In medical imaging is a recent development, the combination of PET and MRI. Nearby MRI anatomical images gives a good contrast in soft tissues, flot PET functional images. PET imaging is based on the principle of radioactive decay by the emission of two photons. If one or both photons are stopped by the patient or their environment before they reach the detector, is called attenuation. Currently, PET combined with CT anatomical images as you want in a PET study. The additional advantage is that it is possible to correct, on the basis of the CT image for the amount of photons that are retained. If this correction is not applied, it would indeed seem that there is much less radioactivity in the central part of the patient was present. PET / MRI is not using more of CT, so that the radiation dose to the patient is much lower. However, converting an MRI image to a measure of attenuation is very difficult and requires special techniques that depend on the quality of the MRI image. There may indeed different effects that distort the image (artifacts). Therefore, there is an alternative way to calculate attenuation which is not based on CT or MRI. These methods use the photons which come out of the patient (emission) may or may not be supplemented by photons from an external source (transmittance). The emission and transmission methods are part better than an MRI-based approach, because one of the attenuation measured in a direct way. Alternatively, the image quality is lower and it takes longer to convert the measured data into an image. One must therefore conclude that neither the MRI-based techniques, neither the emission or transmission methods provide the perfect solution. The purpose of this research is to combine the existing methods for measuring attenuation in PET / MRI, a new approach that works in every clinical situation. For this left a transmission method that is extended by MRI information. A new transmission source will be designed and existing software for PET imaging will be expanded and optimized. In medical imaging is a recent development, the combination of PET and MRI. Nearby MRI anatomical images gives a good contrast in soft tissues, flot PET functional images. PET imaging is based on the principle of radioactive decay by the emission of two photons. If one or both photons are stopped by the patient or their environment before they reach the detector, is called attenuation. Currently, PET combined with CT anatomical images as you want in a PET study. The additional advantage is that it is possible to correct, on the basis of the CT image for the amount of photons that are retained. If this correction is not applied, it would indeed seem that there is much less radioactivity in the central part of the patient was present. PET / MRI is not using more of CT, so that the radiation dose to the patient is much lower. However, converting an MRI image to a measure of attenuation is very difficult and requires special techniques that depend on the quality of the MRI image. There may indeed different effects that distort the image (artifacts). Therefore, there is an alternative way to calculate attenuation which is not based on CT or MRI. These methods use the photons which come out of the patient (emission) may or may not be supplemented by photons from an external source (transmittance). The emission and transmission methods are part better than an MRI-based approach, because one of the attenuation measured in a direct way. Alternatively, the image quality is lower and it takes longer to convert the measured data into an image. One must therefore conclude that neither the MRI-based techniques, neither the emission or transmission methods provide the perfect solution. The purpose of this research is to combine the existing methods for measuring attenuation in PET / MRI, a new approach that works in every clinical situation. For this left a transmission method that is extended by MRI information. A new transmission source will be designed and existing software for PET imaging will be expanded and optimized.