Consecutive Computed Tomography Examinations Research Articles

Low dose pediatric chest computed tomography on a photon counting detector system – initial clinical experience

BackgroundWith the clinical release of a photon counting detector-based computed tomography (CT) system, the potential benefits of this new technology need to be evaluated clinically. Literature concerning this new generation of detector is sparse, especially in the field of pediatric radiology. Therefore, this study outlines our initial experience with ultra-low dose chest CT imaging on the new photon counting CT system.Materials and methodsA pediatric phantom (1-year old, CIRS ATOM phantom, model 704 [CIRS-computerized imaging reference system, Norfolk, VA]) was scanned at different dose levels and different image quality levels to define a protocol for clinical examinations. Next, 20 consecutive pediatric non-contrast ultra-low dose chest CT examinations were evaluated for radiation dose and diagnostic image quality using a 4-point Likert-scale—1 = excellent, 4 = bad image quality—by two radiologists in a consensus reading. This retrospective analysis was approved by the local research ethics committee.ResultsChest CT examinations performed at ultra-low radiation dose (effective dose 0.19 ± 0.07 mSv; size-specific dose estimate 0.45 ± 0.14 mGy) in pediatric patients ages (2.6 ± 1.8 years) show good to excellent image quality for lung structures (1.4 ± 0.4) and moderate image quality for soft tissue structures (2.8 ± 0.2).ConclusionPediatric ultra-low dose chest CT examinations are feasible with the new generation photon counting detector-based CT system. The benefits of this technology must be evaluated for pediatric patients from the outset.

SIMPLE METHOD OF MEASURING SSDE FOR HEAD CT: FACILITATING PRE-CT SCAN DOSE CALCULATION USING SPECIALIZED HEAD SCAN BAND

In this study, scaled scan band was developed to provide size-specific dose estimation (SSDE) values based on head circumference of patients undergoing computed tomography (CT) scans. The scan band was tested in 40 consecutive head CT examinations. The accuracy of the specialized scan band method was determined by comparing SSDEband with SSDE293,forehead, SSDEmean and SSDEcenter. SSDE293,forehead was used as the control value. The results of the linear fit of SSDEband, SSDEmean and SSDEcenter against SSDE293, forehead, were R2=0.958, R2=0.984 and R2=0.936, respectively. There was no significant difference between SSDEband, SSDEmean and SSDEcenter for SSDE293,forehead. Use of the proposed scan band method makes it possible to accurately determine the required radiation dose before a CT examination is performed.

The role of MRI and CT of the brain in first episodes of psychosis and behavioural abnormality

To investigate whether computed tomography (CT)/magnetic resonance imaging (MRI) brain imaging is associated with detection of structural causes of a first episode of psychosis (FEP) or first episode of behavioural abnormality (FEB) in the paediatric population, as this has not been previously documented in the literature. Individuals with FEP/FEB but no neurological signs referred to a tertiary children's centre for cerebral MRI or CT were reviewed retrospectively. Individuals were evaluated independently with one technique (CT or MRI) only. Thirty-four consecutive cerebral MRI and six consecutive CT examinations were identified between 2017 and 2020. No patients were identified as having an organic cause for the psychosis at MRI or CT. Four patients (9%) had incidental findings on MRI, unrelated to the psychosis, such as prominent perivascular spaces, hypoplastic transverse sinus, and sinonasal mucosal wall thickening. No abnormal findings were seen on CT. There was therefore no obvious difference between MRI and CT imaging in detecting organic disease potentially responsible for FEP. Routine structural MRI or CT of the brain is unlikely to reveal disease leading to a significant change in management. MRI demonstrated only a few incidental findings, unrelated to the child's clinical history. Therefore, routine brain structural imaging of FEP/FEB in paediatric patients without focal neurology may not be routinely required. If imaging is requested, then there is no significant difference between CT and MRI in detecting clinically significant lesions.

Acetabular shape and orientation of the spastic hip in children with cerebral palsy.

To see if three-dimensional (3D) methods could bring new understanding to acetabular changes in shape and orientation in the spastic hip and in which direction(s) acetabular orientation might change, which is crucial for planning appropriate hip correction surgery. We performed a retrospective study of pelvic computed tomography (CT) examinations in 20 consecutive patients (10 females, 10 males). The mean age of patients was 12 years 9 months (SD 2y; range: 9-16y) at the time of the CT examination. The control group consisted of 18 consecutive pelvic CT examinations (36 acetabula) of deceased individuals (six females, 12 males) aged 4 to 17 years (mean age: 10y 6mo; SD 5y 2mo) whose whole-body CT scans were taken shortly after their death. We compared 3D CT reconstructions of 28 unstable and dislocated hips in children with bilateral cerebral palsy (Gross Motor Function Classification System levels IV and V) with the unaffected side and typically developing controls to assess spatial orientation (inclination, anteversion, and tilt), acetabular volume, and surface area. Additionally, we analysed the multiple factors that may lead to structural and spatial changes of the acetabulum. Patients with dislocated and spastic hips had significantly lower anteversion (-3.2° and -1.4° respectively, p<0.001), increased inclination (85.2° and 85.3° respectively, p<0.001), and decreased tilt (24.6° [p=0.014] and 20.7° [p=0.013] respectively) compared with typically developing individuals. Regarding acetabular volume and surface area, dislocated and unstable hips had significantly lower volume (17.6ml vs 31.5ml respectively, p<0.001) and surface area (28.9cm2 vs 36.2cm2 respectively, p<0.001) than unaffected hips. Among several factors, only Reimer's migration index had an influence on acetabular orientation (i.e. anteversion, p=0.01), volume (p<0.001), and surface (p=0.004). Acetabula in patients with spastic hip disease were severely retroverted with increased steepness; acetabular orientation was distorted superoposteriorly. In rare cases, acetabular orientation was distorted only superiorly or superoanteriorly. Acetabular orientation was distorted superoposteriorly in most patients with severe bilateral cerebral palsy. More pronounced acetabular changes were found in hips with a higher Reimer's migration index.

Establishing Diagnostic Reference Levels for CT Through a Provincial Medical Informatics Metadata Repository in Ontario.

To determine whether computed tomography radiation dose data could be captured electronically across hospitals to derive regional diagnostic reference levels for quality improvement. Data on consecutive computed tomography examinations from 8 hospitals were collected automatically in a central database (Repository) from April 2017 to September 2017. The most frequently performed examinations were used to determine the standard protocols for each hospital. Diagnostic reference levels across hospitals were derived using statistical distribution for 2 radiation dose metrics. These values were compared between hospitals, within and between hospitals by scanner and against national Health Canada achievable doses and diagnostic reference levels. Three master protocol groups, Head, Abdomen-Pelvis, and Chest-Abdomen-Pelvis, accounted for 43% of all valid studies (N = 40 277). For the Repository, 11 of 12 mean values and 75th percentile diagnostic reference levels were below the Health Canada mean and 75th percentile values, and one was the same as the Health Canada value. Mean radiation dose by protocol varied by as much as 97% between hospitals. There was no consistent pattern in the difference between mean doses between large and small hospitals. This electronic data acquisition process could be used to continually update achievable doses for frequently used computed tomography examinations in Ontario and eliminate the need for nationwide manual surveys. Results compared across institutions will allow hospitals to maintain achievable doses and lower patient exposure.

Investigation of the cumulative number of chromosome aberrations induced by three consecutive CT examinations in eight patients.

In our previous study, we found that chromosomes were damaged by the radiation exposure from a single computed tomography (CT) examination, based on an increased number of dicentric chromosomes (Dics) formed in peripheral blood lymphocytes after a CT examination. We then investigated whether a cumulative increase in the frequency of Dics and chromosome translocations (Trs) formation could be observed during three consecutive CT examinations performed over the course of 3–4 years, using lymphocytes in peripheral bloods of eight patients (five males and three females; age range 27–77 years; mean age, 64 years). The effective radiation dose per CT examination estimated from the computational dosimetry system was 22.0–73.5 mSv, and the average dose per case was 40.5 mSv. The frequency of Dics formation significantly increased after a CT examination and tended to decrease before the next examination. Unlike Dics analysis, we found no significant increase in the frequency of Trs formation before and after the CT examination, and we observed no tendency for the frequency to decrease before the next CT examination. The frequency of Trs formation was higher than that of Dics formation regardless of CT examination. Furthermore, neither analysis of Dics nor Trs showed a cumulative increase in the frequency of formation following three consecutive CT examinations.

Radiation dose metrics in multidetector computed tomography examinations: A multicentre retrospective study from seven tertiary care hospitals in Kerala, South India.

Background:Presently, computed tomography (CT) is the most important source of medical radiation exposure. CT radiation doses vary considerably across institutions depending on the protocol and make of equipment. India does not yet have national or region-specific CT diagnostic reference levels.Aim:To evaluate radiation doses of consecutive multidetector CT (MDCT) examinations based on anatomic region, performed in 1 month, collected simultaneously from seven tertiary care hospitals in Kerala.Settings and Design:Descriptive study.Materials and Methods:We collected the CT radiation dose data of examinations from the seven collaborating tertiary care hospitals in Kerala, performed with MDCT scanners of five different makes. The data included anatomic region, number of phases, CT dose index (CTDIvol), dose-length product (DLP), and effective dose (ED) of each examinations and patient demographic data.Statistical Analysis:We calculated the 25th, 50th, and 75th percentiles of the CTDIvol, DLP, and ED according to anatomic region. We made descriptive comparisons of these results with corresponding data from other countries.Results:Of 3553 patients, head was the most frequently performed examination (60%), followed by abdomen (19%). For single-phase head examinations, 75th percentile of CTDIvol was 68.1 mGy, DLP 1120 mGy-cm, and ED 2.1 mSv. The 75th percentiles of CTDIvol, DLP, and ED for single-phase abdomen examinations were 10.6, 509.3, and 7.7, and multiphase examinations were 14.6, 2666.9, and 40.8; single-phase chest examinations were 23.4, 916.7, and 13.38, and multiphase examinations were 19.9, 1737.6, and 25.36; single-phase neck were 24.9, 733.6, and 3.814, and multiphase neck were 24.9, 2076, and 10.79, respectively.Conclusion:This summary CT radiation dose data of most frequently performed anatomical regions could provide a starting point for institutional analysis of CT radiation doses, which in turn leads to meaningful optimization of CT.

Successful pregnancy without disease progression of radioiodine refractory papillary thyroid carcinoma: a case report

BackgroundPregnancy is an unquantifiable risk to accelerate tumor growth of papillary thyroid carcinoma (PTC), and whether pregnancy induces an unfavorable prognosis of radioiodine refractory papillary thyroid carcinoma (RR-PTC) remains unknown.Case presentationWe investigated the impact of pregnancy on the prognosis of pulmonary metastases in an RR-PTC woman via a long-term clinical follow-up and consecutive computed tomography examinations and serum tests. After a successful pregnancy, the metastatic lesions shrank with serum thyroglobulin slightly fluctuated under sustained thyroid stimulating hormone (TSH) suppression, demonstrating a favorable outcome.ConclusionsThis case study indicates that metastatic RR-PTC may not be aggravated by pregnancy under TSH suppression, and pregnancy should not be contraindicated in RR-PTC patients with stable disease.

Automatic radiation dose monitoring for CT of trauma patients with different protocols: feasibility and accuracy

To demonstrate the feasibility and accuracy of automatic radiation dose monitoring software for computed tomography (CT) of trauma patients in a clinical setting over time, and to evaluate the potential of radiation dose reduction using iterative reconstruction (IR). In a time period of 18 months, data from 378 consecutive thoraco-abdominal CT examinations of trauma patients were extracted using automatic radiation dose monitoring software, and patients were split into three cohorts: cohort 1, 64-section CT with filtered back projection, 200mAs tube current-time product; cohort 2, 128-section CT with IR and identical imaging protocol; cohort 3, 128-section CT with IR, 150mAs tube current-time product. Radiation dose parameters from the software were compared with the individual patient protocols. Image noise was measured and image quality was semi-quantitatively determined. Automatic extraction of radiation dose metrics was feasible and accurate in all (100%) patients. All CT examinations were of diagnostic quality. There were no differences between cohorts 1 and 2 regarding volume CT dose index (CTDIvol; p=0.62), dose-length product (DLP), and effective dose (ED, both p=0.95), while noise was significantly lower (chest and abdomen, both -38%, p<0.017). Compared to cohort 1, CTDIvol, DLP, and ED in cohort 3 were significantly lower (all -25%, p<0.017), similar to the noise in the chest (-32%) and abdomen (-27%, both p<0.017). Compared to cohort 2, CTDIvol (-28%), DLP, and ED (both -26%) in cohort 3 was significantly lower (all, p<0.017), while noise in the chest (+9%) and abdomen (+18%) was significantly higher (all, p<0.017). Automatic radiation dose monitoring software is feasible and accurate, and can be implemented in a clinical setting for evaluating the effects of lowering radiation doses of CT protocols over time.

Double reading of current chest CT examinations: Clinical importance of changes to radiology reports

ObjectivesMisinterpretation of radiological examinations is an important contributing factor to diagnostic errors. Double reading reduces interpretation errors and increases sensitivity. Consultant radiologists in Norwegian hospitals submit 39% of computed tomography (CT) reports for quality assurance by double reading. Our objective was to estimate the proportion of radiology reports that were changed during double reading and to assess the potential clinical impact of these changes. Materials and methodsIn this retrospective cross-sectional study we acquired preliminary and final reports from 1023 consecutive double read chest CT examinations conducted at five public hospitals. The preliminary and final reports were compared for changes in content. Three experienced pulmonologists independently rated the clinical importance of these changes. The severity of the radiological findings in clinically important changes was classified as increased, unchanged, or decreased. ResultsChanges were classified as clinically important in 91 (9%) of 1023 reports. Of these: 3 were critical (demanding immediate action), 15 were major (implying a change in treatment) and 73 were intermediate (affecting subsequent investigations). More clinically important changes were made to urgent examinations and less to female first readers. Chest radiologist made more clinically important changes than other second readers. The severity of the radiological findings was increased in 73 (80%) of the clinically important changes. ConclusionA 9% rate of clinically important changes made during double reading may justify quality assurance of radiological interpretation. Using expert second readers and targeting a selection of urgent cases prospectively may increase the yield of discrepant cases and reduce harm to patients.

Notable Decrease of Malignant Pleural Effusion After Treatment with Sorafenib in Radioiodine-Refractory Follicular Thyroid Carcinoma

Malignant pleural effusion (MPE) caused by metastatic differentiated thyroid carcinoma (DTC) is usually associated with a rapid fatal outcome and should be recognized as a grim prognostic indicator. A standard therapeutic strategy has not been established for this situation. Here, we report a radioiodine-refractory follicular thyroid carcinoma (FTC) patient in whom a notable decrease of MPE was achieved after treatment with sorafenib. A 50-year-old patient underwent a total thyroidectomy and resection of recurrence for poorly differentiated FTC followed by radioiodine therapy with a negative whole body scan. One year later, dissection of the inferior lobe of the left lung was performed because two fluorodeoxyglucose-avid nodules were identified; pathological examination revealed a metastatic poorly differentiated FTC. Half a year later, he was referred to our clinic because of cough, thoracic pain, nausea, and loss of appetite. Chest computed tomography showed right lung multiple nodules, left pleural effusion, and left lung collapse with left-sided pleural thickening. We treated him with sorafenib. Clinical and radiographic assessments were performed periodically. Symptoms and signs improved dramatically and continuously after initiation of sorafenib treatment. A duration of more than 12 weeks of apparent reduction of pleural effusion was achieved, which was confirmed by consecutive computed tomography examinations. Despite grade 1 alopecia, no other obvious treatment-related adverse events occurred. As a grim prognostic indicator for patients with DTC, no standard treatment recommendation for pleural effusion exists. Targeted therapy using sorafenib may be an effective therapeutic strategy in the treatment of MPE caused by FTC.

Head CT for Nontrauma Patients in the Emergency Department: Clinical Predictors of Abnormal Findings

To identify predictors of clinically important abnormal findings in computed tomography (CT) images of the head among emergency department (ED) patients without a history of trauma. Approval was obtained from the institutional research ethics board, and informed consent from patients was not required. This study was a retrospective review of consecutive unenhanced head CT examinations in patients aged 18 years or older who did not have trauma or known intracranial pathologic processes in ED from January 2004 through June 2006. Multivariable logistic regression was used to identify predictors of clinically important abnormal CT findings in the derivation cohort (CT examinations from January 1, 2004, through August 15, 2005), and the reproducibility of findings in a validation cohort (all subsequent CT scans through to June 30, 2006) was assessed. The strength of association of each variable was expressed with clinically important abnormal CT findings as adjusted odds ratio (OR) and 95% confidence interval (CI). Of 29 469 consecutive head CT images performed at a single institution between January 1, 2004, and June 30, 2006, 3967 were eligible for this study. Of the CT images in these patients, 548 (13.8%) revealed clinically important abnormalities. Six independent clinical predictors of important abnormal findings on head CT were identified: age (adjusted OR per 10-year increase: 1.17; 95% CI: 1.08, 1.28), focal neurologic deficit (adjusted OR: 5.39; 95% CI: 3.90, 7.47), altered mental status (adjusted OR: 2.32; 95% CI: 1.66, 3.25), history of malignancy (adjusted OR: 4.11; 95% CI: 2.28, 7.42), nausea and/or vomiting (adjusted OR: 2.22; 95% CI: 1.14, 4.33), and derangements in coagulation profile (adjusted OR: 1.91; 95% CI: 1.07, 3.41). This study identified several potential clinical predictors of abnormal head CT findings in ED patients who did not sustain trauma. Prospective validation of a clinical prediction rule in this population is warranted.

The role of MRI and CT of the brain in first episodes of psychosis

To investigate whether imaging is associated with early detection of the organic causes of the first episode of psychosis (FEP). Individuals with FEP but no neurological signs referred to a tertiary centre for cerebral magnetic resonance imaging (MRI) or computed tomography (CT) were reviewed retrospectively. Two groups were evaluated with either CT or MRI; the two groups were independent and no individual underwent both CT and MRI. One hundred and twelve consecutive cerebral MRI and 204 consecutive CT examinations were identified. Three (2.7%) individuals had brain lesions [brain tumour and human immunodeficiency virus (HIV) encephalopathy] potentially accountable for the psychosis at MRI. Seventy patients (62.5%) had incidental brain lesions, such as cerebral atrophy, small vessel ischaemic changes, unruptured Circle of Willis aneurysm, cavernoma, and arachnoid cysts at MRI. Three patients (1.5%) had focal brain lesions (primary or secondary tumours) potentially accountable for the psychosis at CT. One hundred and thirty-three patients (65.2%) had incidental brain lesions unrelated to the psychosis on CT scan. There was no significant difference between MRI and CT imaging in detecting organic disease potentially responsible for FEP (p < 0.001). Routine MRI or CT imaging of the brain is unlikely to reveal disease leading to a significant change in management. MRI was comparable with CT in terms of diagnosis of both pathological and incidental cerebral lesions. Therefore, routine brain structural imaging of FEP in patients without focal neurology may not be routinely required and if imaging is requested then CT may function equally as well as MRI as the first-line investigation.

ServiceBlueprinting as a service management tool in radiology

Purpose To describe the ServiceBlueprint model as a suitable method of service management in clinical medicine using the example of the routine clinical setting of a radiological department. Materials and methods ServiceBlueprinting is a concept for the analysis, visualization, and optimization of service processes. To investigate whether the model will also provide a suitable representation of medical services, particularly the provision of radiological services, ServiceBlueprints were created for the modality computed tomography (CT). To this end, an independent observer analyzed the workflow of 40 consecutive CT examinations. Results The ServiceBlueprint provided an analysis of the status quo of the service processes in CT imaging modality. Weak points in the processes thus became immediately apparent. The model could also be used for personnel management in that it helped to define the roles of staff members from different categories in the value-added process. It served as a basis for the implementation of quality management systems according to Total Quality Management (TQM) and DIN-EN-ISO-9001:2000. Conclusions The ServiceBlueprint model is a service management concept that is also suitable to visualize medical service processes in routine clinical settings like in a radiology department and has a multifarious potential in process optimization, implementation of quality management systems, and human resources management.

Lossy 3D JPEG2000 Compression of Abdominal CT Images in Patients with Acute Abdominal Complaints: Effect of Compression Ratio on Diagnostic Confidence and Accuracy

To retrospectively assess the effect of lossy three-dimensional (3D) Joint Photographic Experts Group 2000 (JPEG2000) compression on diagnostic confidence and diagnostic accuracy at emergency abdominal computed tomography (CT). In this institutional review board-approved study, transverse images from 104 consecutive multidetector CT examinations (section thickness, 3 mm; reconstruction interval, 2 mm) in patients with acute abdominal complaints were subjected to lossy 3D JPEG2000 compression by using three compression ratios (10:1, 12.5:1, and 15:1, with reference to 384 kB [12 bits] as original image size). Three radiologists independently read the original and compressed CT studies. Patient order and compression ratios were randomized, and readers were blinded to that information. For each organ, the presence of compression artifacts, the diagnosis, the confidence in the diagnosis according to a five-point scale, and the confidence about negative findings were noted. All diagnoses were compared with a standard of reference constructed by an abdominal CT expert by using the original images, surgical reports, and patient follow-up data. Logistic regressions, the Friedman test, and analysis of variance were used for statistical analysis. Primary diagnoses were correct in 91.3% (463 of 507), 90.5% (459 of 507), 89.0% (451 of 507) and 90.1% (457 of 507) of the total number of primary diagnoses at 1:1, 1:10, 1:12.5 and 15:1, respectively. These values did not vary significantly (P = .456) with compression ratios. The radiologists' mean confidence about the primary diagnoses was also almost identical at different compression ratios (4.83, 4.87, 4.77, and 4.84 at 1:1, 1:10, 1:12.5 and 15:1, respectively). However, the radiologists' mean confidence about negative findings in the liver was reduced in 50.3% (157 of 312) of studies at 15:1. Diagnostic accuracy was not impaired at compression ratios up to 15:1. However, because of the significant reduction of the confidence about negative findings at 15:1, compression ratios no higher than 12.5:1 are recommended.

CT in the Evaluation of Nontraumatic Abdominal Pain in Pregnant Women

To retrospectively determine sensitivity and specificity of computed tomography (CT) for the diagnosis of appendicitis in pregnant women with nontraumatic abdominal pain and retrospectively compare findings at CT and ultrasonography (US) in patients who underwent both examinations, with surgery or clinical follow-up as a reference standard. Institutional review board approval was obtained, and the study was HIPAA compliant. Informed consent was waived. Findings of 80 consecutive CT examinations performed in 78 pregnant women (mean age, 25.9 years; range, 17-43 years) for abdominal pain between September 2000 and October 2004 were compared with findings at prior US (n=52), surgery, and clinical follow-up. Sensitivity and specificity were calculated for the diagnosis of appendicitis. The average fetal radiation dose was 16 mGy (1.6 rad) (range, 4-45 mGy [4-4.5 rad]). CT findings were normal in 51 examinations (64%) and abnormal in 29 (36%). Abnormal findings were appendicitis (n=13), urinary tract calculi (n=6), small-bowel obstruction (n=2), cholelithiasis (n=2), pyelonephritis (n=2), diaphragmatic hernia (n=1), cecal bascule (n=1), ileus (n=1), and metastatic lymphadenopathy (n=1). One surgically confirmed case of appendicitis was not detected at CT. For diagnosis of appendicitis, sensitivity of CT was 92% (12 of 13 examinations), specificity was 99% (66 of 67), and negative predictive value was 99% (66 of 67). Fifty-two CT studies were performed after US. US findings were normal in 46 patients (88%) and abnormal in six (12%). Abnormal findings were cholelithiasis (n=3), obstructive hydronephrosis (n=1), small-bowel dilatation (n=1), and appendicitis (n=1). Among 46 patients with normal US findings, CT findings were abnormal in 14, nine of whom required surgery. CT added important diagnostic information in 14 of 46 patients (30%). CT findings established the diagnosis in 35% of examinations in pregnant women with abdominal pain (28 of 80), with a negative predictive value of 99% for appendicitis; when CT followed negative US findings, CT findings established the diagnosis in 30% of patients.

Benefits of routine use of coronal and sagittal reformations in multi-slice CT examination of the abdomen and pelvis

To evaluate the usefulness of coronal and sagittal reformations from isotropic abdomino-pelvic computed tomography (CT) examinations. Fifty consecutive abdomino-pelvic CT examinations were reconstructed into two sets of axial source images: 0.9 mm section width with 0.45 mm reconstruction interval (isotropic) and 4 mm section width with 3 mm reconstruction interval. The isotropic dataset was reformatted into coronal and sagittal stacks with 4 mm section widths. Three readers independently reviewed the three image sets with 4 mm section widths. The coronal and sagittal reformations were compared with the axial images, in the same sitting, for depiction of lesions in various abdominal organs. There was better visualization of lesions in the liver, kidneys, mesentery, lumbar spine, major abdominal vessels, urinary bladder, diaphragm and hips on the coronal reformations compared with source axial images (p<0.05). Sagittal reformations scored better than axial source images for showing lesions in the liver, thoracic spine, abdominal vessels, uterus, urinary bladder, diaphragm and hips (p<0.05). The coronal and sagittal series showed significant additional information in 23 and 17% of patients, respectively. Radiologists should consider the routine review of at least one additional plane to the axial series in the interpretation of abdomino-pelvic CT studies.

The Radiographic Prevalence of Geniculate Ganglion Dehiscence in Normal and Congenitally Thin Temporal Bones

To determine the prevalence of a dehiscent geniculate ganglion on routine temporal bone computed tomography (CT). Retrospective case review. Tertiary referral center. Two hundred seventy-eight consecutive temporal bone CT examinations for a total of 556 sides were reviewed. One hundred ninety-one sides were excluded. Reasons for exclusion included reconstructed coronal views, no coronal views, or a pathologic process, which involved the geniculate ganglion. Six examinations were from patients with clinical superior canal dehiscence confirmed by surgical repair or positive vestibular evoked myogenic potentials. Twenty-four scans were from patients with radiographic superior canal dehiscence confirmed by two independent readings. The incidence of geniculate ganglion dehiscence in patients with and without radiographic or clinical superior canal dehiscence. Dehiscent geniculate ganglion was defined as at least two consecutive cuts on a coronal CT showing no bone overlying the geniculate ganglion. The overall incidence of a dehiscent geniculate ganglion was 14.5% in the 365 sides reviewed. The incidence of a dehiscent geniculate ganglion is increased in patients with radiographic and clinical superior canal dehiscence as compared with normal patients and was significantly different by chi analysis (38.1 versus 11.4%). The presence of radiographic geniculate ganglion dehiscence is common. This finding has particular importance when the middle cranial fossa or subtemporal approach is used, as the facial nerve is more at risk especially when used to address superior canal dehiscence.

0429 ALCOHOL AND ILLICIT DRUG USE IN FIRST-EPISODE PSYCHOSIS –A DESCRIPTIVE STUDY

To investigate whether imaging is associated with early detection of the organic causes of the first episode of psychosis (FEP).Individuals with FEP but no neurological signs referred to a tertiary centre for cerebral magnetic resonance imaging (MRI) or computed tomography (CT) were reviewed retrospectively. Two groups were evaluated with either CT or MRI; the two groups were independent and no individual underwent both CT and MRI.One hundred and twelve consecutive cerebral MRI and 204 consecutive CT examinations were identified. Three (2.7%) individuals had brain lesions [brain tumour and human immunodeficiency virus (HIV) encephalopathy] potentially accountable for the psychosis at MRI. Seventy patients (62.5%) had incidental brain lesions, such as cerebral atrophy, small vessel ischaemic changes, unruptured Circle of Willis aneurysm, cavernoma, and arachnoid cysts at MRI. Three patients (1.5%) had focal brain lesions (primary or secondary tumours) potentially accountable for the psychosis at CT. One hundred and thirty-three patients (65.2%) had incidental brain lesions unrelated to the psychosis on CT scan. There was no significant difference between MRI and CT imaging in detecting organic disease potentially responsible for FEP (p < 0.001).Routine MRI or CT imaging of the brain is unlikely to reveal disease leading to a significant change in management. MRI was comparable with CT in terms of diagnosis of both pathological and incidental cerebral lesions. Therefore, routine brain structural imaging of FEP in patients without focal neurology may not be routinely required and if imaging is requested then CT may function equally as well as MRI as the first-line investigation.

Alternative or additional diagnoses on unenhanced helical computed tomography for suspected renal colic: experience with 1000 consecutive examinations

Objectives. To determine the incidence and spectrum of significant alternative or additional diagnoses established or suggested on unenhanced helical computed tomography (CT) in a large series of patients with suspected renal colic. Methods. One thousand consecutive unenhanced helical CT examinations were performed for suspected renal colic. All official CT reports were retrospectively reviewed, which was followed by review of all available relevant follow-up radiology reports. A selected image and chart review was also performed. Results. Ureteral calculi were identified on 557 examinations, findings consistent with a recently passed stone were discovered on 67 examinations, and 275 CT examinations were unremarkable. An alternative or additional diagnosis was established or suggested on 101 examinations, including in 26 patients with concurrent ureteral calculi. There were 62 genitourinary and 39 nongenitourinary tract diagnoses. Eighty-seven of the diagnoses could be confirmed on retrospective image review combined with patient follow-up. There were two false-positive diagnoses for significant, alternative pathologic findings. Conclusions. A wide spectrum of significant, alternative, and additional genitourinary and nongenitourinary diagnoses can be reliably established or suggested on unenhanced helical CT performed for suspected renal colic. These abnormalities were identified in 10% of cases in this series of 1000 consecutive CT examinations.