8_Dental_Radiography

Student’s Laboratory, Department of Biophysics 

I. Aim 

- radiographic image acquisition and processing 

- analog to digital image conversion 

- radiation doses 

II. Equipment 

- investigated tooth in chamber 

- laboratory X-ray tube 

- scanner 

- radioactivity monitor 

III. Problems 

- X-ray radiation, generation and properties 

- X-ray absorption, interaction of X-rays with matter, radiation doses 

- processing of radiographic film; sensitometer scale 

- analog to digital image conversion 

IV. References 

- P. Sprawls, Physical Principles of Medical Imaging, Med. Phys. Pub., Madison, 

1995, pp. 141-171 and 303-342 

Dental Radiography 1


V. Detailed instruction 

Exercise preparation. Set up a new folder on your private network drive (U). All files 

created during the exercise should be saved in this folder. Any files saved at different 

locations, will be deleted. 

Setting optimal time of exposition of the radiographic films. 

Properties of the radiographic film may be defined by using the sensitometer scale 

(dependence of the blackening of the film upon the exposition). Radiogram with the 

sensitometer scale for this lab was done in such a way: rectangle 1 (lightest) on the scale 

was irradiated with X-ray produced by the lamp with anode voltage 30 kVp, anode 

current 3 μA and the time of exposition 1s. Every next rectangle was irradiated using 

twice larger exposition (3, 6, 12, 24…and so on, in μAs). 

Turn on scanner Agfa SnapScan 1236u and apply program Scan Wise (see Section VI) 

for scanning one of the sensitometer scales. Apply resolution 300 dpi. Save file in BMP 

format in your folder. 

Use Pomiary program (see Section IX) to measure an average value of the grey-scale 

level in each of 21 rectangular areas of the sensitometer scale. Write the measured gray 

levels in the table. 

In Statistica program create the graph of the grey level dependence on exposition (apply 

the logarithm scale for exposition). Interpret the graph course. 

Decide which exposition should be most accurate to achieve the best contrast for 

recognizing differences in absorption (extinction) of radiation by the different regions of 

irradiated object. 

Taking under attention the fact, that the dentist's rtg plate (film) has the similar 

properties to the plate with sensitometer scale, count the optimal exposition as well as 

the optimal time of exposition for anodal current equal to 100 μA. These parameters 

you will apply for settlement of proper exposition times during collection of the tooth’s 

radiograms. 

Collection of radiographic pictures of tooth. 

Radiograms are prepared with laboratory X-ray lamp XR-100 powered with Eclipse II 

power supply (see Section VII). A special radiographic film SD-SPEEDX EXPOSURE 

CHART (see Section VIII) is applied. 

Place the box with a tooth in the openable chamber in column with the X-ray lamp. 

Since radiation is created by the laboratory XR-lamp in form of a narrow cylinder 

(about 2 cm of diameter), the tooth has to be located exactly in centre of the chamber. 

Turn on the power unit of the lamp and set the anodal current equal to 100 μA. 

Four radiograms have to be done using the different settings of anodal voltage and 

different times of exposition (emission of radiation must be turn on and off manually; 

check time of exposition with your clock or stopper): 

(1) anodal voltage equal to 30 kVp; time of exposition equal to calculated earlier optimal 

time of exposition; 

(2) anodal voltage equal to 30 kVp; time of exposition half of the calculated earlier 



optimal time of exposition; 

(3) anodal voltage equal to 20 kVp; time of exposition equal to calculated earlier optimal 

time of exposition; 

(4) anodal voltage equal to 20 kVp; time of exposition twice than calculated earlier optimal 

time of exposition. 

Before irradiating films you should inform the assistant about all calculated parameters of 

exposition. 

After performing the all expositions, films should be developed according to the instruction 

(see Section VIII) and rinsed (the least by two minutes) in current cold water. Then leave 

radiograms to full drying. 

Dried films should be scanned (see Section VI), the best with resolution of 600 dpi, and 

record on disc of your team. The examples of test radiograms are presented in the Fig. V. 1. 

Fig. V. 1. Example radiograms of tooth made with laboratory X-ray lamp for three different 

settings of exposition parameters (voltages and times of exposition). There are 

marked possible regions chosen for contrast determination. 

Analysis of all digital radiograms. 

In this part make the quantitative analysis of radiograms quality and check finally 

if the calculated parameters of exposition were chosen optimally. The quantitative analysis 

will be conducted by enumeration and comparison of the contrasts on all digital 

radiograms of the tooth. To establish differences in contrast of particular radiograms 

(Fig. V. 1.) we have to measure the average degree of the grey-scale level of the chosen 

darker region of the tooth in the picture (ID), the average degree of the grey-scale level of 

different, lighter region (background) of the tooth (IB) and calculate contrast (K) using 

equation [1]: 

I B I 

D K I 

[1] 

Measurements should be done for all radiograms always in the same areas of the tooth; 

the sizes of analysed surfaces should also be similar (e.g. 40 x 40 pixels). 

For execution measurements of the grey-scale levels use the Pomiary program (see 

Section IX). 

Make the report on the basis of the Radiography template. You 

can access the template on T: drive. Follow instruction in the 

template to prepare the Report. 

Dental Radiography 3 

B 

IB 

ID


VI. Manuals for Scanner Agfa SnapScan 1236u and ScanWise program 

Program ScanWise makes possible scanning documents, pictures, slides, radiograms 

and so on using of colourful scanner Agfa SnapScan 1236u installed in the system. 

After placing document in scanner close cover and start the program clicking twice 

ScanWise icon. On the screen appears the window of ScanWise program with previously 

scanned document visible (Fig. VI. 1.). 

1) Preliminary scanning. 

The first operation executes with scanner after achieving temperature of work is 

preliminary scanning (Preview) and displaying in window of preview the results. 

Dimensions and position of frame box in Preview image we can change with help of the 

left mouse's key, establishing what size we want to scan. Scanned area should contain all 

important for further work elements. After exchange of the document on a new one we 

should execute preliminary scanning always first, in this aim press the key Preview in the 

upper part of screen. 

Fig. VI. 1. The start window of the ScanWise program. 

2) The settlement of mode of work. 

Scanner makes possible scanning of pictures, paintings, text (mode "reflective”) as well as 

scanning of slides, negatives, X-ray films (mode ”transparent”). The mode of work is 

chosen in upper part of the window of program. 



3) Options of the program. 

Options of the program are grouped 

below key Preview in several groups: 

Oryginal Type, Destination, Image 

Control and Dimensions. The 

appearance of panel changes in 

dependence on choice of the option and 

shows second level options in the left 

side of screen (on the drawing it is 

showed for option Oryginal type 

opened). 

Fig. VI. 2. Details of the the ScanWise 

program main window: Options setting. 

4) The settlement of type of document to scanning. 

In dependence on what kind of document has to be scanned, scanner in different way 

optimizes its work. Option Oryginal Type permits to choose type of document what has to 

be scanned. In case of work in transparent mode to choice are only two types: Slide and 

Negative. For scanning X-ray films we choose option Slide. 

5) Place of destination of digital painting. 

Digital image is placed after scanning in memory of the computer. Its place of destination 

should be defined before scanning. Option Destination gives several possibilities of 

choice. During laboratory choose option of the recording images in files of BMP type on 

your disc, in aim of processing. To record image on disc in file we choose second level 

option File, unlocking dialogue little window, you should qualify: the name of file (File 

Name), the location (Path) and the type of file (File type). We record all files in team 

folder (!), under any name, and as type of file we choose Bitmaps file (“name".bmp). 

During scanning the next fragments of document or the next document, the program will 

use the same, chosen by us name adding the next numbers, and do it so long, until we do 

not change the name of target file. 

6) Matching quality of image. 

The option of Image Control makes possible matching with sliders quality of images: 

defining the clearness (brightness), the contrast (contrast), the saturation (saturation) and 

the threshold (threshold). Number and the kind of accessible options depends on kind of 

painting that we want to get. The type of painting (or the number of colours of painting) we 

choose using three keys: Color (the colourful painting), Grayscale (painting with using the 

grey-scale), LineArt (the black and white painting). In case of colourful paintings and in 

scale of greyness the additional filter is including also (option PhotoGenie). 

During scanning the sensitometer scale do not alter the value of clearness and the contrast, 

we do not use the additional filter also. We choose as type of the painting Grayscale. 

7) The settlement of size and the resolution of painting. 

The option Dimensions permits to choose the quality of painting across setting the 

resolution. This may be realised in different ways, establishing the linear dimensions of 

painting with known resolution or altering scale; we can change resolution also. The 

change of dimensions does not mark the change of sizes of area marked in field Preview, 



but the size of outcome digital painting creating by use of chosen resolution. The important 

information what displays program is the size of file created. We should always choose the 

compromise among size of file and his quality. For the sensitometer scale scanning we 

should choose resolution of 300 dpi. 

8) Scanning. 

To start scanning, after settlement of way of work scanner, the sizes of file, his approach 

the location and so on, click the large, red, round button with inscription Scan. 



VII. Manuals for the XR-100 laboratory X-ray tube and Eclipse II 

power supply. 

XR-100 X-ray tube is the laboratory device producing small intensity X-ray radiation. 

The tube is installed in the upper part of the aluminum box filled with the lead. The vertical 

position of the tube (its distance from the phantom) may be set with the knob. Phantom is 

placed in the central opened space. Below, inside the box the intensifying radiographic screen 

and the CCD camera for registration of the digital images are placed (Fig. VII.1.): 

Fig. VII.1. Experimental unit for angiographic and radiographic measurements 

with the power supply. 

Attention. High voltage power supply Eclipse II (Fig. VII.2.) is very easy for 

malfunctioning and it is strongly important to applied in details the 

manuals or asking assistant for help. 

Operation of the X-Ray tube XR-100 and high voltage power supply Eclipse II: 

1. Turning of the X-ray tube power supply ON and OFF should be done under supervising of 

the assistant. 

2. Turn ON the power supply with the Power switch (rear panel). 

The X-ray tube setting knob 

Upper aluminum box with internal 

lead core and X-ray tube XR-100 

inside 

Open space in the experimental unit 

for placing the investigated object 

Intensifying screen (inside the 

bottom box) 

CCD camera (inside the bottom 

box) 

Main power ON/OFF (in the rear 

panel of the power supply) 

Power supply Eclipse II 

3. Press and hold the button Preset and set the proper parameters U [kV] and I [μA] with 

knobs E and F respectively (Fig. VII.2.). 

4. Emission of the radiation begins after turning the Enable switch ON and lasts up to 

turning it OFF. 



Attention. If the yellow lamp Fault will light during the measurements turn 

the Enable switch OFF and ask the assistant. 

5. After finishing measurements turn the Power switch OFF (rear panel). 

A 

B C D E F 

Fig. VII.2. The front panel of the power supply Eclipse II: 

A – ON/OFF of the radiation emission (Enable); 

B – HV (High Voltage) - red lamp signaling the operation of the X-ray tube; 

C – Fault, alarm signal lamp for malfunction of the unit 

D – button for setting the power supply parameters (Preset); 

E – setting and display of the high voltage in the X-ray tube; 

F – setting and display of the current in the X-ray tube. 



VIII. Procession of the SD-SPEEDX EXPOSURE CHART 

Procession step-by-step (steps 4 to 8 must be done without any breaks): 



After washing (no less than 2 minutes) the developed film have to be fully 

dried before placing in the scanner for producing the digital version of the tooth 

radiogram. 



IX. Distance, area and grey-scale level measurements – 

Pomiary program 

The Pomiary program allows geometrical measurements on images saved in the BMP 

format. It is possible to measure: 

(1) distances, 

(2) areas of rectangular and elliptical structures, 

(3) an average value of the grey-scale level in rectangular and elliptical structures, 

(4) an area of any structure on binary image. 

Attention. To allow the distance measurement it is necessary to set the appropriate 

image resolution first (see point 6). 

In the cases of (1), (2) and (4) it is possible to choose one of four accessible units: 

millimeters, centimeters, inches or pixels. 

The program window is showed in Fig. IX.1. 

1 

2 

3 

4 

Fig. IX.1. The Pomiary program main window: 1 – main menu, 2 – toolbar, 3 – opened image 

window, 4 – status bar, 5 – measurement tools, 6 – image resolution panel, 7 – 

unit panel, 8 – shape panel (see text for details). 

Details of the application of the Pomiary program: 

1) Main menu bar. The main menu options open sub-menus. 

2) Toolbar. The buttons placed in the toolbar have the same function as the most important 

options in the main menu. 

Dental Radiography 11 

5 

6 

7 

8


3) Image window. It is possible to open more than one image at the same time. Management 

of all opened windows is performed with: the Okno (Window) option in the Main menu, 

or the three last buttons in the Toolbar. 

4) Status bar. There is an additional help displayed in the status bar when some window 

elements are pointed with the cursor. 

5) Measurement tools. 

area 

distance measurements 

measurements of the area of elliptical or rectangular regions 

measurements of the area of any shape on the binary image 

measurements of the average grey-scale level of a rectangular or elliptical 

remove the measurement results from the image (all) 

zoom out / zoom in 

The first step in all measurements is to mark a region or a distance, which will be 

measured. In order to define the line segment, click with the left mouse button the start point 

and pressing the mouse button drag to the segment end. The area can be defined in the same 

way but in this case an area diagonal is defined. 

6) Image resolution panel: Rozdzielczość (resolution). There are three edit boxes connected 

to the image resolution setting. The image resolution in Rozdzielczość edit box should be 

expressed in dpi units (dot per inch). The Rozdzielczość edit box can be used when the 

real image resolution is known. In that case the pxl edit box displays number of pixels 

within the unit distance (the unit can be defined in Jednostki panel - see point 7). 

Use the procedure described below to calculate the image resolution if the real image 

resolution is not known: 

a) Find the known distance on the image (e.g. a scale visible on the picture, total width of 

the radiogram film or any defined, given dimension), 

b) Check pixel unit in Jednostki panel, 

c) Measure the known distance using the pixel unit and remember (or mark in the 

picture) the result, 

d) Change the unit in Jednostki panel accordingly to your needs and put the result into 

the pxl edit box, 



e) Put the real measured distance expressed in chosen unit into the third, left edit box 

designed for the real distances in Rozdzielczość panel. It is labeled by the unit chosen 

in point d. 

7) Unit panel: Jednostki (units). The Jednostki panel allows a choice of units used for the 

measurement. It is possible to choose between millimeters, centimeters, inches and pixels. 

When the last option is checked (pixel) all distances will be expressed in image pixel unit. 

8) Shape panel: Kształt obszaru (area shape). In the case of area measurements it is 

necessary to define the area shape. The rectangular and elliptical shapes can be measured. 

Help in the program. Like most applications in MS Windows system the Pomiary 

program displays help (the short messages concerning the object pointed by the cursor, in 

Polish) as labels nearby the cursor or as a text in the status bar. Point a desired element and 

wait few seconds without any button click. 

How to open an image file? The image file can be opened by the main menu option Plik 

(file) and Otwórz (open) sub-option. The Otwórz dialog window appears. It can be activated 

also by the first button ( ) in the toolbar. 

How to save an image file? The results of measurement are marked on the image. It is 

possible to save the image with marked results. Choose Plik option and Zapisz (save) suboption 

in order to save the image with the original name. In order to save the image with 

a new name, choose Plik option and Zapisz jako (save as) sub-option. 

How to use clipboard? The program allows copying the whole image to the clipboard. 

The image saved in the clipboard is accessible from all applications run in the system. The 

clipboard is the easiest way to move the image to other applications. In order to copy the 

image from an active window, choose Edycja (edit) menu option and the sub-option Kopiuj 

(copy). It is possible to use the toolbar too. The third button from the left has the same 

meaning as the Edycja->Kopiuj option.

8_Dental_Radiography

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?