10 Shocking Human - Animal Relationships - YouTube

The main challenge in combining PET and MRI has been the development of compact MRI-compatible PET detector technology. Detectors for the 511 keV gamma rays emitted following positron decay are the key component of all PET scanners (Lewellen et al , Peng and Levin ). The vast majority of PET systems constructed to date have been based on some configuration of an inorganic scintillation crystal array optically coupled to a small number, typically four, of photomultiplier tubes (PMT). The PMTs detect the light that is emitted when a 511 keV gamma ray interacts with the scintillator and enable the position, energy and time of the interaction to be determined. Unfortunately, the performance of standard PMTs is severely degraded in even a weak magnetic field of several mT (Pichler et al ). The main challenge in developing a PET scanner that can operate within or in close proximity to an MRI scanner, where the field within the magnet bore is typically between 0.5 and 10 T, has therefore been either to develop a PET detector that can operate within such a high field, or to find other ways to circumvent this problem. Whilst many different solutions have been implemented for small animal imaging (with less need for good energy and timing resolution), the development of viable human PET-MRI systems capable of simultaneous PET and MRI acquisition has been associated with the emergence of robust and reliable MRI compatible solid state photodetectors such as avalanche photodiodes (APDs) (Renker ) and more recently silicon photomultipliers (SiPMs) (Britvitch et al , Roncali and Cherry ). These devices have many desirable properties that make them of great interest as alternatives to photomultiplier tubes in many applications (including non-MRI-compatible PET), but as they are essentially insensitive to large magnetic fields, they were required for developing integrated simultaneous PET-MRI with high performance. It is important to note that there are important differences between small animal and clinical imaging regarding the MRI field. Most human PET-MRI scanners have been developed around 3 T MRI magnets. However for small animal systems there is a wide variety of MRI systems depending on the type of studies required, from low field 0.3 T systems up to 11 T, with 7 T being one of the most used field strengths. The lower field systems are more oriented towards anatomical imaging while the stronger fields are used for more challenging imaging tasks.

Surrendered is a funny look at family and pets, satirizing our self ..

Currently available human PET systems for clinical and research imaging all follow a very similar overall configuration comprising an annulus of scintillation detectors (as shown in figure ) that surround the patient in order to detect pairs of 511 keV gammas in coincidence (Muehllehner and Karp ). The inner diameter of the scintillator ring is typically in the range of 85–90 cm, in the axial direction the detectors extend 15–25 cm and with a patient aperture of typically 70–80 cm diameter. The scintillation detectors that make up the ring are known as 'block detectors' each comprising a segmented block of inorganic scintillator coupled to an array of, usually four, photomultiplier tubes (PMTs). Processing of the signals from the PMTs allows the position, energy and time of a gamma ray interaction in scintillator to be determined. The scintillator material most commonly used is Lutetium Oxyorthosilicate (LSO or LYSO) which is chosen because of its high effective Z and density, coupled with very good light output and timing properties, resulting in high spatial resolution, sensitivity and temporal resolution. Detectors have a thickness in the range of 1.5–3 cm to have sufficient stopping power at 511 kev. The most recent systems now have detectors with good energy resolution (11–12 percent) for limiting the detection of scattered coincidences originating in the patient. There is also the trend towards excellent time resolution. This allows the accurate measurement of the time difference between the arrival of both photons. With this information the position of the annihilation can be localised along the line joining the two detection positions. The uncertainty in position is proportional to the uncertainty in measuring the difference in gamma arrival times. A typical 'time-of flight' resolution of 500 ps results in a positional uncertainty of 7.5 cm, and this additional information is used to improve the quality of the reconstructed image (Karp et al ). Depending on the length of the object a typical PET acquisition requires one or more (step and shoot acquisition) bed positions. The majority of studies are for oncological investigations and will acquire an image of the whole torso. The most recent scanners have high sensitivity enabling the acquisition of a whole body in under 20 min. For brain imaging one bed position will cover the whole object, which also enables dynamic imaging with time frames below one min.

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Broadcast on 24/05/2016
Tom Peters sacrificed his relationship to continue being a human puppy. He's joined by his ex-fiancée Rachael Watson to explain what his lifestyle entails.

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A Cat's Guide To Taking Care Of Your Human - YouTube

Feeding tubes are not right for every situation and case selection requires thoughtful consideration – keeping the patient’s best interest in mind – not the human’s. For cats that are suffering from a chronic, terminal illness such as renal failure or cancer, it is my feeling that a feeding tube is not necessarily appropriate to use in these cases. It is a matter of personal choice to prolong the inevitable in our pets and caregivers need to think long and hard before they put a feeding tube in a patient with a terminal illness when euthanasia may be a much more humane and loving decision to make.

You're Petting Your Cat All Wrong! - YouTube