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J B Olsen

Publications and source records attributed to J B Olsen.

At least 19 recordsLinked to original sources
PubMed2006

Detection of simulated microcalcifications in fixed mammary tissue: An ROC study of the effect of local versus global histogram equalization.

PURPOSE: To investigate whether sliding window adaptive histogram equalization (SWAHE) of digital mammograms improves the detection of simulated calcifications, as compared to images normalized by global histogram equalization (GHE). MATERIAL AND METHODS: Direct digital mammograms were obtained from mammary tissue phantoms superimposed with different frames. Each frame was divided into forty squares by a wire mesh, and contained granular calcifications randomly positioned in about 50% of the squares. Three radiologists read the mammograms on a display monitor. They classified their confidence in the presence of microcalcifications in each square on a scale of 1 to 5. Images processed with GHE were first read and used as a reference. In a later session, the same images processed with SWAHE were read. RESULTS: The results were compared using ROC methodology. When the total areas AZ were compared, the results were completely equivocal. When comparing the high-specificity partial ROC area AZ,0.2 below false-positive fraction (FPF) 0.20, two of the three observers performed best with the images processed with SWAHE. The difference was not statistically significant. CONCLUSION: When the reader's confidence threshold in malignancy is set at a high level, increasing the contrast of mammograms with SWAHE may enhance the visibility of microcalcifications without adversely affecting the false-positive rate. When the reader's confidence threshold is set at a low level, the effect of SWAHE is an increase of false positives. Further investigation is needed to confirm the validity of the conclusions.

Breast Diseases↗
PubMed2003

Evaluation of the present breeding programme against copper toxicosis in Danish Bedlington terriers.

A breeding programme to eradicate copper toxicosis in Danish Bedlington terriers has been established based on a DNA marker test. Genotyping of both parents is compulsory and after 1 January 2000, only homozygous non-carriers are used for breeding. In this study, two groups of Bedlington terriers were genotyped at 18 microsatellite loci. One group represented the original population of Bedlington terriers before introducing the breeding programme (n = 23); the other represented a group of homozygous non-carriers (n = 24) available for breeding after year 2000. Allele numbers, allele frequencies, observed heterozygosities (Ho), expected heterozygosities (He), locus-specific coefficients of inbreeding (Fl) and Nei's genetic distance (D) was calculated. Individual coefficients of inbreeding (Fi) were calculated from the pedigrees and an assignment test was performed. Four rare alleles were lost in the group of homozygous non-carriers. No significant differences were observed between the mean values of allele numbers, Ho, He, Fl and Fi of the two populations of dogs. Nei's genetic distance between the two populations was 0.06 and 88% of the homozygous non-carriers were assigned correctly in the assignment test. The overall diversity of the breed was low (Ho = 0.41) and the breeders were advised to include the heterozygous carriers again.

Alleles↗
PubMed1999

An anthropomorphic phantom for receiver operating characteristic studies in CT imaging of liver lesions.

The purpose of the study was to develop a methodology that allowed quantitative assessment of image quality in CT and its relationship to dose. An anthropomorphic phantom was designed for use in receiver operating characteristic (ROC) studies of the detectability of liver lesions with CT. The lesions were simulated by different mixtures of glycerol and water that were filled into holes of different diameters in a liver tissue substitute. A pilot study was carried out on five different scanners that were operated at various exposure settings. A positive correlation was demonstrated for each of the scanners between the weighted CT dose index (CTDIW) and the area under the ROC curve. For the exposure settings used in the clinical routine in the five laboratories, the CTDIW ranged from 15 to 31 mGy. Three observers who read the corresponding set of five phantom images agreed, as judged from the areas under the ROC curves, that there was a marked difference in quality between the three best images and the other two. The two newest scanners in the study had the lowest CTDIW, and at the same time the best ROC results. The phantom and the ROC methodology may, with a set of suggested improvements, be used for comparison of the performance in different CT laboratories, and to establish the dose needed to ensure adequate image quality for a particular scanner.

Anthropometry↗
PubMed1999

Diagnostic value of ultrasonography in patients with palpable mammographically noncalcified breast tumors.

PURPOSE: To analyze the diagnostic accuracy of mammography, ultrasonography (US), and both methods combined in evaluation of palpable noncalcified breast tumors. MATERIAL AND METHODS: Mammograms and sonograms of 200 patients with palpable noncalcified breast masses were retrospectively analyzed independently by four experienced radiologists in 3 sessions: Mammography or US interpretations in the first two and combined reading in the last session. Nonneoplastic abnormalities and mammographically obvious cancers were excluded. Receiver operating characteristic (ROC) analyses were performed for 115 (60 benign and 55 malignant) tumors and subgroups according to tissue density and tumor size. A single ROC curve for each diagnostic test was obtained by pooling the individual ratings. The area under the ROC curve was used as a measure of diagnostic performance. RESULTS: US revealed significantly higher diagnostic performance than mammography for tumors larger than 2 cm. Combined reading showed significantly higher performance than mammography except for tumors smaller than 2 cm. The performance of all three tests was reduced in dense parenchyma, and significantly so for mammographic and combined interpretation. CONCLUSION: The accuracy of US in patients with palpable mammographically noncalcified and not obviously malignant breast tumors is lower than reported for mixed sample populations. The accuracy of US may be influenced by breast parenchyma density. Combined reading offers the highest diagnostic accuracy.

Breast Neoplasms↗
PubMed1999

Variability in the interpretation of ultrasonography in patients with palpable noncalcified breast tumors.

PURPOSE: To analyze interobserver variability of ultrasonography (US) as an adjunct to mammography in patients with palpable noncalcified breast tumors. MATERIAL AND METHODS: Mammographic, US, and combined reading of 200 patients with palpable noncalcified breast masses were performed independently by four experienced radiologists. Nonneoplastic abnormalities and mammographically obvious cancers were excluded. Receiver operating characteristic (ROC) analysis based on 115 tumors was carried out for mammography, US, and both combined for each radiologist. The US diagnoses of the 45 cancers excluded from ROC analysis and the 55 cancers included were compared. RESULTS: One radiologist revealed a significantly higher diagnostic performance with US than with mammography. Combined reading showed the highest performance for all observers, but the improvement as compared with mammography was significant for only two. Higher accuracy on combined reading was mainly caused by correct upgrading of tumors with benign or indeterminate mammographic findings. One radiologist had benefit of US for downgrading of tumors. All four radiologists made a malignant US diagnosis twice as often in mammographically obvious cancers than in mammographically nonconclusive tumors. CONCLUSION: Radiologists differ substantially in interpretation of breast imaging. Combined reading offers the highest diagnostic accuracy mainly by correct upgrading of tumors on US. The role of US for downgrading tumors is operator-dependent.

Breast Neoplasms↗
PubMed1998

Detectability of simulated masses and calcifications in mammography. Development of a phantom and a new method for determination of receiver operating characteristics.

PURPOSE: To develop a method for receiver operating characteristics (ROC) studies in mammography. MATERIAL AND METHODS: We developed a phantom based on excised breast tissue and overlay tiles that could be arranged in an arbitrary pattern across the surface of the breast tissue. Some of the tiles contained structures simulating calcifications or masses that produced image contrast near the experimentally determined detection threshold. Based on this phantom, a methodology for performing ROC studies in mammography was developed. The ROC curves were constructed from reporting schemes filled in by radiologists at five different laboratories. The curves were determined by a novel method: a non-linear least-squares fit of a mathematical model to the data. RESULTS: There were large differences among the areas under the ROC curves obtained from the five laboratories.

Breast Diseases↗
PubMed1998

Assessment of image quality and total performance in Norwegian mammography laboratories. Findings in a national survey based on different phantoms and ROC methodology.

PURPOSE: To assess the image quality at different mammography laboratories. MATERIAL AND METHODS: Two commercial mammographic test phantoms and one phantom based on excised mammary tissue were used in an assessment of the imaging chain and total performance at 45 Norwegian mammography laboratories. The breast-tissue phantom was used for a receiver operating characteristics (ROC) analysis. This was carried out by putting overlays with identifiable regions (some of which contained a cluster of simulated calcifications) on top of the mammary tissue, and then having a radiologist report the confidence of a finding for each region. RESULTS AND CONCLUSION: The areas under the ROC curves were in general high. In nearly all the laboratories, performance was improved when a magnification technique was applied. There were wide variations among the laboratories in total performance as measured by the area under the ROC curve, and also in the physical parameters derived by means of the commercial phantoms. In general, a good ROC performance was associated with a good physical performance in the imaging chain.

Female↗
PubMed1996

Semiautomated multilocus genotyping of Pacific salmon (Oncorhnychus spp.) using microsatellites.

We report the development of a semiautomated multilocus genotyping system for Pacific salmon using four-color fluorescent detection of microsatellites. An initial screening of microsatellites was conducted on five species of Pacific salmon (Oncorhynchus spp.) and Atlantic salmon (Salmo salar) using 35 primer pairs developed from six species of salmonid. The number of loci that amplified varied by species from 11 (chum salmon) to 22 (chinook salmon). We then tested co-amplification of microsatellites in chinook, coho, and sockeye salmon and developed six-locus multiplex systems. The species-specific multiplex systems were applied to two populations using a sequencer/gene scanner (Perkin-Elmer Applied Biosystems, Inc. [ABI] 373A). The genetic variability at each locus was calculated to evaluate the utility of this system for genetic studies. Significant differences in allele frequencies were observed between populations in 14 of 18 pair-wise comparisons. Average heterozygosity ranged from 0.47 in Togiak River coho salmon to 0.75 in Dungeness River chinook salmon. Observed heterozygosities ranged from 0 at One mu 1 in Togiak River coho to 0.96 at Ssa85 in Dungeness River chinook. The probability of match (PM) for each six-locus multiplex system was 4.0 x 10(-10), 7.2 x 10(-8), and 3.2 x 10(-7) for chinook, coho, and sockeye, respectively. The average polymorphic information content (PIC) was 0.77, 0.56, and 0.60 for chinook, coho, and sockeye, respectively. The microsatellite loci used here show promise for high-resolution genetic studies of Pacific salmon such as fine-scale population analysis kinship, and parentage studies.

Animals↗
PubMed1995

[Mediastinoscopy in bronchogenic carcinoma].

During recent years it has been discussed whether mediastinoscopy could be replaced or supplemented by other diagnostic procedures for detection of mediastinal lymph node metastases in patients with pulmonary cancer. The results of 289 mediastinoscopies were analyzed and correlated to thoracotomy in order to evaluate the procedure. Two hundred and six males and 83 females were included in the study. The mean age was 63 years for men and 58 years for women. Mediastinoscopy was positive (N2 disease) in 113 cases (39%) and negative in 176 cases. The 113 N2 patients were not operated upon. One hundred and seven patients (37%) had thoracotomy performed. 12% of these patients had metastases at the time of thoracotomy. Mediastinoscopy is still the most reliable method in selecting patients with bronchogenic carcinoma for thoracotomy. It is important to make a careful dissection during the mediastinoscopy at both tracheo-bronchial angles as well as at the subcarinal. Eleven percent of the metastatic lymph nodes were found only at the subcarinal or at the contralateral tracheo-bronchial angle. Sixteen (5.5%) of the 289 patients are still alive, with a follow up of more than six years. Only resected patients survived.

Adult↗
PubMed1995

[Randomized trial on the value of diagnostic laparoscopy before appendectomy].

Two groups of 30 women with clinical signs of appendicitis were randomized to immediate appendicectomy or diagnostic laparoscopy. In the latter group, appendicectomy was performed if a diagnosis of acute appendicitis was established or if the appendix could not be visualized. Eleven patients who underwent immediate operation had unnecessary appendicectomy, compared with two who underwent laparoscopy. This difference of 30% (95% confidence interval 11-49%) was significant (p = 0.01). There was no significant difference in postoperative morbidity rate in the two groups. Diagnostic laparoscopy is a useful preliminary investigation in women with clinical signs of acute appendicitis.

Adolescent↗
PubMed1995

Subjective evaluation of image quality based on images obtained with a breast tissue phantom: comparison with a conventional image quality phantom.

A breast tissue phantom was used for assessment of mammographic image quality. Three images, exposed to give a reference area film density of 1.25 +/- 0.03, were obtained for each of five different film/kV combinations. Each of three radiologists carried out a series of three blind readings, in which the 15 films were ranked according to sharpness and contrast. In a similar experiment with a conventional image quality phantom, scores for the visualization of simulated calcifications and contrast-detail performance, and measures for resolution and contrast were obtained. In both experiments, the judgements of the readers were highly consistent, and both the intraobserver and interobserver variabilities were non-significant. No significant differences between the film/kV combinations were found with respect to high-contrast resolution and visualization of the simulated calcifications. The contrast measures obtained with the conventional phantom correlated well with the contrast scores obtained with the breast tissue phantom. The contrast-detail scores obtained with the conventional phantom showed no correlation with the scores obtained with the breast tissue phantom, nor with the contrast measures obtained with the conventional phantom.

Biopsy↗
PubMed1994

[Esophageal resections in Denmark 1985-1988. A retrospective study of complications and early mortality].

In a retrospective investigation, 17 Danish Departments of Surgery reported on morbidity and mortality following surgical treatment of cancer of the oesophagus and cardia in the years 1985-1988. The study comprised 352 men and 112 women, representing 98% of the total number of resections performed in Departments of General Surgery (11%), Departments of Surgical Gastroenterology (24%) and Departments of Thoracic Surgery (65%). Nine departments performed less than five resections per year. Frequency of anastomotic leaks were 8.2%, and the mean hospital mortality was 16.6%. Mortality was significantly lower (median 9.6% and 7.0%) in departments performing more than 20 resections per year. It is concluded that in Denmark, surgical treatment of cancer of the oesophagus or cardia should be centralized to departments performing more than 20 resections per year.

Aged↗
PubMed1993

Randomized study of the value of laparoscopy before appendicectomy.

Two groups of 30 women with clinical signs of appendicitis were randomized to immediate appendicectomy or diagnostic laparoscopy. In the latter group, appendicectomy was performed if a diagnosis of acute appendicitis was established or if the appendix could not be visualized. Eleven patients undergoing immediate operation had unnecessary appendicectomy, compared with two having laparoscopy. This difference of 30 per cent (95 per cent confidence interval 11-49 per cent) was significant (P = 0.01). There was no significant difference in postoperative morbidity rate in the two groups. Diagnostic laparoscopy is a useful preliminary investigation in women with clinical signs of acute appendicitis.

Acute Disease↗
PubMed1991

Adenocarcinoma arising in a foregut cyst of the mediastinum.

A case of malignant transformation in a mediastinal cyst of the esophageal reduplication type is presented. The cyst had been recognized 39 years previously, but remained asymptomatic until sudden growth occurred. It was resected totally from the esophagus and the patient recovered well. A review of the literature showed that malignancy in mediastinal foregut cysts is extremely rare.

Adenocarcinoma↗
PubMed1990

[Primary retroperitoneal seminoma].

A case of primary retroperitoneal seminoma is presented and 73 cases from the literature are reviewed. The mean age was 41 years. The presenting symptoms were abdominal pain in 53% of the cases, low back pain in 43% and in 7% the only symptom was a palpable mass. It is concluded that seminomata exist as primary tumors in the retroperitoneum, but thorough examinations of the patients is necessary in order to arrange correct treatment and to exclude a primary testicular focus or CIS. Ultrasound sonography to discover non-palpable testicular tumors is recommended as well as surgical biopsies of the testis to reveal CIS. In patients treated with combined surgical resection and radiotherapy, the success rate was 92%. The overall success rate was 68%. It is expected that the curability for all patients is significantly improved with the introduction of combination of radiation and chemotherapy, as it has been seen in advanced testicular cancers.

Adult↗