The Comparison of Innovative Image Processing and Goniometer Methods in Q Angle Measurement

Q angle is defined as an acute angle between two imaginary lines drawn from the ASIS to the center of patella and from the center of the patella to the tibial tuberosity. Measuring of Q angle usually was conducted in the supine position by two main methods, invasive methods such as radiography and CT scan and non-invasive methods, including goniometer and photogrammetry. The purpose of this study was to examine the validity of a new method for measuring of the Q angle. The Q angle of 9 subjects (18 knees), with mean and standard deviation of age 23.55±2.24 (years), mean weight of 73.00±10.47 (kg), thigh length of 43.11±3.17 cm, pelvis width of 39.66±3.00, using CT scan method, innovative method of image processing and goniometer in the supine position were calculated and the correlation between the innovative method of image processing, goniometer and CT scan was measured via Pearson Correlation Coefficient. The findings of this study revealed a significant relationship between Q angles obtained through the innovative method of image processing and CT scan method in the supine (r=0.92), It also showed significant relation between Q angle obtained with the goniometer and CT scan in the supine position(r=0.81)(p=0.001). According to the result of this research, tools and instruments applied for Q angle calculation can be rated according to the correlation rate that they have with the CT scan method. Therefore, the innovative method of image processing can be an appropriate substitute for goniometer method in measuring Q angle in the supine position. Keyword: Supine position CT scan Goniometer Innovative method Q angle Validity INTRODUCTION angle is conducted by two main methods; invasive Q angle is defined as an acute angle between two non-invasive methods such as goniometer [2,10] and imaginary lines drawn from the ASIS to the center of photogrammetry [7,11] in supine and stand position. patella and from the center of the patella to the tibial Invasive methods include ordinary radiography (Xtuberosity [1-6]. A normal Q angle value in men is ranged Ray) and local scan using computer (CT scan). These between 10 to14 degrees and in women it ranges between methods are considered to be the most accurate and valid 14.5 to 17 [2]. Although the Q angle is widely used in ones and are applied to every new measurement method clinical research and treatments, few studies have been as the validity criteria [12,13]. Although these methods conducted to examine the validity of Q angle measuring have high advantages such as accuracy and precision, methods [4,7]. Therefore, a method with a high validity is because of being invasive, expensive, time consuming, of a great significance to measure this angle [7]. Validity not always available and subject dissatisfaction, they are of a test or tool is considered to be the ability or capability less used in research and clinics [14]. of the test or the tool to measure what it claims to measure Goniometer method is however widely used in [8]. Validity as the most critical characteristics of a measurement tool is equal to pertinence, significance and usefulness of deductions and interpretations that are inferred based on the test values and also it expresses the generalizability of the test [9]. The measurement of the Q methods including radiography and CT scan [2,10] and clinical therapies for range of motion assessment [15,7]. Among the advantages that can be attributed to goniometer are its low-cost and availability [7]; however it also makes researchers face some problems. Various studies have reported various levels of validity and World Appl. Sci. J., 18 (2): 226-232, 2012 227 reliability for this tool [4,16,11,7,17], when it used in a the second step, with palpation the Anterior Superior Iliac research with repeated measures design, the Rezontal Spine (ASIS), the Patella Center (PC) and the Tibial effect may occur (expectations test), hence this factor can Tubercle Center (TTC) were recognized and marked. Also affect the generalizability degree or the external validity participant's the pelvis width and thigh length were [18], Another limitation is mostly referred to as boring and measured [1-6]. Pelvis width was measured by use of time consuming (especially if it is needed to calculate the meter according to the distance between the right and left angle more than once). ASIS in frontal plane while the participants were in With the advent of technology, digital measurement standing position [22]. The thigh length was measured is more concerned with measuring angles and linear from the frontal plane of the joints center (thigh great quantities. Photogrammetry makes the exact record of throchanter and thigh lateral condyle) of the participants physical changes and relations among various parts of in standing position [22]. In the third step, the participants the body possible, that the measurement of which is not were transported to a radiology center and CT scan easy by other tools [7,19]. This method has the following images were taken. In this method, first some markers were benefits: the restore process is easily conducted in tagged on the marked areas. Because of iliac bone density photogrammetry [7], reduction of measurement errors overlapping with the density of ASIS bone and caused by goniometers alternations and also reduction of innovative method was used to place marked needles on investigator errors compared to that of goniometers the three intended points to insure a better recognition of method [11], recorded files are always much more the points on the CT scan image. Then the participants in accessible, digital photogrammetry is always possible to a supine position with relaxed quadriceps muscle, knee be conjugated with computerized measuring processes. full extension [11], bare foot, their legs straight up with a Therefore computerized photogrammetry is the 12 cm trapezoid shape sponge placed between the medial combination of digital photography and software such as malleolus [23] were asked to lie down on the bed and, the Corel Draw [20,7]. picture was taken. Next, a radiology specialist measured In order to decrease universal goniometer the Q angle with the help of DICOM Eye software. measurement errors, a method is intended to invent to In the fourth step, the participants were transported measure the Q angle with the most possible minimum to the testing location and lied down on the ground in a measurement error. With the advent of technology, digital supine position with knee full extension [11], bare foot measurement is more concerned with measuring angles and their legs straight up with a 12 cm trapezoid shape and linear quantities. The purpose of this study was to sponge placed between the medial malleolus [23]. examine the validity of a new non-invasive method in Their background was meant to be non-reflexive [11]. measuring Q angle. For this purpose, the researcher will Then marker were labeled white and digital camera compare each one of the prevailing methods with the (cannon 5mega pixel) was placed on a tripod in superior criterion (CT scan method). view from the lower body parts. The lens was fixed in line MATERIALS AND METHODS position the Q angle of the right and left feet was This is a correlation and comparative study that investigator pictured the participants in the above trying to design and build a software in order to measure mentioned position again. Q angle using photography method, different methods of measurement like CT scan [21], goniometer and the Measuring the Q Angle in the Supine Position Using innovative image processing method and finally Goniometer Method : In order to measure the Q angle, the calculating the coefficient of correlation between the universal goniometer with one degree accuracy was used. gathered data from the goniometer method and the The Q angle was measured in a supine position. innovative image processing method with that of the CT Goniometers center was placed on the patella scan method. The study was conducted by 9 male center and its stationary arm in the ASIS direction and volunteers (18 knees, right and left) between 18 to 26 mobile arm in the tibial tubercle center direction. The years, the subjects who all signed the consent form. number on the goniometer was then written down In order to measure the Q angle, four steps were [4,11,7,23]. This process was repeated for three times and taken. In the first step the participants filled out the the average of the three measurements was registered as personal questionnaire together with the consent form. In the Q angle. with the longitudinal center of thigh. Then in the same measured with the universal goniometer. Finally the World Appl. Sci. J., 18 (2): 226-232, 2012 228 Fig 1: Photography by CT scan Fig 2: An example of image used for measurement of Q angle Fig 3: Selected area that its dimension being magnified Measuring the Q Angle in the Supine Position with the Innovative Image Processing Method: In order to extract Fig 6: The values that are approximate to one is indicator the Q angle from the digital picture, the markers positions of the rate of roundness in markers Fig 4: Compatible threshold application on image and markers related point extraction Fig 5: Three continuous morphological operator’s application (Disk close, Line Erode and Line dilate) respectively from left to right