Subjective image quality scores and and quantitative attenuation measurements of LD and ULD and HYPR-LR post-processed BPCT data sets.

<p>Note: Subjective quality score are reported as mean values.</p

Example images of ultra low dose (ULD), HYPR-LR-post-processed ultra low dose (ULD+HYPR), low dose (LD) and HYPR-LR-post-processed low dose (HYPR+LD) brain perfusion CT of a 58-years old male patient with no pathology.

<p>The images are all reconstructed with the same slice thickness (5 mm) and presented with identical window settings.</p

Low dose (LD, a), HYPR-LR-post-processed low dose (LD+HYPR, b), ultra low dose (ULD, c) and HYPR-LR-post-processed ultra low dose (ULD+HYPR, d) brain perfusion CT of a 75-year old male patient with a lung cancer metastasis adjacent to the right thalamus and chronic left frontal infarction.

<p>Last image of the 60 s time series (1) and the normalized cerebral blood flow (CBF, 2), mean transit time (MTT, 3), time to peak (TTP, 4), cerebral blood volume (CBV, 5) maps. The utilized software does not use reduced matrix reconstructions or spatial smoothing, the images are left noisy. The pathology is recognizable in a, b and d with excellent subjective image quality and low noise in b. No diagnosis possible in c.</p

Mean attenuation values in a corresponding 60 s time series of the ultra low dose (ULD), the HYPR-LR-post-processed ultra low dose (ULD+HYPR), the low dose (LD) and the HYPR-LR-post-processed low dose (HYPR+LD) images.

<p>Mean attenuation values in a corresponding 60 s time series of the ultra low dose (ULD), the HYPR-LR-post-processed ultra low dose (ULD+HYPR), the low dose (LD) and the HYPR-LR-post-processed low dose (HYPR+LD) images.</p

Correlation of mean attenuation between original and post-processed data sets.

<p>Correlation of mean attenuation between original and post-processed data sets.</p

Ultra low dose (ULD), HYPR-LR-post-processed ultra low dose (ULD+HYPR), low dose (LD) and HYPR-LR-post-processed low dose (HYPR+LD) brain perfusion CT of a 35-years old patient with no pathology.

<p>This patient has slightly moved his head several times starting after 8 seconds of the data acquisition. As the HYPR-algorithm is using information of all time frames in the composite image for the calculation of the individual images, this resulted in an artifact visible in all HYPR-LR-post-processed images of this patient with a double contour of the skull and the brain on the right side and a frontal right hypodensity. The frontal right hypodensity was also visible in some non-post-processed images. The subjective image quality of the LD+HYPR image (rated 3) was still preferred to LD and ULD+HYPR (both rated 4). The ULD image was subjectively non-diagnostic (5). In the case of motion artifacts image registration might further improve image quality if used before the HYPR-LR algorithm is applied.</p

Initial and follow-up digital subtraction angiography of a 44-year-old female patient (Table 1, #21) 8 years after bleeding.

<p><i>A</i> Right ICA angiogram (lateral view) obtained in 2005 depicting a 2 x 2 mm aneurysm of the right distal ICA <i>(arrow)</i>, which was not initially detected. <i>B</i> Pre-operative angiogram of the right ICA (lateral view) in 2013; since 2005 the morphology and extension of the distal ICA aneurysm remained stable <i>(arrow)</i>. ICA = internal carotid artery.</p

Clinical details of patients with cryptogenic nonperimesencephalic subarachnoid hemorrhage.

<p>1 = male, 2 = female, tEVD = need of an temporary external ventricular drainage, lSD = long term shunt dependency, rVS = radiographic vasospasm, DCI = delayed cerebral ischemia, mRS = mean Rankin scale, mHS = mean hospital stay <i>(day)</i>, mICUS = mean intensive care unit stay (day), FU yrs = follow-up years, AA = aneurysm,° = follow-up data missing</p><p>Clinical details of patients with cryptogenic nonperimesencephalic subarachnoid hemorrhage.</p

MRI follow-up eight years after nonperimesencephalic subarachnoid hemorrhage of a 73-year-old male patient (Table 1, #17).

<p>Post-hemorrhagic sulcal siderosis is indicated by arrows. <i>A-D</i> show no residuals after bleeding. <i>E</i> shows sulcal siderosis on the parietal and occipital left hemisphere. <i>F</i> depicts no aneurysm in TOF-angiography. Sequences: <i>A</i> = T2 TIRM weighted, <i>B</i> = T1-TIRM weighted, <i>C</i> = diffusion-weighted, <i>D</i> = T2 weighted, <i>E</i> = T2* weighted, <i>F</i> = time-of-flight-angiography.</p

Initially undetected aneurysm found 8 years after SAH of a 44-year-old female patient (Table 1, #21).

<p><i>A</i> CT scan at admission in 2005 revealing nSAH in the frontal interhemispheric fissure, in the premedullary cisterns and the bilateral sylvian fissures. The consecutive digital subtraction angiography was false negative. <i>B</i> Intracranial TOF-angiogram of the same patient in July 2013 demonstrating an aneurysm of the right internal carotid artery <i>(arrow)</i> which was retrospectively visible in the initial post-hemorrhagic digital subtraction angiography (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117925#pone.0117925.g003" target="_blank">Fig. 3</a>).</p