Dear Benard, could you please add some more detail to your question? Which kind of image quality and above all for which purpose? What do you mean with "large" CT dataset? This could help whom would be willing to give some replies. Tnks.

Dear Bernard

Try to use this program (free software):

http://fiji.sc

I have been working for many years on the evaluation of a medical imaging software (known as MIMsoftware) developed by a company in Cleveland, Ohio. There are some articles of mine pertaining to this in this ResearchGate, which might be useful for your problem at hand. Their software (FDA cleared) can be used for analysis and manipulation of Ultrasound, X-ray, CR, DR, CT, MRI, SPECT and PET images. They are popular in many countries of the world.  They have a cloud for storage of images from clients at a nominal cost. Although it was developed for gigabyte storage, display and transmission of images using ultrabooks, iPads and smartphones, the software is similar to the ones employed in medical workstations. Incidentally all imaging workstations will be using one or other of their proprietary softwares. I have also given in my articles the details of the other softwares developed in Canada, Germany and Switzerland, which are also used extensively. There are also DICOM viewers available for free downloading to analyze the images from CT, MRI and PET modalities. Special phantoms such as the Catphan 700 phantom are also utilized to assess the quality of images (in one or two hospitals in West African countries) from multislice CT scanners. Please also see my lengthy review article on QA of CT scanners in this website..

I hope the above will be helpful. 

Sorry I wish I could help further, but in addition to the MIM soft wear, could you just send the images of the phantoms to ACR for them to evaluate and see if they meet their quality criteria?

There is a new company using phantoms and image analysis software that can help. They have some papers out on it. Their software is based (to the best of my knowledge) on the open source toolkit ITK. You could use ITK directly if you wanted to implement something yourself. See http://accumetra.com/ and http://itk.org.

Dear Amanda Cordero: The Catphan 700 phantom is a widely used/tested phantom since the past several years and can be used for a variety of image quality tests on CT scanners.These tests are discussed in great detail in their manual. There are also other phantoms which are equally popular: the AAPM CT image quality assessment phantom, Interventional triple-modality 3-D abdominal phantom, anthropomorphic chest phantom, CIRS Electron density phantom for treatment planning,etc. See also the UK imPACT website. As I am retired and working at home now, I am unfortunately only able to provide information. I am sure ACR must have evaluated some of these phantoms. Anyway, this work can be taken up by Mr Benard Botway. My articles describe the AAPM standard images, the SMPTE test pattern and the Wellhofer and breast phantom images using ultrabook, iPad and Smartphone. OSIRIX website provides a number of free DICOM test patient images. These details are currently in my ResearchGate website. I would like to add that I have tested these images from a physicist's perspective (I am not a radiologist). More information may be sought from MIMsoftware website (mimsoftware.com) or from them. Please note MIMsoftware cannot be used for mammography images on Apple devices and smartphones. otherwise, it is a fully FDA cleared software. I hope the above will be of help. THANKS.

I hope this information will be helpful. Thanks.

IQWorks is a useful software that allows automated image analysis. We use it in our department for a range of modalities including CT and MRI.

you can find it at the link below, free and simple to use:

http://wiki.iqworks.org/Main

Thank you all for the useful suggestions. I shall contact you again if necessary. However, if you have any further Idea please don't hesitate to help.

@ Alberto Signoroni, you wanted more detail. Particularly, we want to objectively assess image qualities of CT images (of patients) (say 500 images) acquired from different machines (say 100 each) in order to compared the qualities (objectively) for each body parts. The question is how can I  do that??