Evaluation of institutional whole-body and extremity occupational radiation doses in nuclear medicine.

This study evaluated nuclear medicine occupational radiation doses at Sultan Qaboos University Hospital, a 700-bed tertiary care teaching hospital in Oman. Personal effective whole-body doses, Hp(10), and extremity doses, Hp(0.07), were collected for 19 medical radiation workers over a 7-year period (2015-2021). Personal doses for four professional groups were measured using calibrated thermo-luminescence dosemeters ((LiF:Mg,Ti) TLD-100). The average, median and maximum cumulative doses were compared against the annual whole-body and extremity dose limits (20 mSv and 500 mSv y-1, respectively) and local dose investigation level (DIL; 6 mSv y-1). Personal whole-body doses (average:median:maximum) for technologists, medical physicists, nuclear medicine physicians and nurses were 1.8:1.1:7.8, 0.3:0.3:0.4, 0.1:0.1:0.2 and 0.1:0.1:0.2 mSv, respectively. Personal extremity doses for left and right hand (average and maximum doses) follow similar trends. Average annual effective whole-body and extremity doses were well below the recommended annual dose limits. The findings suggest lowering local DIL for all staff except for technologists.

Establishment of diagnostic reference levels in computed tomography in two large hospitals in Oman.

This study aimed to estimate diagnostic reference levels (DRLs) for the most frequent computed tomography (CT) imaging examinations to monitor and better control radiation doses delivered to patients. Seven CT imaging examinations: Head, Chest, Chest High Resolution (CHR), Abdomen Pelvis (AP), Chest Abdomen Pelvis (CAP), Kidneys Ureters Bladder (KUB) and Cardiac, were considered. CT dosimetric quantities and patient demographics were collected from data storage systems. Local typical values for DRLs were calculated for CTDIvol (mGy), dose length product (DLP) (mGy·cm) and effective doses (mSv) were estimated for each examination. The calculated DRLs were given as (median CTDIvol (mGy):median DLP (mGy·cm)): Head: 39:657; Chest: 13:451; CHR: 6:228; AP: 12:578; CAP: 20:807; KUB: 7:315, and Cardiac: 2:31. Estimated effective doses for Head, Chest, CHR, AP, CAP, KUB and Cardiac were 1.3, 12.7, 6.3, 12.5, 18.1, 5.8 and 0.8 mSv, respectively. The estimated DRLs will act as guidance doses to prevent systematic excess of patient doses.

Optimization of BMI-Based Images for Overweight and Obese Patients - Implications on Image Quality, Quantification, and Radiation Dose in Whole Body 18F-FDG PET/CT Imaging.

Purpose: In PET/CT imaging, the activity of the 18F-FDG activity is injected either based on patient body weight (BW) or body mass index (BMI). The purpose of this study was to optimise BMI-based whole body 18F-FDG PET images obtained from overweight and obese patients and assess their image quality, quantitative value and radiation dose in comparison to BW-based images. Methods: The NEMA-IEC-body phantom was scanned using the mCT 128-slice scanner. The spheres and background were filed with F-18 activity. Spheres-to-background ratio was 4:1. Data was reconstructed using the OSEM-TOF-PSF routine reconstruction. The optimization was performed by varying number of iterations and subsets, filter's size and type, and matrix size. The optimized reconstruction was applied to 17 patients' datasets. The optimized BMI-, routine BMI- and the BW-based images were compared visually and using contrast-to-noise ratio (CNR) and standardized uptake values (SUV) measurements. Results: The visual assessment of the optimized phantom images showed better image quality and contrast-recovery-coefficients (CRCs) values compared to the routine reconstruction. Using patient data, the optimized BMI-based images provided better image quality compared to BW-based images in 87.5% of the overweight cases and 66.7% for obese cases. The optimized BMI-based images resulted in more than 50% reduction of radiation dose. No significant differences were found between the three series of images in SUV measurements. Conclusion: The optimized BMI-based approach using 1 iteration, 21 subsets, and 3 mm Hamming filter improves image quality, reduces radiation dose, and provides, at least, similar quantification compared to the BW-based approach for overweight and obese patients.

Physiological Intracranial Calcifications in Children: A computed tomography-based study.

Objectives: This study aimed to examined the frequency of physiological intracranial calcifications (PICs) in paediatric population using computed tomography (CT). Methods: The brain CT scans of consecutive patients (age range: 0-15 years) who had visited Sultan Qaboos University Hospital, Muscat, Oman, from January 2017 to December 2020 were retrospectively assessed for the presence of PICs. The presence of calcifications was identified using 3 mm-thick axial images and coronal and sagittal reformats. Results: A total of 460 patients were examined, with a mean age of 6.54 ± 4.94 years. The frequency of PIC in boys and girls was 35.1% and 35.4%, respectively. PICs were most common in choroid plexus, observed in 35.2% (age range: 0.4-15 years, median: 12 years) of subjects, followed by the pineal gland in 21.1% (age range: 0.5-15 years, median: 12 years) and the habenular nucleus in 13.0% of subjects (age range: 2.9-15 years; median: 12 years). PICs were less common in falx cerebri, observed in 5.9% (age range: 2.8-15 years; median: 13 years) of subjects, and tentorium cerebelli, observed in 3.0% (age range: 7-15 years, median: 14 years) of subjects. PICs increased significantly with increase in age (P <0.001). Conclusion: Choroid plexus is the most frequent site of calcification. Choroid plexus and pineal gland calcifications may be present in infants younger than one year. Recognising PICs is clinically important for radiologists as they can be mistaken for haemorrhage or pathological entities such as neoplasms or metabolic diseases.

Radiologic Assessment of Orbital Dimensions among Omani Subjects: A computed tomography imaging-based study at a single tertiary centre.

Objectives: This study aimed to determine the orbital dimensions of Omani subjects who had been referred for computed tomography (CT) of the brain at Sultan Qaboos University Hospital, Muscat, Oman. Good knowledge of the normal orbital dimensions is clinically essential for successful surgical outcomes. Racial, ethnic and regional variations in the orbital dimensions have been reported. Methods: A total of 273 Omani patients referred for CT scans of the brain were retrospectively evaluated using an electronic medical records database. The orbital dimensions were recorded using both axial and sagittal planes of CT images. Results: The mean orbital index (OI) was found to be 83.25 ± 4.83 mm and the prevalent orbital type was categorised as the mesoseme. The mean orbital index was 83.34 ± 5.05 mm and 83.16 ± 4.57 mm in males and females, respectively, with their difference not being statistically significant (P = 0.76). However, a statistically significant association was observed between the right and left orbits regarding horizontal distance (P <0.05) and vertical distance (P <0.01) of orbit and OI (P <0.05). No significant difference between the OI and age groups was observed in males and females. The mean interorbital distance and interzygomatic distance were found to be 19.45 ± 1.52 mm and 95.59 ± 4.08 mm, respectively. These parameters were significantly higher in males (P <0.05). Conclusion: Results of the present study provide reference values of orbital dimensions in Omani subjects. Mesoseme, a hallmark of Caucasian people, is discovered to be the prevalent orbital type of Omani subjects.

Two-step machine learning to diagnose and predict involvement of lungs in COVID-19 and pneumonia using CT radiomics.

OBJECTIVE: To develop a two-step machine learning (ML) based model to diagnose and predict involvement of lungs in COVID-19 and non COVID-19 pneumonia patients using CT chest radiomic features. METHODS: Three hundred CT scans (3-classes: 100 COVID-19, 100 pneumonia, and 100 healthy subjects) were enrolled in this study. Diagnostic task included 3-class classification. Severity prediction score for COVID-19 and pneumonia was considered as mild (0-25%), moderate (26-50%), and severe (>50%). Whole lungs were segmented utilizing deep learning-based segmentation. Altogether, 107 features including shape, first-order histogram, second and high order texture features were extracted. Pearson correlation coefficient (PCC≥90%) followed by different features selection algorithms were employed. ML-based supervised algorithms (Naïve Bays, Support Vector Machine, Bagging, Random Forest, K-nearest neighbors, Decision Tree and Ensemble Meta voting) were utilized. The optimal model was selected based on precision, recall and area-under-curve (AUC) by randomizing the training/validation, followed by testing using the test set. RESULTS: Nine pertinent features (2 shape, 1 first-order, and 6 second-order) were obtained after features selection for both phases. In diagnostic task, the performance of 3-class classification using Random Forest was 0.909±0.026, 0.907±0.056, 0.902±0.044, 0.939±0.031, and 0.982±0.010 for precision, recall, F1-score, accuracy, and AUC, respectively. The severity prediction task using Random Forest achieved 0.868±0.123 precision, 0.865±0.121 recall, 0.853±0.139 F1-score, 0.934±0.024 accuracy, and 0.969±0.022 AUC. CONCLUSION: The two-phase ML-based model accurately classified COVID-19 and pneumonia patients using CT radiomics, and adequately predicted severity of lungs involvement. This 2-steps model showed great potential in assessing COVID-19 CT images towards improved management of patients.

ASSESSMENT OF OCCUPATIONAL RADIATION DOSES IN DIFFERENT DIAGNOSTIC, INTERVENTIONAL AND THERAPEUTIC RADIOLOGY AND MOLECULAR IMAGING SERVICES IN OMAN.

This study aimed at assessing occupational radiation doses in different diagnostic, interventional and therapeutic services. Personal dose equivalent, Hp(10), of 116 medical radiation workers, all with 3 y of dose records (2015-18), were collected from the TLD dosimetry service at the Sultan Qaboos University Hospital-a 700-bed tertiary care teaching hospital in Oman. The doses were measured using calibrated thermo-luminescence dosemeters (TLD-100 (LiF:Mg,Ti)). Five occupational groups, diagnostic radiology, interventional radiology, nuclear medicine, medical physicists and nurses, were considered. Average, maximum and median cumulative doses were estimated and compared against the annual dose limit (20 mSv per y) and the local dose investigation level (DIL) (6 mSv per y). Personal doses (average:maximum:median) for diagnostic radiology, interventional radiology, nuclear medicine, medical physicists and nurses group were found to be 0.05:0.90:0.00, 0.05:0.50:0.00, 1.20:7.40:0.40, 0.16:1.40:0.00 and 0.10:2.10:0.00 mSv, respectively. The findings of this study suggest, at the exception of nuclear medicine, lower DILs for all occupational groups.

Artificial intelligence-driven assessment of radiological images for COVID-19.

Artificial Intelligence (AI) methods have significant potential for diagnosis and prognosis of COVID-19 infections. Rapid identification of COVID-19 and its severity in individual patients is expected to enable better control of the disease individually and at-large. There has been remarkable interest by the scientific community in using imaging biomarkers to improve detection and management of COVID-19. Exploratory tools such as AI-based models may help explain the complex biological mechanisms and provide better understanding of the underlying pathophysiological processes. The present review focuses on AI-based COVID-19 studies as applies to chest x-ray (CXR) and computed tomography (CT) imaging modalities, and the associated challenges. Explicit radiomics, deep learning methods, and hybrid methods that combine both deep learning and explicit radiomics have the potential to enhance the ability and usefulness of radiological images to assist clinicians in the current COVID-19 pandemic. The aims of this review are: first, to outline COVID-19 AI-analysis workflows, including acquisition of data, feature selection, segmentation methods, feature extraction, and multi-variate model development and validation as appropriate for AI-based COVID-19 studies. Secondly, existing limitations of AI-based COVID-19 analyses are discussed, highlighting potential improvements that can be made. Finally, the impact of AI and radiomics methods and the associated clinical outcomes are summarized. In this review, pipelines that include the key steps for AI-based COVID-19 signatures identification are elaborated. Sample size, non-standard imaging protocols, segmentation, availability of public COVID-19 databases, combination of imaging and clinical information and full clinical validation remain major limitations and challenges. We conclude that AI-based assessment of CXR and CT images has significant potential as a viable pathway for the diagnosis, follow-up and prognosis of COVID-19.

Prevalence and distribution of sesamoid bones of the hand in Omani subjects: a radiological study.

Sesamoid bones show considerable variations in their occurrence among various ethnicities. This study aims to evaluate the prevalence and distribution patterns of the sesamoid bones of the hands among Omani patients who were referred for radiological investigations. The influence of gender and different age groups on the occurrence of sesamoid bones of the hand was determined using the Chi-square test. Spearman's rank correlation was used to determine the coexistence of sesamoid bones at the metacarpophalangeal joints. A total of 541 hand radiographs were reviewed. A high prevalence of sesamoid bones at the fifth metacarpophalangeal joint and the interphalangeal joint of the thumb was noted with a frequency of 64% and 49.7%, respectively. There were ten different patterns of sesamoid bones detected, the most common of which was the presence of sesamoid bones at the first and fifth metacarpophalangeal joints found in 32.9% of the radiographs. A statistically significant gender difference was observed at the interphalangeal joint of the thumb (p = 0.025) and fifth metacarpophalangeal joint (p = 0.027) with a female dominance. A significant association between the age and prevalence of sesamoid bones was noted at the fifth metacarpophalangeal joint (p = 0.03). The prevalence of the sesamoid bones of the hand in Omani subjects seems to differ from other Middle Eastern populations, particularly at the fifth metacarpophalangeal joint and the interphalangeal joint of the thumb. In the meantime, the baseline data of our study can be helpful while treating the patients complaining of hand discomfort or pain.

Radiological Study on Sesamoid Bones of the Foot among Omani Subjects.

OBJECTIVES: The prevalence and appearance of sesamoid bones in the foot vary considerably among different populations and ethnic groups. We sought to evaluate the prevalence and distribution patterns of foot sesamoid bones among Omani patients referred for radiological investigation. METHODS: We conducted a retrospective study among patients who had been referred for foot X-ray from January to December 2018. We used the chi-square test to determine the gender and age influence on the prevalence of sesamoid bones, and the Spearman's correlation coefficient to assess the coincidence of specific distributions of sesamoid bones at the metatarsophalangeal (MTP) joints. RESULTS: A total of 774 foot radiographs composed of 442 right foot radiographs and 332 left foot radiographs were reviewed for the presence of sesamoid bones at MTP and interphalangeal (IP) joints of the foot. We observed a high prevalence rate of sesamoid bones at the fifth MTP joint (13.7%), and first IP of the great toe (9.9%). There were nine distinctive patterns of sesamoid bones. The coincidence of sesamoid bones at two or more MTP joints was 14.6%, with a high prevalence rate at first and fifth MTP joints (10.3%). Moreover, the prevalence rate of sesamoid bones increased with increasing age at the fifth MTP joint. CONCLUSIONS: The prevalence of sesamoid bones in the foot is considerably high in Omani subjects and needs further prospective studies. Meanwhile, our findings could be helpful for clinicians to consider ailments of sesamoid bones during differential diagnosis in Omani patients who present with foot pain and discomfort.

Ossification of Posterior Longitudinal Ligament of Cervical Spine Among Omani Patients Referred for CT Scan at a Tertiary Care Hospital in Oman.

OBJECTIVES: We sought to evaluate the proportion of ossification of the posterior longitudinal ligament (OPLL) of the cervical spine and associated factors among Omani patients. METHODS: We reviewed the cervical spine computed tomography (CT) scans of all patients referred to the Radiology Department, Sultan Qaboos University Hospital, from 2011 to 2017. Descriptive statistics were employed to determine the proportion of OPLL. We used the chi-square test to determine the association of age, gender, and diabetes mellitus with OPLL. RESULTS: A total of 843 patients aged ≥ 20 years were included in the study. The proportion of OPLL was 2.7% and was more frequent in men (3.2%) than women (1.9%). The male to female ratio of OPLL was 1.7:1.0. OPLL occurrence was significantly more in non-diabetic patients (p < 0.001). No significant association was found between OPLL with gender (p = 0.281) and age (p = 0.878). CONCLUSIONS: The observed proportion of OPLL in this single-center study is relatively low, but the finding is important as the condition can eventually lead to debilitating neurologic outcomes affecting the patient's quality of life. OPLL occurrence was significantly more in non-diabetic patients, which necessitate further research on OPLL in a larger sample across Oman.

Noninvasive assessment and risk factors of liver fibrosis in patients with thalassemia major using shear wave elastography.

OBJECTIVES: This study aimed to estimate the prevalence of liver fibrosis and assess the risk factors for developing significant liver fibrosis in patients with Thalassemia Major (TM). METHODS: All patients with TM over the age of 10 years were included in the study. RESULTS: A total of 94 eligible patients underwent 2-D SWE. The median age was 26.7 years. The median of the average 5-year serum ferritin (5yrSF) and liver iron concentration (LIC) assessed by MRI T2* were 1326 µg/L and 6.7 mg/g dw, respectively. Hepatitis C and hepatitis B core antibodies were positive in 38% and 1% of the patients respectively. The proportion of patients with significant fibrosis was 60%. Male gender increased the risk of significant fibrosis (Odds ratio of 0.4; p = .0373). Additionally, the 5yrSF (p = .00661), the LIC (p = .0225) and the lowest LIC of the previous 5 years (p = .0211) were significant. In the multivariable logistic regression model, only 5yrSF (p = .0035) and gender (p = .00984) remained significant. CONCLUSIONS: The risk of liver fibrosis is associated with iron overload and gender in patients with TM.

Prevalence of diffuse idiopathic skeletal hyperostosis among elderly subjects referred for radiological investigation in tertiary hospital at Oman.

Diffuse idiopathic skeletal hyperostosis (DISH) is characterized by calcification of different entheseal sites including the anterior longitudinal ligament of the spine. There is no documented information about DISH in Oman. This study determined the prevalence of DISH and associated factors among elderly subjects in a national tertiary care referral hospital in Oman. This retrospective study reviewed chest X-rays of all patients aged more than 50 years, referred to the radiology department of Sultan Qaboos University Hospital in the year 2016, based on the Resnick's criteria. The prevalence was expressed as proportions across age groups and sex. Chi-square test and logistic regression analysis was done to determine the association of the age and sex with DISH. A total of 1305 chest X-rays of patients were reviewed. The overall prevalence of DISH was 10%, with male to female ratio of 1.56:1. The odds ratio for males and increasing age were 1.63 (95% confidence interval [CI], 1.12-2.3; P<0.05) and 1.34 (95% CI, 1.14-1.58; P<0.001) respectively. The prevalence increased with age to maximum of 13% in the age group of ≤80. The pre-stage DISH prevalence was 9.3% and more frequently observed among males. Prevalence of DISH in the national tertiary care referral center in Oman is lower than in Jewish population, almost similar to Japanese, but higher than in Koreans. DISH prevalence is positively associated with age and sex. It is necessary to take appropriate precautionary measures to target the ageing population in Oman, especially elderly males.

First Reported Case of Arrhythmogenic Right Ventricular Cardiomyopathy in Oman.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a rare genetic disorder characterized by fatty degeneration of the right ventricular myocardium with variable involvement of the left ventricle. The condition is associated with exercise-mediated ventricular tachycardia and is one of the recognized causes of sudden cardiac death in the young and in athletes. Here, we report the first confirmed case of ARVC in Oman and present its electrocardiographic, echocardiographic features, and radiological findings on gated, contrast-enhanced cardiac computed tomography. Our patient was a 22-year-old male who had presented to our hospital for evaluation and investigation of syncope and symptomatic palpitations.

Vascular Anomalies in Children Misdiagnosed with Asthma: Case series.

In most asthmatic children, inhaled steroids can relieve and control the symptoms of asthma. Persistent wheezing and respiratory symptoms in young children despite appropriate treatment may indicate other diagnostic considerations. Delays in this diagnosis can result in unnecessary investigations, inappropriate treatment and further complications. We report three patients who presented to Sultan Qaboos University Hospital, Muscat, Oman, in the period between September 2010 and May 2012 with persistent wheezing due to compression of the trachea caused by vascular anomalies. All patients had double aortic arches putting pressure on the trachea, leading to respiratory manifestations and feeding problems. Following surgery, all cases showed improvement and no longer required medication. Without clinical suspicion and appropriate imaging, congenital vascular anomalies may remain undetected for years. Infants and children with chronic wheezing should be evaluated for vascular anomalies as soon as possible. General practitioners should refer all such patients to a tertiary-level hospital for further investigations and management.

IAEA survey of paediatric computed tomography practice in 40 countries in Asia, Europe, Latin America and Africa: procedures and protocols.

OBJECTIVE: To survey procedures and protocols in paediatric computed tomography (CT) in 40 less resourced countries. METHODS: Under a project of the International Atomic Energy Agency, 146 CT facilities in 40 countries of Africa, Asia, Europe and Latin America responded to an electronic survey of CT technology, exposure parameters, CT protocols and doses. RESULTS: Modern MDCT systems are available in 77 % of the facilities surveyed with dedicated paediatric CT protocols available in 94 %. However, protocols for some age groups were unavailable in around 50 % of the facilities surveyed. Indication-based protocols were used in 57 % of facilities. Estimates of radiation dose using CTDI or DLP from standard CT protocols demonstrated wide variation up to a factor of 100. CTDI(vol) values for the head and chest were between two and five times those for an adult at some sites. Sedation and use of shielding were frequently reported; immobilisation was not. Records of exposure factors were kept at 49 % of sites. CONCLUSION: There is significant potential for improvement in CT practice and protocol use for children in less resourced countries. Dose estimates for young children varied widely. This survey provides critical baseline data for ongoing quality improvement efforts by the IAEA.

First case report of familial hypercholesterolemia in an Omani family due to novel mutation in the low-density lipoprotein receptor gene.

Familial hypercholesterolemia (FH) is an autosomal dominant genetic disorder. Mutations have been found in at least 3 genes: the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin type 9 (PCSK9). We report the first case of FH in an Omani family due to a novel mutation in the LDLR gene. A 9-year-old female was referred to our lipid clinic with eye xanthelasmata and thickening of both Achilles tendons. Evaluation of the lipid profile showed the off treatment total cholesterol of 896 mg/dL (23.2 mmol/L), low-density lipoprotein cholesterol (LDL-C) of 853 mg/dL (22.1 mmol/L), APOB of 4.5 g/L, triglyceride of 71 mg/dL (0.8 mmol/L), and high-density lipoprotein cholesterol of 0.74 mmol/L. Genetic analysis of the LDLR gene showed a homozygous frameshift deletion mutation (272delG) at exon 3. The female patient was treated with a combination of rosuvastatin/ezetimibe and LDL apheresis.

IAEA survey of pediatric CT practice in 40 countries in Asia, Europe, Latin America, and Africa: Part 1, frequency and appropriateness.

OBJECTIVE: The purpose of this study was to assess the frequency of pediatric CT in 40 less-resourced countries and to determine the level of appropriateness in CT use. MATERIALS AND METHODS: Data on the increase in the number of CT examinations during 2007 and 2009 and appropriate use of CT examinations were collected, using standard forms, from 146 CT facilities at 126 hospitals. RESULTS: The lowest frequency of pediatric CT examinations in 2009 was in European facilities (4.3%), and frequencies in Asia (12.2%) and Africa (7.8%) were twice as high. Head CT is the most common CT examination in children, amounting to nearly 75% of all pediatric CT examinations. Although regulations in many countries assign radiologists with the main responsibility of deciding whether a radiologic examination should be performed, in fact, radiologists alone were responsible for only 6.3% of situations. Written referral guidelines for imaging were not available in almost one half of the CT facilities. Appropriateness criteria for CT examinations in children did not always follow guidelines set by agencies, in particular, for patients with accidental head trauma, infants with congenital torticollis, children with possible ventriculoperitoneal shunt malfunction, and young children (< 5 years old) with acute sinusitis. In about one third of situations, nonavailability of previous images and records on previously received patient doses have the potential to lead to unnecessary examinations and radiation doses. CONCLUSION: With increasing use of CT in children and a lack of use of appropriateness criteria, there is a strong need to implement guidelines to avoid unnecessary radiation doses to children.

Acute unilateral third nerve palsy as an early manifestation of central nervous system relapse in a patient with acute myeloid leukemia.

The reported incidence of central nervous system (CNS) involvement by acute myeloid leukemia (AML) ranges widely from less than 10-30%. Acute unilateral third nerve palsy is an unusual first manifestation of such an event. We describe a rare ophthalmologic manifestation of CNS relapse in a 25-year-old patient with AML who had undergone allogeneic stem cell transplant, and demonstrate the value of MRI in the early diagnosis.