Biomedical subjects

Bo-Anders Jönsson

Publications and source records attributed to Bo-Anders Jönsson.

4 recordsLinked to original sources

PubMed2005

A case study of successful e-learning: a web-based distance course in medical physics held for school teachers of the upper secondary level.

Learning activities and course design in the new context of e-learning, such as in web-based courses involves a change both for teachers and students. The paper discusses factors important for e-learning to be successful. The development of an online course in medical physics and technology for high school teachers of physics, details of the course, and experience gained in connection with it are described. The course syllabus includes basics of radiation physics, imaging techniques using ionizing or non-ionizing radiation, and external and internal radiation therapy. The course has a highly didactic approach. The final task is for participants to design a course of their own centered on some topic of medical physics on the basis of the knowledge they have acquired. The aim of the course is to help the teachers integrate medical physics into their own teaching. This is seen as enhancing the interest of high school students in later studying physics, medical physics or some other branch of science at the university level, and as increasing the knowledge that they and people generally have of science. It is suggested that the basic approach taken can also have applicability to the training of medical, nursing or engineering students, and be used for continuing professional development in various areas.

Biomedical Engineering↗

PubMed2005

Dosimetry calculations on a tissue level by using the MCNP4c2 Monte Carlo code.

OBJECTIVE: The aim of this study was to develop a MCNP4c2-code and to further refine the small-scale anatomy intestinal dosimetry model based on a EGS4-code developed by Jonsson et al.(1,2) METHOD: The small intestine was modeled as a hexagonal tube system and includes cross-dose contribution from activity in nearby intestine loops. The model includes villi (height, 500 microm), radiosensitive crypt cells (height, 150 microm), and an overlying mucus layer of thicknesses (5-200 microm). The developed intestinal model used in either of the two Monte Carlo codes make it possible to calculate S-values and subsequent mean absorbed dose to the radiation-sensitive crypt cells in the small intestinal wall by considering contributions from the self-dose and from the cross-dose from nearby intestinal loops. Results are given for monoenergetic electrons and photons and for full decay schemes of (99m)Tc, (111)In, (131)I, (67)Ga, (90)Y, and (211)At. RESULTS: Results show that the cross-dose from nearby intestinal loops is significant, and that the fraction of cumulated activity in the intestinal wall contents is important for accurate absorbed-dose estimation. CONCLUSION: It is evident from our study that previous Medical Internal Radiation Dose (MIRD) and International Conference on Radiological Protection (ICRP) models tend to overestimate the absorbed dose to the wall. Our work on the gastrointestinal tract model includes several noticeable refinements, as compared to the MIRD- and ICRP model, and the "onion shell" geometry can easily be transferred to similar geometrical dosimetry applications.

Astatine↗

PubMed2003

Crypt cell dosimetry for 99Tcm-sestamibi in a new small intestinal dosimetry model.

The aim of the study was to calculate the absorbed dose to the crypt cells in the small intestine from (99)Tc(m)-sestamibi excreted through the intestinal tract. The absorbed dose was calculated taking into consideration the biodistribution of the radiopharmaceutical in the small intestinal wall and its contents, based on data gathered in rats. Absorbed dose calculations were performed using a new intestinal model in which S values for crypt cells are given both for the intestinal wall and for the intestinal contents as source organs. A maximum of 6% of the injected activity was found to be located in the intestinal wall at 30 minutes after injection and 13% in the intestinal contents at 2 h, resulting in an absorbed dose of 8.9 microGy/MBq to the crypt cells. Assuming the activity to be located only in the wall, we calculate an absorbed dose to the crypt cells 2.5 times higher than if all the activity is assumed to be present in the intestinal contents. Using the new intestinal dosimetry model, together with detailed biokinetic data for the radiopharmaceutical from animal studies, it is possible to calculate the absorbed dose to the crypt cells, which is not possible when using external imaging.

Animals↗

PubMed2002

A dosimetry model for the small intestine incorporating intestinal wall activity and cross-doses.

UNLABELLED: Current internal radiation dosimetry models for the small intestine, and for most walled organs, lack the ability to account for the activity uptake in the intestinal wall. In existing models the cross-dose from nearby loops of the small intestine is not taken into consideration. The aim of this investigation was to develop a general model for calculating the absorbed dose to the radiation-sensitive cells in the small intestinal mucosa from radionuclides located in the small intestinal wall or contents. METHODS: A model was developed for calculation of the self-dose and cross-dose from activity in the intestinal wall or contents. The small intestine was modeled as a cylinder with 2 different wall thicknesses and with an infinite length. Calculations were performed for various mucus thicknesses. S values were calculated using the EGS4 Monte Carlo simulation package with the PRESTA algorithm and the simulation results were integrated over the depth of the radiosensitive cells. The cross-organ dose was calculated by summing the dose contributions from other intestinal segments. Calculations of S values for self-dose and cross-dose were made for monoenergetic electrons, 0.050-10 MeV, and for the radionuclides (99m)Tc, (111)In, (131)I, (67)Ga, (90)Y, and (211)At. RESULTS: The self-dose S value from activity located in the small intestinal wall is considerably greater than the S values for self-dose from the contents and the cross-dose from wall and contents except for high electron energies. For all radionuclides investigated and for electrons 0.10-0.20 MeV and 8-10 MeV in energy, the cross-dose from activity in the contents is higher than the self-dose from the contents. The mucus thickness affects the S value when the activity is located in the contents. CONCLUSION: A dosimetric model for the small intestine was developed that takes into consideration the localization of the radiopharmaceutical in the intestinal wall or in the contents. It also calculates the contribution from self-dose and cross-dose. With this model, more accurate calculations of absorbed dose to radiation-sensitive cells in the intestine are possible.

Electrons↗