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- Choularton, T. W., et al.
(författare)
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The Great Dun Fell Cloud Experiment 1993 : An overview
- 1997
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Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2393-2405
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Tidskriftsartikel (refereegranskat)abstract
- The 1993 Ground-based Cloud Experiment on Great Dun Fell used a wide range of measurements of trace gases, aerosol particles and cloud droplets at five sites to study their sources and sinks especially those in cloud. These measurements have been interpreted using a variety of models. The conclusions add to our knowledge of air pollution, acidification of the atmosphere and the ground, eutrophication and climate change. The experiment is designed to use the hill cap cloud as a flow-through reactor, and was conducted in varying levels of pollution typical of much of the rural temperate continental northern hemisphere in spring-time.
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| 2. |
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| 3. |
- Swietlicki, Erik, et al.
(författare)
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Source identification during the Great Dun Fell Cloud Experiment 1993
- 1997
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Ingår i: Atmospheric Environment. - 1352-2310. ; 31:16, s. 2441-2451
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Tidskriftsartikel (refereegranskat)abstract
- A characterisation of the sources influencing the site for the final field campaign of the EUROTRAC subproject GCE (Ground-based Cloud Experiment) at Great Dun Fell, Cumbria, Great Britain in April-May 1993 is presented. The sources were characterised mainly by means of aerosol filter and cascade impactor data, single particle analysis, gas data, data on aromatic organic compounds, cloud water ionic composition, measurements of aerosol size distributions and hygroscopic properties and various meteorological information. Receptor models applied on the aerosol filter and impactor data sets separately revealed two major source types being a marine sea spray source and a long-range transported anthropogenic pollution source. The results of the receptor models were largely consistent with the other observations used in the source identification. Periods of considerable anthropogenic pollution as well as almost pure marine air masses were clearly identified during the course of the experiment.
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| 4. |
- West, Jay B., et al.
(författare)
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Comparison and evaluation of retrospective intermodality image registration techniques
- 1997
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Ingår i: SPIE - The International Society for Optical Engineering. - : SPIE - International Society for Optical Engineering. ; , s. 332-347
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Konferensbidrag (refereegranskat)abstract
- All retrospective image registration methods have attached to them some intrinsic estimate of registration error. However, this estimate of accuracy may not always be a good indicator of the distance between actual and estimated positions of targets within the cranial cavity. This paper describes a project whose principal goal is to use a prospective method based on fiducial markers as a ’gold standard’ to perform an objective, blinded evaluation of the accuracy of several retrospective image-to-image registration techniques. Image volumes of three modalities – CT, MR, and PET – were taken of patients undergoing neurosurgery at Vanderbilt University Medical Center. These volumes had all traces of the fiducial markers removed, and were provided to project collaborators outside Vanderbilt, who then performed retrospective registrations on the volumes, calculating transformations from CT to MR and/or from PET to MR, and communicated their transformations to Vanderbilt where the accuracy of each registration was evaluated. In this evaluation the accuracy is measured at multiple ’regions of interest,’ i.e. areas in the brain which would commonly be areas of neurological interest. A region is defined in the MR image and its centroid C is determined. Then the prospective registration is used to obtain the corresponding point C’ in CT or PET. To this point the retrospective registration is then applied, producing C’ in MR. Statistics are gathered on the target registration error (TRE), which is the disparity between the original point C and its corresponding point C’. A second goal of the project is to evaluate the importance of correcting geometrical distortion in MR images, by comparing the retrospective TRE in the rectified images, i.e., those which have had the distortion correction applied, with that of the same images before rectification. This paper presents preliminary results of this study along with a brief description of each registration technique and an estimate of both preparation and execution time needed to perform the registration.
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| 5. |
- Björk-Eriksson, Thomas, 1960, et al.
(författare)
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The in vitro radiosensitivity of human head and neck cancers
- 1998
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Ingår i: Br J Cancer. - 0007-0920. ; 77:12, s. 2371-5
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Tidskriftsartikel (refereegranskat)abstract
- A study was made of the intrinsic radiosensitivity of 140 biopsy and surgical specimens of malignant head and neck tumours of different histologies. Using a soft-agar clonogenic assay, the material was assessed for the ability to grow in culture (colony-forming efficiency; CFE) and inherent tumour radiosensitivity (surviving fraction at 2 Gy, SF2). The success rate for obtaining growth was 74% (104/140) with a mean CFE of 0.093% (median 0.031) and a range of 0.002-1.3%. SF2 was obtained for 88 of 140 specimens, representing a success rate of 63% with a mean SF2 of 0.48 (median 0.43) and a range of 0.10-1.00. There were no significant differences in radiosensitivity between different sites of the head and neck region. There were no significant relationships between SF2 and disease stage, nodal status, tumour grade, patient age, primary tumour growth pattern and CFE. The results were compared with those for other tumour types previously analysed with the same assay. The distribution of the SF2 values for the head and neck tumours was similar to that for 145 cervix carcinomas and there was no significant difference in mean radiosensitivity between the two tumour types. Also, there was no significant difference in radiosensitivity between head and neck tumours and either breast or colorectal cancers. However, a group of eight lymphomas was significantly more radiosensitive. These results confirm the feasibility of carrying out radiosensitivity measurements using a soft-agar clonogenic assay on head and neck tumours. In addition, the work has shown that radiosensitivity is independent of many clinical parameters and that the mean value is similar to that reported for cervix carcinomas.
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| 6. |
- Björk-Eriksson, Thomas, 1960, et al.
(författare)
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The lack of correlation between proliferation (Ki-67, PCNA, LI, Tpot), p53 expression and radiosensitivity for head and neck cancers
- 1999
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Ingår i: Br J Cancer. - 0007-0920. ; 80:9, s. 1400-4
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Tidskriftsartikel (refereegranskat)abstract
- A study was made of the relationship between measurements of radiosensitivity versus proliferation and p53 status in head and neck cancers. Inherent tumour radiosensitivity was assessed as surviving fraction at 2 Gy (SF2) using a clonogenic soft agar assay (n = 77). The results were compared to data on proliferation obtained by both flow cytometry (labelling index (LI), the potential doubling time (Tpot) n = 55) and immunohistochemistry (Ki-67 and PCNA; n = 68), together with immunohistochemical p53 expression (n = 68). There were no overall significant differences in the median values of the various parameters analysed for the different sites within the head and neck region, disease stages, grades of tumour differentiation or nodal states. A subgroup analysis showed that oropharyngeal (n = 22) versus oral cavity (n = 35) tumours were more radiosensitive (P = 0.056) and had a higher Ki-67 index (P = 0.001). Node-positive tumours had higher LI (P = 0.021) and a trend towards lower Tpot (P = 0.067) values than node-negative ones. No correlations were seen between SF2 and any of the parameters studied. The long-standing dogma of an increased radiosensitivity of rapidly proliferating cells in contrast to slowly proliferating cells was not confirmed. The study shows that parallel measurements of different biological markers can be obtained for a large number of patients with head and neck cancers. The independence of the various parameters studied suggests that there may be potential for their combined use as prognostic factors for the outcome of radiotherapy.
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