CT Number and Linear Attenuation Coefficient Variation in Hypertensive Patients with Brain Hemorrhage and Infarction Using CT Scan

The aim of this paper is to study the variation of brain matter of Nepalese patients using CT scan. CT number and linear attenuation coefficient (LAC) of cortical bone are found largest among other brain matters, indicating the largest density. All brain matters except cortical bone show low association indicating slight changing trend with age. The cortical bone under 10 years shows low value of LAC and CT number, indicating cortical bone towards maturation whereas cortical bone shows no significant increase with age above 10 years. There is no much significant relation by gender in brain hemorrhage and infarction.


INTRODUCTION
Major innovation, X-ray computed tomography (CT), was introduced into diagnostic imaging in early 1970s.This innovation is recognized as the most significant event in medical imaging.The importance of CT is related to several of its features, including provision of crosssectional images of anatomy, availability of contrast resolution superior to traditional radiology, construction of images from x-ray transmission a "black box".The productions of images from digital data are processed by computer and can be manipulated to yield widely varying appearances (Hendee & Ritenour, 2002).
The gray levels in a CT slice image correspond to X-ray attenuation reflecting the proportion of X-rays scattered or absorbed as passing through each voxel.X-ray attenuation is primarily a function of X-ray energy and the density and composition of the material being imaged (Ketcham, 2012).LAC (µ t ) of each tissue pixel is compared with LAC of water (µ w ) using following expression.Water is used as reference material because its LAC is close to those of soft tissue and it is reproducible material for machine calibration.The LAC of typical bone and water are of 0.38 cm -1 and 0.19cm -1 respectively and the CT number of bone is +1000 (Farr & Allisy-Roberts, 2002).
Hypertension is a condition and characterized with an abnormal increase in blood pressure where systolic blood pressure is greater than 160 mmHg and /or a diastolic blood pressure is 95mmHg or greater (Segen & Wade, 2004).Hypertension predisposes to atherosclerosis and has specific effect on particular organs of heart, brain, kidneys, and blood vessels (Waugh & Grant, 2006).
Brain hemorrhage is known as bleeding in the brain which caused due to swell of an artery in the brain and then it bursts, which can resulted the brain cells being killed anywhere in or on the brain.CT findings of brain hemorrhage are done by clinical practice and acute hemorrhage (0-72hrs) appears hyperdense to human brain unrestricted semi liquid clot appears hypodense within the acute hematoma.Sub-acute hemorrhage (4-14 days) becomes virtually isodense with the adjacent brain parenchyma.It shows a peripheral post contrast enhancement.Chronic hemorrhage (>2 weeks) appears hypodense to the adjacent brain.High attenuation within chronic hematomas is usually secondary to the re-bleeding.A target sign on post contrast image can be seen if re-hemorrhage takes place within an organizing hematoma; if re-bleeding occurs outside an organized hematoma and it can resemble with a tumorial hemorrhage (Bhargava, 2006).
The brain is prevented from receiving blood, leading to tissue damage, stroke, and possible fatality is known as a brain infarction (http://www.wisegeek.com).Acutely infracted tissue is isodense with brain initially, it then becomes darker (decreased attenuation) in the acute phase, returns to a more normal attenuation during the next 2-3 weeks (fogging effect), and then markedly decreases in attenuation as it enters the chronic phase.Contrast-enhanced images often show gyriform enhancement during the fogging period (Jonathan & Allen, 2006).In this context, the objective of this paper is to find the CT number and LAC of brain matters, and also to know the relation of brain hemorrhage and infarction by age-gender along with LAC of gray and white matter by gender.

MATERIALS AND METHODS
The non-systematic prospective experimentobservational study was undertaken at the Department of Radiology and Imaging, Om Hospital and Research Centre, Kathmandu, Nepal.The experimental observations conducted during May to September, 2011.CT scanner of Siemens Company, Somatom Esprit and co-operative equipment of Om Hospital, has been selected and it conducted with fixed photon energy by keeping 130kVp and 260mAs the dependency, which is only carried out by the density of brain matters.The brain matters are of different densities, hence CT number and LAC of brain matter varies.The parameters are collected as Hounsfield Unit (HU) of white matter, gray matter, CSF, Cortical bone, ICB and infarction.In the experimental observations, 20 patients are from brain hemorrhage while 20 from brain infarction including equal number of each sex.The data are organized and then analyzed by using tabulation and diagrams.Mean, correlation, and the test of independence are used.

RESULTS AND DISCUSSION
The results of the CT number and LAC of brain matter of hemorrhagic male and female patients are presented in Table 1.It is found that in both hemorrhagic male and female brain CT number and LAC of CSF, white matter, gray matter, ICB and cortical bone are gradually in increasing order and are distinct, which indicating that CT diagnosis of brain hemorrhage is more effective.However, other brain diseases may have CT number as close as in brain hemorrhage which needs proper diagnosis.It is commonly observed that CT number of ICB ranges from 50 and reaches below 80 in the most observational cases.CT number for other brain matter does not change appreciably from that of the normal brain.This finding is similar for both male and female patients.variations usually depend on how old the disease was.The CT number of ICB is nil as bleeding is absent in present case.Other brain matter variation is found insignificant as in previous case of brain hemorrhage compared with normal brain.
Variation between LAC of ICB and age of male and female patients shows no significant association (Fig. 1).It is also seen that the correlation between LAC of ICB and age of each sex in brain hemorrhage patients is found insignificant.This result indicates that the disease can occur at any age.In both the cases the value of correlation coefficient is low.However, in male patients the correlation is negative while in female patients the correlation coefficient is found small but positive.
Large number of patients were recorded with increasing age as risk factors like obesity, stress, consumption of more fat and others are more likely at that age.

13429) between LAC of infarction and age of brain infarction female patient
Variation between LAC of infarction and age of male and female patients' brain shows no significant association (Fig. 2).The result shows that degree of correlation is low between LAC of infarction and age of each sex in case of brain infarction patient.In both sexes correlation coefficient is small and negative.This reveals that the disease is possible at any age groups of patients.However, the people of higher age are at higher risk due to sedentary lifestyle, stress and lack of physical exercise, which are usually observed less in the lower age groups of patients.
(a) (b)  Fig. 3 shows that the variation between LAC of white and gray matter of male brain is found significantly associated for both diseases.It is also seen that there is a positive relation between LAC of white and gray matter in brain hemorrhage and brain infarction patients for male.This result equally holds in case of female patients for both the diseases.In addition to this result, the development of white and gray matter goes side by side.Table 3 presents the association between male and female patients in case of brain hemorrhage and infarction.The insignificant chi-square values suggest that there is no association between LAC of infarction of infracted male and female brain.This shows that there is no evidence of the occurrence of hemorrhage in male, which linked with occurred in female.This result also holds good for the patients of brain infarction for both sexes.
The ICB and infraction can be detected easily through The range of CT number and LAC of brain matters mentioned lies clinically accepted range and is also in agreement with similar studies conducted by Reddinger (1998), Mishra (2009) and Silwal (2010) shows no significant increase with age in male whereas in female slightly decreasing value of cortical is observed.These findings are found consistent with the several findings elsewhere (Reddinger, 1998;Mishra, 2009;Silwal, 2010;Cosgrove et al. 2007;Good et al. 2001;Koenraad et. al. 2001).
The white and gray matter of brain are found to be significantly associated.The hemorrhagic patients by gender are found significantly different where male patients shows lower association than that of female patients.Indeed brain infarction patients showed similar results for gender, however; gender differences in size vary by more specific brain regions.Studies revealed that men have a relatively larger amygdalae and hypothalamus whereas women have a relatively larger caudate and hippocampi.Women have a higher gray matter as compared to that of men but men have a higher white matter and cerebrospinal fluid as compared to that of female.Indeed, high variability between individuals is well established elsewhere (Cosgrove et al. 2007).
The significant dynamic change is well observed in brain structure through adulthood and aging with substantial variation between individuals (Good et al. 2001).It is also showed that men had a steeper decline in global grey matter volume, although in both sexes, which varied by region with some areas exhibiting little age effect.Further overall white matter volume does not appear to decline with age, although there is variation between brain regions.In fact, the discrepancy observed is accounted as from the head circumferences, which do not change significantly through childhood, but increase is due to mostly to an increase in skull thickness, not in brain size (Koenraad et. al. 2001).The brain is also found to be 12 per cent larger for male on average as compared to that of female where the difference is statically significant even controlling height and weight.The study also conducted shows that woman has 4.3 per cent higher gray matter content than that of men.The gray matter gradually loosed due to ageing, however; CSF volume has found to be lower in female with age as compared to that of male.

CONCLUSION
The present paper concludes as follows: • The CT number and LAC of brain matters observed from this study are in agreement with clinically accepted range.
• ICB is only found in hemorrhagic brain where infarction is completely absent and infarction is only found in infracted brain where ICB is entirely absent.
• There is low degree of association between CT number of brain matters and age but the association is high between age and CT number of cortical bone.However it is found nearly constant in male with increase in age and low in child under age of 10 years irrespective of the sex.
• The association is found high in the development of white and gray matter whereas CT number of CSF is found slightly decreasing with age for both sexes.
• Insignificant association is found individually in the CT number and LAC variation of brain matters of brain hemorrhage and brain infarction.
Fig 1.(a) Graph showing no significant correlation (r= -0.09144) between LAC of ICB and age of brain hemorrhage male patient (b) Graph showing no significant correlation (r=0.18962) between LAC of ICB and age of brain hemorrhage female patient Fig 2. (a) Graph showing no significant correlation (r=-0.1369) between LAC of infarction and age of brain infarction male patient, and (b) Graph showing no significant correlation (r=-0.13429) between LAC of infarction and age of brain infarction female patient

Fig 3 .
Fig 3. (a) Graph showing correlation (r=0.19246) between LAC of gray matter and white matter of brain hemorrhage male patient (b) Graph showing correlation(r=0.44186)between LAC of white and gray matter of brain infarction male patient Fig 4. Hemorrhagic brain (a) (35/F) and (b) (25/M)

Table 2 . CT number and LAC of brain matter of infracted male and female brain SN Age/ Sex Attenuation (HU) of X-rays with
NOTE: SN-Serial Number, WM -White Matter, GM-Gray Matter, CSF-Cerebrospinal fluid, CB-Cortical Bone, ICB-Intracranial Bleed

Table 2
gives the brain matter variation in case of brain infarction for males and females.It is found that CT number of infarction in infracted brain ranges from more than 10 to less than 22 in most cases, it greatly resembles with the CT number of CSF in certain cases therefore careful speculation only yield proper diagnosis.These

Table 3 : χ 2 test for ICB of hemorrhagic male and female brain patient and infarction of infracted male and female brain patient
. The CT number and LAC of cortical bone are found largest among other brain matters indicating largest density.It is found that all brain matters except cortical bone shows lower association indicating slight change trend with age.The cortical bone associated with age under 10 years shows low value of LAC and CT number indicating cortical bone towards maturation.Above 10 years, cortical bone