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Digital Radiography 101 or How to be a Digital Radiography Expert in 1 Easy Lesson By Walter Golub, DMD.

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Presentation on theme: "Digital Radiography 101 or How to be a Digital Radiography Expert in 1 Easy Lesson By Walter Golub, DMD."— Presentation transcript:

1 Digital Radiography 101 or How to be a Digital Radiography Expert in 1 Easy Lesson By Walter Golub, DMD

2 About This Course This course is not intended to sell you on the idea of going digital. This course is not intended to sell you on the idea of going digital. Claims being made can be confusing, if not misleading. This course will help the clinician understand how the technology works.

3 A Brief History Late 1980’s – the first sensors Late 1980’s – the first sensors Very large Very large Used TV – not computer Used TV – not computer No way to store or manipulate the images electronically. No way to store or manipulate the images electronically. Very expensive Very expensive Mid 1990s’s – the next generation Multiple size sensors (more like film) Multiple size sensors (more like film) Personal computer became affordable Personal computer became affordable Sensor prices became affordable Sensor prices became affordableToday Many different systems Many different systems Technology is proven Technology is proven How do you choose? How do you choose?

4 2 Kinds of Digital Radiography Phosphor Plates – ‘just like film’ in many regards, except more time consuming and more expensive. Research shows phosphor plates need to be replaced after as few as 50 uses* – making it far more expensive. Research shows phosphor plates need to be replaced after as few as 50 uses* – making it far more expensive. This technology is not covered in this course This technology is not covered in this course Direct Sensors This is the technology that I recommend. This is the technology that I recommend. Citation: Bedard A, Davis TD, Angelopoulos C. Storage Phosphor Plates: How Durable are they as a Digital Dental Radiographic System? J Contemp Dent Pract 2004 May;(5)2:

5 Digital System Basics Every Digital Radiography System Consists of these 6 components: X-ray Source X-ray Source Sensor Sensor Interface Interface Computer Computer Monitor Monitor Software Software

6 Digital System Basics Interface Monitor Personal Computer Software X-ray Source Sensor

7 Notes On Image Quality The sensor is the single most important component in regards to image quality. The monitor is the second most important. Software cannot compensate for a poor raw image (the image created by the sensor) – Garbage in = Garbage Out

8 Sensor Design Basics The DETECTOR reads the image and converts it to a digital output. The FIBEROPTIC PLATE guides light onto the detector. The SCINTILLATOR converts x-ray energy to light energy. These components, all fit into a metal or plastic enclosure, sometimes referred to as the CAN. The CABLE enters the can where many hair- like wires are attached to the detector. The STRAIN RELIEF is a critical component. Most failures occur at where the cable enters the can.

9 The Scintillator digital radiography sensors are not sensitive to x-rays The detectors in digital radiography sensors are not sensitive to x-rays, they are sensitive to visible light. The SCINTILLATOR converts x-ray energy to light energy. When x-rays pass through a SCINTILLATOR, it emits a glow of visible light. The more or less radiation – the brighter or dimmer the glow. This converts the x-ray pattern of the radiograph into a pattern of visible light. scintillator

10 The Fiberoptic Plate The FIBEROPTIC PLATE (F.O.P.) serves 3 very important functions It protects the detector (CCD or CMOS) from being damaged by the high energy x- rays It prevents the detector (CCD or CMOS) from reading the x-ray energy as light (and therefore interpreting it as image data) 3 3. It takes the image created by the scintillator and focuses it on the detector, keeping the image sharp and coherent. F.O.P.

11 Radiation passes through the sensor The scintillator glows (in all directions). The brightness of a given spot is in proportion to the x-ray energy that hits it. The FOP guides the light from the scintillator down to the pixel.

12 The Fiberoptic Plate Sensors without a Fiber Optic Plate can be made much thinner, but they lack all of the advantages that the FOP provides: 1. 1.Protection of the detector from damaging x-rays 2. 2.Protection from false image data caused by x-rays being ‘read’ by the detector The focused transmission of the scintillator image onto the pixels.

13 The Detector (CCD or CMOS) CCD and CMOS refer to either the design (CCD) or the material (CMOS) of the detector. Several years ago – CCD were considered a superior detector, now CMOS is considered equal, if not better. Either technology is capable of producing excellent image quality. There is only ONE significant advantage of one over the other – CMOS requires very little power compared to CCD. This means CMOS systems generally have smaller interfaces and/or more flexible installation options (i.e. no external power needed) This means CMOS systems generally have smaller interfaces and/or more flexible installation options (i.e. no external power needed) Detector TYPE is not important

14 How the Detector Creates an Image The Original Image

15 How the Detector Creates an Image The scintillator glows in proportion to the radiation that hits it. This creates a pattern of bright and dim pixels. This light intensity is measured by each pixel, based upon the level of light/dark the pixel ‘sees’. It converts that quantity into a number. For purposes of this example we’ll use the numbers from 1 to 9.

16 How the Detector Creates an Image Here is the pixel value map without the original image overlaid. Each of the pixel values is then sent to the computer. Since the computer ‘knows’ the location of each pixel…

17 How the Detector Creates an Image It is a simple matter to reconstruct the pixel value data into a similar size grid. The jagged effect is caused when the pixel lies along a transition in density. This effect is called ‘pixelization’ This image may not look very good, but you have to consider the scale involved…

18 So you can begin to realize how excellent these sensors are… This square would be far less than a millimeter across… <1 mm How the Detector Creates an Image At resolving extremely minute details… If this image were taken by a good digital sensor… As small as 8/100th of a mm…

19 Specifications and Sensor Image Quality Spatial Resolution aka ‘line pairs per millimeter’ (lp/mm) How ‘small’ the sensor can see How ‘small’ the sensor can see Signal to Noise Ratio (SNR) The amount of ‘pure’ data (signal) vs. the amount of ‘false’ data (noise) The amount of ‘pure’ data (signal) vs. the amount of ‘false’ data (noise) Dynamic Range The ability of the system to accurately reproduce both very light and very dark objects in the same image. The ability of the system to accurately reproduce both very light and very dark objects in the same image.Contrast How well does the sensor differentiate 2 adjacent areas of subtly different densities How well does the sensor differentiate 2 adjacent areas of subtly different densities

20 Spatial Resolution aka ‘Line Pairs’ 22 or 23 lp/mm = must be a ‘theoretical value’ 12.5 lp/mm = the ability to see an Item of 0.04 mm diameter This is a radiograph of a ‘line pair’ phantom. Each pair of converging lines (1 light/1 dark) equals one ‘line pair’. Ask a sales rep to create a 20+ lp/mm image in your office. THEY CAN’T Many companies use this specification to ‘prove’ image quality.

21 Spatial Resolution aka ‘Line Pairs’ Why so much confusion about this specification? It’s easy to ‘visualize’. Companies that promote this specification use it to convince a doctor of image quality without taking a single live image in their office. Companies that promote this specification use it to convince a doctor of image quality without taking a single live image in their office. Why doesn’t lp/mm work as an indicator of image quality? Increasing spatial resolution is easy: use lots and lots of very small pixels use lots and lots of very small pixels The problem: a small pixel generates more noise than a larger pixel a small pixel generates more noise than a larger pixel lots and lots of small pixels = lots and lots of NOISE lots and lots of small pixels = lots and lots of NOISE

22 Spatial Resolution aka ‘Line Pairs’ A very misleading specification. FACT – ‘High resolution’ sensors (20+ lp/mm) have inherently more noise. This is a physical attribute of small pixels that cannot be avoided. Noise hurts image quality. FACT - ‘High resolution’ sensors require more radiation to get good images – due to the increased in noise they generate. FACT – 12.5 lp/mm sensors can resolve to 0.04mm. How small do you need to see? FACT - The difference between the resolving power of 20 lp/mm and 12.5 lp/mm is negligible – mm.

23 FACTS About High Line Pair/mm ‘Mega Pixel’ Sensors. This article details the reasons why small pixel, ‘Mega-Pixel’ imagers are not ideal for medical applications. The following slides contain excerpts from this important article.

24 FACTS About High Line Pair/mm ‘Mega Pixel’ Sensors. 1.…the consumer market has produced a new generation of mega- pixel CCDs. But even with more than a million pixels, these devices have small physical pixels areas that…have drawbacks for more demanding industrial, scientific, and medical applications. Here, larger pixel areas are better. 2.Responsivity is a measure of the signal that each pixel can produce and is directly proportional to pixel area. As responsivity increases, the same amount of signal can be collected in a shorter period of time. Or…more signal can be realized during a fixed exposure time. Article Excerpts:

25 FACTS About High Line Pair/mm ‘Mega Pixel’ Sensors. 3.Another benefit of increased responsivity is… the image will have a higher signal/noise ratio and appear less grainy. 4.Pixel [size] also affects the dynamic range of the [system]. Each pixel is like a well that stores up [data] before it is read out. The larger the pixel area, the larger the [data] capacity, and the higher the signal level. 5.…dynamic range allows areas of high brightness and low brightness to be seen clearly and simultaneously… [and] thus easily distinguish objects in shadows. It is also easier to discern variations in dark or shadowed areas of an image, such as in digital x-ray images. Article Excerpts:

26 What does this mean to you? A sensor designed to be ‘high resolution’, compromises in these equally important areas of image quality: Signal to Noise Signal to Noise Dynamic Range Dynamic Range Contrast Contrast As well as the ability to take a high quality, very-low-dose image. As well as the ability to take a high quality, very-low-dose image.

27 Signal to Noise Ratio ‘Noise’ can be defined as any image data that is not 100% accurate. By contrast, ‘signal’ is image data that accurately represents the image. ‘Noise’ makes the image look grainy

28 Signal to Noise Ratio ‘FACT: High lp/mm sensors have poorer signal to noise ratio due to their small pixel size. This results in GRAINIER IMAGES The noise created by smaller pixels most likely eliminates any advantage created by the increase in spatial resolution.

29 Signal to Noise Ratio Most digital radiography systems offer a wide range of noise filtering software as part of their tool set. These ‘filters’ can not compensate for poor original image data coming from the pixels on the sensor. These ‘filters’ can not compensate for poor original image data coming from the pixels on the sensor. Many of these filter actually create artifacts of their own. Many of these filter actually create artifacts of their own. GIGO = Garbage in, Garbage out. GIGO = Garbage in, Garbage out. For this reason - when evaluating/comparing digital systems – it important to make sure any software filters are turned OFF.

30 Signal to Noise Ratio Here is an image with no ‘enhancements’ or software filters. Note how easy it is to see distinct line pairs all the way to the bottom of the image.

31 Signal to Noise Ratio Here is a close-up of the same image with the software filter enhancements turned ‘ON’ Note how much worse the lp/mm rating becomes.

32 Always evaluate image quality with ALL software filters ‘OFF’

33 Dynamic Range and Contrast They are not exactly the same thing… Dynamic Range refers to the amount of different grays that the pixel can generate. This is important. Dynamic Range refers to the amount of different grays that the pixel can generate. This is important. Contrast refers to how well light and dark objects are differentiated on the computer screen. Contrast refers to how well light and dark objects are differentiated on the computer screen. Contrast can be manipulated by software – Dynamic range is an inherent function of the sensor and cannot be manipulated. ….but they are directly related. The more levels of gray you start with (dynamic range) the more flexibility you have when fine tuning your contrast. The more levels of gray you start with (dynamic range) the more flexibility you have when fine tuning your contrast. Contrast adjustments can reveal many details not immediately seen.

34 Dynamic Range and Contrast Dynamic range is expressed in ‘bits’ 8 bit = 256 levels of gray 8 bit = 256 levels of gray 10 bit = 1024 levels of gray 10 bit = 1024 levels of gray 12 bit = 4096 levels of gray 12 bit = 4096 levels of gray A common trick of manufacturers is to quote the dynamic range of the analog-to-digital converter (ADC) The ADC is the microchip that takes the pixel output and converts it to a digital signal). The ADC is the microchip that takes the pixel output and converts it to a digital signal). The ADC very often can support a MUCH higher dynamic range than the output of the sensor pixels. The ADC very often can support a MUCH higher dynamic range than the output of the sensor pixels. Though the high dynamic range of the ADC may sound impressive, it does absolutely zero for image quality if it the pixels cannot support it. Though the high dynamic range of the ADC may sound impressive, it does absolutely zero for image quality if it the pixels cannot support it. Larger Pixels = lower lp/mm = BETTER DYNAMIC RANGE

35 The Clinical Fact About High Line Pair/mm ‘Mega Pixel’ Sensors lp/mm sensor Exposure setting:.10 X-ray Head: Yoshida Kaycor X-70S (70 kvp/15ma) Same patient, same x-ray head, 2 new sensor systems… 22 lp/mm sensor Exposure setting:.15 (50% higher dose) X-ray Head: Yoshida Kaycor X-70S (70 kvp/15ma)

36 What have we learned about specifications? 1.They are confusing – and don’t always mean what you think they mean. 2.Some manufacturers use them to mislead potential buyers. 3.Don’t use them as a basis to judge image quality.

37 Part Three - How to Choose a System 1.Take some x-rays in your office BEFORE you make any commitment. 2.Only use the x-rays that YOU take to evaluate the system’s image quality. 3.Take a variety of images on a live volunteer.

38 Take some x-rays in your office BEFORE you make ANY commitment. Live images ensure the system will work with your existing equipment x-ray heads. A sales rep or experienced user should be present show you how to operate the system. A sales rep or experienced user should be present show you how to operate the system.

39 Only use the x-rays that YOU take to evaluate the system’s image quality. All companies have a set of ‘perfect images’ they use during sales presentations. These are not ‘typical clinical images’ These are not ‘typical clinical images’ The history of these images is unknown. The history of these images is unknown. Exposure setting? Exposure setting? What type x-ray head? What type x-ray head? Cadaver or live patient? Cadaver or live patient? Modified? Modified?

40 Take a variety of images on a live volunteer. This is critical. By actually taking images on yourself or a staff member, you’ll answer questions you may not even know to ask; Can it take vertical bitewings? Can it take vertical bitewings? Is the sensor to big/small? Is the sensor to big/small? Do the positioners work? Do the positioners work? Is it comfortable? Is it comfortable? Is there some other operating ‘issue’ – such as a remote button to push – that is unwieldy? Is there some other operating ‘issue’ – such as a remote button to push – that is unwieldy?

41 Evaluating Digital Systems – Image Quality Resize all images to fill the screen before evaluation. This is how you’ll most often view. This is how you’ll most often view. Some systems have the original image come up very small. This can hide image defects. Some systems have the original image come up very small. This can hide image defects. No enhancements Turn off all software filters. They can make a poor image look good at first glance. Turn off all software filters. They can make a poor image look good at first glance. Diagnostic quality is only as good as the original, raw image. Diagnostic quality is only as good as the original, raw image. Check Exposure Settings Ensure images to be evaluated are properly exposed. Ensure images to be evaluated are properly exposed. Check the exposure setting; it should be much lower than what you now use for film. Check the exposure setting; it should be much lower than what you now use for film.

42 Evaluating Digital Systems – Usability Vertical Bitewings Not all systems can take a vertical bitewing. If this is important to you, make sure you try taking some during the live demo. Not all systems can take a vertical bitewing. If this is important to you, make sure you try taking some during the live demo.Bitewings The most common intraoral image. The most common intraoral image. How many teeth are captured with each image? Are you getting as many with the size 2 sensor as you would with size 2 film? How many teeth are captured with each image? Are you getting as many with the size 2 sensor as you would with size 2 film?Pediatric Does the system have a solution for small mouths? Does the system have a solution for small mouths?

43 Evaluating Digital Systems – Software Auto-template Advance When taking multiple images (e.g. FMX series) you shouldn’t have to reset the system – keystroke, button, etc - in any way between images. When taking multiple images (e.g. FMX series) you shouldn’t have to reset the system – keystroke, button, etc - in any way between images.Retakes This common task should be automated so it’s quick and easy. This common task should be automated so it’s quick and easy.Auto-save Each image should be saved immediately and automatically upon acquisition. Individual saving of each image is tedious and may lead to accidentally deleted images Each image should be saved immediately and automatically upon acquisition. Individual saving of each image is tedious and may lead to accidentally deleted images

44 Evaluating Digital Systems – Software Image file type All images should be saved in a non-proprietary file format, without the need for conversion. This allows you great flexibility for sharing and future expansion. All images should be saved in a non-proprietary file format, without the need for conversion. This allows you great flexibility for sharing and future expansion. Viewable image size upon capture Does the image appear in full screen mode automatically? Does the image appear in full screen mode automatically? This is esp. valuable when taking more than one image – it allows the operator to quickly check positioning/exposure/etc. from across the room if needed. This is esp. valuable when taking more than one image – it allows the operator to quickly check positioning/exposure/etc. from across the room if needed.

45 Evaluating Digital Systems – Warranty Compare all costs for at least 5 years, assuming 2 sensor replacements per year What is covered? What is the companies policy on accidental damage? What is the companies policy on accidental damage? Replacement cost What are the costs associated with sensors under the ongoing service plan (the post-warranty period)? What are the costs associated with sensors under the ongoing service plan (the post-warranty period)? Replacement turnaround time. What is the quoted turnaround time on replacements? What is the quoted turnaround time on replacements? Is this guaranteed? Is this guaranteed? Can it be confirmed by referrals? Can it be confirmed by referrals?

46 Evaluating Digital Systems – Service 800# Tech Support Call during the demo. How long does it take to get a tech on the line? Call during the demo. How long does it take to get a tech on the line? Local Installer/ Service Technician Who is it and where are they located? Who is it and where are they located? Are they a direct employee of the company selling the sensor? Are they a direct employee of the company selling the sensor? What is the typical wait time for a service call? Can it be verified by referral? What is the typical wait time for a service call? Can it be verified by referral? Routine Visits Will a representative of the company be willing and able to visit your office regularly, after the sale is complete, if desired? Will a representative of the company be willing and able to visit your office regularly, after the sale is complete, if desired? What if you’re not happy with the sale? Does the company have any satisfaction guarantee in writing? Does the company have any satisfaction guarantee in writing? What is the return policy if you are not satisfied? What is the return policy if you are not satisfied?

47 Evaluating Digital Systems – References Are they local? How long have they had the system? What do they like/dislike about the system?

48 Evaluating Digital Systems – Price “Cheap things are seldom good, and good things are seldom cheap” – Zig Ziglar No other dental technology saves you money – by eliminating films – at the same time it makes you money – by increasing productivity. Digital radiography is a no lose financial proposition, assuming: You buy everything you need to go film-less You buy everything you need to go film-less Don’t cut corners – spend a little more to get high quality equipment/service Don’t cut corners – spend a little more to get high quality equipment/service Use it everyday, on every patient Use it everyday, on every patient

49 Evaluating Digital Systems – Price How much can you afford to spend? Step 1 - Take what you spent on film, processing chemicals, processor maintenance last year. Step 2 - Multiply the number of films you took last year and increase your fee by $1 each. Step 3 - Add the above two $ numbers together and divide by 12. You now have the amount you can spend on a monthly lease payment, without costing you a penny more than what you already are spending!

50 Why Go Digital? Efficiency Patient Communication ALARA Reduction of overhead Practice Marketing/New Patient referrals Consistency

51 Downloads Download a checklist that outlines the digital radiography evaluation process covered in this presentation. Click here Click here Download other documents referenced in this presentation from the internet. UMKC study – Durability of Phosphor Plates UMKC study – Durability of Phosphor Plateshttp://www.thejcdp.com/issue018/index.htm Optoelectronics World – The Need for Large Pixels Optoelectronics World – The Need for Large Pixelshttp://www.kodak.com/US/en/digital/pdf/largePixels.pdf Dr. AG Farman - Digital Radiography ’04 Dr. AG Farman - Digital Radiography ’04http://www.aadmrt.com/static.aspx?content=currents/farman_spring_04

52 About the Author Walter Golub, DMD 1962Rutgers University 1966 Tufts University School of Dental Medicine US Air Force Active Duty Full-time Faculty -Tufts Private Practice of Dentistry (3 locations) Co-Developer of the Victor Voice Chart; Discus Dental Software-National Sales Mgr present Schick Technologies Director of Clinical Affairs Dr. Golub has traversed the dental landscape. His career includes teaching, private practice, software development, writer and lecturer. In his younger days, he was heavily involved in rugby both playing and coaching, and he has served as a small town school board member and a justice of the peace. He is not licensed to perform marriages in Canada.


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