List of top Medical Imaging Systems Questions on Physics asked in GATE BM

The half-life of \(^{113m}In\) nuclei is \(1.7\) hours, and the \(^{99m}Tc\) nuclei is \(6.0\) hours. If the initial activity levels of \(^{113m}In\) and \(^{99m}Tc\) in their respective samples are \(100\) Gigabecquerels (GBq) and \(20\) GBq, the time at which their activity levels become equal is hours. (Round off to one decimal place)
A radiographic system is using X-ray tube operating at 80 kVp. In order to filter the low energy X-rays, an aluminum (Al) filter of 2.5 mm thickness is used. The Al filter is replaced with a copper (Cu) filter to have the same energy filtered. The mass attenuation coefficients of Al and Cu at 80 kVp are 0.02015 m²/kg and 0.07519 m²/kg, respectively. The densities of Al and Cu are 2699 kg/m³ and 8960 kg/m³, respectively. The thickness of the new Cu filter is \(\underline{\hspace{2cm}}\) mm. (rounded off to two decimal places)
In a radioactive isotope, \(N\) nuclei are needed to produce radioactivity level of 2 mCi. Assuming decay constant of \(3.22 \times 10^{-5}\) s\(^{-1}\) and atomic weight of 98 g/mol and Avogadro's number \(6.02 \times 10^{23}\) mol\(^{-1}\), the mass of \(N\) radionuclide is \(\underline{\hspace{2cm}}\) picograms.
The radioactivity of a radionuclide with decay constant \(3.22 \times 10^{-5}\) s\(^{-1}\) is 6 mCi at 10:30 AM. The radioactivity at 4:30 PM the same day will be \(\underline{\hspace{2cm}}\) mCi. (rounded off to two decimal places)