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Frequently Asked Questions from Researchers and Downloaders

1. What format are the images and packages?

1.1. What format is each package of images and documents?

All the files are grouped together in a single tar file, which is then bzip2 compressed.

1.2. My system does not understand bzip2 or tar files - where can I get a tool to decompress them?

Recent versions of compression tools such as Power Archiver for Windows and Stuffit Expander for Macs support bzip2'd and tar'd files.

Most modern Unix systems and Macs already have bzip2 and tar utilities installed. If not, command line utilities can be obtained from the bzip2 site. Windows executables are also available here.

1.3. Is the package available as a zip file instead?

No; bzip2 is generally more effective at compressing images and the smaller package reduces download time and cost of bandwidth.

1.4. What file format are the images?

Generally they are uncompressed DICOM files (in Explicit VR Little Endian Transfer Syntax).

1.5. What file format are the report documents?

If the scanned paper documents were submitted, regardless of their original format, they are uncompressed single-frame secondary capture DICOM files.

If electronic reports were provided, depending on the de-identification process, other formats may be preserved.

1.6. Is there a DICOMDIR?

Yes; a DICOMDIR is generated for each set of DICOM files. Note that any originally contributed DICOMDIR is discarded and replaced (rather than de-identified).

2. Can the images be viewed on line or accessed individually?

2.1. Can the images be viewed on line?

No. The purpose of the PCIR is to provide images for research, and typically this requires downloading rather than viewing.

2.2. Can the images be accessed or downloaded individually?

No. The purpose of the PCIR is to provide images for research, and typically this requires downloading entire sets.

2.3. Are the images available in alternative formats?

No. DICOM is universally used for clinical imaging, is generally sufficient for research purposes, and preserves the fidelity of the original supplied data. Tools are available to convert and view DICOM images as necessary once downloaded.

3. How can I download the files?

3.1. Can I download image sets manually from within my browser?

Yes. Each image set has a download link that when clicked on will cause your browser to download the bzip2'd tar file and prompt you to save it.

3.2. Can I download image sets in bulk?

Yes. You can use a command-line tool like wget to perform this task. If it is not already installed on your system, you can obtain wget from here.

3.3. Can I download just those image sets that are new or have been updated since I last downloaded them?

Yes. The wget tool can be use used for this.

For example, the following command executed on your local machine in a directory containing all the files that you may have downloaded from the PCIR in the past will download only the new or changed files:

wget -np -nd -r -N -l 2 -A .bz2 -H -D pcir.org,homepage.mac.com http://www.pcir.org/researchers/downloads_available.html

3.4. Can I download image sets with a "shopping cart" style interface?

No. Though other sites that provide access to collections of images have used a "shopping cart" paradigm that involves selecting sets using queries and then downloading them as a batch, our experience has been that such interfaces make it difficult to download and update very large selections or the entire collection. Since we expect that most researchers will download everything and want to regularly update their collection of what is new or changed, we believe that the basic http access mechanism and the use of wget and similar tools should suffice.