ART are iterative procedures for solving systems of linear equations or inequalities that were first proposed by Kaczmarz and introduced to the biomedical field by Gordon et al.. Blobs are spherically symmetric volume elements that are superior to voxels for the Eleutheroside-E estimation 
of the shapes of biological objects and allow for the fact that biological elements usually lack perpendicular edges. Blobs also account for overlap creating smooth transitions, a property useful for reconstruction of Echinacoside influenza virions with the large number of surface spikes. In this work, it is shown that ART offers reasonable resolution and fidelity for the differentiation of the HA and NA surface spikes. In the work presented, the structure of Influenza B/Lee/40 is investigated by cryo-EM tomography and projection image analysis. B/Lee/40 was used as an influenza vaccine component in the 1940’s and is currently used as the high yield gene donor for preparation of reassortant vaccine candidates with improved growth characteristics in ovo. As a first step in the detailed morphological classification of type B/Lee/40 influenza virus, both projection images and tomogram slices reconstructed by ART with blobs of the viral particles were collected and analyzed. Together, they were utilized to characterize the pleomorphic forms of B/Lee/40; determine the relationships of the RNPs to viral shape and size; and differentiate the surface spike protein elements. Our overall goal in this paper is to identify the fundamental structural and morphological features of a type B virus. It is noted that two types of surface spikes which are resolved in the collected images correspond to the HA trimers and NA tetramers. Additionally the observations are significant in regard to the quantization of the HA content on the viral surfaces of both types A and B influenza viruses. For tilt series with fiducial markers, tomographic alignment and reconstruction was performed using IMOD software. Tilt series without fiducial markers were aligned and reconstruction using Protomo software. In this method, alignment of the original projection images is iterated until relative image shifts are less than 1 pixel and geometrical correction factors are within 1%. Both packages use R-weighted backprojection for tilt series alignment in the reconstruction. The best results were achieved using the fiducial markers, and these reconstructions were used to manually identify virion centers in 3D. The center coordinates were reprojected into the tilt series, and then used to excise smaller boxed tilt series for individual particles. After reconstruction, contrast was enhanced by applying a non-linear anisotropic diffusion filter implemented in the SPIDER image processing suite. In general, 60 cycles of this filter was found to yield good results. The boxed tilt series were also used as input for the ART reconstruction in XMIPP. Three dimensional visualizations were generated using Amira software. Since the larger, irregular-shaped virions have internal vacant areas, it suggests that breaking the contact between the inner matrix and the RNPs disrupts the overall RNP configuration. Harris et al. reports that in type A influenza the RNP segments are also in contact with the inner matrix at discrete points. It is conceivable that the expanded matrix of atypical-large virion disrupts an RNP attachment site, leading to increased RNP disorder. The type B tomograms do not show the 7 plus 1 configuration for RNP segments as reported for type A during budding. The large irregular particles show some clustering of the RNP in spite of the overall disorder, suggesting the RNP segments may have some attachment to each other.