A variety of space occupying lesions or mass lesions may involve the orbit. Pathology of these lesions range from benign to malignant. Tumours form an important portion of them. Patients with intraorbital tumours often present with debilitating clinical fea-tures. Early diagnosis and prompt treatment can reduce their complications. Hassan et al. (2016) mentions that the overall age adjusted incidence rate of malignant orbital tumours in USA was 3.39 (95% CI: 3.27-3.52) per million person-years. From his study it was observed that orbital tumours are mainly diagnosed at the age of above 50 years whereas most of the soft tissue sarcomas occurred in the young age. It is further mentioned that lymphomas were the dominant subtype in the adult population. It was also noticed that the incidence rates were higher in males than females mainly caused by the increase in car-cinoma subtypes. Koopman et al. (2011) stated that in Netherlands the average age-adjusted incidence of malignant orbital tumours was 10.9. Lymphoma had a relative frequency of 67%, rhabdomyosarcoma 12%, adenocarcinoma 6%, and adenoid cystic car-cinoma 5%. Nowadays in Netherlands primary malignant orbital tumours had been diagnosed more. In Bangladesh no definite statistical information is available regarding prevalence or incidence of in-traorbital benign and malignant tumours in general population (Hasibuzzaman et al., 2022).

Computed tomography scan is an important preo-perative diagnostic imaging modality to detect and characterize tumours yielding information on their size, shape, location, extension and perilesional fea-tures. Accurate information regarding extent of the tumour and its surroundings is essential for preo-perative planning. It is also a necessity to differen-tiate between malignant and benign tumours and nontumorous lesions. Increasing wide availability of CT scan machines and their capability to produce high resolution images along with multiplanar refor-mation facilitates diagnosis of the intraorbital tumours. Furthermore its faster image acquisition minimizes motion related artifacts. Although CT scan is useful to evaluate the intraorbital tumours, it has some limitations (Ushalatha et al., 2016). 

CT scan provides detailed visualization of regional bony anatomy and landmarks, but some soft tissue details such as delineation of necrotic or cystic components and inflammatory conditions are often not possible. Intralesional calcification and hemor-rhage are well visualized with CT scan, but soft tissue interfaces and outline of inflammatory con-ditions are better identified with MRI (Ushalatha et al., 2016). Some studies have been conducted world-wide on evaluation of the diagnosis of the intra-orbital tumours in paediatric and adult subjects by Computed Tomography (CT). But no such study has been conducted in general population of Bangladesh. With this view the present study was undertaken and designed to assess the usefulness of CT scan image to diagnose the intraorbital tumours and its histo-pathological correlation. 

Objectives of the study

The study was designed to assess the diagnosis of the intraorbital tumours with the help of Computed Tomography (CT). Specific objectives were to eva-luate CT scan findings in cases with clinical sus-picion of intraorbital mass lesions and thus diagnose the lesions, to compare the CT scan and histo-pathological diagnoses of intraorbital mass lesions. Moreover it was found out the sensitivity and speci-ficity of CT scan and also predictive value of CT scan was analyzed to evaluate the accuracy of CT scanning for diagnosis of intraorbital mass lesions.  

This cross sectional study took place in the Depart-ment of Radiology and Imaging, Dhaka Medical College Hospital and Department of Radiology and Imaging, National Institute of Ophthalmology during the period of January 2017 to December 2018. 

The sampling technique was purposive and sample size was 67. Patients attending outdoor and indoor patient facilities of the ophthalmology department of afore-mentioned Institute and Hospital and referred to their respective Radiology and Imaging Depart-ments with suspicion of intraorbital tumours were included in the study. After selection of the patients, informed written consent was obtained from the patients or their legal guardians upon describing the purpose, method, benefit and hazards of the study. Data were collected from preformed data collection sheet and analyzed by SPSS computer program.

Mean age of the included patients was 26.69 years with standard deviation of 16.84 years. Largest num-bers of patients jointly belong to 10-20 years and 31-40 years age group. Most common presentation of the included patients was proptosis (49.25%), follo-wed jointly by headache (32.83%) and visual impair-ment (32.83%).

Table 1: Relation between age group and diagnosis.

Table 2: Relation between gender and diagnosis.

Table 3: Correlation between CT scan diagnosis and histopathological diagnosis.

For malignant tumours CT scan had an accuracy of 85.07% with sensitivity 93.54%, specificity 77.77%, positive predictive value (PPV) 78.38% and negative predictive value (NPV) 93.33%. For benign tumours CT scan had an accuracy of 97.01% with sensitivity 100%, specificity 96.23%, PPV 87.50%, NPV 100%.

Fig 1: Post-contrast axial CT scan appearance of orbital lymphoma.

Fig. 2: Post-contrast axial CT scan appearance of optic nerve meningioma.

The study was carried out to determine the diag-nostic performance of CT scan in the diagnosis of the malignant and benign intraorbital tumours com-pared with histopathological diagnosis. This cross-sectional study was carried out with an aim to esta-blish the role of CT scan in preoperative diagnosis of the intraorbital tumours and their correlation with histopathology of resected tissue by calculating sen-sitivity, specificity, PPV, NPV and accuracy. The age range of the participants of this study was from 1 year to 62 years. The mean age was 26.69 years with a standard deviation of 16.84 years. In this study, largest numbers of patients with clinical suspicion of the intraorbital space occupying lesion belong to 10-20 years age group (20.9%) and 31-40 years age group (20.9%). The study showed a male dominance (57%) for clinical suspicion of intraorbital mass les-ion with a male-female ratio of 1.3:1. In age groups upto 30 years male predominance is noted. It is also observed that age groups above 30 years have female predominance. In this study largest number of patients presented with proptosis (49.25%). Other presentations include headache (32.84%), visual impairment (32.84%), dry eye (19.4%) and leuko-coria (17.91%). This study showed that malignant tumour is relatively more common in patients with age less than 10 years and above 40 years both on CT scan and histopathology. It is also showed that benign tumour is relatively more common in patients with age ranging from 10 years to 30 years both on CT scan and histopathology. 37 cases were diag-nosed with malignant tumour on CT scan. Of them 18 were male and 19 were female. Benign tumour was diagnosed in 16 cases. Of them 14 were male and 2 were female. 31 cases were diagnosed histo-pathologically with malignant tumour. Of them 14 were male, 17 were female. 14 cases were diagnosed with benign tumour. All of them were male. On histopathology, benign tumour was not found in case of female patients. Out of 37 patients diagnosed with malignant tumour on CT scan, most of them had complained of proptosis (17), visual impairment (12), leukocoria (12). The clinical history of head-ache and dry eye was less common. On the other hand when 31 cases were investigated on histo-pathology, proptosis, visual impairment, leukocoria were also most common complaint with freq-uency13, 12, 10 nos. respectively. Patients diagnosed with benign tumour on CT scan, 8, 6, 4, 4 patients among 16 cases presented with visual impairment, proptosis, dry eye and headache respectively while it was 8, 4, 4 and 4 patients out of 14 cases presented with visual impairment, headache, proptosis and dry eye respectively diagnosed histopathologically with benign tumour. Out of 67 cases 37 (55.22%), 16 (23.88%) and 14 (20.9%) patients were diagnosed by computed tomography with malignant tumour, benign tumour and nontumorous lesion respectively. More-over, 12 (17.91%), 12 (17.91%), 10 (14.93%), 8 (11. 94%), 7 (10.45%), 6 (8.96%), 4 (5.97%), 4 (5.97%), 2 (2.99%) and 2 (2.99%) patients were diagnosed respectively with retinoblastoma, pseudotumour, metastasis, melanoma, cavernous haemangioma, pleomorphic adenoma, meningioma, lacrimal gland abscess and capillary haemangioma on CT scan. 

When 67 cases were investigated on histopathology, 31 (46.3%), 14 (20.9%), and 22 (32.8%) patients were diagnosed with malignant tumour, benign tumour and nontumorous lesion respectively. To be more specific after histopathological test it was found that 17 (25.37%), 10 (14.93%), 10 (14.93%), 8 (11.94%), 5 (7.46%), 5 (7.46%), 4 (5.97%), 4 (5. 97%), 2 (2.99%), 1 (1.49%) and 1 (1.49%) patients had  pseudotumour, retinoblastoma, metastasis, mel-anoma, lymphoma, cavernous haemangioma, pleo-morphic adenoma, meningioma, PHPV, capillary haemangioma and lacrimal gland abscess respect-ively. Malignant tumour and nontumorous lesion were found in 29 and 8 cases respectively after his-topathological test of 37 patients; no cases were diagnosed histopathologically with benign tumour. 16 patients were diagnosed with benign tumour on CT scan. Of them 14 and 2 cases were diagnosed with benign tumour and nontumorous lesion respect-ively on histopathology; no cases were diagnosed with malignant tumour. On CT scan 14 patients were diagnosed with nontumorous lesion. Of them 2 and 12 cases were diagnosed with malignant tumour and nontumorous lesion respectively on histopathology. 

No cases were diagnosed histopathologically with benign tumour. In case of investigation of the mali-gnant intraorbital tumours, accuracy of CT scan was 85.07% with sensitivity 93.54%, specificity 77.77%, positive predictive value (PPV) 78.38% and negative predictive value (NPV) 93.33%, while for benign intraorbital tumours investigation, accuracy of CT scan was 97.01% with sensitivity 100%, specificity 96.23%, positive predictive value 87.50% and negative predictive value 100%.

CT scan showed good sensitivity, specificity, predi-ctive value and accuracy in the diagnosis of the intra-orbital tumours. For the benign tumours the validity tests showed relatively more accuracy. Therefore it can be concluded that CT scan is a useful modality in the diagnosis of the intraorbital tumours.

I would like to acknowledge and give my warmest thanks to my supervisor who made this work possible. His guidance and advice carried me through all the stages of writing my article. I would also like to give special thanks to my family as a whole for their continuous support and understanding when under-taking my research and writing my article. Their prayer for me was what sustained me this far. Finally, I would like to thank Allah, for letting me through all the difficulties. 

The authors declare that there is no conflict of interest.