Digital mammography. ROC studies of the effects of pixel size and unsharp-mask filtering on the detection of subtle microcalcifications

We investigated the spatial resolution requirement and the effect of unsharp-mask filtering on the detectability of subtle microcalcifications in digital mammography. Digital images were obtained by digitizing conventional screen-film mammograms with a 0.1 X 0.1 mm2 pixel size, processed with unsharp masking, and then reconstituted on film with a Fuji image processing/simulation system (Fuji Photo Film Co., Tokyo, Japan). Twenty normal cases and 12 cases with subtle microcalcifications were included. Observer performance experiments were conducted to assess the detectability of subtle microcalcifications in the conventional, the unprocessed digital, and the unsharp-masked mammograms. The observer response data were evaluated using receiver operating characteristic (ROC) and LROC (ROC with localization) analyses. Our results indicate that digital mammograms obtained with 0.1 X 0.1 mm2 pixels provide lower detectability than the conventional screen-film mammograms. The detectability of microcalcifications in the digital mammograms is improved by unsharp-mask filtering; the processed mammograms still provide lower accuracy than the conventional mammograms, however, chiefly because of increased false-positive detection rates for the processed images at each subjective confidence level. Viewing unprocessed digital and unsharp-masked images in pairs resulted in approximately the same detectability as that obtained with the unsharp-masked images alone. However, this result may be influenced by the fact that the same limited viewing time was necessarily divided between the two images.     

Transmission of Syphilis by Solid Organ Transplantation

Two organ recipients developed serologic evidence of syphilis infection after renal transplantation from a common deceased donor with a history of treated syphilis. Testing of donor serum for syphilis, which occurred after transplantation, gave results interpreted as consistent with past infection. However, subsequent serologic results in the recipients suggested transmission of infection at transplantation due to active infection of the donor. This may be explained by recent donor re-infection in view of the current syphilis epidemic in the United Kingdom. An initial error in the treatment of recipients further served to highlight unfamiliarity in managing this resurgent infection in the context of organ transplantation.     

Digital radiography of subtle pulmonary abnormalities: an ROC study of the effect of pixel size on observer performance

Forty conventional radiographs with examples of mild interstitial infiltrates and subtle pneumothoraces and 40 normal studies of the chest were selected and digitized, with pixel sizes of 1.0, 0.5, 0.2, and 0.1 mm. Observer performance tests were carried out using receiver operating characteristic analysis. Conventional radiographs and digitized images were compared. The results indicate that, in such cases, diagnostic accuracy increases significantly as the pixel size is reduced, at least to the 0.1-mm level. We conclude that, for digital systems using screen-film or similar image receptors, use of a pixel size substantially larger than 0.1 mm may result in some loss of diagnostic accuracy.     

Data compression: effect on diagnostic accuracy in digital chest radiography

High-resolution digital images make up very large data sets that are relatively slow to transmit and expensive to store. Data compression techniques are being developed to address this problem, but significant image deterioration can occur at high compression ratios. In this study, the authors evaluated a form of adaptive block cosine transform coding, a new compression technique that allows considerable compression of digital radiographs with minimal degradation of image quality. To determine the effect of data compression on diagnostic accuracy, observer tests were performed with 60 digitized chest radiographs (2,048 x 2,048 matrix, 1,024 shades of gray) containing subtle examples of pneumothorax, interstitial infiltrate, nodules, and bone lesions. Radiographs with no compression, with 25:1 compression, and with 50:1 compression ratios were presented in randomized order to 12 radiologists. The results suggest that, with this compression scheme, compression ratios as high as 25:1 may be acceptable for primary diagnosis in chest radiology.     

International multicenter pilot study of the first comprehensive self-completed nonmotor symptoms questionnaire for Parkinson's disease: the NMSQuest study.

Nonmotor symptoms (NMS) of Parkinson's disease (PD) are not well recognized in clinical practice, either in primary or in secondary care, and are frequently missed during routine consultations. There is no single instrument (questionnaire or scale) that enables a comprehensive assessment of the range of NMS in PD both for the identification of problems and for the measurement of outcome. Against this background, a multidisciplinary group of experts, including patient group representatives, has developed an NMS screening questionnaire comprising 30 items. This instrument does not provide an overall score of disability and is not a graded or rating instrument. Instead, it is a screening tool designed to draw attention to the presence of NMS and initiate further investigation. In this article, we present the results from an international pilot study assessing feasibility, validity, and acceptability of a nonmotor questionnaire (NMSQuest). Data from 123 PD patients and 96 controls were analyzed. NMS were highly significantly more prevalent in PD compared to controls (PD NMS, median = 9.0, mean = 9.5 vs. control NMS, median = 5.5, mean = 4.0; Mann-Whitney, Kruskal-Wallis, and t test, P < 0.0001), with PD patients reporting at least 10 different NMS on average per patient. In PD, NMS were highly significantly more prevalent across all disease stages and the number of symptoms correlated significantly with advancing disease and duration of disease. Furthermore, frequently, problems such as diplopia, dribbling, apathy, blues, taste and smell problems were never previously disclosed to the health professionals.     

Home ventilation in Northern Ireland.

Thirteen patients were identified as receiving assisted ventilation at home in Northern Ireland in 1994. Two patients have since died. An increasing number of patients are starting home ventilation, especially by nasal mask. Recognition of the needs of these patients and provision of care require further consideration.     

Outcome of acute intussusception in a regional paediatric centre

It has been suggested recently that acute intussusception should only be managed in a specialised paediatric centre. The aim of this study is to assess the incidence and outcome of acute intussusception in a comprehensive paediatric unit in Waterford Regional Hospital. It is a retrospective medical records study over a ten year period from June 1990 to June 2000. Our results showed that we had 24 cases giving an incidence of 2.4 cases per year. Contrast enema was performed in 23(95%) cases, successfully reduced in 14(61%) cases, unsuccessfully reduced in 7(30%). Surgical intervention was necessary in 7(30%) cases. Three (12.5%) cases were transferred to a specialised paediatric surgical centre. There were no perforation or death. We conclude from this study that management of acute intussusception can be successfully undertaken in a regional paediatric centre. It requires adequate throughput of cases and close co-operation between paediatrician, radiologist, anaesthetist, surgeons and of course a dedicated paediatric nursing staff.     

Measurement of mesothelioma on thoracic CT scans: a comparison of manual and computer-assisted techniques

Our purpose in this study was to evaluate the variability of manual mesothelioma tumor thickness measurements in computed tomography (CT) scans and to assess the relative performance of six computerized measurement algorithms. The CT scans of 22 patients with malignant pleural mesothelioma were collected. In each scan, an initial observer identified up to three sites in each of three CT sections at which tumor thickness measurements were to be made. At each site, five observers manually measured tumor thickness through a computer interface. Three observers repeated these measurements during three separate sessions. Inter- and intra-observer variability in the manual measurement of tumor thickness was assessed. Six automated measurement algorithms were developed based on the geometric relationship between a specified measurement site and the automatically extracted lung regions. Computer-generated measurements were compared with manual measurements. The tumor thickness measurements of different observers were highly correlated (r > or = 0.99); however, the 95% limits of agreement for relative inter-observer difference spanned a range of 30%. Tumor thickness measurements generated by the computer algorithms also correlated highly with the average of observer measurements (r > or = 0.93). We have developed computerized techniques for the measurement of mesothelioma tumor thickness in CT scans. These techniques achieved varying levels of agreement with measurements made by human observers.     

Prophylaxis in RSV infection (Palivizumab)--is it worthwhile?

Respiratory syncytial virus (RSV) is a recognised cause of lower respiratory tract infection in infants and young children. It causes severe respiratory disease in preterm infants with or without chronic lung disease. This study, conducted at Waterford Regional Hospital, evaluates the incidence of RSV infection in hospitalised children, its seasonal variation, and effectiveness of its prevention. Thirty eight percent of admitted children with bronchiolitis were RSV positive in the year 1999 November to March is the peak season for this infection. A highly selected group of 7 preterm children with or without chronic lung disease received Palivizumab prophylaxis. Not one of them acquired RSV infection. The high cost of Palivizumab was the main factor for its restricted use. Palivizumab was found to be effective in preventing RSV infection in our study. Since we had a small number of patients, further studies are needed for its economic and judicious use. Respiratory syncytial virus (RSV) is virulent easily transmissible and the most common cause of lower respiratory tract disease in children of less than 2 years of age. Up to 98% of children attending day care will be infected in single RSV season. Between 0.5% and 3.2% of children with RSV infection require Hospitalisation. Approximately 90,000 hospital admissions and 4500 deaths per year were reported in United States. In Ireland 2807 patients were admitted with Bronchiolitis in 1998. Major risk factors for hospitalisation due to RSV are Prematurity, chronic lung disease, congenital heart disease, compromised immunity and age younger then 6 weeks in otherwise healthy children. No effective treatment of RSV positive bronchiolitis beside supportive care in the form of adequate nutrition and oxygen therapy is available. Antiviral therapies such as Ribavirin has not been proved to be effective in RSV infection. Bronchodilators show variable results. Corticosteroids were not found effective. There is no effective vaccine available as yet. There is no proven method for active immunity. Various immunoglobulins are available for acquiring passive immunity against RSV infection. PREVENT study group in Jan. 1997 showed intravenous immunoglobulin (RSV- IGIV) use in reducing 41% to 63% hospitalisation in RSV patients. But RSV-IGIV was not licensed outside the United States because of risk of transmission of blood borne products, difficulty in administration ie. intravenous access, large fluid volume (15 ml/kg), high protein load (750 mg/kg), shortage of supply and need to postpone live vaccine (eg. MMR, varicella). monoclonal antibody Palivizumab was developed for prophylaxis against RSV infection. Clinical safety and efficacy of Palivizumab were demonstrated in IMpact trial published in Sept. 1998. Reduction in hospitalisation up to 55% was noted in this study. It was a pivotal randomised, double blind, placebo controlled phase 3 study conducted in 139 centres throughout Canada, United States and United Kingdom. We looked at our experience in patients admitted with bronchiolitis in Waterford Regional Hospital. We described the outcome of carefully selected Seven children of high risk group for Palivizumab prophylaxis. Its clinical Implications and cost effectiveness was evaluated in this study.