Ultrasound Physics Chapter 1 The Basics

Ultrasound Physics Chapter 1 The Basics Physics: The Basics  Graphs ◦ 2 axes  Horizontal axis, x-axis; runs side to side  Vertical axis, y-axis; runs up & down Applying Graphs to Ultrasound • This is a spectral Doppler tracing that is used to measure blood velocity. • In this case: • The x axis is time • The Y axis represents velocity of blood • In m-mode ultrasound the xaxis represents time and the y axis represents the depth of reflectors • M-mode is used to take fetal heart rate and is used in echocardiography Relationships • In ultrasound physics, we often describe the relationships between two different parameters or variables. • Two items are related or proportional when they are associated with each other such that when one changes, the other will also change in some way. No relationship or unrelated • Two items that are not associated or have no bearing upon each other. • Examples: • Hair color is unrelated to intelligence • Your income is unrelated to your eye color. Direct Relationships • Two items are associated in a way that when one increases the other increases. • When one decreases the other decreases. • When one increases the other increases. • Examples: • Clothing size is directly proportional to the age of a child (older child/larger child) • The age of a tree and its size are directly related Indirect/Inverse Relationships • Two items are associated with each other such that when one increases the other decreases. • When one decreases the other increases. • When one increases the other decreases. • Examples: • Golf scores are inversely related to skills • A car’s gas mileage is indirectly proportional to its size Reciprocal Relationships • A type of inverse relationship • When two numbers are multiplied together the result is one. (1) Reciprocal Relationships • When one increases the other proportionally decreases. • Examples of reciprocals: • 2 and ½ are reciprocals • 1 and 1/10th are reciprocals • 1/100,000th and 100,000 are reciprocals Reciprocals cont. • Reciprocal relationships: if one factor changes the other changes proportionally So… If factor A is doubled, factor B will be halved If factor A is tripled, factor B will be 1/3 what it was If factor B is quartered, factor A will quadruple Let’s Practice • Factor A and B are reciprocals. Factor A increases 8 times. What happens to factor B? • Factors C and D are reciprocals. Factor D is doubled. What will happen to factor C? Units and Presentation • All numerical values must have units • Units give the numerical value meaning. • Example: • You state that you are 6 tall. • You must give a unit to define 6 “what?” tall • You could be stating that you are six inches tall or six feet, six miles etc. Units and Presentation • Unless a number is a percentage or it is directly stated that it is a “unitless” number, you MUST use units to define your number. • You can use any unit that is technically correct. • You can measure a mile in inches, you wouldn’t usually, but it would still be technically correct. 1 mile=63,360 inches Scientific Notation • Scientific notation is used to define the numbers of a measurement that are in each unit. • Very large or very small numbers are often expressed in scientific notation. • This is a shorthand way to express these numbers. • Example: • 0.000000124 =1.24 x 10-7 • 1,000,000 = 1.0 x 106 • Count the zeros! • You can use scientific notation in converting units but there is an easier Using the Metric System • In science, we use the metric system to express measurements. • For Ultrasound and specifically for the physics registry, we MUST understand how to convert numbers within the metric system. Using the Metric System Mega (M) 106 = 1,000,000 kilo (k) 103 = 1,000 hecto (h) 102 = 100 deka (da) 101 = 10 no prefix 100 deci (d) 10-1 = 0.1 centi (c) 10-2 = 0.01 milli (m) 10-3 = 0.001 micro (µ) 10-6 = 0.000,001 Metric Units & Converting • To remember the prefixes in order, you can use the following sentence: • King Henry Doesn't [Usually] Drink Chocolate Milk • kilo- hecto- deka- [unit] deci- centimilli• Unit is meters, Hertz, Grams, Liters etc. Converting with Metrics (the easy way) • Create a number line. M k h da d c m m 6_5 _4 _ 3_ 2_ 1_ 0 _-1 _-2 _-3 _ -4_-5_ -6 • Figure out how many spaces are between the prefix that you have and the prefix that you need. Converting with Metrics • • • • 8 m = ___ mm m = 100 mm= 10-3 Ask how many spaces are between meters (100) and mm (10-3) M k h da d c m m 6_5 _4 _ 3_ 2_ 1_ 0 _-1 _-2 _-3 _ -4_-5_ -6 • 3 spaces  • our number is going to be moving towards the smaller prefixes. So we move the decimal to the right. Converting with Metrics • 5000 mHz = ___ kHz • mHz = 10-3 • kHz = 103 M k h da d c m m 6_5 _4 _ 3_ 2_ 1_ 0 _-1 _-2 _-3 _ -4_-5_ -6 • • • • • • 6 spaces between the mHz and kHz We are going to a larger prefix so we move to the left! 5000.  0.0.0.5.0.0.0. 0.005 km in 5000 mm Converting with Metrics • 0.003 km = ___ cm • km= 103 • cm= 10-2 M k h da d c m m 6_5 _4 _ 3_ 2_ 1_ 0 _-1 _-2 _-3 _ -4_-5_ -6 • 5 spaces between km and cm • we are going to a smaller prefix so we move to the right •  • move the decimal point 5 spaces to the right • 0.0.0.3.0.0. • 300 cm • 0.003 km = 300 cm • Lets practice a few of these! • 5000 cL = _____________ L • 8 cm = ____________ mm • 0.002 m = ____________mm • 0.05 ks = ____________ s • 70000 cHz = ____________ MHz  Did you get them all? 5000 cL = 50 L  8 cm = 80 mm  0.002 m = 2 mm  0.05 ks = 50 s  70000 cHz = 0.0007 MHz 