Evaluation of average glandular dose (AGD) in screening and diagnostic digital mammography and digital breast tomosynthesis (DBT) towards establishing a reference dose range band (DRB): a developing country experience.

This study represents the first national survey conducted in Sri Lanka to establish national diagnostic reference levels (NDRLs) for screening and diagnostic acquisitions in digital mammography (2D-DM) and digital breast tomosynthesis (DBT). Additionally, the study investigated the relationship between average glandular dose (AGD) and compressed breast thickness (CBT) and introduced a novel concept called dose range bands (DRBs) as a tool for optimizing radiation dose in mammography. DICOM metadata was used to extract dose data and exposure parameters from women undergoing either screening (350) or diagnostic (750) DM. The analysis included both craniocaudal and mediolateral oblique views of each breast, acquired using 2D-DM and DBT imaging techniques. The NDRL (AGD per view) was 1.97 mGy and 2.01 mGy for diagnostic DM and DBT, respectively. The corresponding NDRLs for screening acquisition were 2.44 mGy and 2.30 mGy. The mean DBT/DM AGD ratio was 1.39 and 0.97 for diagnostic and screening, respectively. Further, the association between the average glandular AGD per view and CBT is stronger in DBT than in 2D-DM. The study findings highlight the need for standardisation of compression practices, considering factors such as the radiographer's experience, imaging equipment, breast density, age, breast size, and pain threshold.

Dose reference level based on size-specific dose estimate (SSDE) and feasibility of deriving effective body diameter using tube current and time product (mAs) for adult chest and abdomen computed tomography (CT) procedures.

This study aimed to establish dose reference level (NDRLSSDE) based on size-specific dose estimate (SSDE) derived using effective diameter (Deff) for adult chest and abdomen computed tomography (CT) procedures and to explore the feasibility of drivingDeffusing the product of tube current and time (mAs). In this retrospective study, dose data, scan parameters and patient body dimensions at the mid-slice level from 14 CT units (out of 63 total) were extracted. Additionally, the mAs values of the axial slice at the samez-location where the diameter measurements were made (mAsz) were recorded. Pearson's correlation (r) analysis was used to determine the relationship ofDeffwith patient BMI, weight, and mAsz. The NDRLSSDEfor the chest and abdomen were 9.72 mGy and 13.4 mGy, respectively. The BMI and body weight were less correlated (r= 0.24 andr= 0.33, respectively) withDeff. The correlation between mAszandDeffwas considerably strong (r= 0.78) and can be used to predictDeffaccurately. The absolute dose differences between SSDEs calculated using the AAPM-204 method and mAszwas less than 1.1 mGy (15%). Therefore, mAszis an efficient parameter to deriveDeff. Further, the direct conversion factors to estimate SSDEs at different locations along thez-direction in the scan region from corresponding mAs and CTDIvolwere calculated. The NDRLSSDEsuggested in the present study can be used as a reference for size-dependent dose optimisation in Sri Lanka, and existing NDRL based on CTDIvolunderestimate the average adult CT dose by 36.0% and 39.7% for chest and abdomen regions respectively. The results show that using mAszto determine SSDE is a simple and practical approach with an accuracy of 95% and 85% for abdomen and chest scans, respectively. However, the obtained linear relationship betweenDeffand mAs is highly dependent on the ATCM technique and the user-determined noise levels of the scanning protocol. Finally, the phantom study resulted in the strongest correlation (r= 0.99) between theDwzand mAsz, and the prediction of patient size would be more precise thanDeffmethod.

Age and sex related variations of adult human ocular volumes in the Sri Lankan population: an evaluation using magnetic resonance imaging.

INTRODUCTION: Variations in the human ocular volumes are related to ocular pathologies including congenital glaucoma, microphthalmus, buphthalmus, and macrophthalmus. As the currently published reference ocular volumes are prone to physiological and racial variations, population specific values may provide more precision in ophthalmological interventions. This study was conducted to assess the age and sex dependent differences in ocular volumes in Sri Lankan individuals using magnetic resonance imaging (MRI). METHODS: The study was undertaken using the brain MRI scans from 200 patients which were reported as normal. Study sample consisted of patients between 18 years and 90 years of age with 91 male subjects and 109 female subjects. Two independent observers measured ocular volumes using a software-based method and an MRI planimetry based method. Age and sex of the study participants were recorded for the further analysis. RESULTS: Statistically significant differences in both ocular volumes were found between males and females (p < 0.05) when using both volume analysis methods. The mean ± SD ocular volumes obtained as right software based volume, right MRI planimetry volume, left software based volume and left MRI planimetry volume were 6.8 ± 0.6, 6.0 ± 0.6, 6.6 ± 0.7 and 5.9 ± 0.6 cm3 in females and 6.9 ± 0.8, 6.3 ± 0.7, 6.9 ± 0.8 and 6.2 ± 0.7 cm3 in males. While software-based measurements show a significant linear correlation with age in both eyeball volumes, MRI planimetry measurement showed a significant linear correlation with age only in the left eyeball (p < 0.05). Weak negative correlations were found with age in right ocular volume in both MRI planimetry based (r = -0.121) and software based (r = -0.168) measurements and in left ocular volume in MRI planimetry based (r = -0.151) and software based (r = -0.179) measurements. Furthermore, ocular volumes obtained from the software-based method were significantly greater than the MRI planimetry based ocular volumes (p < 0.05) in both eyes, despite having a strong positive correlation. CONCLUSION: The mean ocular volumes obtained from this study revealed a significant variation between the right and left eyes as well as a sexual dimorphism. Moreover, since the two measurement methods show a significant difference, the choice of measurement method should depend on the required accuracy of the eye volume decided with respect to the clinical implication. IMPLICATIONS FOR PRACTICE: Since there are no reference values for Sri Lankan adult ocular volumes, this study may serve that purpose in the current population, while supporting ophthalmologists and radiologists to quantitatively evaluate ocular pathologies and to follow precise interventions.

Patient size as a parameter for determining Diagnostic Reference Levels for paediatric Computed Tomography (CT) procedures.

INTRODUCTION: The paediatric radiation dose has never been studied in Sri Lanka, nor has a national diagnostic reference level (NDRL) established. Therefore, the primary aim of this study was to propose diagnostic reference levels (DRL) and achievable dose (AD) values for paediatric CT examinations based on size. METHODS: A total of 658 paediatric (0-15 years) non-contrast-enhanced (NC) studies of head, chest and abdomen regions performed during six months in two dedicated paediatric hospitals (out of the three such institutions in the country) were included. For head examinations, the dose indexes were analysed based on age, while for body examinations, both age and effective diameter (Deff) were used. The median and the third quartile of the pooled dose distribution were given as AD and NDRL, respectively. RESULTS: The AD ranges for the head, chest and abdomen regions based on CTDIvol were 45.8-57.2 mGy, 2.9-10.0 mGy and 3.8-10.3 mGy. The corresponding NDRL ranges were 45.8-95.8 mGy, 3.5-14.1 mGy and 4.5-11.9 mGy. The AD ranges based on SSDEdeff and deff were 3.5-9.6 mGy and 4.1-10.3 mGy in chest and abdomen regions. The corresponding NDRL were 4.5-14.1 mGy and 6.1-10.6 mGy. CONCLUSION: Other institutions can use the present study DRLs as a reference dose for paediatric CT. The AD values can be used as a baseline for target dose optimisations, reducing doses up to 90%.

IMPACT OF COLLIMATION ON RADIATION EXPOSURE IN ADULT AND PAEDIATRIC DIGITAL X-RAY IMAGING.

This study aimed to evaluate the collimation practices and quantify the overexposure due to extensive X-ray field area. The study was carried out in four digital X-ray units (including one paediatric X-ray unit). A total of 749 X-ray projections (555 adult and 194 paediatric) were evaluated. In adult X-ray units, the radiation field size was two times larger than the electronically collimated field. In the paediatric unit, the radiation field was 3.7 times larger than the electronic collimated field. The average additional entrance surface dose due to the excess radiation field used in a paediatric X-ray unit varied between 9.3 (2.5%) and 201.4 $\mu $Gy (10.9%). Therefore, proper pre-patient collimation should be applied whenever feasible, which reduces the patient radiation dose considerably.

Size-specific dose estimates (SSDEs) for computed tomography and influencing factors on it: a systematic review.

The actual dose received during a computed tomography (CT) examination depends on both the patient size and the radiation output of the scanner. To represent the actual patient morphometry, a new radiation dose metric named size-specific dose estimates (SSDEs) was developed by the American Association of Physicists in Medicine in 2011. The purpose of this article is to review the SSDE concept and the factors influencing it. Moreover, the appropriate methodology of SSDE determination and the application of SSDE as a diagnostic reference-level quantity is critically analyzed based on the data available in the literature. It is expected that this review could potentially increase awareness among CT users of the effective utilization of SSDE as a tool to aid in the optimization of radiation dose in CT.

Paediatric diagnostic reference levels in computed tomography: a systematic review.

This study aims to review the existing literature on diagnostic reference levels (DRLs) in paediatric computed tomography (CT) procedures and the methodologies for establishing them. A comprehensive literature search was done in the popular databases such as PubMed and Google Scholar under the key words 'p(a)ediatric DRL', 'dose reference level', 'diagnostic reference level' and 'DRL'. Twenty-three articles originating from 15 countries were included. Differences were found in the methods used to establish paediatric CT DRLs across the world, including test subjects, reference phantom size, anatomical regions, modes of data collection and stratification techniques. The majority of the studies were based on retrospective patient surveys. The head, chest and abdomen were the common regions. The volume computed tomography dose index (CTDIvol) and dose-length product (DLP) were the dosimetric quantities chosen in the majority of publications. However, the size-specific dose estimate was a growing trend in the DRL concept of CT. A 16 cm diameter phantom was used by most of the publications when defining DRLs for head, chest and abdomen. The majority of the DRLs were given based on patient age, and the common age categories for head, chest and abdomen regions were 0-1, 1-5, 5-10 and 10-15 years. The DRL ranges for the head region were 18-68 mGy (CTDIvol) and 260-1608 mGy cm (DLP). For chest and abdomen regions the variations were 1.0-15.6 mGy, 10-496 mGy cm and 1.8-23 mGy, 65-807 mGy cm, respectively. All these DRLs were established for children aged 0-18 years. The wide range of DRL distributions in chest and abdomen regions can be attributed to the use of two different reference phantom sizes (16 and 32 cm), failure to follow a common methodology and inadequate dose optimisation actions. Therefore, an internationally accepted protocol should be followed when establishing DRLs. Moreover, these DRL variations suggest the importance of establish a national DRL for each country considering advanced techniques and dose reduction methodologies.

Dental age estimation using radiographs: Towards the best method for Sri Lankan children.

Research supports the need for regionally and ethnically specific validated data as the reference base for age estimation techniques. This retrospective study evaluated the accuracy of three dental age estimation methods; Demirjian et al. (1973), Willems et al. (2001), and Blenkin and Evans (2010), for use in Sri Lanka for medico-legal purposes. Panoramic radiographs of 688 Sri Lankan children ranging in age from 8.00 to 16.99 years were used to determine their appropriateness to a Sri Lankan population. The mean age and standard deviations (±SD) were calculated separately for males and females of each age group. Paired t-test and mean absolute errors (MAE) were calculated to compare the calculated dental age (DA) with the chronological age (CA) across the nine age groups. The results revealed the mean CA of the entire sample was 12.38 ± 2.68 years, while the mean DA calculated using the Blenkin and Evans method was 11.83 ± 2.20 years, using the Demirjian et al. method was 12.57 ± 2.53 years, and using the Willems et al. method was 11.99 ± 2.43 years. The Demirjian et al. method consistently overestimated the age of males except in the 2 groups aged over 15 years, whereas the Blenkin and Evans method consistently underestimated the age except for the 11.00-12.99 age range. The method of Willems et al. produced DA quite close to CA up until 12.99 years of age, and then underestimated the age for all higher age groups. In females, the Demirjian et al. method consistently overestimated the age up until 13.99 years and then underestimated the higher age groups, while the Willems et al. method underestimated the age in all age groups except 10.00-10.99 years. The Blenkin and Evans method also consistently underestimated the age except in the 10.00-10.99 and 12.00-12.99-year age groups. The percentages of either overestimation or underestimation calculated for ±0.5 years of the true age were 41.0% for the Blenkin and Evans method, 42.8% for the Demirjian et al. method and 49.1% for the Willems et al. method. In conclusion, while all three methods could be applicable in the estimation of dental age for medico-legal purposes, the Willems et al. method appears to be more appropriate in overall measures for the Sri Lankan reference sample, up to the age of 12.99 years.

A case report of melioidosis complicated by infective sacroiliitis in Sri Lanka.

BACKGROUND: Melioidosis is an infection caused by a facultative intracellular Gram-negative bacterium, Burkholderia pseudomallei. It can present as septicemia, localized infection with/without septicemia, asymptomatic infections, ulcers, pneumonia, visceral abscesses, neurological infection, musculoskeletal infections and can involve any organ. CASE PRESENTATION: A 56 year old Sri Lankan diabetic female presented with fever, chills and rigors for 2 weeks. She also had malaise and loss of appetite, but no other features. On examination, she was febrile (temperature was 101.4 0 F) and rest of the examination was unremarkable. Her blood culture was positive for Burkholderia pseudomallei and she was started on IV antibiotics, on day 3. During her 2nd week of hospital stay, she developed right sided low back pain with buttock pain, right hip joint pain and restricted hip joint movements suggestive of right sacroiliitis. CE CT and MRI scans confirmed the diagnosis of right iliopsoas abscesses and right sacroiliitis.Incision and drainage was performed and a pigtail catheter was left in place for continuous drainage of abscesses. Her intensive phase was initiated with IV ceftazidime 2 g every 6 h for 12 days, then changed over to IV meropenem 2 g every 8 h together with oral co-trimoxazole. 2 weeks later, oral co-trimoxazole was replaced by oral doxycycline for another 6 weeks (due to transient pancytopaenia). She made a complete and uneventful recovery with oral co-trimoxazole for another 6 months, in her eradication phase.We report this case to show the importance in early diagnosis of melioidosis, and to consider it in the differential diagnosis of multiple abscesses and to emphasize the importance in suspecting melioidosis as a causative agent in infective sacroiliitis. DISCUSSION: Melioidosis can have 2 major presentations; acute infection (symptoms lasting less than 2 months) and chronic infection (symptoms lasting more than 2 months). Musculoskeletal melioidosis is a well-recognized manifestation of the disease, which can manifest as soft tissue abscesses, septic arthritis, spondylitis, sacroiliitis and osteomyelitis.Management of melioidosis consists of 2 phases. The intensive phase and the eradication phase. These are aimed at the importance of rapidly treating the septicemia, the need of eradication of the persistent disease and the prevention of recurrent infections or relapses. The intensive phase consists of minimum 10-14 days of IV antibiotics: IV ceftazidime or IV carbapenem (meropenem/ imipenem). Eradication phase should be followed by 3-6 months of oral co-trimoxazole alone or in combination with oral doxycycline/ oral amoxiciliin-clavulanic acid.

Magnetic resonance imaging findings of patients with suspected tuberculosis from a tertiary care centre in Sri Lanka

Introduction: Spinal tuberculosis (TB) is a relatively common cause for spinal pathology in Sri Lanka and a common indication for magnetic resonance imaging (MRI). Objectives: The objective of the study was to describe the MRI imaging pattern of spinal TB in a series of patients. Methods: One hundred and nine patients with clinically confirmed spinal tuberculosis who had undergone MRI scans at the National Hospital of Sri Lanka from 2012-2016 were included in the study. Results: The commonest vertebral level of spinal TB involvement was at L4/5 level, followed by L5/S1 level. L5 vertebral body involvement was the commonest and L4 was second commonest. Single level involvement (68.8%) was commoner than multiple (31.2%) involvement or contiguous involvement. Wedging (24.8%), erosions (89%), end plate changes (96.3%), canal stenosis (77.1%), paravertebral collection (65.1%), prevertebral collection (39.4%), psoas abscess (23.9%) and epidural collection (45.9%) were noted. No significant difference was seen between females and males. Conclusions: Spinal tuberculosis commonly involves L4/5 level.

A study to establish international diagnostic reference levels for paediatric computed tomography.

The article reports results from the largest international dose survey in paediatric computed tomography (CT) in 32 countries and proposes international diagnostic reference levels (DRLs) in terms of computed tomography dose index (CTDI vol) and dose length product (DLP). It also assesses whether mean or median values of individual facilities should be used. A total of 6115 individual patient data were recorded among four age groups: <1 y, >1-5 y, >5-10 y and >10-15 y. CTDIw, CTDI vol and DLP from the CT console were recorded in dedicated forms together with patient data and technical parameters. Statistical analysis was performed, and international DRLs were established at rounded 75th percentile values of distribution of median values from all CT facilities. The study presents evidence in favour of using median rather than mean of patient dose indices as the representative of typical local dose in a facility, and for establishing DRLs as third quartile of median values. International DRLs were established for paediatric CT examinations for routine head, chest and abdomen in the four age groups. DRLs for CTDI vol are similar to the reference values from other published reports, with some differences for chest and abdomen CT. Higher variations were observed between DLP values, based on a survey of whole multi-phase exams. It may be noted that other studies in literature were based on single phase only. DRLs reported in this article can be used in countries without sufficient medical physics support to identify non-optimised practice. Recommendations to improve the accuracy and importance of future surveys are provided.

Meckel's scan in children: a review of 183 cases referred to two paediatric surgery specialist centres over 18 years.

AIM: To review our practice of Meckel's Tc-99m pertechnetate scans over 18 years with regard to indications for the test, sensitivity and specificity in our particular referral patients' population. MATERIALS AND METHODS: This is a retrospective review of Meckel's scans performed in two paediatric tertiary care teaching hospitals from April 1993 to March 2011 and followed up till October 2011. The scan was performed according to published international guidelines. 183 patients were included in this study. We classified the patients into two groups: group 1, which included 77 patients (42 %) presenting with painless per rectum bleeding, and group 2, which included 106 patients (58 %) presenting with other non-specific symptoms (e.g. abdominal pain, possibly associated with nausea and/or vomiting, failure to thrive). Data were analysed using Chi square test, considering P value less than 0.05 as significant. The age of the patients ranged from 4 days to 16.5 years (median 3 years). RESULTS: 161 of the total 183 children on the study (88 %) had a negative Meckel's scan, and 22 children (12 %) had a positive scan. In the group with a positive Meckel's scan (22 children), all patients underwent surgical exploration and ectopic gastric mucosa was found in 17 cases (77 %, true positives). In the remaining 5 cases (23 %), there was no evidence of ectopic gastric mucosa (false positives). Within the group with a negative scan, 8 children (5 %) underwent surgery; only 1 child had a ectopic gastric mucosa detected following surgery (false negative). In other 52 children (32 %) of the group with a negative Meckel's scan, an endoscopy was done, which showed a normal result in 21 children and was abnormal in 31 children. Of the remaining 101 (63 %) children with a negative Meckel's scan, 74 children (46 %) improved without any further intervention. In 13 cases (8 %), other pathologies were identified. The sensitivity and specificity of the Meckel's scan for ectopic gastric mucosa were 94 and 97 %, respectively. The Meckel's scan was positive in 26 % of the patients of group 1 and in only 2 % patients of group 2. The difference between the two groups was highly significant [P < 0.0001 (Yates-corrected Chi square); odds ratio 18 (Woolf-logit method 95 % CI)]. CONCLUSION: The Meckel's scan retains a high diagnostic accuracy in children for detecting a Meckel's diverticulum with ectopic gastric mucosa within it, when performed according to the recommended guidelines. The test yields its highest positive result in children presenting with significant per rectum bleeding.