Developmental Dysplasia of the Hip: An Audit of the Ultrasound Screening Programme.

Aims Developmental dysplasia of the hip (DDH) is an important cause of disability in children and young adults. Early diagnosis and treatment can help avoid more invasive interventions and long-term morbidity. This study examines the ultrasound screening programme conducted in University Hospital Waterford (UHW), and the outcomes for infants with DDH in the Southeast of Ireland. Methods We conducted an audit of all the DDH screening ultrasounds performed in UHW in the year 2020, a total of 992 infants. Data included referral and ultrasound times, screening results, interventions, and outcomes. Results Of those screened, 255 (26%) were referred to the Orthopaedic clinic, with a significant female majority of nearly 3:1. At the time of writing, only two infants were ultimately referred for further management of persistent DDH, the rest being successfully treated by less invasive interventions such as harnessing and bracing. There were no babies scanned within the recommended 6 weeks who later presented with a dislocated hip or required tertiary referral for DDH management. Conclusion The ultrasound screening programme in UHW is shown to be successful in the prompt diagnosis and early treatment of DDH. This plays a significant role in avoiding the lifelong disabling outcomes of untreated DDH, and the invasive surgical procedures required in the management of late-stage disease.

Gallbladder disease and pancreatic cancer risk: a multicentric case-control European study.

BACKGROUND AND AIMS: The overall evidence on the association between gallbladder conditions (GBC: gallstones and cholecystectomy) and pancreatic cancer (PC) is inconsistent. To our knowledge, no previous investigations considered the role of tumour characteristics on this association. Thus, we aimed to assess the association between self-reported GBC and PC risk, by focussing on timing to PC diagnosis and tumour features (stage, location, and resection). METHODS: Data derived from a European case-control study conducted between 2009 and 2014 including 1431 PC cases and 1090 controls. We used unconditional logistic regression models to estimate odds ratios (ORs) and corresponding 95% confidence intervals (CIs) adjusted for recognized confounders. RESULTS: Overall, 298 (20.8%) cases and 127 (11.6%) controls reported to have had GBC, corresponding to an OR of 1.70 (95% CI 1.33-2.16). The ORs were 4.84 (95% CI 2.96-7.89) for GBC diagnosed <3 years before PC and 1.06 (95% CI 0.79-1.41) for ≥3 years. The risk was slightly higher for stage I/II (OR = 1.71, 95% CI 1.15-2.55) vs. stage III/IV tumours (OR = 1.23, 95% CI 0.87-1.76); for tumours sited in the head of the pancreas (OR = 1.59, 95% CI 1.13-2.24) vs. tumours located at the body/tail (OR = 1.02, 95% CI 0.62-1.68); and for tumours surgically resected (OR = 1.69, 95% CI 1.14-2.51) vs. non-resected tumours (OR = 1.25, 95% CI 0.88-1.78). The corresponding ORs for GBC diagnosed ≥3 years prior PC were close to unity. CONCLUSION: Our study supports the association between GBC and PC. Given the time-risk pattern observed, however, this relationship may be non-causal and, partly or largely, due to diagnostic attention and/or reverse causation.

Risk of pancreatic cancer associated with family history of cancer and other medical conditions by accounting for smoking among relatives.

Background: Family history (FH) of pancreatic cancer (PC) has been associated with an increased risk of PC, but little is known regarding the role of inherited/environmental factors or that of FH of other comorbidities in PC risk. We aimed to address these issues using multiple methodological approaches. Methods: Case-control study including 1431 PC cases and 1090 controls and a reconstructed-cohort study (N = 16 747) made up of their first-degree relatives (FDR). Logistic regression was used to evaluate PC risk associated with FH of cancer, diabetes, allergies, asthma, cystic fibrosis and chronic pancreatitis by relative type and number of affected relatives, by smoking status and other potential effect modifiers, and by tumour stage and location. Familial aggregation of cancer was assessed within the cohort using Cox proportional hazard regression. Results: FH of PC was associated with an increased PC risk [odds ratio (OR) = 2.68; 95% confidence interval (CI): 2.27-4.06] when compared with cancer-free FH, the risk being greater when ≥ 2 FDRs suffered PC (OR = 3.88; 95% CI: 2.96-9.73) and among current smokers (OR = 3.16; 95% CI: 2.56-5.78, interaction FHPC*smoking P-value = 0.04). PC cumulative risk by age 75 was 2.2% among FDRs of cases and 0.7% in those of controls [hazard ratio (HR) = 2.42; 95% CI: 2.16-2.71]. PC risk was significantly associated with FH of cancer (OR = 1.30; 95% CI: 1.13-1.54) and diabetes (OR = 1.24; 95% CI: 1.01-1.52), but not with FH of other diseases. Conclusions: The concordant findings using both approaches strengthen the notion that FH of cancer, PC or diabetes confers a higher PC risk. Smoking notably increases PC risk associated with FH of PC. Further evaluation of these associations should be undertaken to guide PC prevention strategies.

A systems approach identifies time-dependent associations of multimorbidities with pancreatic cancer risk.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is usually diagnosed in late adulthood; therefore, many patients suffer or have suffered from other diseases. Identifying disease patterns associated with PDAC risk may enable a better characterization of high-risk patients. METHODS: Multimorbidity patterns (MPs) were assessed from 17 self-reported conditions using hierarchical clustering, principal component, and factor analyses in 1705 PDAC cases and 1084 controls from a European population. Their association with PDAC was evaluated using adjusted logistic regression models. Time since diagnosis of morbidities to PDAC diagnosis/recruitment was stratified into recent (<3 years) and long term (≥3 years). The MPs and PDAC genetic networks were explored with DisGeNET bioinformatics-tool which focuses on gene-diseases associations available in curated databases. RESULTS: Three MPs were observed: gastric (heartburn, acid regurgitation, Helicobacter pylori infection, and ulcer), metabolic syndrome (obesity, type-2 diabetes, hypercholesterolemia, and hypertension), and atopic (nasal allergies, skin allergies, and asthma). Strong associations with PDAC were observed for ≥2 recently diagnosed gastric conditions [odds ratio (OR), 6.13; 95% confidence interval CI 3.01-12.5)] and for ≥3 recently diagnosed metabolic syndrome conditions (OR, 1.61; 95% CI 1.11-2.35). Atopic conditions were negatively associated with PDAC (high adherence score OR for tertile III, 0.45; 95% CI, 0.36-0.55). Combining type-2 diabetes with gastric MP resulted in higher PDAC risk for recent (OR, 7.89; 95% CI 3.9-16.1) and long-term diagnosed conditions (OR, 1.86; 95% CI 1.29-2.67). A common genetic basis between MPs and PDAC was observed in the bioinformatics analysis. CONCLUSIONS: Specific multimorbidities aggregate and associate with PDAC in a time-dependent manner. A better characterization of a high-risk population for PDAC may help in the early diagnosis of this cancer. The common genetic basis between MP and PDAC points to a mechanistic link between these conditions.

Comparison of CT volumetric measurement with RECIST response in patients with lung cancer.

PURPOSE: To examine the correlations between uni-dimensional RECIST and volumetric measurements in patients with lung adenocarcinoma and to assess their association with overall survival (OS) and progression-free survival (PFS). MATERIALS AND METHODS: In this study of patients receiving chemotherapy for lung cancer in the setting of a clinical trial, response was prospectively evaluated using RECIST 1.0. Retrospectively, volumetric measurements were recorded and response was assessed by two different volumetric methods at each followup CT scan using a semi-automated segmentation algorithm. We subsequently evaluated the correlation between the uni-dimensional RECIST measurements and the volumetric measurements and performed landmark analyses for OS and PFS at the completion of the first and second follow-ups. Kaplan-Meier curves together with log-rank tests were used to evaluate the association between the different response criteria and patient outcome. RESULTS: Forty-two patients had CT scans at baseline, after the first follow up scan and second followup scan, and then every 8 weeks. The uni-dimensional RECIST measurements and volumetric measurements were strongly correlated, with a Spearman correlation coefficient (ρ) of 0.853 at baseline, ρ=0.861 at the first followup, ρ=0.843 at the 2nd followup, and ρ=0.887 overall between-subject. On first follow-up CT, partial responders and non responders as assessed by an "ellipsoid" volumetric criteria showed a significant difference in OS (p=0.008, 1-year OS of 70% for partial responders and 46% for non responders). There was no difference between the groups when assessed by RECIST criteria on first follow-up CT (p=0.841, 1-year OS rate of 64% for partial responders and 64% for non responders). CONCLUSION: Volumetric response on first follow-up CT may better predict OS than RECIST response. CLINICAL RELEVANCE STATEMENT: Assessment of tumor size and response is of utmost importance in clinical trials. Volumetric measurements may help to better predict OS than uni-dimensional RECIST criteria.

Daytime sleep in Parkinson's disease measured by episodes of immobility.

Excessive daytime sleepiness (EDS) is common in Parkinson's Disease (PD). Actigraphy uses periods of immobility as surrogate markers of nighttime sleep but there are no examples of its use in assessing EDS of PD. A commercial wrist worn system for measuring bradykinesia and dyskinesia also detects 2 min periods of immobility, which have a 85.2% concordance with the detection of sleep by ambulatory daytime polysomnography, (p < 0.0001 Chi Squared). High Epworth Sleepiness Scores (ESS) were associated with a proportion of time immobile (PTI) (p = 0.01 Mann-Whitney U). The median PTI between 0900 and 1800 h w in 30 age matched control subjects was 2%, representing 10 min and PTI at or above the 75th percentile (5% or 27 min) was taken as a high level. PD patients had higher PTI (median 4.8%) than controls (p < 0.0001, Mann-Whitney U). PD subjects with a high PTI had more bradykinesia, less dyskinesia and higher PDQ39 scores than those with low PTI. There was no relationship between PTI and dose or type of PD medications. However, in 53% of subjects, PTI increased in the 30-60 min after levodopa confirming that in some subjects levodopa results in increased sleepiness. In summary, immobility is a surrogate marker of daytime sleep in PD, confirmed by correlation with PSG and ESS. PD subjects measured this way are more likely to be sleepy and sleepy PD subjects are more likely to be bradykinetic and have a higher PDQ39. Levodopa leads to an increase in sleepiness in more than half of subjects post dosing.

Ocular health among radiologists in the age of PACS: is it time for our profession to open its eyes to this issue in light of existing European legislation?

The regular use of visual display units (VDUs) at work has been shown to cause the development of a constellation of symptoms ranging from dry eyes to temporary myopia. European workers who use VDUs are now protected under detailed legislation enacted by the European Union (Directive 90/270/EEC). The use of picture archiving and communications systems, which are almost ubiquitous in European countries, means that, as a profession, radiologists fall under the remit of this legislation. This paper aims to assess the impact that full implementation of this law would have on a radiologist's practice and to more broadly examine the issue of eye care as an occupational health issue in radiology. The authors conclude that eye care in the setting of regular VDU use among radiologists is an important quality control and occupational health issue. There is a clear legal basis requiring employers to provide regular eye examinations and reporting breaks. In the absence of leadership from employers on this issue individual radiologists have a responsibility to ensure that their work practices reflect the legal situation and minimise the effect of eye strain on their performance.

Daily online bony correction is required for prostate patients without fiducial markers or soft-tissue imaging.

AIM: To compare online position verification strategies with offline correction protocols for patients undergoing definitive prostate radiotherapy. MATERIALS AND METHODS: We analysed 50 patients with implanted fiducial markers undergoing curative prostate radiation treatment, all of whom underwent daily kilovoltage imaging using an on-board imager. For each treatment, patients were set-up initially with skin tattoos and in-room lasers. Orthogonal on-board imager images were acquired and the couch shift to match both bony anatomy and the fiducial markers recorded. The set-up error using skin tattoos and offline bone correction was compared with online bone correction. The fiducial markers were used as the reference. RESULTS: Data from 1923 fractions were analysed. The systematic error was ≤1 mm for all protocols. The average random error was 2-3mm for online bony correction and 3-5mm for skin tattoos or offline-bone. Online-bone showed a significant improvement compared with offline-bone in the number of patients with >5mm set-up errors for >10% (P<0.001) and >20% (P<0.003) of their fractions. CONCLUSIONS: Online correction to bony anatomy reduces both systematic and random set-up error in patients undergoing prostate radiotherapy, and is superior to offline correction methods for those patients not suitable for fiducial markers or daily soft-tissue imaging.

Can actigraphy measure sleep fragmentation in children?

OBJECTIVE: The gold standard assessment for sleep quality is polysomnography (PSG). However, actigraphy has gained popularity as an ambulatory monitor. We aimed to assess the value of actigraphy in measuring sleep fragmentation in children. METHODS: 130 children aged 2-18 years referred for assessment for sleep disordered breathing (SDB) were recruited. The arousal index (AI) scored from PSG was compared to the actigraphic fragmentation index (FI) and number of wake bouts/h. RESULTS: The ability of actigraphic measures to correctly classify a child as having an AI>10 events/h rated as fair for the FI and poor for wake bouts/h (area under the receiver operator characteristic curve, 0.73 and 0.67, respectively). CONCLUSION: Actigraphy provides only a fair indication of the level of arousal from sleep in children. While the limitations of actigraphy prevent it from being a diagnostic tool for SDB, it still has a role in evaluating sleep/wake schedules in children.

First evidence of azaspiracids (AZAs): A family of lipophilic polyether marine toxins in scallops (Argopecten purpuratus) and mussels (Mytilus chilensis) collected in two regions of Chile.

Azaspiracids are a family of lipophilic polyether marine biotoxins that have caused a number of human intoxication incidents in Europe since 1995 following the consumption by consumers of intoxicated shellfish (Mytilus edulis). These azaspiracids have now been identified in mussels (Mytilus chilensis) and scallops (Argopecten purpuratus) from two Chilean locations. This is the first report of the occurrence of azaspiracid toxins in these species (Mytilus chilensis and Argopecten purpuratus) from Chile. The areas studied were Bahía Inglesa (III Region, 27 degrees SL) and Chiloé Archipelago, both important scallop and mussels farming areas. Separation of azaspiracid (AZA1), azaspiracid isomer (AZA6) and its analogues, 8-methylazaspiracid (AZA2) and 22-demethylazaspiracid (AZA3), was achieved using reversed-phase LC and toxins were identified using a turbo electrospray ionisation (ESI) source, to a triple quadrupole mass spectrometer. In mussels, AZA1 was the predominant toxin in mussel hepatopancreas with AZA2, AZA3 and AZA6 present in approximate equivalent amounts in the remaining tissues, 20-30% of the AZA1 level. AZA2 predominated in the scallop samples with the toxin almost entirely present in the hepatopancreas (digestive gland). AZA1 was only observed in some of the scallop samples and was present at 12-15% of the AZA2 levels. Whilst the levels of AZAs in Chilean samples are below the EU regulatory limit of 160mug/kg, it is significant that this toxin is present in Pacific Ocean species. Consequently measures should be taken by regulatory authorities to implement regular seafood monitoring to ensure safety of harvested product.

Is there under-treatment of pancreatic cancer? Evidence from a population-based study in Ireland.

Although clinical trials suggest that chemotherapy can improve survival for both resected and unresected pancreatic cancer patients, the extent to which it is used in routine clinical practice is unclear. We conducted a population-based investigation of treatment patterns and factors influencing treatment receipt and mortality for pancreatic cancer. We included 3173 patients with primary invasive pancreatic cancer, diagnosed in 1994-2003, from the National Cancer Registry (Ireland). Analysis was done by joinpoint regression, logistic regression and Cox proportional hazards. Propensity score methods were used to compare mortality in those who received chemotherapy and in 'matched' patients who did not. Seven percent of patients had a resection and 12% received chemotherapy. The resection rate did not change significantly over time and less than a quarter of patients with localised disease underwent resection. Chemotherapy use increased by 20% per annum, reaching 20% among unresected and 39% among resected patients in 2002-2003. Forty two percent of patients were untreated, and this percentage was unchanged over time. After adjusting for clinical factors, patient characteristics were significantly associated with treatment receipt; older and unmarried patients were less likely to be treated. Among resected patients, risk of death fell by 10% per annum. Chemotherapy receipt was associated with significantly reduced mortality among both surgical (hazard ratio (HR)=0.50, 95% confidence intervals (CIs) 0.27-0.91) and non-surgical patients (HR=0.48, 95% CI 0.38-0.61). Our findings suggest that there may be potential for extended dissemination of chemotherapy, and possibly also for greater utilisation of curative resection, in routine practice which, in turn, has potential to improve survival at the population level.

Adaptive servo-ventilation and deadspace: effects on central sleep apnoea.

Central Sleep Apnoea (CSA) occurs commonly in heart failure. Adaptive servo-ventilation (ASV) and deadspace (DS) have been shown in research settings to reverse CSA. The likely mechanism for this is the increase of PaCO(2) above the apnoeic threshold. However the role of increasing FiCO(2) on arousability remains unclear. To compare the effects of ASV and DS on sleep and breathing, in particular effects on Arousal Index (ArI), ten male patients with heart failure and CSA were studied during three nights with polysomnography plus measurements of PetCO(2). The order of the interventions control (C), ASV and DS was randomized. ASV and DS caused similar reductions in apnoea-hypopnoea index [(C) 30.0 +/- 6.6, (ASV) 14.0 +/- 3.8, (DS) 15.9 +/- 4.7 e h(-1); both P < 0.05]. However, DS was associated with decreased total sleep time compared with C (P < 0.02) and increased spontaneous ArI compared to C and ASV (both P < 0.01). Only DS was associated with increased DeltaPetCO(2) from resting wakefulness to eupnic sleep [(C) 2.1 +/- 0.9, (ASV) 1.3 +/- 1.0, (DS) 5.6 +/- 0.5 mmHg; P = 0.01]. ASV and DS both stabilized ventilation however DS application also increased sleep fragmentation with negative impacts on sleep architecture. We speculate that this effect is likely to be mediated by increased PetCO(2) and respiratory effort associated with DS application.

Symptom burden of sleep-disordered breathing in mild-to-moderate congestive heart failure patients.

The symptom burden resulting from sleep-disordered breathing (SDB) in patients with mild-to-moderate congestive heart failure (CHF) is unclear. The current authors monitored 24-h activity levels and compared subjective and objective measures of daytime sleepiness in 39 CHF patients, New York Heart Association class 2-3, on optimal medication. A total of 22 patients were classified as SDB (apnoea/hypopnoea index (AHI) median (range) 22.3 (16.6-100) events.h-1), and 17 as no SDB (NoSDB; AHI 3.7 (0-12.3) events.h-1). SDB was defined as AHI>or=15 events.h-1. Patients were assessed by 24-h activity monitoring (actigraphy) for a period of up to 14 days, a single objective sleepiness test (Oxford Sleep Resistance test) and Epworth Sleepiness Scale. The duration of daytime activity was significantly shorter in the SDB group compared with the NoSDB group. The SDB group also had increased time in bed and poorer sleep quality, as shown by the fragmentation index. Objectively the SDB group when compared with the NoSDB group were significantly sleepier, subjectively the groups did not differ. The amount of napping was similar for both groups. Despite the lack of subjective symptoms of daytime sleepiness, congestive heart failure patients with sleep-disordered breathing were objectively sleepier during the day and had reduced daytime activity with longer periods in bed and poorer sleep quality when compared with those without sleep-disordered breathing.

The interaction between respiratory and autonomic function during sleep-related changes in pharyngeal airway patency.

Sleep-related changes in pharyngeal function result in an increased resistance to airflow and in some people complete pharyngeal occlusion. Clinically, pharyngeal occlusion causes obstructive sleep apnoea syndrome (OSA). This is a prevalent disorder, which is an independent risk factor for the development of systemic hypertension. Several mechanisms contribute to the sleep-related changes in pharyngeal function in both health and disease, including a reduction in respiratory-related muscle activation, and an increase in latency of the pharyngeal reflex to negative intralumenal pressure. Arousal from sleep causes increases in ventilation and autonomic cardiovascular function that far exceed physiological requirements--the so-called 'waking reflex'. In patients with OSA the waking reflex is augmented either by hypoxemia, hypercapnia, or large swings in intrathoracic pressure. How these factors interact to cause the acute surges in heart rate and systemic blood pressure that occur at the termination of an apnoea will be reviewed, together with the longer term consequences of pharyngeal occlusion during sleep.

Screening with breast ultrasound in a population at moderate risk due to family history.

OBJECTIVE: To perform a pilot study to compare ultrasound and mammographic screening with particular respect to specificity, in a cohort of women at moderate family history risk of breast cancer. MATERIAL AND METHODS: High resolution ultrasound of both breasts was undertaken in 149 women at moderate risk of breast cancer who were referred for mammographic screening. The two tests were read blind to the other. Core biopsy was undertaken for solid lesions found on ultrasound. RESULTS: 149 Patients, mean age 42.15 years, were screened with bilateral ultrasound. 90 Examinations were normal. 46 Women had cysts, two had lesions previously biopsied and found to be benign, and one had a lymph node. 10 Focal solid lesions were biopsied on account of their ultrasound findings, 6.7% (95% confidence intervals (95% CIs) 2.7% to 10.7%). All but one of the 149 mammograms were normal. In this case both mammography and ultrasound showed a focal solid lesion that at core biopsy was found to be a fibroadenoma. Histology showed seven fibroadenomata, two areas of fibrocystic change, and one adenoid cystic carcinoma. Positive predictive value for biopsy was 10%. Mean follow up was 13.7 months. There was one interval cancer. CONCLUSION: Screening with breast ultrasound, in a cohort of women at moderate risk of breast cancer due to family history, has an acceptable biopsy rate. Screening with ultrasound and mammography in patients with an increased risk of breast cancer may be beneficial and a randomised study to examine issues of acceptability, reproducibility, and cost effectiveness is apt.

Lobular carcinoma in situ on core biopsy-what is the clinical significance?

AIM: To retrospectively review the surgical histological findings in all cases where lobular carcinoma in situ(LCIS) was identified on percutaneous core biopsy (CB) performed as part of the Cambridge and Huntingdon breast screening programme. MATERIALS AND METHODS: We retrospectively reviewed all the core biopsies performed in our department for screen detected abnormalities over a 5-year period between 1 April 1994 and 31 March 1999. All patients where LCIS was identified on CB were reviewed. As the significance of LCIS on CB was unclear all went on to surgical excision. We reviewed the clinical and imaging findings, biopsy technique and subsequent surgical histology of each patient. RESULTS: During the study period 60 769 women were invited for screening, of whom 47 975 attended (attendance rate = 79%). Of these, 2330 (4.9%) were recalled for assessment and 749 (1.6%) underwent CB. A malignant diagnosis was obtained in 311 (42%), 211 invasive and 100 in situ lesions. LCIS was identified on CB in 13 (2%). LCIS was the only lesion identified in seven cases. All seven cases subsequently underwent surgical excision. Surgical histology revealed a single case of LCIS and invasive lobular carcinoma. There were two cases of LCIS and DCIS one with a probable focus of invasive ductal carcinoma. In one case LCIS was identified in association with a radial scar. In three of the seven cases LCIS was the only abnormality on both CB and surgical biopsy. CONCLUSION: Our series shows that isolated LCIS on CB following mammographic screening is an infrequent finding, and it may be associated with either an invasive cancer or DCIS. It is therefore advisable that when LCIS is identified on CB, surgical excision of the mammographic abnormality should be performed. Decisions on management should be undertaken in a multidisciplinary setting taking into account clinical and imaging findings.

Interval cancer peer review in East Anglia: implications for monitoring doctors as well as the NHS breast screening programme.

AIM: To devise a method for reviewing interval cancers that will both educate radiologists and facilitate improvement of breast screening practice. To evaluate different methods for case classification to find one that best serves this purpose. METHOD: The method of peer review and the means by which interval cancers are classified is described. The way in which cases are designated false-negative is an issue of acceptability for radiologists, and so three different methods are evaluated. Each is applied to the data set collected in this region over a 3-year period. RESULTS: For cases read by five readers, when a consensus method was used for classifying cases, the proportion of cases classified as false-negative was 14%. Using a method in which only one of the five readers had to classify a case as false-negative for it to be categorized as such, the proportion of false-negative cases rose to a maximum of 38%. The minimum proportion of cases that could be considered to be false-negative was 6% and was obtained when all five readers had to classify a case as false-negative for it to be so categorized. Consistent with its majority viewpoint, the consensus method gave results for proportions of total cases classified as false-negative which were similar to those given by methods in which cases are classified as false-negative if either three of five readers, or at least 60% of readers, classified it as such. CONCLUSION: For the peer review method to achieve its dual aims of educating radiologists and auditing performance, the participating radiologists must share ownership of the results and view the analysis as fair. The method used to classify interval cancers as false-negative will influence the number so classified. A consensus method has been found to give a result that is both fair and acceptable to our radiologist. Using this method 16% of all reviewed cases were classified as false-negative and 60% as true interval cancers. Britton, P. D. (2001). Clinical Radiology56, 44-49.