1naresh2naresh<pre>Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [33b1939a-d860-4dde-84fe-00f943fdbcd8] => Array
        (
            [runtime-id] => 33b1939a-d860-4dde-84fe-00f943fdbcd8
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [d5a77471-df0f-4e7f-91bb-fd644fc5dbbe] => Array
                        (
                            [runtime-id] => d5a77471-df0f-4e7f-91bb-fd644fc5dbbe
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;2609800349c353abe53ca0d00e7caa46c15225b3
                )

        )

)
1naresh2naresh<pre>Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [0944b174-6ec4-42a2-8200-1b478b529509] => Array
        (
            [runtime-id] => 0944b174-6ec4-42a2-8200-1b478b529509
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [e2dad58f-974e-4ab3-b92e-77f8372c4343] => Array
                        (
                            [runtime-id] => e2dad58f-974e-4ab3-b92e-77f8372c4343
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;2609800349c353abe53ca0d00e7caa46c15225b3
                )

        )

)
PT  - JOURNAL ARTICLE
AU  - Mullins, Mark E.
AU  - Lev, Michael H.
AU  - Bove, Peter
AU  - O’Reilly, Cara E.
AU  - Saini, Sanjay
AU  - Rhea, James T.
AU  - Thrall, James H.
AU  - Hunter, George J.
AU  - Hamberg, Leena M.
AU  - Gonzalez, R. Gilberto
TI  - Comparison of Image Quality Between Conventional and Low-Dose Nonenhanced Head CT
DP  - 2004 Apr 01
TA  - American Journal of Neuroradiology
PG  - 533--538
VI  - 25
IP  - 4
4099  - http://www.ajnr.org/content/25/4/533.short
4100  - http://www.ajnr.org/content/25/4/533.full
SO  - Am. J. Neuroradiol.2004 Apr 01; 25
AB  - BACKGROUND AND PURPOSE: Increasing use of CT for evaluating neurologic disease may expose patients to considerable levels of ionizing radiation. We compared the image quality of low-mAs head CT scans with that of conventional nonenhanced scans.METHODS: Conventional head CT scans were obtained in 20 patients (all &amp;gt;65 years with history of non-CNS malignancy) by using a multidetector technique: 170 mA and 1-second scanning time (ie, 170 mAs), 140 kVp, table speed of 7.5 mm per rotation, pitch of 0.75, section thickness of 5 mm, and field of view of 25 mm. A limited volume helical data acquisition covering four 5-mm-thick images was obtained by using 90 mAs but otherwise the same parameters. Three neuroradiologists visually rated the resulting images for quality in a blinded comparison. Representative 1- to 4-mm2 regions of interest were chosen in gray matter and white matter locations. Conspicuity and the contrast-to-noise ratio were analyzed. Statistical comparisons were done by using the Student t test.RESULTS: Mean gray matter conspicuity was not significantly different between the 170- and 90-mAs groups (0.39 ± 0.19 vs 0.41 ± 0.03, P = .32). Mean gray matter contrast-to-noise ratio was approximately 22% higher with 170 mAs than with 90 mAs (1.77 ± 0.52 vs 1.39 ± 0.38, P = .005). All 90-mAs images were rated as having slightly greater image noise than the 170-mAs scans but with sufficient perceived resolution.CONCLUSION: Although 90-mAs head CT images were moderately noisier than 170-mAs images, they were rated as having acceptable diagnostic quality.