Establishment of local diagnostic reference levels for computed tomography with cloud-based automated dose-tracking software in Turkey.

PURPOSE: The purpose of this study is to establish local diagnostic reference levels (LDRLs) for computed tomography (CT) procedures using cloud-based automated dose-tracking software. METHODS: The study includes the dose data obtained from a total of 104,272 examinations performed on adult patients (>18 years) using 8 CT scanners over 12 months. The protocols included in our study were as follows: head CT without contrast, cervical spine CT without contrast, neck CT with contrast, chest CT without contrast, abdomen-pelvis CT without contrast, lumbar spine CT without contrast, high-resolution computed tomography (HRCT) of the chest, and coronary CT angiography (CTA). Dose data were collected using cloud-based automatic dose-tracking software. The 75th percentiles of the distributions of the median volume CT dose index (CTDIvol) and dose length product (DLP) values were used to determine the LDRLs for each protocol. The LDRLs were compared with national DRLs (NDRLs) and DRLs set in other countries. Inter-CT scanner variability, which is a measure of how well clinical practices are standardized, was determined for each protocol. Median values for each protocol were compared with the LDRLs for dose optimization in each CT scanner. RESULTS: The LDRLs (for DLP and CTDIvol, respectively) were 839 mGy.cm and 41.2 mGy for head CT without contrast, 530.6 mGy.cm and 19.8 mGy for cervical spine CT without contrast, 431.9 mGy.cm and 15.5 mGy for neck CT with contrast, 364.8 mGy.cm and 9.3 mGy for chest CT without contrast, 588.9 mGy. cm and 11.2 mGy for abdomen-pelvis CT without contrast, 713 mGy.cm and 24.3 mGy for lumbar spine CT without contrast, 326 mGy.cm and 9.5 mGy for HRCT, and 642.3 mGy.cm and 33.4 mGy for coronary CTA. The LDRLs were comparable to or lower than NDRLs and DRLs set in other countries for most protocols. The comparisons revealed the need for immediate initiation of an optimization process for CT protocols with higher dose distributions. Furthermore, protocols with high inter-CT scanner variability revealed the need for standardization. CONCLUSION: There is a need to update the NDRLs for CT protocols in Turkey. Until new NDRLs are established, local institutions in Turkey can initiate the optimization process by comparing their dose distributions to the LDRLs established in our study. Automated dose-tracking software can play an important role in establishing DRLs by facilitating the collection and analysis of large datasets.

T1 relaxation time is prolonged in healthy aging: a whole brain study.

BACKGROUND: : Measurement of tissue characteristics such as the longitudinal relaxation time (T1) provides complementary information to the volumetric and surface based structural analyses. We aimed to investigate T1 relaxation time characteristics in healthy aging via an exploratory design in the whole brain. The data processing pipeline was designed to minimize errors related to aging effects such as atrophy. METHODS: Sixty healthy participants underwent MRI scanning (28 F, 32 M, age range: 18-78, 30 young and 30 old) in November 2017-March 2018 at the Bilkent University UMRAM Center. Four images with varying flip angles with FLASH (fast low angle shot magnetic resonance imaging) sequence and a high-resolution structural image with MP-RAGE (Magnetization Prepared - RApid Gradient Echo) were acquired. T1 relaxation times of the entire brain were mapped by using the region of interest (ROI) based method on 134 brain areas in young and old populations. RESULTS: T1 prolongation was observed in various subcortical (bilateral hippocampus, caudate and thalamus) and cortical brain structures (bilateral precentral gyrus, bilateral middle frontal gyrus, bilateral supplementary motor area (SMA), left middle occipital gyrus, bilateral postcentral gyrus and bilateral Heschl's gyrus) as well as cerebellar regions (GM regions of cerebellum: bilateral cerebellum III, cerebellum IV V, cerebellum X, cerebellar vermis u 4 5, cerebellar vermis u 9 and WM cerebellar regions: left cerebellum IX, bilateral cerebellum X and cerebellar vermis u 4 5). DISCUSSION: T1 mapping provides a practical quantitative MRI (qMRI) methodology for studying the tissue characteristics in healthy aging. T1 values are significantly increased in the aging group among half of the studied ROIs (57 ROIs out of 134).

Evaluation of cortical thickness and brain volume on 3 Tesla magnetic resonance imaging in children with frontal lobe epilepsy.

BACKGROUND: Frontal lobe epilepsy (FLE) is the most common epilepsy syndrome in the pediatric population; however, brain magnetic resonance imaging (MRI) of the children with FLE is frequently normal. We use both cortical thickness and brain volume measurements to report on cortical changes in children with FLE. Our aim was to determine cortical thickness and brain volume changes on 3 Tesla MRI of children with FLE and normal brain magnetic resonance imaging. METHODS: Twenty-seven children with FLE and 27 healthy controls received brain magnetic resonance imaging. Cortical thickness and regional brain volumes were assessed using three-dimensional volumetric T1-weighted imaging and patients were compared with controls. RESULTS: In children with FLE, statistically significant (p < 0.05) cortical thinning were found in the bilateral middle frontal gyrus, bilateral occipitotemporal and medial lingual gyrus, left subcallosal gyrus, left short insular gyrus, and right long insular gyrus. Statistically significant volume reductions in right and left hemisphere cortical white matter, total cortical white matter, bilateral thalamus, bilateral putamen, bilateral globus pallidus, right caudate nucleus, brain stem, and right cerebellar cortex were found. CONCLUSION: Cortical thinning in frontal and extra-frontal lobes and volume loss in a variety of brain regions were found in children with FLE.

Evaluation of Neuroimaging Findings of Central Nervous System Complications in Heart Transplant Recipients.

OBJECTIVES: In this study, we presented neuroradiologic findings and diagnoses of neurologic complications in a series of heart transplant recipients. MATERIALS AND METHODS: A retrospective review was conducted at Baskent University Hospital. We searched the hospital and radiology databases and identified 109 heart transplant recipients. Thirty-one of these recipients had neuroradiologic evaluations secondary to presentation of neurologic symptoms after heart transplant, with 18 patients evaluated with computed tomography and 22 patients evaluated with magnetic resonance imaging (overlap of imaging-defined groups occurred in 9 recipients). Computed tomography and magnetic resonance imaging studies were retrieved from the Picture Archiving and Communication System, with each type of imaging retrospectively evaluated on consensus by 2 radiologists. RESULTS: Radiopathologic findings related to symptoms were detected in 12 of the 31 study patients. The most common abnormality was posterior reversible leukoencephalopathy syndrome (5 patients, 4.6%). The other abnormalities were ischemic stroke (3 patients, 2.8%), hemorrhagic stroke (1 patient, 0.9%), intracranial abscess (2 patients, 1.8%), and intracranial dissemination of sinusoidal fungal infection and related hemorrhagic infarct (1 patient, 0.9%). The other 19 heart transplant recipients who underwent computed tomography and/or magnetic resonance imaging for neurologic complaints showed no neuroradiologic findings related to neurologic symptoms. CONCLUSIONS: Posterior reversible leukoencephalopathy syndrome and ischemic stroke were the most common neurologic complications in our heart transplant recipients. The other complications were hemorrhagic stroke, intracranial abscess, and intracranial dissemination of sinusoidal fungal infection. Neurologic complications are common in heart transplant recipients and should be identified promptly for early treatment. For the recognition of these complications, computed tomography should be performed for initial evaluation to rule out edema or hemorrhage. However, in the presence of serious neurologic symptoms that cannot be explained by computed tomography, magnetic resonance imaging should be indicated.

Can unenhanced brain magnetic resonance imaging be used in routine follow up of meningiomas to avoid gadolinium deposition in brain?

PURPOSE: We hypothesized that unenhanced brain MRI can be used in follow up of patients with intracranial meningioma to avoid gadolinium deposition in the brain and allow measurement of meningioma dimensions from pre-contrast T2-weighted images. METHODS: Dimensions of meningiomas were measured on pre-contrast T2, post-contrast T1 weighted images. RESULTS: The sizes of meningiomas in post-contrast axial T1-weighted images were similar with that in pre-contrast axial T2-weighted images. Signal intensity increase was detected in dentate nucleus and globus pallidus (P < 0.05). CONCLUSION: Gadolinium deposition could be avoided in patients with meningioma by using unenhanced brain MRI for follow up scans.

Does renal function affect gadolinium deposition in the brain?

OBJECTIVE: Was to compare T1 signal intensity ratios of dentate nucleus to cerebellar white matter (DN/cerebellum), dentate nucleus to pons (DN/pons) and globus pallidus to thalamus (GP/thalamus) in patients with normal renal function and in patients on chronic hemodialysis. To find out if renal function affects the deposition of gadolinium in brain after administration of linear gadolinium based contrast agents (GBCA). METHODS: Seventy eight contrast enhanced brain MRIs (Magnetic Resonance Imaging) with linear GBCA of 13 patients on chronic hemodialysis and 13 patients with normal renal function retrospectively evaluated. The DN/pons, DN/cerebellum and GP/thalamus signal intensity ratios were measured from each brain MRI on unenhanced axial T1 weighted images. RESULTS: In hemodialysis group statistically significant increase in the signal intensity ratios of DN/pons, DN/cerebellum and GP/thalamus were found between the first and the last brain MRIs (p = .001). The increase in the signal intensity ratios of DN/pons, DN/cerebellum and GP/thalamus between the first and the last brain MRIs in control group were not significant (p > 0.05). The signal intensity increase in DN and globus pallidus were significantly higher in hemodialysis group than control group (p < 0.05). CONCLUSIONS: Patients on hemodialysis had significantly higher DN and GP signal intensity increase compared to the patients with normal renal function. Renal function affects the rate of gadolinium deposition in the brain after administration of linear GBCA.

Can strain elastography combined with ultrasound breast imaging reporting and data system be a more effective method in the differentiation of benign and malignant breast lesions?

PURPOSE: To investigate whether a novel method that combines breast imaging reporting and data system (BI-RADS) with strain elastography contributes to diagnostic performance in differentiation of malignant and benign breast lesions. METHODS: In 81 patients, 81 breast lesions were prospectively investigated. Breast lesions were separately evaluated with ultrasonography and strain elastography. While evaluations with ultrasonography were based on 2003 BI-RADS-US, strain elastography evaluations were based on a 5-point scale and strain ratio. Diagnostic performances of ultrasonography, strain elastography, and the combined method were compared. RESULTS: Among 81 lesions, 43 (53.1%) were benign and 38 (46.9%) were malignant. When a cutoff point of category 3 was used, sensitivity, specificity, positive and negative predictive values, and accuracy for BI-RADS were 100, 11.6, 50, 100, and 53%, respectively. When BI-RADS and strain ratio were combined, sensitivity, specificity, positive and negative predictive values, and accuracy were 89.5, 93, 91.9, 90.9, and 91.3%, respectively. When BI-RADS and elastography scores were combined, sensitivity, specificity, positive and negative predictive values, and accuracy were 86.8, 97.7, 97.1, 89.4, and 92.5%, respectively. CONCLUSIONS: The combination of strain elastography and BI-RADS was found to have better diagnostic performances to diagnose breast lesions than BI-RADS alone.

Utility of Diffusion-Weighted MRI to Detect Changes in Liver Diffusion in Benign and Malignant Distal Bile Duct Obstruction: The Influence of Choice of b-Values.

PURPOSE: The study sought to evaluate the potential of diffusion-weighted magnetic resonance imaging to detect changes in liver diffusion in benign and malignant distal bile duct obstruction and to investigate the effect of the choice of b-values on apparent diffusion coefficient (ADC). METHODS: Diffusion-weighted imaging was acquired with b-values of 200, 600, 800, and 1000 s/mm2. ADC values were obtained in 4 segments of the liver. The mean ADC values of 16 patients with malignant distal bile duct obstruction, 14 patients with benign distal bile duct obstruction, and a control group of 16 healthy patients were compared. RESULTS: Mean ADC values for 4 liver segments were lower in the malignant obstruction group than in the benign obstruction and control groups using b = 200 s/mm2 (P < .05). Mean ADC values of the left lobe medial and lateral segments were lower in the malignant obstruction group than in the benign obstructive and control groups using b = 600 s/mm2 (P < .05). Mean ADC values of the right lobe posterior segment were lower in the malignant and benign obstruction groups than in the control group using b = 1000 s/mm2 (P < .05). Using b = 800 s/mm2, ADC values of all 4 liver segments in each group were not significantly different (P > .05). There were no correlations between the ADC values of liver segments and liver function tests. CONCLUSION: Measurement of ADC shows good potential for detecting changes in liver diffusion in patients with distal bile duct obstruction. Calculated ADC values were affected by the choice of b-values.

Recurrent childhood PRES.

The purpose of the study was to review the recurrent posterior reversible encephalopathy syndrome (PRES) and emphasize the possibility of repeated attacks on the basis of particular clinical situations. 32 children, diagnosed with PRES were included in our study. The recurrent cases were determined; their radiological features such as involved localizations and clinical information such as presenting symptoms, underlying diseases and clinical prognosis are retrospectively assessed. Of the 32 children (8 months to 18 years old; mean age 11), four of the patients had recurrent episodes of PRES. They had different underlying diseases. One had Chediak-Higashi syndrome, one had ALL, one had chronic renal disease on hemodialysis and one was a renal transplant recipient. Three of the children recovered with no residual neurological deficits, one of them passed away due to multiorgan failure. Three of them had high blood pressures at the time of either one or both PRES, and the renal transplant recipient had also high blood levels of Tacrolimus. Recurrent PRES is encountered most commonly because of repeated increasing blood pressures due to various underlying diseases, immune system disorders or side effects of the treatments.

Predisposing factors in posterior circulation infarcts: a vascular morphological assessment.

INTRODUCTION: The aim of the study is to assess the effect of shape, diameter, elongation and deviation criteria of basilar artery (BA), convergence angle and diameter variations of vertebral arteries, and concurrent chronic diseases on posterior circulation infarcts. METHODS: Between January 2010 and May 2013, 186 patients who underwent brain and diffusion magnetic resonance imaging (MRI) with suspected cerebrovascular accident and were diagnosed with posterior circulation infarct and 120 infarct negative control subjects were included in this case-control retrospective study. Vertebral artery (VA) and BA diameter, right (R) and left (L) VA angles at the level of bifurcation, and BA elongation-deviation, and shape of BA were assessed in a total of 306 subjects. Ischemic lesions in the posterior circulation were classified according to their anatomical location and vascular perfusion areas. RESULTS: No significant difference was noted between the control and patient groups with respect to BA diameter (p = 0.676). The most effective risk factors for posterior circulation infarcts were as follows: BA elongation of 2 or 3, BA transverse location of 2 or 3, increase in left VA angle, and history of hypertension, hypercholesterolemia, and diabetes mellitus. CONCLUSION: Our results suggest that prominent elongation and deviation, C and J shape of BA, and increased L VA angle may be the predictors of at-risk patients in posterior circulation infarcts. Reporting marked morphological BA and VA variations detected at routine brain MRI will aid in selection of patients. Timely detection and treatment of at-risk patients may be life-saving.

Acute necrotizing encephalopathy secondary to diphtheria, tetanus toxoid and whole-cell pertussis vaccination: diffusion-weighted imaging and proton MR spectroscopy findings.

We present a previously healthy 6-month-old boy who was admitted to our hospital with lethargy, hypotonia and focal clonic seizures 6 days following diptheria, tetanus toxoid and whole-cell pertussis vaccination. A diagnosis of acute necrotising encephalopathy was made with the aid of MRI, including diffusion-weighted imaging and proton MR spectroscopy.

STIR sequence for depiction of degenerative changes in posterior stabilizing elements in patients with lower back pain.

OBJECTIVE: The aims of this study were to investigate whether degenerative posterior paraspinal changes are a cause of lower back pain and to determine the age- and sex-related distribution of these changes on MR images acquired with a STIR sequence. SUBJECTS AND METHODS: The lumbar MRI findings of 372 patients (141 men, 231 women; mean age, 51.2 years) with nonradicular lower back pain and of 249 healthy persons acting as controls (126 men, 123 women; mean age, 49.3 years) were analyzed. The sagittal STIR sequence was used for all MRI examinations. Presence of interspinous ligament edema, facet joint effusion, neocysts, paraspinal muscle edema, subcutaneous edema, disk herniation, and disk degeneration was evaluated, and the incidence of each finding was determined. All findings were grouped according to age and sex. Chi-square, Fisher's exact, and independent-samples Student's t tests and Spearman's rank correlation analysis were used for statistical analysis. RESULTS: The incidences of facet joint effusion, interspinous ligament edema, neocyst formation, and paraspinal muscle edema were found to be statistically significantly higher in patients with lower back pain than in controls. The incidences of intervertebral disk degeneration, disk herniation, and subcutaneous edema in persons with and those without lower back pain were similar. Intervertebral disk degeneration, disk herniation, subcutaneous edema, and muscle edema were found to increase with age in both persons with and those without symptoms. CONCLUSION: Degenerative changes in the posterior paraspinal structures were found in a higher percentage of subjects with lower back pain than in controls. Use of a STIR sequence with homogeneous fat suppression facilitates visualization of these changes.

Evaluation of cerebral glioma grade by using normal side creatine as an internal reference in multi-voxel 1H-MR spectroscopy.

PURPOSE Our purpose was to evaluate cerebral glioma grade by using normal side creatine (Cr) as an internal reference in multi-voxel 1H-MR spectroscopy. MATERIALS AND METHODS We examined 25 adult patients with glial brain tumors. Ratios of maximum Cho/Cr (normal) (max- Cho/Cr(n)) and minimum NAA/Cr(normal) (min-NAA/ Cr(n)) were determined using Cr levels in the normal parenchyma. In addition, maximum Cho/Cr (max- Cho/Cr) and minimum NAA/Cr (min-NAA/Cr) were calculated from spectrum in the tumor areas. Tumors were graded according to metabolite ratios and the findings were compared to histopathological test results. The sensitivity, specificity, positive and negative predictive values of metabolite ratios were determined. RESULTS The ratio of max-Cho/Cr(n) was lower than that of max-Cho/Cr in the high-grade group (P = 0.001). Min-NAA/Cr(n), min-NAA/Cr, and max-Cho/Cr ratios demonstrated statistically significant differences between high-grade (n = 19) and low-grade tumors (n = 6). The min-NAA/Cr and min-NAA/Cr(n) ratios were inversely correlated with tumor grade (P = 0.027 and P = 0.009, respectively). CONCLUSION Use of normal side Cr as an internal reference provides a more objective evaluation for brain tumor grading. Our data showed that Cr tended to be low in the high-grade tumors. In addition to conventional metabolite ratios, the Min-NAA/Cr(n) ratio might be useful in brain tumor grading. Combined use of metabolite ratios might be helpful in grading brain tumors in cases without significantly increased Cho/Cr ratios.

Proton MR spectroscopy in the diagnosis of early-stage subacute sclerosing panencephalitis.

Subacute sclerosing panencephalitis (SSPE) is a progressive, fatal neurological disorder of childhood and early adolescence. In this report, we present brain magnetic resonance spectroscopy (MRS) and conventional magnetic resonance MR imaging findings of early-stage (stage II) SSPE in an 8-year-old child. MRS demonstrated increased myo-inositol/creatine and choline/creatine ratios, and a decreased N-acetyl aspartate/creatine ratio. Conventional MR imaging demonstrated nonspecific, patchy T2 hyperintensities in the periventricular white matter and a nonspecific focus of T2 hyperintensity in the right frontal subcortical white matter. The MRS findings suggested active inflammation and demyelination as is seen in early-stage SSPE.

Preoperative local staging of rectal cancer with endorectal MR imaging: comparison with histopathologic findings.

The purpose of this prospective study was to assess the accuracy of endorectal MR imaging in the preoperative local staging of rectal cancers. In 20 cases, we correlated endorectal MR imaging findings with postoperative histopathologic staging according to TNM classification. The accuracy of endorectal MR for determining the T stage of rectal cancer was 85%. The sensitivity and specificity for detecting lymph node metastases were 90.9% and 55.5%, respectively.

Contrast-enhanced magnetic resonance angiography: evaluation of renal arteries in living renal transplant donors.

One of the most important steps before living-donor nephrectomy is assessment of renal vascular anatomy. The number, origins and lengths of the renal arteries and variations of renal veins must be determined in order to identify the kidney that is most suitable for transplantation. Digital subtraction angiography was long considered the standard procedure for this purpose, but this method has been replaced by non-invasive techniques. Contrast-enhanced magnetic resonance angiography is an accurate, safe and reliable method for imaging vasculature. This article reviews the technique and the clinical features of this method in the evaluation of living renal transplant donors.

Local staging of prostate cancer with endorectal surface coil MR imaging in a mid-field magnetic system.

To investigate the accuracy of endorectal surface coil magnetic resonance imaging (ecMRI) in a 1.0-T magnetic field for the local staging of prostate cancer, 25 patients were studied. In 14 Stages T1 and T2 tumors, 11 were correctly identified and 3 were overstaged. In 11 Stage T3 neoplasms, ecMRI was accurate in 7 cases, and the other 4 were understaged. The overall accuracy of ecMRI in 1.0 T was 72% and that was comparable to the reported accuracy of this technique in high-field systems.