PURPOSE: This study proposes the keyhole method in order to improve the time resolution of the proton resonance frequency(PRF) MR temperature monitoring technique. The values of Root Mean Square (RMS) error of measured temperature value and Signal-to-Noise Ratio(SNR) obtained from the keyhole and full phase encoded temperature images were compared. MATERIALS AND METHODS: The PRF method combined with GRE sequence was used to get MR temperature images using a clinical 1.5T MR scanner. It was conducted on the tissue-mimic 2% agarose gel phantom and swine's hock tissue. A MR compatible coaxial slot antenna driven by microwave power generator at 2.45GHz was used to heat the object in the magnetic bore for 5 minutes followed by a sequential acquisition of MR raw data during 10 minutes of cooling period. The acquired raw data were transferred to PC after then the keyhole images were reconstructed by taking the central part of K-space data with 128, 64, 32 and 16 phase encoding lines while the remaining peripheral parts were taken from the 1st reference raw data. The RMS errors were compared with the 256 full encoded self-reference temperature image while the SNR values were compared with the zero filling images. RESULTS: As phase encoding number at the center part on the keyhole temperature images decreased to 128, 64, 32 and 16, the RMS errors of the measured temperature increased to 0.538, 0.712, 0.768 and 0.845degrees C, meanwhile SNR values were maintained as the phase encoding number of keyhole part is reduced. CONCLUSION: This study shows that the keyhole technique is successfully applied to temperature monitoring procedure to increases the temporal resolution by standardizing the matrix size, thus maintained the SNR values. In future, it is expected to implement the MR real time thermal imaging using keyhole method which is able to reduce the scan time with minimal thermal variations.
Hot Temperature ; Magnetics ; Magnets ; Microwaves ; Protons ; Sepharose ; Tarsus, Animal ; Thermography

OBJECTIVES: A field investigation was done to identify the level of epidemic and to evaluate the infection route of Salmonellosis occurred in a baby's first birthday banquet in Jeju Island. METHODS: Among participants in the banquet given on a baby's first birthday, persons showing gastrointestinal symptoms were conducted by the structured questionnaire and stool culture. The symptomless persons were also surveyed by self-responded structured questionnaire. The causal relationship between food items and gastrointestinal symptoms was proved by odds ratio and Wilcoxon rank-sum test. RESULTS: Salmonella london was identified in the stools of 12 subjects among 20 participants showing gastrointestinal symptoms, as well as in the boiled pork hock. CONCLUSIONS: This outbreak event is thought to happen after participants took the boiled pork hock that contaminated with S almonella london during the storage process.
Humans ; Odds Ratio ; Salmonella ; Salmonella Food Poisoning ; Salmonella Infections* ; Tarsus, Animal ; Surveys and Questionnaires