This study described the performance of an array of high-purity Germanium detectors, designed with two different end cap materials-steel and carbon fibre. The advantages and disadvantages of using this detector type in the estimation of the minimum detectable activity (MDA) for different energy peaks of isotope (152)Eu were illustrated. A Monte Carlo model was developed to study the detection efficiency for the detector array. A voxelised Lawrence Livermore torso phantom, equipped with lung, chest plates and overlay plates, was used to mimic a typical lung counting protocol with the array of detectors. The lung of the phantom simulated the volumetric source organ. A significantly low MDA was estimated for energy peaks at 40 keV and at a chest wall thickness of 6.64 cm.