PubMed · 8461199
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M D Anderssohn. 1993-04-10. BDJ re-design.. https://doi.org/10.1038/sj.bdj.4808138
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A new type of graphical tool for explaining and analyzing magnetic resonance imaging pulse sequences is developed and illustrated. This tool combines the partition diagram, which shows the evolution of multiple echoes with the application of multiple RF pulses, and k-space graphs, which show the evolution of the transverse magnetization as gradients are applied. The strength of the new tool lies in its ability to depict clearly the progression of complex imaging pulse sequences. Several complicated excitation sequences are used to illustrate this method.
A new stimulus display reveals that humans summate the motion energies of all components consistent with a single velocity, rather than optimizing sensitivity by ignoring noise.
OBJECTIVES: To evaluate the precision and accuracy of digital measurements in digital panoramic radiography. METHODS: A series of 70 digital panoramic radiographs were obtained of a dry skull in seven different positions with metallic pins and spheres fixed to the mandible. Three replicate measurements were performed with the mouse-driven cursor by one reader at 1:1 and 2:1 magnification. Precision was assessed with the reliability index (R) and Malony/Rastogi test and the effect of magnification on accuracy by paired Wilcoxon test. RESULTS: Vertical measurements were less reproducible than horizontal measurements. There were significant differences in assessments between images at 1:1 and 2:1 magnification (P < 0.05). The maximum variation in mean difference was 0.4% of actual object length for pins and 1.2% for spheres. The difference did not exceed 0.1 mm. R was lower for 2:1 magnification and consistently lower for spheres compared with pins. CONCLUSION: The most reliable measurements were obtained of linear objects in the horizontal plane. Digital measurements are sufficiently accurate for clinical use.