الموجات جزيئات الوسط (غالبا الهواء) حول حالة وسطية وتنتشر بسرعة خاصة ، ويرمز لسرعة الصوت c.وتنقل الموجات طاقة صوتية. ولا ينتشر الصوت في الفراغ. وتعتمد سرعة الصوت على الوسط الذي ينقلها. وتبلغ سرعة الصوت في الهواء 343 متر في الثانية عند درجة حرارة 20 درجة مئوية و 1407 متر /ثانية في الماء عند درجة الصفر المئوي. يمكن حساب طول الموجة الصوتية λ من تردد الموجة f وسرعة الصوت c بواسطة المعادلة:
وفي العادة تكون اختلافات في الضغط أو في الكثافة سببا في تغير سرعتها. ويتضح هذا عندما نتصور مستوي لضغط الصوت يقدر ب 130 dB ديسيبل. وهذ يبلغ درجة تألم أذن الإنسان ، ويمثل به الضغط الجوي العادي : يبلغ الضغط الجوي للهواء الساكن 101325 باسكال ، في حين أن مستوي ضغط صوت قدره 130 dB له قيمة فعلية لضغط الصوت p تبلغ 63 باسكال فقط.
اسرع من الصوت (خارق الصوت TRANS SONIC)
يستخدم مصطلح "خارق صوت" للإشارة للسرعة التي تزيد عن سرعة الصوت (1 ماخ). في درجة حرارة 21 مئوية (70 فهرنهايت) تعد القيمة المطلوبة بداية لأي جسم ليتحرك بسرعة خارقة صوت هي تقريبا 344 متر في الثانية (1.129 قدم/ثانية أو 761 ميل في الساعة أو 1,238 كيلومتر في الساعة). يطلق أحيانا مصطلح هايبر سونيك على السرعات التي تزيد 5 مرات عن سرعة الصوت. تسمى السرعات التي يكون بعض أجزاء الهواء حول الجسم فيها (مثل نهاية شفرات المحرك الدوار) تصل لسرعة خارقة الصوت ترانس سونيك (تقريبا ما بين 0.8 الى 1.2 ماخ).
medical uses of ultrasound
The medical uses of ultrasound may be divided into diagnostic imaging, surgical or interventional procedure guidance and therapeutic (diathermy). These three major categories use approximately the same ultrasound frequency range. What differs more significantly between them is the mode of operation of the ultrasound equipment and the output power levels.
The choice of transducer frequency used in diagnostic ultrasound is limited by two basic factors. The first is tissue penetration or imaging depth, and the second is image resolution. On the one hand, we must consider the distance that the sound must travel, and on the other, how well the structure of interest can be displayed. To image a structure the sound must be able to reach it and return to the transducer. The best images are produced using the highest frequency that will penetrate to the region of interest. Selecting a transducer is always a compromise between penetration and resolution. The transducer range used in diagnostic imaging offers the best compromise between these two factors. Remember, low frequency for penetration, high frequency for resolution.
(TYPICAL SCANNING FREQUENCY RANGE (MHz
General abdomen 2 - 5
Gallbladder 3 - 5
ObGyne 2 - 5
Adult heart 2 - 3
Pediatric heart 3 - 5
Neck, breast, scrotum 5 - 10
Eyes 7 - 10
The frequency range for diagnostic ultrasound transducers is generally stated as 1 to 10 MHz however the upper limit of the range is being pushed higher all the time especially with the advent and availability of very high frequency intracavitary probes. These probes may have frequencies as high as 20 MHz with penetration limits of 1 to 2 cm. The transducers are tiny and located at the end of a flexible catheter which is inserted into a vessel, duct, uterine cavity, or other lumen (GI tract, ureter). Applications reported to date include intravascular assessment of atherosclerotic disease of the carotid arteries and certain abdominal arteries; assessment of pathology in the uterine cavity and endometrium including very early gestations; assessment of the stomach and duodenal wall for neoplasia; and assessment of the bile duct for intraductal disease such as neoplasia or calculus disease. For testing purposes, you should know that intracavitary probes are very high frequency and can be inserted into any small luminal space for detailed examination of the surrounding tissues. The diagnostic frequency range of ultrasound transducers is based on the ability to penetrate and the ability to visualize small structures. Higher frequencies are preferred but have limited penetration. Lower frequencies offer poorer resolution but can penetrate more than higher frequencies. So the optimal choice of transducer for a diagnostic ultrasound study is a compromise between the need to penetrate the area of interest and the need to adequately display detail.
The speed of sound is the speed a sound wave travels or propagates in a medium along a specified line or direction. It is the speed the wave energy advances from one point to another. It is sometimes referred to as the propagation velocity. This is different than the particle motion velocity which is the speed a particle moves when sound is passing in the medium. Particle motion velocity is not something that is discussed very much or even mentioned in most diagnostic ultrasound textbooks. It will be mentioned again in the section on bioeffects in module 4, but it is not a parameter which receives a lot of attention.
What's the difference between speed and velocity? Velocity is speed along a specified line or direction. For our purposes, we can interchange the words velocity and speed.
The speed of sound is the speed with which a particular value of an acoustic variable moves. A value of an acoustic variable which is typically used to define the speed of a wave is its maximum value. The speed with which this maximum value moves through a medium is the speed of sound in the medium. This reference point is shown in the adjacent diagram. The acoustic variable in question is pressure and the reference point (indicated by the dot) is the peak pressure. The movement of peak pressure in the wave over a Speed of Sound specified distance and time is the speed of sound in the medium. Other acoustic variables (density, temperature, etc...) can also be used to express the speed of the sound wave. Speed is distance over time. If a wave moves 10 meters in one second, the speed is 10 meters per second or 10 m/s.
What determines the speed of sound in a medium? The speed of sound in a medium depends specifically on the properties of the medium. Which ones? Density and compressibility. An alternate word for compressibility is elasticity.
The speed of sound in a medium is inversely related to both density and compressibility as follows:
The tilde symbol (-) means approximately related to.
Density is the mass of the medium per unit volume. The higher the density of a medium the more mass it contains within a given volume. The unit of density is kilograms per cubic
3 3 meters (kg/m ) or grams per cubic centimeters (g/cm ).
What happens to the speed of sound if density increases and compressibility remains the same?
Under this condition, the speed of sound decreases. The denser a medium, the slower the speed of sound assuming the compressibility is the same. The speed of sound in the medium is lower because the greater mass per unit volume (density) requires more force to move the particles from their resting positions. Also, once the molecules are vibrating, the denser medium has more inertia and it is more difficult to cause particles to change direction with changes in the direction of the pressure wave.
On the basis of density alone, you would expect the speed of sound to be highest in low density media and lowest in high density media. But in fact, most of the time, the speed of sound is highest in the high density medium. This is often confusing to students and I will attempt to explain why.
The other property of a medium which affects the speed of sound in media is compressibility.
To understand the effects of density on speed of sound, one must appreciate the relationship of density and compressibility as well. Compressibility or elasticity is the ease with which a medium is compressed. It is the change in volume when a specific pressure is applied. The easier a medium is compressed (less resistance to the applied pressure), the greaterthe compressibility. Compressibility is the reciprocal of stiffness. Stiffness is frequently used in lieu of compressibility when describing the speed of sound. The speed of sound is inversely related to compressibility and, therefore directly related to the medium's stiffness. That means the stiffer a material (less compressible), the higher the speed of sound. In most liquids, an increase in density is accompanied by a proportional increase in stiffness. This means that as density increases, compressibility decreases. It is this increase in stiffness that accompanies an increase in density that causes the increase in the speed of sound in the medium. An increase in density alone will cause a decrease in the speed of sound.
Dense materials are very difficult to compress. They are stiffer than low density materials. The lower the compressibility (higher the stiffness) of a medium, the greater the speed of sound. When comparing two media, if the density differences are greater than the compressibility (stiffness) differences, the medium with the lower density will have the highest speed of sound. Conversely, if the compressibility (stiffness) differences are greater than the density differences, the medium with the lower compressibility (higher stiffness) will have the highest speed. In general, because of the inverse relationship between compressibility and density, denser media such as solids (bone, metal, plastics) have higher speed of sound than do less dense media such as liquids (water, blood, amniotic fluid), and soft tissues. Gases have the lowest speed of sound because they are very compressible (low stiffness).
The following example of two liquids with very different density and compressibility should help you understand the relationship between density, compressibility, and speed. The density of mercury is 13.6 times greater than water. The speeds are 1450 and 1480 m/s respectively. With the density of mercury being 13.6 times greaterthan water, and knowing that dense materials result in slower waves, one would expect the speed of mercury to be much lower than that of water i.e. 13.6 times lower. Yet the speed of sound in mercury and water is almost the same. Why?
The explanation is found in the relative compressibility (stiffness) of the two liquids. Mercury is 13.4 times less compressible than water. The lower the compressibility of a material (stiffer it is), the higher the speed of sound. The difference in stiffness is slightly less than the difference in density by a factor of 0.98 (13.4/13.6). Therefore, we would expect the speed of sound in mercury to be slightly less than the speed of sound in water by a factor of 0.98. Comparing the two, we find that the speed of sound in water is 1480 m/s and the speed of sound in mercury is 1450 m/s. Indeed, mercury does propagate sound slightly slower than water - by a factor of 0.98.
Table 1.2 lists the speed of sound through some biological tissues and non-biological materials. For testing purposes, you should know the ones which are indicated with an asterisk. What is often asked on examinations is the relative increasing or decreasing order of materials based on the speed of sound i.e. bone, soft tissue, fat, air (highest velocity to lowest).
TABLE 1.2
Propagation Speeds in Soft Tissues and Other Materials
MEDIUM m/s
air* 330 mercury 1,450 fat* 1,460 water (20oC) 1,480
o 6% saline (20 C) 1,540 soft tissue(average)* 1,540
o water (50 C) 1,540 liver 1,550 muscle* 1,580 perspex 2,680 bone* 4,000
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Amplitude is the maximum variation in an acoustic variable. It is the difference between the mean, resting value (when no sound is applied) and the maximum value of an acoustic variable. For testing purposes, be prepared to identify amplitude from a line diagram of a sine wave.
Amplitude is the distance between the baseline to the peak of the wave in the plus direction (+), or the distance between the baseline to the peak of the wave in the minus (-) direction. Amplitude is not the difference between the minimum and maximum values of an acoustic variable.
Amplitude relates to the strength of the sound wave. Think of waves on the surface of water. If you drop a small stone, the waves caused by the force of the stone disturbing the water will be relatively small and will radiate away from the drop site for a relatively short distance. If you drop a large rock, the waves will be much bigger and stronger, and will travel a lot farther before losing all their energy.
The amplitude of a wave can be described in terms of any acoustic variable, but the most commonly used variables are particle motion and pressure. The unit for amplitude depends on the acoustic variable being measured:
! pressure: newton/square meter ! particle motion: micrometer ! density: grams/cubic cm ! temperature: degrees
The initial amplitude of a sound wave is determined by the ultrasound system and the transducer. The greater the voltage or electric power applied to the transducer from the ultrasound transmitter or pulser, the greater the initial amplitude of the ultrasound wave produced by the transducer.
The initial amplitude of an ultrasound wave also depends on the electromechanical efficiency of the transducer (how well the transducer converts electric energy to mechanical energy). Two transducers of the same frequency, diameter, and output power may not generate waves with the same amplitude.
Amplitude decreases as the ultrasound waves travels in tissue. What causes this amplitude loss? Attenuation.
Increasing the amplitude of the outgoing ultrasound wave increases sensitivity and effectively increases the depth of penetration. It allows the system to receive and display echoes from small or more distant interfaces.
Does the sonographer have any control over the initial amplitude of the outgoing ultrasound pulse? Is this something the operator can change?
Amplitude can be controlled or changed by the operator by changing the control on the ultrasound machine which regulates the amount of voltage or electric power to the transducer. This control may be labelled a variety of ways including, OUTPUT, POWER, dB, TRANSMIT, and others. Amplitude does NOT change with changes in receiver controls like time gain compensation (TGC). System controls are considered in detail in Module 3.
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A sound wave reflected at an interface is referred to as an echo or reflection. When a sound wave encounters an interface, part of the incident wave energy is reflected and part is transmitted into the second medium. The sum of the energy in the reflected and transmitted waves is equal to the energy in the incident wave. The terms propagation and transmission are frequently interchanged in the literature however they do not mean quite the same thing. Propagation is the travel or progression of sound energy through a material. Transmission is the transfer of sound energy through an interface into a second material.
SCATTERING
Scattering is the reflection of wave energy at interfaces which are small (approximately equal to or smaller than the wavelength of the incident sound wave). Scattering also occurs at "rough" boundary interfaces. A rough boundary interface defines a specular interface which is not smooth but rather having an irregular surface which predisposes to scattering. A synonym for scattering is diffuse reflection.
The portion of the wave energy returning to the transducer is known as backscatter and is typically detected as relatively weak echoes (compared to echoes due to specular reflection). In comparison to echoes from specular reflection, backscattered echoes from organ parenchyma are typically 30 dB less intense (weaker by a factor of 1000). In the body, the parenchyma of organs is the result of scattering. In fact, backscatter from organ parenchyma is the most significant information in grey scale images. Normal tissue parenchyma produce typical scattering patterns (echo dot size and brightness) referred to as the texture or speckle pattern of the tissue.
REFRACTION
Refraction is the change in the direction of the transmitted sound wave at a specular interface.
When a sound beam crosses an interface, frequency remains constant but wavelength may change to accommodate a new speed of sound in the second medium. Remember that wavelength is a function of frequency emitted by the crystal and the speed of sound in the medium. As frequency is determined by the transducer and for a selected transducer is constant in different media, the wavelength must change with a change in speed of sound.
The amount of refraction depends on the speed of sound differences between medium 1 and medium 2 as calculated by Snell's Law: The greater the speed of sound difference, the greater the amount of refraction.
The direction of the refracted beam depends on the speed of sound in the second medium relative to the first medium. If medium 2 has a higher speed of sound, the beam is always refracted away from the normal as shown in the diagram to the right. Therefore, when V2 > V1, the angle of transmission is greater than the angle of incidence.
Edge Shadowing
Refraction at the edge of a curved interface may produce a relatively thin acoustic shadow seen at the edge of cystic masses, vessels, and less frequently with solid masses. This type of acoustic shadowing is referred to as edge shadowing.
If the incident sound beam strikes a specular interface at a large oblique angle (referred to as grazing incidence) and the two media have a different speed of sound, the sound beam will be refracted towards the medium with the lowest speed of sound.
An edge or refractive shadow is frequently seen at the edge of the gallbladder neck . The speed of sound is lower in the gallbladder than the adjacent tissue thus the beam is refracted towards the gallbladder and is not transmitted at the edge of the gallbladder.
Although relatively uncommon, edge shadowing may be seen with a solid mass with a lower speed of sound than the surrounding medium (such as a lipoma in the liver).
CRITICAL ANGLE REFLECTION
Synonym: total internal reflection
Critical angle reflection (CAR) is total reflection of the incident sound beam at an oblique interface due to extreme refraction which causes the angle of the transmitted beam to be parallel to the interface. In effect, the transmitted beam is 90 degrees to the incident beam. Only if the speed of sound in medium 2 is greater than that of medium 1, the possibility of CAR exists. If the speed of sound in medium 2 is lower than in medium 1, CAR cannot occur.
The critical angle is the incident beam angle which results in the transmission angle being equal to 90 degrees. The incident angle which will cause CAR depends on the speed of sound in medium 1 and medium 2 therefore the critical angle is not the same for all interfaces. The critical angle may be calculated using Snell's Law. The greater the difference in the speed of sound in medium 1 and medium 2, the smaller the angle of incidence or the critical angle which will cause CAR.
Critical angle reflection results in the display of an acoustic shadow known as a reflective shadow at the extreme edge of a curved surface such as the fetal skull. fluid. If the sound beam is scanned in a REFLECTIVE EDGE SHADOWS simple, linear fashion or if a linear array transducer is used, the angle of incidence at the edge of the head is extreme and because the skull has a much higher speed of sound than the surrounding scalp and amniotic fluid, the beam is refracted towards the medium with the lower speed of sound and an edge shadow is seen due to critical angle reflection
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عدد المساهمات : 2690نقاط : 4494السٌّمعَة : 9الجنس : علم بلدك : تاريخ الميلاد : 03/04/1950تاريخ التسجيل : 30/07/2012العمر : 74 الموقع : السودان - سنارالعمل/الترفيه : طبيب عمومى وموجات صوتيةالساعة الان : دعائي :
•US is recognized as an important adjunct to clinical examination in care of patients with many common diseases. It is now a routine examination in OB. & GYN. it is an easy, safe, noninvasive, accurate, cost-effective, available, quick
BASIC U/S PHYSICS
•Medical uses of US include: 1. diagnostic imaging 2. surgical or interventional procedure guidance. 3. therapeutic( diathermy) •These three major categories use approximately the same US frequency range, but Differ in : a) the mode of operation of the US equipment . b) the output power levels. •sound is a form of energy which propagates in matter in the form of mechanical longitudinal waves. Fig .page 9 (p.9). Initially start with slides 231 to 241 •TERMINOLOGY •Anechoic: ( echo free , echo lucent, sonolucent) no internal echoes & enhanced posterior through transmission (e.g. GB,UB , cysts) •Echogenic: very bright echoes within a structure ; i.e. more echo dense than liver parenchyma (e.g. gallstones, calcifications). echogenicity is the grayscale level assigned to each pixel and represents the acoustic impedance mismatch at interfaces. An area showing weak or no reflection is echolucent. Tissue characteristics that affect echogenicity include : a) reflection & scattering at acoustic interfaces b) attenuation & absorption . c) depth of the reflector d) technical considerations: + gain setting with a linear relation b/w gain & image brightness + transducer frequency. , with high frequencies reducing echogenicity & time Gain settings & dynamic range
• sound attenuation
The rate of sound attenuation depends on the characteristics of both the source & the medium. REMEMBER, attenuation of sound in air is relatively slow. The absorption processes depend primarily on :a) the physical characteristics of media (rigidity or stiffness), & b) the Frequency of the TX. in use. The amount of absorption is determined by :a) viscosity of the medium. b) the relaxation time of the medium ( i.e. resiliency). c) US freq. (increased absorption with higher frequency explains why high freq. TXs. cannot be used for examining deep structures). Molecular motion is incited in tissues by coupling the TX. to the pt. skin. Particle motion decreases & internal friction increases with increasing viscosity, and more energy is needed to displace the molecules (increased viscosity leads to increased absorption)
SPATIAL RESOLUTION
•SPATIAL RESOLUTION defines the ability of TX. and US system to RESOLVE reflectors or interfaces (closely related or adjacent reflectors must be displayed as separate echoes in the image i.e. spacing). The two components of the spatial resolution include : •A)AXIAL (Depth; longitudinal; range; AR) p.104 is the minimum reflector spacing ALONG the beam axis that results in separate echoes being detected and displayed. TX. AR is determined by the SPATIAL PULSE LENGTH(SPL). •SPL is the length of space over which a pulse occurs i.e. the length of the outgoing US pulse; it is the product of wavelength and the number of cycles in the pulse in mm.
•TO RECOLLECT p.165 :
•A) DISPLAY FORMAT comprises :
•1) linear sequenced arrays : 1. larger footprint TX. is a disadvantage 2. rectangular format (FOV) the most popular for small parts including peripheral vascular Doppler e.g. carotids 3. relatively wide near field which equals the far field 4. parallel scan lines ; less interpolation (fill-in b/w scan lines) •2 ) convex sequenced array : 1. most popular for general abdomen and ObGyne studies. 2. trapezoid format with relatively wide near field and a wide far field •3. disadvantages include large footprint and interpolation needed in the far field.
• ARTIFACTS
•Are display phenomena not properly representing the structure being imaged. US scanners are designed to make certain assumptions about the way sound interacts with tissues, BUT these assumptions are often contradicted by the way in which the sound beam actually behaves in tissues. This results in errors in presentation of echo information. These assumptions include : 1. sound travels only in straight lines (not true). it may be refracted or reflected before returning to TX. 2. echoes originate only from objects located from the central beam axis (not true) . they may originate from anywhere in the beam cross-section including beam edges) 3. amplitude of returning echoes is directly related to the reflection amplitude of the reflectors (not true) .
•1) CLEANING : + is the removal of soil to reduce the number of organisms from the surface + achieved by washing with soap & water (99% of microbial load reduction) or WIPING with 70% alcohol •+ it is an essential 1st step prior to sterilization or disinfection. + it is appropriate for low risk or non-critical procedures e.g. Txs. used for normal TAS.
• the AIUM is a multi-disciplinary, non profit organization dedicated to advancing the art and science of US in medicine and research through its educational, scientific, literary & professional activities. Membership is open to physicians, scientists, & Sonographers. The AIUM provides US professionals with formal position statements on relevant topics including safety, training, & other US practice issues. The AIUM has an elected seat on the AMERICAN MEDICAL ASSOCIATION (AMA) House of Delegates which allows the voice of AIUM members to be heard throughout the medical community.
Basic US summary
What is Ultrasound:
Sound is made up of several different frequency waves. The very high frequency range is inaudible to the human ear and is known as ultrasound. Ultrasound was used by the Navy during World War II to detect submarines, and is widely used by fisherman to help find schools of fish.
In each case, an ultrasound machine is used. With the help of a microphone-shaped device (known as a transducer) ultrasound waves are created and beamed through water. When the beam encounters a boundary or interface between liquid (water) and a solid (submarine or fish) with a different density or compactness, part of the beam is reflected back to the transducer. The remaining waves move through the object and reach the back boundary between solid and water. Here, some more of the ultrasound waves are reflected back to the transducer. In other words, the transducer transmits ultrasound and constantly receives waves that are reflected back every time the beam travels from one density to another.
The reflected ultrasound waves are collected and analyzed by the machine. Determining the amount of time it took for the beam to travel from and to the transducer (plus the the consistency and changes in position of the different structures that it passed through), the ultrasound machine can determine the shape, size, density and movement of all objects that lay in the path of the ultrasound beam.
The information is presented "real time" on a monitor screen and can also be printed on paper or recorded on tape, a CD or a computer disk. That is how warships detect submarines, fishermen identify choice fishing spots, an obstetrician evaluates the fetus of a pregnant woman, and a cardiologist examines the heart of a patient.
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عدد المساهمات : 2690نقاط : 4494السٌّمعَة : 9الجنس : علم بلدك : تاريخ الميلاد : 03/04/1950تاريخ التسجيل : 30/07/2012العمر : 74 الموقع : السودان - سنارالعمل/الترفيه : طبيب عمومى وموجات صوتيةالساعة الان : دعائي :
As stated previously it has been estimated by several writers that ultrasonic imaging is now used in 20% of pregnancies in the United States. Some doctors feel that in the future it nay well be used routinely in all pregnancies to check for abnormalities. A few people would even go so far as to say that universal imaging would be desirable because it would help the mother bond to her child when she sees it moving on the screen. I feel that this would be going much too far, both because of the expense and also because of the worrisome issue of the biological safety of ultrasound.
In 1979 the American Institute of Ultrasound in Medicine published a booklet titled, “Who’s Afraid of a Hundred Milliwatts Per Square Centimeter?” The conclusion of this publication was that no deleterious biological effects have ever been measured at less than 100 milliwatts per cm2 of tissue. Present ultrasound machines deliver less than 100 mW cm2, and many go as low as 40 mW/cm2.
A conference in 1982 on the safety of ultrasound was co-sponsored by the March of Dimes and the Pediatrics Department of Columbia University’s College of Physicians and Surgeons. Most of the studies presented indicated that there was no increase in birth defects or cancer in children who received ultrasound in utero.
However, as reported by the popular press, experiments in vitro were less reassuring.8Several of these investigations seemed to indicate that there might be biological damage to cells at diagnostic levels of ultrasound. For instance, one experiment suggested that there was an effect on chromatid exchanges in human white blood cells. However, a basic dictum of science is that a scientist’s work must be reproducible by other scientists before an experiment is valid. The results of this experiment , as well as several others, could not be confirmed by other investigators.
Despite these reassuring negative results, it is still good to be cautious when using a new modality. Many of us can remember when the danger from X-rays was considered to be so minimal that irradiation was a standard treatment for swollen tonsils and acne.
The following quote sums up the current status of the question of safety of ultrasound:
In terms of identifiable hazards, obstetric ultrasound receives a clean bill of health. In addition to the substantial literature relating specifically to the fetus, we find no study in the entire body of biomedical ultrasound which clearly demonstrates that there is any effect on the mammalian fetus from pulse-echo ultrasound.
However, a responsible and vigorous scientific community will continue the search for effects.
د.كمال سيد Admin
عدد المساهمات : 2690نقاط : 4494السٌّمعَة : 9الجنس : علم بلدك : تاريخ الميلاد : 03/04/1950تاريخ التسجيل : 30/07/2012العمر : 74 الموقع : السودان - سنارالعمل/الترفيه : طبيب عمومى وموجات صوتيةالساعة الان : دعائي :
موضوع: short notes الإثنين أبريل 08, 2024 8:38 pm
Choose a probe Linear array probe: High-frequency (eg, 5 to 10 MHz) high-resolution image, little depth of penetration, flat footprint, rectangular image; choose for imaging superficial structures in detail (eg, for vascular cannulation or arthrocentesis) Curvilinear probe: Low-frequency (eg, 1 to 5 MHz), lower-resolution image, greater depth of penetration, convex footprint, fanned image; choose for general imaging of deeper structures (eg, for E-FAST or aortic aneurysm evaluation) Phased array probe: Typically low resolution and high depth, very small footprint that can fit in tight spaces (eg, between the ribs); often chosen specifically for cardiac imaging Intracavity probe: Tight curvilinear probe, high frequency; choose for imaging… Operate the ultrasound console B (brightness) mode: This is the commonly used 2-dimensional imaging mode. M (motion) mode: In M mode, the operator sees a one-dimensional image in the y-axis over time in the x-axis. The monitor shows 2 images: a single acoustic beam (solid line) imposed on the smaller B mode image on one portion of the monitor, and that single beam presented as a vertical line moving across the monitor in a separate M mode area. Motion, such as the beating of a heart, appears as repeating linear disturbances, and static structures create solid, undisturbed horizontal lines as the beam moves across the screen. Color flow Doppler: This mode is diagnostic for the direction of blood flow. It also shows flow velocity. … Standard probe orientation: With correct placement, the right side of the patient should appear on the left side of the monitor. The probe orientation mark on one side of the probe should face the patient's right side (or cephalad if the probe is oriented longitudinally), and the marker dot on the ultrasound monitor is at the upper left corner of the ultrasound monitor. Cardiac examination orientation: By selecting the cardiac preset, the marker dot will be on the right side of the monitor. Coat the probe tip with ultrasound gel. When using a covered probe, apply gel to the probe and then pull a glove or probe cover tightly over the probe tip to eliminate all air bubbles in the gel, and wrap rubbe… Position the patient before the examination in a way to optimize probe positioning and to maximize sonographer and patient comfort.
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عدد المساهمات : 2690نقاط : 4494السٌّمعَة : 9الجنس : علم بلدك : تاريخ الميلاد : 03/04/1950تاريخ التسجيل : 30/07/2012العمر : 74 الموقع : السودان - سنارالعمل/الترفيه : طبيب عمومى وموجات صوتيةالساعة الان : دعائي :
موضوع: short notes الإثنين أبريل 08, 2024 8:44 pm
Bedside ultrasonography is increasingly used in acute care settings to assist both diagnosis (eg, fluid accumulations or foreign bodies) and treatment (eg, intravenous catheterization or arthrocentesis). Ultrasonography equipment includes probes, consoles or instrument controls, and monitors. Some portable devices work on software apps in handheld devices. Point-of-care ultrasonography should be done only by trained personnel. Indications Bedside ultrasonography has many uses, including Abdominal aortic aneurysm evaluation Abscess identification and location for incision and drainage Arthrocentesis Biliary pathology, including cholelithiasis and … Step-by-Step Description of Procedure Hysterogram. Also called a hysterosalpingogram, or HSG, this test enables your doctor to view the reproductive organs for anatomical problems and conditions, such as fibroids, that can lead to miscarriage.
What is the difference between a missed abortion and an incomplete abortion? The gestation would be termed a missed abortion only if the diagnosis of incomplete abortion or inevitable abortion was excluded. The condition may present as an anembryonic gestation (empty sac or blighted ovum) or as fetal demise prior to 20 weeks gestation. Does misoprostol cause pain during miscarriage? Within a few hours you will start to have cramping and light bleeding. This will progress until there is heavier bleeding then finally passage of tissue that appears whitish. After tissue is passed, your pain and bleeding should lessen. You may take pain medicine during this time.
د.كمال سيد Admin
عدد المساهمات : 2690نقاط : 4494السٌّمعَة : 9الجنس : علم بلدك : تاريخ الميلاد : 03/04/1950تاريخ التسجيل : 30/07/2012العمر : 74 الموقع : السودان - سنارالعمل/الترفيه : طبيب عمومى وموجات صوتيةالساعة الان : دعائي :
موضوع: short notes الثلاثاء أبريل 09, 2024 9:11 pm
Time gain compensation (TGC) is a setting applied in diagnostic ultrasound imaging to account for tissue attenuation. By increasing the received signal intensity with depth, the artifacts in the uniformity of a B-mode image intensity are reduced. This means that a TGC module will increase the amount of gain given to an input signal, as its sampling time increases monotonically. This counteracts the excessive sound-dampening Focus There is an optimum depth that object of interest will have the best lateral resolution on screen. Lateral resolution is the ability to distinguish two small objects at the same depth. This depth can be adjusted by manipulating the focus control. It is usually shown as a small arrow near the hash marks. Activate focus function and then use trackball or touchpad to adjust the arrow to the same depth with area of interest Volume measurements LENGTH X WIDT X HEIGHT X 0.523 Prostate V = less than 25 ml L 4 cm / W 4 cm / AP 3 cm
Thyroid V = less than 25 ml L 4 - 6 cm / W 1.5 - 2 cm / AP 1.5 - 2 cm / Ismuth 4 - 6 cm
UB (Prevoid) = less than 750 ml UB V (Postvoid) = less than 50 ml
Testes = L 3 - 5 cm/ W 1.5 - 2 cm / AP 2 - 3 cm Epididymis Length = 3.8 cm
Ovary V (Premenopause) = less than 14 ml. Ovary V (Postmenopause) = less than 8 ml L 2.5 - 5 cm / W 1 - 3 cm / Thickness 0.6 - 2.3. cm
In new US machines volume is automatically calculated 1-2-3 RULE (OVARY) LENGTH = 2.5 - 5 CM WIDTH = 1 - 3 CM THICKNESS = 0.6 - 2.2 cm
1-2-3 RULE is a simple aid - memoire describing the nomenclature of any small simple anechoic structure in the ovary on US :: Less than 1 cm = follicle 1 - 2 cm dominant follicle More than 3 cm = cyst
موضوع: Basic Ultrasound Physics 
الإثنين أبريل 22, 2019 5:57 pm
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