In external or internal irradiation either diagnostic or therapeutic nuclear medicine, estimation of absorbed dose in each organ is very important. Most accurate way for this estimation is the use of Monte Carlo method in which many processes, physical systems and phenomena are simulated by statistical methods employing random numbers. Computerized anthropomorphic phantoms can either be defined by mathematical (analytical) functions or digital (voxel) volume arrays. Because these results could be used for some quantities\' determination for different patients, such as time of scan, power of source, dose of radionuclide and etc. we chosen analytical phantoms that more general than voxel phantoms and on the other hand the prediction bone cancer risk, required estimation of absorbed dose in \"bone surface\" that can\'t be calculated in voxel simulation. Then we simulated modified Cristy and Eckerman\'s heterogeneous, hermaphrodite and anthropomorphic phantoms designed in six age groups, by MCNP4C Monte Carlo code. In these phantoms we modified the thyroid and neck models. The results of calculations of Specific Absorbed Fractions (SAFs) from internal photon sources, in most cases are in agreement with Eckerman\'s results but because of adding the neck, in some organs such as thyroid and brain, differences appear. Also some disagreements occur in large intestine wall.

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