Biomedical subjects

K C Young

Publications and source records attributed to K C Young.

At least 37 records · Page 2Linked to original sources

PubMed2000

Additional factors for the estimation of mean glandular breast dose using the UK mammography dosimetry protocol.

The UK and European protocols for mammographic dosimetry use conversion factors that relate incident air kerma to the mean glandular dose (MGD) within the breast. The conversion factors currently used were obtained by computer simulation of a model breast with a composition of 50% adipose and 50% glandular tissues by weight (50% glandularity). Relative conversion factors have been calculated which allow the extension of the protocols to breasts of varying glandularity and for a wider range of mammographic x-ray spectra. The data have also been extended to breasts of a compressed thickness of 11 cm. To facilitate the calculation of MGD in patient surveys, typical breast glandularities are tabulated for women in the age ranges 40-49 and 50-64 years, and for breasts in the thickness range 2-11 cm. In addition, tables of equivalent thickness of polymethyl methacrylate have been provided to allow the simulation for dosimetric purposes of typical breasts of various thicknesses.

Adipose Tissue↗

PubMed2000

Radiation doses received in the UK Breast Screening Programme in 1997 and 1998.

The mean glandular doses (MGDs) to samples of women attending for mammographic screening are measured routinely at screening centres in the UK Breast Screening Programme (NHSBSP). This paper reviews the data collected during screening in the NHSBSP in 1997 and 1998 for 23,752 films, using 171 X-ray sets, for 8745 women. Average MGD was 2.03 mGy per oblique film and 1.65 mGy per craniocaudal film, similar to the MGDs found previously in the NHSBSP for the years 1994 and 1995. MGD was found to increase with compressed breast thickness where the tube potential was selected manually, so that the average dose for 10 cm thick breasts was 2.7 times the average for all breasts. For large breasts (> 70 mm) the use of X-ray sets such as the IGE DMR, which automatically select the beam quality for each breast, resulted in lower doses compared with sets using manual tube potential selection. MGD to the standard breast was found to vary from 0.7 to 2.2 mGy and to be correlated with the average MGD per mediolateral oblique film for the women screened on that system (R = 0.79). No correlation between age and MGD was found within the invited age range of 50-64 years.

Age Factors↗

PubMed2000

Skin edge perception in mammograms: a comparison of two film-screen combinations.

The entire skin edge is not always seen on mammograms. The importance of demonstrating the full extent of the breast on a mammogram is uncertain, but there are implications for optimizing film design and use. The new Agfa HDR film has been designed to improve visualization of the skin edge without compromising overall contrast. A quantitative and qualitative comparison between Agfa HDR and the Fuji UMMA film has been performed. A total of 216 mammograms from 54 symptomatic women were analysed. For each view on each woman, one breast was imaged using Fuji UMMA film and the other using Agfa HDR film. The target density achieved on quality control films of PMMA blocks was 1.70 +/- 0.10 for both film types. A radiologist graded the skin edges of all the films as visible, just visible or dark. Measurements were made of the optical densities in the skin edge region and on the fully exposed black part of the film, adjacent to the skin line. 70% of the HDR films had visible skin edges compared with 43% of the UMMA films. 2% of the HDR films had dark skin edges compared with 26% of the UMMA films. Optical densities at the skin edge were broadly similar for the two films and in the range 3.6 +/- 0.3. However, the density of the black part of the Agfa film was about 0.5 higher than with the Fuji film and it appears that this was the main reason the skin edge region was better visualized with the Agfa film.

Female↗

PubMed1999

Analysis of optical density and contrast in mammograms.

The objective of this project is the development of tools for the UK NHSBSP to assess image quality quantitatively in clinical films, for the purposes of optimizing imaging procedures and audit. As an initial step, 120 mammograms of 46 women on a single day of screening were digitized and analysed to produce indices of optical density (OD) and contrast. Analysis was performed on three regions of interest (ROI): pectoral muscle, main breast and skin edge. Two radiologists independently graded the quality of information in the different parts of each mammogram, and categorized breast type as either "dense", "mixed density" or "fatty". Measurements of contrast and OD generally correlated well with the opinions of the radiologists. For the oblique mammograms, the mean OD in the main breast ranged between films from 1.25 to 2.24 with a mean of 1.69 +/- 0.02. In the craniocaudal mammograms, the mean OD in the main breast ROI ranged from 1.14 to 1.94 with a mean of 1.61 +/- 0.05. The OD for a quality control film of a 40 mm block of PMMA exposed on the same day with this system was 1.53. A contrast index (CI) was calculated for each mammogram as the difference between the points of maximum and minimum OD in the main breast. Mean CI was 1.02 +/- 0.09 for fatty breasts, 1.50 +/- 0.10 for mixed density breasts and 2.05 +/- 0.23 for dense breasts. A review of the radiologist assessments indicated that the main breast was satisfactorily displayed when glandular and fatty tissues were displayed within the OD range 0.8-2.9. An analysis of the dynamic range requirements showed that 17% of films had a dynamic range that lay above that calculated using the suggested OD limits.

Breast Neoplasms↗

PubMed1999

Plastic microchip electrophoresis for analysis of PCR products of hepatitis C virus.

BACKGROUND: Electrophoresis on polymeric rather than glass microstructures is a promising separation method for analytical chemistry. Assays on such devices need to be explored to allow assessment of their utility for the clinical laboratory. METHODS: We compared capillary and plastic microchip electrophoresis for clinical post-PCR analysis of hepatitis C virus (HCV). For capillary electrophoresis (CE), we used a separation medium composed of 10 g/L hydroxypropyl methyl cellulose in Tris-borate-EDTA buffer and 10 micromol/L intercalating dye. For microchip electrophoresis, the HCV assay established on the fused silica tubing was transferred to the untreated polymethylmethacrylate microchip with minimum modifications. RESULTS: CE resolved the 145-bp amplicon of HCV in 15 min. The confidence interval of the migration time was <3.2%. The same HCV amplicon was resolved by microchip electrophoresis in <1.5 min with the confidence interval of the migration time <1.3%. CONCLUSION: The polymer microchip, with advantages that include fast processing time, simple operation, and disposable use, holds great potential for clinical analysis.

DNA, Viral↗

PubMed1998

Tissue distribution and cDNA cloning of a human fatty acid transport protein (hsFATP4).

Fatty acid uptake is partly controlled by the FATP gene family, of which at least five members are known in mice. Using the mmFATP1 cDNA as hybridization probe, a 1.6 kb partial cDNA clone was isolated from a human heart cDNA library. With 5' and 3' RACE procedures, the complete cDNA was isolated. Sequence comparisons with its mouse homologues identified this clone as hsFATP4.

Amino Acid Sequence↗

PubMed1998

Plasminogen activation by streptokinase via a unique mechanism.

The mechanism of human plasminogen (HPlg) activation by streptokinase (SK)-type activator was investigated with recombinant truncated SK peptides. An enzyme-substrate intermediate of HPlg.SK. HPlg ternary complex was demonstrated by a sandwich-binding experiment. Formation of the ternary complex was saturable, HPlg-specific, and inhibited by 6-aminocaproic acid. Three interaction sites between SK and HPlg were demonstrated. SK-(220-414) bound to HPlg with two binding sites: one to the micro-HPlg region, the catalytic domain of HPlg, and one to the kringle 1-5 region, with Kd values of 1.50 x 10(-7) and 2.44 x 10(-6) M, respectively. SK-(16-251) bound to a single site on the kringle 1-5 region of HPlg with a Kd of 4.09 x 10(-7) M. SK-(220-414) and SK-(16-251) competed for binding on the same or nearby location on the human kringle 1-5 domain. Combination of SK-(220-414) and SK-(16-251), but not either peptide alone, could effectively activate HPlg. In addition, SK-(16-251) dose-dependently enhanced the activation of HPlg by SK-(16-414), while the HPlg activation by SK-(16-414) was inhibited by SK-(220-414). We conclude that the HPlg that binds to the COOH-terminal domains of SK functions as an enzyme to catalyze the conversion of substrate HPlg that binds to the NH2-terminal domain of SK to human plasmin.

Aminocaproic Acid↗

PubMed1998

Preparation of a novel streptokinase mutant with improved stability.

The novel mutant streptokinase, SK-K59E, can activate human plasminogen as efficiently as the purified commercially available streptokinase. Several peptide bonds including Lys59-Ser60 in native streptokinase were hydrolyzed in reaction with plasmin and peptides of small molecular masses were generated. The plasminogen activator activity of native streptokinase in reaction with human plasmin declined to 25% of the original activity in a 120-min incubation. On the other hand, the NH2-terminal peptide of SK-K59E remained intact in reaction with plasmin and the activator activity of streptokinase decreased to 75% of the original activity in 120 min. The major degraded peptide fragments of native streptokinase in reaction with plasmin had molecular masses of 36 and 30 kDa. However, two major peptide fragments of 42 and 34 kDa were observed in the reaction of SK-K59E with human plasmin. The 42 kDa peptide fragment, which contained NH2-terminal of streptokinase, could activate human plasminogen as efficiently as the native streptokinase. SK-K59E can induce greater degree of caseinolysis and fibrinolysis than the native streptokinase. In conclusion, the results demonstrate that the prevention of cleavage at Lys59 of streptokinase prolongs the half-life of streptokinase in complex with plasmin and that the NH2-terminal of streptokinase (Ile1-Lys59) plays an important role in maintaining its stability.

Enzyme Stability↗

PubMed1997

Are HTLV-II-seropositive injection drug users at increased risk of bacterial pneumonia, abscess, and lymphadenopathy?

Disease associations of HTLV-II are poorly defined, despite a high seroprevalence among injection drug users (IDU). One hundred twenty-four HTLV-II-seropositive emergency room and clinic patients were matched by age, sex, and clinic to 120 HTLV-I/II-seronegative patients. Medical records were reviewed blinded to HTLV-II status, and International Classification of Disease 9th Clinical Modification (ICD-9CM)-coded diagnoses were compared between seropositive patients and controls. After adjustment for relevant confounding variables such as human immunodeficiency virus infection, HTLV-II-seropositive IDU had an increased risk of bacterial pneumonia (odds ratio [OR], 3.45; 95% confidence interval [CI], 1.58, 7.56), abscess (OR, 8.30; 95% CI, 4.02, 17.11), and lymphadenopathy (OR, 3.91; 95% CI, 1.24, 12.32) compared with HTLV-II-negative non-IDU patients. In contrast, HTLV-II-negative IDU were at only marginally increased risk of the same conditions, with OR of 1.76 (95% CI, 0.42, 7.40), 3.00 (95% CI, 0.94, 9.59), and 1.31 (95% CI, 0.15, 11.66), respectively. These results indicate that HTLV-II seropositivity may define a subgroup of IDU who are at particularly high risk of bacterial pneumonia, skin and soft tissue abscess, and lymphadenopathy. Whether HTLV-II has an etiologic role in predisposing IDU to bacterial infections and lymphadenopathy will require further investigation.

Abscess↗

PubMed1997

Influence of number of views and mammographic film density on the detection of invasive cancers: results from the NHS Breast Screening Programme.

The National Health Service Breast Screening Programme (NHSBSP) has recommended the adoption of two view mammography at the prevalent screen, and the use of a target film density in the range 1.4-1.8. The aim of this study was to review the impact of number of views and optical density on the detection of invasive cancers. The last four annual returns for screening centres in the NHSBSP have been analysed retrospectively for 2827342 women aged 50-64 years attending their first (prevalent) screening examination. The detection of invasive cancers was assessed in relation to the number of views and film density using the age adjusted, Standardized Detection Ratio measure of screening performance. Typical film densities were reported for each screening year by local physicists, and the average value for all mammography sets at each programme calculated, and found to vary from 0.85 to 1.85. The mean film density across the NHSBSP rose progressively from 1.30 (SD = 0.21) in 1991/2 to 1.57 (SD = 0.12) in 1994/5. Programmes using single view mammography (MLO) and an optical density less than 1.4 detected 76% (95% CI 74-79%) of the expected invasive cancers. Programmes using two view mammography (MLO and CC) and an optical density equal to or greater than 1.4 detected 95% (95% CI 92-98%) of the expected invasive cancers. In 1994/95 when more programmes used the recommended screening modes, the NHSBSP detected 96% (95% CI 92-101%) of the expected invasive cancers at prevalent screening. The detection of invasive cancers was highest where programmes used two views with a film density in the range 1.4-1.8. The results provide evidence of the benefit of the recommended protocol for prevalent screening and indicate that from 1995/96 when all programmes will be using the recommended protocol, it is likely that the detection rates and interval cancer rates from prevalent screens in the NHSBSP will be close to the figures in the Swedish-Two County Trial.

Breast Neoplasms↗

PubMed1997

Effect of automatic kV selection on dose and contrast for a mammographic X-ray system.

The effect of automatic tube potential (kV) selection on breast dose and contrast has been assessed using a Philips MammoDiagnost 3000 mammography X-ray set. The performance of the X-ray set using automatic kV selection has been compared with that found using a fixed kV of 28. The AUTOKV mode selected 25 kV for breasts with thickness up to about 50 mm, which increased the contrast by 5-10%, and increased the mean glandular dose (MGD) per film by, on average, 30-40%. For large breasts with a compressed thickness of 70 mm and above, kVs up to 30 were selected so that the average MGD per film was reduced by 19% from 3.62 to 2.94 mGy, with an estimated loss in contrast of about 4-8%. For all breasts the mean MGD per film was 1.85 +/- 0.05 mGy where AUTOKV was used, and 1.74 +/- 0.08 mGy per film when 28 kV was used. The overall image quality of the mammograms was found to be higher when AUTOKV was used. Overall, the AUTOKV facility on this X-ray set generally worked well and resulted in slightly higher contrast and slightly better image quality at the price of a small increase in the average dose for this patient group when compared with the usual UK procedure of using a fixed 28 kV.

Breast Neoplasms↗

PubMed1996

Hepatitis C virus RNA in peripheral blood mononuclear cells: comparing acute and chronic hepatitis C virus infection.

Hepatitis C virus (HCV) can infect peripheral blood mononuclear cells (PBMC) of patients with chronic HCV infection. No data are available on PBMC testing for HCV RNA in acute hepatitis C. This study investigated the presence of HCV RNA in PBMC of patients with acute posttransfusion hepatitis C, compared with those with chronic HCV infection. Nested polymerase chain reaction (PCR) was applied to detect HCV RNA in 111 and 48 paired samples of serum and PBMC of 11 patients with acute posttransfusion hepatitis C and 48 patients with chronic HCV infection, respectively. In patients with acute posttransfusion hepatitis C, HCV RNA was detected in 17 of 29 (59%) and 67 of 82 (82%) serum samples collected during the incubation period and acute phase, respectively. Meanwhile, of the 48 patients with chronic HCV infection, 41 had serum HCV RNA (85%). HCV RNA was not detected in PBMC samples from incubation period or from acute-phase hepatitis, although it was detected in 12 of the 48 PBMC samples of chronically infected patients (25%) P < .005). Of the 12 PBMC specimens positive for positive-stranded HCV RNA, 6 were also positive for negative-stranded HCV RNA. Among patients with chronic HCV infection, HCV infection of PBMC was not related to age, sex, blood transfusion, serum alanine transaminase (ALT) levels, or serum virus titers. In conclusion, HCV infection of PBMC rarely exists in patients with acute hepatitis C. As HCV infection persists, the incidence of HCV infection of PBMC becomes higher.

Acute Disease↗

PubMed1996

Incidence of post-transfusion hepatitis in Taiwan before and after introduction of anti-HCV testing.

The effectiveness of second-generation anti-hepatitis C virus antibody (anti-HCV) screening of blood donations for the prevention of non-A, non-B post-transfusion hepatitis (NANB PTH) was assessed. A prospective study of 192 transfusion recipients was performed to compare the incidence of NANB PTH after the introduction of the second-generation anti-HCV test with the incidence before its introduction. We used a polymerase chain reaction to detect HCV-RNA and HBV-DNA in the sera of patients with NANB PTH. The incidence of acute post-transfusion hepatitis C was 11% (8 of 71) before the screening for anti-HCV as compared with 2.5% (3 of 121) after the screening (p < 0.05). Viremia was detected within the first five weeks of infection in 10 patients with acute post-transfusion hepatitis C. However, there was no significant difference in the incidence of non-A, non-B, non-C (NANBNC) PTH before screening (3 of 71, 4.2%) compared with after screening (3 of 121, 2.5%). Usually, NANBNC PTH was not clinically important. Anti-HCV screening of blood donors significantly reduces the incidence of post-transfusion hepatitis C, but not the incidence of NANBNC PTH.

Adolescent↗

PubMed1996

Dose and image quality in mammography with an automatic beam quality system.

Radiation dose, contrast and image quality for automatic beam quality selection (OPDOSE) with the Siemens Mammomat 3000 has been investigated for different breast thicknesses and compared with those found using manually set tube potentials and a molybdenum target and filter. Automatic beam quality selection was found to have a negligible effect for breasts with a compressed breast thickness of less than 45 mm. However, for larger breasts substantial dose savings were achieved for a loss in contrast. For mammograms of compressed breast with a thickness in excess of 60 mm the mean glandular dose (MGD) per film was 2.90 mGy for manually selected tube potentials with a molybdenum/molybdenum target filter combination as compared with 1.87 mGy using 26 kVp and a tungsten target with rhodium filtration. The contrast loss in using OPDOSE was measured with a test object to be about 10% for breast thicknesses in excess of 45 mm. The standard breast model, which assumes a 50% glandular content, did not provide a good fit to the MGD for women attending for breast screening in the age range 50 to 64 years.

Breast↗

PubMed1995

Interaction of streptokinase and plasminogen. Studied with truncated streptokinase peptides.

The interaction of streptokinase (SK) with human plasminogen (HPlg) was investigated using truncated SK peptides prepared by gene cloning techniques. SK(16-414) and SK(16-378) could activate HPlg as efficiently as the authentic SK. SK(60-414), which had been preincubated with SK(1-59), could also activate HPlg. SK(91-414), SK(127-414), and SK(158-414), at a concentration of one-tenth of HPlg, all failed to activate HPlg. However, the truncated SK peptides in complexes with equimolar HPlg could form amidolytically active virgin enzymes that slowly converted to human plasmin (HPlm) after a lag period of 15 min. SK(16-316) could not activate HPlg. No virgin enzyme was detected when SK(16-316) was incubated with equimolar HPlg, but the HPlg in the complex was modified to HPlm after reaction for 20 min. SK(220-414) and SK(16-251) had no ability to transform HPlg to virgin enzyme or to HPlm in equimolar complex with HPlg, although they could bind to HPlg. The functions of five regions in the SK molecule (a, Ile1-Lys59; b, Ser60-Asn90; c, Val158-Arg219; d, Tyr252-Ala316; e, Ser317-Ala378) in interaction with HPlg are deduced. Region a is important in stabilizing the conformation of the SK molecule, and region b is essential for HPlg activation. Region c is required for induction of the conformational changes of HPlg to virgin enzyme. Regions c and d are required for the conversion of HPlg to HPlm in the HPlg.SK equimolar complex. Coordination of regions c, d, and e of SK is essential for a virgin enzyme formation, and coordination of regions b, c, d and e is required for an effective SK-type HPlg activator.

Base Sequence↗

PubMed1994

Intrafamilial transmission of hepatitis C virus: the important role of inapparent transmission.

To evaluate the intrafamilial transmission of hepatitis C virus (HCV) 104 index patients with type C chronic liver disease and their 307 family contacts were interviewed. After a questionnaire on the risk factors of parenteral exposure, blood samples were obtained and tested for liver biochemistry and anti-HCV antibody by enzyme-linked immunosorbent assay (Abbott II). Overall, 52 family contacts (17%) were positive for anti-HCV, indicating a higher anti-HCV prevalence among family contacts than among the general population in Taiwan. The anti-HCV prevalences in parents, spouses, children, and other contacts of the patients were 54% (14/26), 28% (25/91), 6.9% (10/143), and 6.4% (3/47), respectively. The contacts of index patients had increasingly greater risk of HCV infection when they became older and had lived longer with index patients. All family contacts were divided into two groups categorized by whether the index patients had or did not have a history of parenteral exposure. Among 126 family contacts of the 42 patients without parenteral exposure, blood transfusion and surgery were the factors significantly associated with HCV infection in these family contacts (odds ratio = 7.26, 95% confidence interval = 2.32-32.67; odds ratio = 3.95, 95% CI = 1.29-12.11, respectively). Risk factors were not significantly associated with HCV infection among 181 family contacts of the 62 index patients with parenteral exposure. It is concluded that the index patients without parenteral exposure appeared to have acquired the disease from HCV-infected family members with risk factors. Most of the index patients had a history of parenteral exposure and in turn served as the source of the disease for family members.

Adult↗

PubMed1994

Interobserver variation in the detection of osteopenia by radiography and comparison with dual X-ray absorptiometry of the lumbar spine.

In 100 patients (20 male, 80 female) radiographs of the lumbar spine were obtained in both planes, anteroposterior and lateral. Nine readers independently and without specific criteria or training assessed the radiographs for presence of osteopenia in the form of a binary decision. A posteranterior dual x-ray absorptiometry (PA DXA) measurement of the lumbar spine was performed in all patients using the Hologic QDR 1000 bone densitometer. A bone mineral density (BMD) of 0.83 g/cm2 (T-score about 2 SD and 2.5 SD lower than BMD in normal young female and male subjects respectively) was used as a threshold for the diagnosis of osteopenia. Complete agreement amongst the 9 readers was achieved in 43 patients. In 26 more patients at least 8 readers agreed. kappa-coefficients for interobserver variation ranged from 0.458 to 0.691 for reader pairs. For agreement between the observer ratings and the DXA results, kappa-coefficients ranging between 0.347 and 0.555 were found. The vast majority of readers agreed in the diagnosis of osteopenia in cases where the BMD was less than 0.73 g/cm2. Where the BMD was between 0.73 and 1.03 g/cm2 a substantial disagreement was found between reader evaluation and DXA measurement, and also amongst the readers. We conclude from our results that osteopenia can reliably be detected from lumbar spine radiographs by all readers only after a substantial amount of BMD is lost. On the other hand, a diagnosis based solely on PA DXA measurement of the spine may also lack accuracy, due to a substantial influence of degenerative changes of the lumbar spine and aortic calcification.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗

PubMed1994

Mammographic film density and detection of small breast cancers.

From its inception, the UK National Breast Screening Programme (NHSBSP) has recognized that optimum image quality of the mammographic screening test is a key objective. The overall optical density of the mammography film is one of the factors expected to have a significant effect on the image quality of the mammogram with the potential to influence cancer detection. In a previous review of the performance of mammography equipment in the NHSBSP, it was observed that there was a very wide range in the mammographic film densities used at different breast screening centres. In this study a mammography test object was used to show experimentally that, for a typical mammography system, image quality increased substantially with increased film density. Summary data was therefore requested from radiologists in the NHSBSP on the rate of detection of small invasive cancers (diam. < or = 10 mm) and the typical film density used during that year. Proforma were completed for 61 annual sets of results from 31 screening centres involving over 500,000 women. Where centres reported using film densities of less than 1.2D the average small cancer detection rate was 0.12% +/- 0.01%, as compared to an average of 0.17% +/- 0.01% for centres using higher film densities. The results indicate that there is a need for national guidelines in the setting of film densities, and a range for target film densities of 1.4D to 1.8D has been suggested. Attention to optimizing image quality by increasing film density is of particular importance to any screening centre where film densities of less than 1.2D are used, as there may be the potential to increase the detection of small breast cancers by as much as 50%.

Breast Neoplasms↗