Ch 01 Basic Concepts of Medical Instrumentation. 1.1 Terminology of Medicine and Medical Devices.

Ch 01 Basic Concepts of Medical Instrumentation

1.1 Terminology of Medicine and Medical Devices

1.2 Generalized Medical Instrumentation System

Figure 1.1 Generalized instrumentation system The sensor converts energy or information from the measurand to another form (usually electric). This signal is the processed and displayed so that humans can perceive the information. Elements and connections shown by dashed lines are optional for some applications.

Measurand AccessibilityInternal On body surface Emanate from the body Derived from a tissue sample CategoriesBiopotential Pressure Flow Dimension Imaging Displacement (velocity, acceleration, force) Impedance Temperature Chemical concentration

1.3 Alternative Operational Modes

1.4 Medical Measurement Constraints

Ballistic = Gastric = Antimony = Sb,

galvanic skin response definition Function: n : a change in the electrical resistance of the skin that is a physiochemical response to emotional arousal which increases sympathetic nervous system activity abbreviation GSRnervous systemabbreviation Merriam-Webster's Medical Dictionary, 2007 Merriam-Webster, Inc. Source: Dictionary.com, "galvanic skin response," in Merriam-Webster's Medical Dictionary. Source location: Merriam- Webster, Inc. http://dictionary.reference.com/browse/galvanic skin response. Available: http://dictionary.reference.com. Accessed: February 23, 2011.http://dictionary.reference.com/browse/galvanic skin response http://dictionary.reference.com

pneumo- or pneum- pref. 1. Air; gas: pneumothorax . 2. Lung; pulmonary: pneumoconiosis . 3. Respiration: pneumography a. . b. . c. X . Pneumotachography . 4. Pneumonia: pneumococcus ,

To cope variability use assume empirical statistical and probabilistic distribution functions Variability of measured quantities: with time, among patients, anatomocal, interactions among physiological systems, feedback loops, internal variability (at molecular and organ levels),

1.5 Classification of Biomedical Instruments According to what?Examples Quality that is sensedPressure, flow, temperature TransductionResistive, inductive, capacitive, ultrasonic, electrochemical Organ systemCardiovascular, pulmonary, nervous, endocrine Clinical medicine specialtiesPediatrics, obstetrics, cardiology, radiology Different classifications:

1.6 Interfering and Modifying Inputs

1.7 Compensation Techniques

1.8 Biostatistics

1.9 Generalized Static Characteristics

1.10 Generalized Dynamic Characteristics

1.11 Design Criteria

Figure 1.8 Design process for medical instruments Choice and design of instruments are affected by signal factors, and also by environmental, medical, and economic factors. (Revised from Transducers for Biomedical Measurements: Application and Design, by R. S. C. Cobbold. Copyright 1974, John Wiley and Sons, Inc. Used by permission of John Wiley and Sons, Inc.) BMD = (Bone Mineral Density) ?

1.12 Commercial Medical Instrumentation Development Process

1.13 Regulation of Medical Devices

Classification of Medical Devices (Taiwan) 13 2

Categories of Medical Devices (Taiwan) 3 (Clinical chemistry and toxicology devices) (Hematology and pathology devices) (immunology and microbiology devices) (Anesthesiology devices) (Cardiovascular devices) (Dental devices) (Ear, nose, and throat devices) (Gastroenterology-Urology devices) (General and plastic surgery) (General hospital and personal use devices) (Neurological devices) (Obstetrical and gynecological devices) (Ophthalmic devices) (Orthopedic devices) (Physical medicine devices) (Radiology devices) (Other categories specified by the Central Competent Health Authority)

FDA Classification (USA) FD&C Act 513 Class I 27% FDA FDA GMP FDA Class II Class III Class II (Special Controls) FDA 60% FDA (mandatory performance standards) Class III Class III 8% FDA PMA Source:

1930sFederal Food, Drug, and Cosmetics Act May 28, 1976Medical Device AmendmentsClasses I, II, III 7 Categories 1990Safe Medical Devices ActFurther amendments

Medical Device definition by FDA [Source: Wikipedia] Definition in USA by the Food and Drug Administration Medical Device Definition A device is: "an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component part, or accessory which is: - recognized in the official National Formulary, or the United States Pharmacopoeia, or any supplement to them, -intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, or - intended to affect the structure or any function of the body of man or other animals, and which does not achieve any of it's primary intended purposes through chemical action within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of any of its primary intended purposes.

Medical Device (defined by FDA) [Source FDA website] Medical Device Definition Medical devices range from simple tongue depressors and bedpans to complex programmable pacemakers with micro-chip technology and laser surgical devices. In addition, medical devices include in vitro diagnostic products, such as general purpose lab equipment, reagents, and test kits, which may include monoclonal antibody technology. Certain electronic radiation emitting products 3 with medical application and claims meet the definition of medical device. Examples include diagnostic ultrasound products, x-ray machines and medical lasers. If a product is labeled, promoted or used in a manner that meets the following definition in section 201(h) of the Federal Food Drug & Cosmetic (FD&C) Act it will be regulated by the Food and Drug Administration (FDA) 4 as a medical device and is subject to premarketing and postmarketing regulatory controls.radiation emitting productsFood and Drug Administration (FDA)

Medical Device (defined by FDA) [Source FDA website] Medical Device Definition A device is: "an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including a component part, or accessory which is: recognized in the official National Formulary, or the United States Pharmacopoeia, or any supplement to them, intended for use in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease, in man or other animals, or intended to affect the structure or any function of the body of man or other animals, and which does not achieve any of it's primary intended purposes through chemical action within or on the body of man or other animals and which is not dependent upon being metabolized for the achievement of any of its primary intended purposes." This definition provides a clear distinction between a medical device and other FDA regulated products such as drugs. If the primary intended use of the product is achieved through chemical action or by being metabolized by the body, the product is usually a drug. Human drugs are regulated by FDAs Center for Drug Evaluation and Research 5 (CDER). Biological products which include blood and blood products, and blood banking equipment are regulated by FDAs Center for Biologics Evaluation and Research 6 (CBER). FDAs Center for Veterinary Medicine 7 (CVM) regulates products used with animals. If your product is not a medical device but regulated by another Center in the FDA, each component of the FDA has an office to assist with questions about the products they regulate. In cases where it is not clear whether a product is a medical device there are procedures in place to use DSMICA Staff Directory 8 to assist you in making a determination.Center for Drug Evaluation and ResearchCenter for Biologics Evaluation and ResearchCenter for Veterinary MedicineDSMICA Staff Directory

FDA Classification [Source: Wikipedia] United States The Food and Drug Administration has recognized three classes of medical devices based on the level of control necessary to assure the safety and effectiveness of the device. [7] The classification procedures are described in the Code of Federal Regulations, Title 21, part 860 (usually known as 21 CFR 860). [8] [7]Code of Federal Regulations [8] Class I: General controls Class I devices are subject to the least regulatory control. Class I devices are subject to General Controls as are Class II and Class III devices. General controls include provisions that relate to adulteration; misbranding; device registration and listing; premarket notification; banned devices; notification, including repair, replacement, or refund; records and reports; restricted devices; and good manufacturing practices. Class I devices are not intended for use in supporting or sustaining life or to be of substantial importance in preventing impairment to human health, and they may not present a potential unreasonable risk of illness or injury. Most Class I devices are exempt from the premarket notification and/or good manufacturing practices regulation. Examples of Class I devices include elastic bandages, examination gloves, and hand-held surgical instruments.

FDA Classification (cont.) [Source: Wikipedia] Class II: General controls with special controls Class II devices are those for which general controls alone are insufficient to assure safety and effectiveness, and existing methods are available to provide such assurances. In addition to complying with general controls, Class II devices are also subject to special controls. [9] A few Class II devices are exempt from the premarket notification. [9] Special controls may include special labeling requirements, mandatory performance standards and postmarket surveillance. [9] [9] Devices in Class II are held to a higher level of assurance than Class I devices, and are designed to perform as indicated without causing injury or harm to patient or user. Examples of Class II devices include powered wheelchairs, infusion pumps, and surgical drapes. [7][9] [7][9] Class III: general controls and premarket approval A Class III device is one for which insufficient information exists to assure safety and effectiveness solely through the general or special controls sufficient for Class I or Class II devices. [7][9] [7][9] Such a device needs premarket approval, a scientific review to ensure the device's safety and effectiveness, in addition to the general controls of Class I. [7][9] [7][9] Class III devices are usually those that support or sustain human life, are of substantial importance in preventing impairment of human health, or which present a potential, unreasonable risk of illness or injury. [9] [9] Examples of Class III devices which currently require a premarket notification include implantable pacemaker, pulse generators, HIV diagnostic tests, automated external defibrillators, and endosseous (placed or contained within a bone) implants. [9] [9]

FDA Medical Device Categories

FDA Medical Device Categories (cont.)

Category: Preamendment devices

Category: Postamendment devices Fetoprotein ; radioimmunoassay (RIA) Radioimmunoassay (RIA), an in vitro nuclear medicine, is a very sensitive technique used to measure concentrations of antigens (for example, hormone levels in the blood) by use of antibodies. (Source: Wikipedia)in vitronuclear medicine antigenshormoneblood Extracorporeal shock wave lithotripsy (ESWL) is the non-invasive treatment of kidney stones (urinary calculosis) and biliary calculi (stones in the gallbladder or in the liver) using an acoustic pulse. (Source: Wikipedia)non-invasivekidney stones biliary calculigallbladderliver

Category: Substantially equivalent devices Tampon , ; ELISA (Enzyme-linked immunosorbent assay) ;

Category: Implanted devices Phrenic

Category: Custom devices

Category: Investigational devices

Category: Transitional devices Transitional ; Gonorrhea ; heterograft An intraocular lens (IOL) is an implanted lens in the eye, usually replacing the existing crystalline lens because it has been clouded over by a cataract, or as a form of refractive surgery to change the eyes optical power. [Source: Wikipedia]lenseyecrystalline lenscataractrefractive surgeryoptical power

From 3 rd Edition

Figure 1.2 Simplified electrocardiographic recording system Two possible interfering inputs are stray magnetic fields and capacitively coupled noise. Orientation of patient cables and changes in electrode-skin impedance are two possible modifying inputs. Z 1 and Z 2 represent the electrode-skin interface impedances. Electrodes 60-Hz ac magnetic field Displacement currents Differential amplifier + +V cc - V cc Z1Z1 Z body Z2Z2 vovo v ecg

(x d H f y)G d = y(1.1) x d G d = y(1 + H f G d )(1.2) (1.3) (1.4) (1.8) (1.7) (1.6) (1.5)

Figure 1.3 (a) Static-sensitivity curve that relates desired input x d to output y. Static sensitivity may be constant for only a limited range of inputs. (b) Static sensitivity: zero drift and sensitivity drift. Dotted lines indicate that zero drift and sensitivity drift can be negative. [Part (b) modified from Measurement Systems: Application and Design, by E. O. Doebelin. Copyright 1990 by McGraw-Hill, Inc. Used with permission of McGraw-Hill Book Co.] Intercept b xdxd y x' d y' y (Output) y = mx d + b x d (Input) (a) Slope m = yy xdxd Total error due to drift Characteristic with zero and sensitivity drift + Zero drift + Sensitivity drift Sensitivity drift Zero drift (b) y (Output) x d (Input)

(1.11) (1.9) (1.10)

Figure 1.4 (a) Basic definition of linearity for a system or element. The same linear system or element is shown four times for different inputs. (b) A graphical illustration of independent nonlinearity equals A% of the reading, or B% of full scale, whichever is greater (that is, whichever permits the larger error). [Part (b) modified from Measurement Systems: Application and Design, by E. O. Doebelin. Copyright 1990 by McGraw-Hill, Inc. Used with permission of McGraw-Hill Book Co.] x d (Input) B% of full scale A% of reading Overall tolerance band Least-squares straight line (a) (b) Point at which A% of reading = B% of full scale y (Output) x1x1 (x 1 + y 2 ) y1y1 x2x2 Kx 1 Ky 1 y2y2 Linear system Linear system Linear system Linear system and (y 1 + y 2 )

(1.12) (1.13) (1.14) (1.15) (1.16) (1.17)

Figure 1.5 (a) A linear potentiometer, an example of a zero-order system. (b) Linear static characteristic for this system. (c) Step response is proportional to input. (d) Sinusoidal frequency response is constant with zero phase shift.

(1.18) (1.19)

Figure 1.6 (a) A low-pass RC filter, an example of a first- order instrument. (b) Static sensitivity for constant inputs. (c) Step response for larger time constants ( L ) and small time constants ( S ). (d) Sinusoidal frequency response for large and small time constants. t 1 (c) (a) C + + y(t)y(t) Output y(t) Input x(t) Slope =K = 1 (b) Y (j X (j Log scale 1.0 0.707 Log scale (d) 0 45 90 Log scale t 1 0.63 LL SS LL SS SS LL LL SS y(t)y(t) x(t)x(t) x(t)x(t) y(t)y(t) R

(1.20) (1.21) (1.22) (1.23) (1.24)

Figure 1.7 (a) Force-measuring spring scale, an example of a second-order instrument. (b) Static sensitivity. (c) Step response for overdamped case = 2, critically damped case = 1, underdamped case = 0.5. (d) Sinusoidal steady-state frequency response, = 2, = 1, = 0.5. [Part (a) modified from Measurement Systems: Application and Design, by E. O. Doebelin. Copyright 1990 by McGraw-Hill, Inc. Used with permission of McGraw-Hill Book Co.] Output displacement Outputy(t) (b)(a) (d)(c) 1 KsKs x(t)x(t) y(t)y(t) ynyn y n + 1 Resonance 2 Log scale 1 2 -90 0.5 1 2 -180 1 0.5 Log scale K 1 t t Input x(t) Slope K = 1 KsKs Input Force x(t) 0 00 nn nn Y (j X (j y(t)y(t)

where (1.25) (1.26) (1.27) (1.28)

Overdamped, Underdamped, Critically damped, (1.29) (1.30) (1.31) (1.32) (1.33) (1.34) (1.35)

and(1.36) (1.37) (1.38) (1.39) (1.40)

Ch 01 Basic Concepts of Medical Instrumentation. 1.1 Terminology of Medicine and Medical Devices.

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Transcript of Ch 01 Basic Concepts of Medical Instrumentation. 1.1 Terminology of Medicine and Medical Devices.