The comparison of hounsfield unit values calculated on computed tomography images and dual energy x-ray absorpsiometry scores for the diagnosis osteoporosi̇s

ABSTRACT Purpose: In this study, our goal is to make a comparison between the values of dual energy X-ray absorptiometry, the gold standard method to diagnose osteoporosis (DEXA) scoring and Computed Tomography (CT) measured in Hounsfield units (HU) and to investigate the contribution of CT densitometry to osteoporosis diagnosis. In addition, by making volumetric measurement of lumbar spines and femoral head-neck cut, we tried to show radiologically whether the volume change is significant or not and the bone mass loss according to the World Health Organization (WHO) classification. Materials and Methods: Between January 2013 and May 2015, at Yuzuncuyıl University School of Medicine Dursun Odabaş Medical Center Radiology unit, all patients above 10 years of age without gender differences were included in this study whose both abdominal CT and DEXA 's taken and requested by the various clinics. From our archives total of 102 patients were defined who hadn't had lumbar and femoral surgery, no implants, no bone neoplasia, and not had the diseases as rheumatoid arthritis, SLE, ankylosing spondylitis, or multiple myeloma. From L1-L2-L3-L4 vertebraes and femoral neck, T score which measured by the DEXA method, BMD, with WHO classification, the CT volume measurements were made, whose HU values were measured by Abdominal CT in the L1-L2-L3-L4 vertebral bodies and femoral head-neck. DEXA measurements were performed in the standard position with the Hologic 2000 dexa device. From femoral neck and lumbar spine and L1-L2-L3-L4 vertebras, bone mineral density (BMD), area, T-Z score was measured and WHO classification was determined. According to the WHO classification T-score of -1 or above normal, between -1 and -2.5 osteopenia, and -2.5 and below is defined as osteoporosis. CT images were obtained by 16-detector multislice computed tomography device (Somatom Emotion 16-slice; CT2012E- Siemens AG Berlin and München- Germany). By establishing three different levels ROI from the abdomen CT of the lumbar spine of patients (L1-L2-L3-L4) and femoral neck of the corpus, HU values were measured and the average of it was taken. In addition; to make volumetric measurement, two different values, such as the lower limit of 100 and 200 HU , the upper limit 1500 HU was set. Vertebral bodies and femoral head-neck area boundaries drawn and entry of tissues outside the bone prevented Then, volume values were measured automatically-interactive. DEXA calcification determined according to the WHO, T score, the relationship between BMD values and lumbar spine-femoral neck HU values and volumes measured by CT method were statistically analyzed SPSS was used. Results: 102 patients were included in our study, of which 51 men and 51 were women (50%). All our patients whose age was 10 and above were divided into three groups. Group 1 between 10-30 years old, 31-60 years of age Group 2 and Group 3 was defined as over 60 years of age. There were 21 people in the first group (20.6%), 52 people in the second group (51%) and 29 people in the third group (28.4%). The averge height of patients 163.3 (± 8.9) cm and the average weight measured as 69.5 (± 14.9) kg . In measurements made from lumbar region based on DEXA WHO classification, 44 patients were normal (24 males, 20 females, mean age 44), 35 patients had osteopenia (19 male, 16 female, mean age 45) and 23 patients (8 male, 15 female, mean age 55 ) had osteoporosis. In 102 patients; L1 vertebra T-score average -1.27, L2 vertebra T-score average -1.06, L3 vertebra T-scores average -1.25, L4 vertebra T-score average -1.32 and total lumbar area T-score average -1,24 was found. In DEXA measurements made from the femur, according to WHO; the number of normal patients 50 (30 male, 20 female, mean age 44), osteopenic patient number 41 (19 male, 22 female, mean age 50), osteoporosis patient number 11 (2 men, 9 women average age 52) . The average femur T score of 102 patients' was -0.83. The comparison of HU values of CT densitometry which was measured from L1-L2-L3-L4 lumbar spine separately with age groups was made and in three age groups, HU values were decreased as age increases inversely proportional. p values are <0.01 and this is meaningful. HU values measured at the femoral neck compared with the age groups. As age group increased HU values decreased. p values are <0.01 and this is meaningful. According to DEXA, in the correlation tests which made by lumbar spine bone mineral density (BMD) value and CT HU values , the HU results of each vertebrae (L1-L2-L3-L4) and BMD values were consistent. p values <0.01 are meaningful. That is, as long as BMD value increases, the HU values increase correlatively. According to DEXA; the results of femur bone mineral density (BMD) with CT HU values and HU results and BMD values measured from femoral neck in correlation test were consistent. p values are <0.01 and this is meaningful. That is, as long as BMD value increases, the HU values increase correlatively. CT HU values nn the lumbar vertebraes measured from L1-L2-L3-L4 and spine volumes compared with DEXA scores which measured from femur neck and CT HU values and volumes from same neck of the femur. According to DEXA, divided into three groups as normal, osteopenia and osteoporosis were considered. HU measurements and volume values made in the lumbar and femoral area were also compatible with the three groups of DEXA. Progressed towards the osteoporotic patients to normal patients, HU value and volume were significantly reduced. P-values for the lumbar spine and femoral <0.01 is meaningful. A correlation test done between volume values measured at the lumbar spine and DEXA BMD values. In volumetric analysis, volume 1 the lower limit of the threshold value 100 HU and volume 2 the lower limit of the threshold value 200 HU was selected. There was a significant correlation coefficient between the two variables. p values <0.01. BMD increases, the volume is increasing. A correlation test between femoral head-neck region of volumetric measurements our patients and femur BMD values of femur measured by DEXA method was done. In volumetric analysis, volume 1 the lower limit of the threshold value 100 HU and volume 2 the lower limit of the threshold value 200 HU was determined. Volume 1 and volume 2 values were compatible with femoral BMD. p values <0.01. As BMD increased, volume growth was also observed. Each of the values taken from lumbar spine (L1, L2, L3, L4) and CT HU values measured from femoral neck were compared with T scores through spousetest. A positive linear relationship was observed between the spouses in all measurements. This relationship is statistically significant. (p values <0.01). As T score gets higher, CT HU values also show a linear increase. In addition, CT volumetric measurements made from lumbar spine and femoral head-neck were compared through spousetesting with T scores. The same linear relationship was observed between volume and T scores. (p values <0.01). T-score increases, the measured volume value is also increasing. In order to obtain the appropriate cut-off value of each lumbar vertebrae (L1, L2, L3, L4) and HU values measured from and femur from the T score of the same place , ROC (Receiver Operating Characteristic) analysis was performed. In the average HU value of lumbar spine and T-score assessment, in ROC analysis the area under curve was 68%. The ideal place for lumbar vertebrae is L1, cut-off value of 161 HU. So, when measured by CT from L1 vertebrae, values below 161 HU are at risk of osteoporosis. In CT HU-DEXA T- score evaluation measured of femur neck, the area under the curve in ROC analysis 83%, CT HU from the femur and the total DEXA T-score under the curve 88% was found. The cut-off value for femoral neck 110 HU, the total femur cut-off value is 96 HU. So, if the height of the femur measured by CT is under 96 HU, bears risk of osteoporosis. Discussion: In our study, DEXA T-score of the HU values of the lumbar spine and femoral neck measured by establishing ROI were compared with BMD and osteoporosis degrees. CT HU values, showed a strong positive correlation with T score and BMD, according to the WHO classification, from normal towards osteoporosis, a significant decrease was observed in HU values. In addition, the falling of CT HU values as age increases , was one of the results we expected. The results we found were in similar manner as literature. In our study, first, the volume of the vertebral bodies and proximal femur was measured . The volume significantly reduced from normal to osteoporotic patients and from elderly patients to the young patients. The thinning of the cortex and reducing medulla density was demonstrated visually in patients with osteoporosis . With emphasis on common literature, degenerative changes in elderly patients (osteophytes, sclerosis), causes such as aortic calcification, bone islets, scoliosis, fractures causes impede the safe DEXA results. We faced with similar restrictions in our study group . CT can largely overcome these limitations. Conclusion: In the diagnosis of osteoporosis which is a major health problem in the world, new searches will continue due to the limitations of the gold standard method DEXA, mentioned above and not being able to make cortex medulla differentiate. We believe, in the future, T-score which enables three-dimensional examination CT HU showing strong compliance with BMD values and age in many studies can be used for the diagnosis of osteoporosis. In particular, we believe that standardized and low-dose CT applications towards specific area offer more important information for patients than DEXA, in terms of osteoporosis and fracture risk . For this, there is a need for wider research. In addition, with the volume measurements that we have done, we have proved radiologically loss of bone in osteoporosis and reduction in its density.