CT Neuro Perfusion in Ischemic Stroke Management

-H Whitepaper CT Neuro Perfusion in ischemic stroke 14 . management Whole brain dynamic imaging with automated perfusion analysis Prachi Pandit, Brandon Ratliff, Dena Cunningham, Markus Juergens, Andrew Primak siemens-healthineers.us SIEMENS Healthineers Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Table of Contents Introduction 03 Infarct core (non-viable tissue) and penumbra (tissue at risk) 04 CT Perfusion 04 Acquisition 06 Postprocessing 08 Conclusion 12 Appendix 13 References 17 2 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis The goal of stroke therapy is Studies have suggested that Y to protect the tissue before advanced neuroimaging-based development of irreversible selection for thrombectomy injury, and time is of essence. nearly doubles the probability of good functional outcomes. Introduction Imaging is essential to the management of stroke. Non-contrast head CT imaging is excellent in Stroke is a common disease. It affects one in four people discriminating the presence of intracranial hemorrhage over their lifetime, and there are estimated to be 13.7 which typically precludes patients from thrombolytic million incidences of strokes globally each year. This is treatment. If no signs of hemorrhage are detected, if expected to increase with an ageing population. Stroke is indicated, additional dynamic imaging including CT the second leading cause of death, and third leading angiography (CTA) and CT perfusion (CTP) studies are cause of disability in adults globally1. Strokes are broadly performed. CTA is helpful for evaluation of large vessel categorized as either ischemic strokes or hemorrhagic intracranial stenoses and occlusions, while CTP helps strokes. Ischemic stroke, the most common kind of characterize the functional properties of brain tissue. stroke, occurs due to insufficient brain perfusion. Based on the results of the DAWN2 and DIFFUSE33 trials Perfusion is the process by which oxygen and nutrition in early 2018, AHA/ASA updated the Acute Ischemic are delivered to the biological tissues and carbon dioxide Stroke Management and Treatment Guidelines4. Figure 1 and cellular waste are carried away from the biological shows the timeline for treatment and imaging as tissue, via the vascular system. More specifically the term recommended in the 2018 AHA guidelines. The window perfusion refers to blood flow, which conventionally for potential endovascular thrombectomy (EVT) represents how many milliliters of blood enter 100 g of treatment was extended beyond 6 hours and up to 24 tissue in 1 minute [ml/100 g/min]. An ischemic stroke hours from symptom onset. Studies have suggested that occurs when blood flow, and hence the oxygen delivery advanced neuroimaging-based selection for endovascular to the brain is hindered, thereby causing damage to the thrombectomy nearly doubles the probability of good cerebral tissue. The goal of stroke therapy is to protect functional outcomes5-6, as the selection is based on the tissue before development of irreversible injury, and stroke physiology as opposed to an approximate time time is of essence. window. The AHA 2018 guidelines recommend CTP or MR perfusion (MRP) for selection of eligible patients for this extended treatment by mechanical thrombectomy. CTP is readily accessible and typically requires less time to acquire compared to MRP. Early Window Extended Window 0 – 4.5 hours 0 – 6 hours 6 – 24 hours Treatment Treatment Treatment IV thrombolysis Thrombectomy Thrombectomy with beneficial evidence Imaging Imaging Imaging Non-contrast CT Head CT or MR Angiography CT or MR Perfusion Figure 1: Treatment and imaging guidance as per the 2018 AHA guidelines for stroke management. This is a representation, please see [4] for the detailed discussion. 3 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Q CTP can be used to identify the presence and extent of the infarct core and the penumbra to make informed decisions on revascularization treatment. Infarct core (non-viable tissue) CT Perfusion and penumbra (tissue at risk) In CTP imaging, a short and fast bolus of contrast media The infarct core defines the non-viable tissue in an acute is injected intravenously, and images are continuously ischemic stroke, the portion that is irreversibly damaged acquired before, during, and slightly after the first and cannot be salvaged by reperfusion. The penumbra is passage of contrast media through the brain. Attenuation the surrounding tissue that is at risk due to being changes over time are considered proportional to the hypoperfused but can potentially be salvaged with timely contrast media and hence the perfusion. By fitting the reperfusion treatment. CTP can be used to identify the measured data to physical models, different perfusion presence and extent of the infarct core and the parameters are derived, and brain perfusion maps are penumbra to make informed decisions on produced during CTP analysis. Figure 2 shows schematics revascularization treatment. Presence of a substantial of the time attenuation curve with different perfusion penumbra is a good indicator for extending the parameters for the Maximum Slope (MS) (Figure 2a) and intravascular therapeutic window7, and CTP can be used Deconvolution (DC) (Figure 2b) models. Figure 3 shows to predict the benefit of such therapeutic treatments8. representative brain perfusion maps produced by CTP analysis using the DC model. Table 1 describes the Studies have shown good agreement of CTP findings various CTP parameters and how they change in the with the gold standard techniques like Diffusion- presence of an ischemic stroke. weighted imaging (DWI) and MRP9,10. a b CBV (maximum enhancement) CBV CBF Tmax (CBF x MTT) (TTS + MTT/2) HU HU of curve) MTT CBF (maximum gradient TTP TTD* (TTD - TTS) TTS TTS* CBF x E Contrast bolus Time (sec) Time (sec) arrival Figure 2: Time attenuation curve schematic showing different CT Perfusion parameters18. (a) Maximum Slope model (b) Deconvolution model. *DC parameters are defined relative to the arterial input function (AIF), and do not depend on the baseline (unlike the MS model). E is a constant, assuming there is no backflow from the extravascular region to the capillaries. 4 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Table 1: CTP Parameters Parameter Name Definition Cerebral Blood Flow (CBF) The amount of blood flowing through a given volume of brain in a specific amount of time (mL/100 mL/min). CBF identifies areas of hypoperfusion, including the infarct core and the penumbra. The infarct core has markedly decreased CBF compared to the penumbra. Relative CBF (rCBF) The ratio of the CBF in the affected hemisphere to that in the contralateral hemisphere. Cerebral Blood Volume The volume of the blood flowing through a given volume of brain (mL/100 mL). (CBV) The ischemic penumbra has a normal or increased CBV due to autoregulation. Relative CBV (rCBV) The ratio of the CBF in the affected hemisphere to that in the contralateral hemisphere. Mean Transit Time (MTT) The average amount of time it takes for blood to flow through a given volume of brain (sec). MTT increases as a vasodilatory response to reduced flow. Time To Peak (TTP) The time required to reach peak enhancement (sec). Increased TTP indicates delayed flow due to stenosis or occlusion. Time To Start (TTS) The time required for the contrast bolus to enter the given volume of brain (sec). Time To Drain (TTD) The time required for the contrast bolus to exit the given volume of brain (sec). This is a Siemens specific parameter. Tmax The time required to reach peak after deconvolution (sec). Increased Tmax indicates delay in arrival of the contrast bolus. Temporal Maximum The maximum value image in every projected plane from the time-phase direction on Intensity Projection (tMIP) all timepoints from a CTP acquisition. tMIP improves the detection of ischemic area as compared to non-contrast CT and helps assess the vessels, i.e., the collateral status. Mismatch Volume The difference in volume between the total hypoperfused region and the infarct core. This equals the ischemic penumbra, the volume of salvageable tissue. Mismatch Ratio The ratio of the volumes of the total hypoperfused region and the infarct core. A CURRENT CURRENT CURRENT 1,8 100.00 2,8 3,8 201 IMA n.a SP H176.0 202 IMA n.a. 203 IMA n. a SP H176.0 SP H176.0 R R R 1 cm E 1 cm E F F F SL min SL min SL min 80 0.00 EXSTOO 0.1 W 100 MPR 39 MPR C oral Blood Flow (d) 49 C WOK Temporal MIP MPR MIP / HU CBFD / (mL/100mL/min) Cerebral Blood Volume (d) CBVD / (mL/100mL) CURRENT CURRENT CURRENT 4.8 5.8 6,8 206 IMA n.a. 12.00 205 IMA n. a. 15.00 SP H176.0 204 IMA n.a. 10.00 SP H176.0 SP H176.0 Cop R R R 1cm 1 cm 1 cm FA F F SL min SL min SL min EXTOO 0.1 EXTUO 0.1 EXTOO 0.1 W 12 W 15 W 10 MPR C 6 C 7 C 5 TMax (d) MPR MPR TMAXD / s "ime to Drain (d) TTDD / s Mean Transit Time (d) MTTD / s Figure 3: VPCT Neuro multi-parameter analysis with DC model showing axial views of Temporal Maximum Intensity Projection (tMIP), Cerebral Blood Flow (CBF), Cerebral Blood Volume (CBV), Tmax, Time To Drain (TTD) and Mean Transit Time (MTT). Figure shows a case with left MCA occlusion, the left hemisphere has decreased cerebral blood flow as seen in the CBF map (top center). The increased cerebral blood flow is also reflected in the increased Tmax (bottom left) as well as the TTD (bottom center) and MTT (bottom right). The CBV values (top right) on the other hand are not lowered to the same extent as the CBF values indicating a potential tissue at risk area. 5 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis In the Adaptive 4D Spiral (A4DS) and Flex 4D Spiral (F4DS) modes the table continuously performs a smooth (but relatively fast) dynamic scan with periodic motion between two end positions. A number of different post-processing methods for CTP Time is Brain analysis have been studied and based on a combination In this paper we summarize the Siemens Healthineers’ of different CTP parameters and thresholds, multiple approach for CTP acquisition and analysis to enable definitions for the best predictors of infarct core and reliable and quick image interpretation and assist with penumbra have been proposed. Review of these methods accurate and timely responses to ischemic stroke. and definitions can be found in literature (eg., see12) and is beyond the scope of this paper. Some of these studies are based on thresholds for a single parameter, like Acquisition absolute CBF. While others are based on the concept of cerebral vascular autoregulation, where autoregulation All major vendors have developed different approaches is preserved in the penumbra, but lost in the core. These to extend the CTP scan coverage range to 8 cm and studies use a combination of parameters, like CBF and beyond to allow evaluation of the entire brain volume. CBV, or CBV and MTT, to name a few. The Siemens Healthineers’ approach to extend perfusion coverage is based on a periodic spiral technique with Differences in CTP hardware and software, along with variable pitch. In the Adaptive 4D Spiral (A4DS) and Flex non-standardized triaging protocols for individual 4D Spiral (F4DS) modes the table continuously performs institutes is a confounding factor with quantitative CTP. a smooth (but relatively fast) dynamic scan with periodic A consensus regarding the CTP parameter (or combination motion between two end positions (Figure 4). This of parameters) that most accurately predicts the core and technique allows sufficient temporal sampling to analyze penumbra has not been reached. Significant discrepancies subtle changes of regional cerebral mean transit time (MTT). Brain volume perfusion CT (VPCT) with the A4DS have been shown in volumes of infarct core and hypoperfusion when generated using software from mode is available on all scanners in the SOMATOM different vendors13. Nevertheless, feasibility of achieving Definition family and the SOMATOM Edge Plus, Drive and high concordance between different post-processing Force. For sampling rates from 1 to 1.5 s, VPCT offers software packages, both in terms of core and penumbra flexible scan range coverages. The default recommended volume as well as therapeutic decision making, has scan range coverage, to optimally cover the brain, using the A4DS mode is 11.4 cm on SOMATOM Force; and 10 been shown14. cm on SOMATOM Definition Edge, SOMATOM Edge Plus, Detector width and SOMATOM Drive. The scan range coverage for the F4DS mode is 10 cm on SOMATOM X.cite; and 8.5 cm on SOMATOM go.All and go.Top. Figure 4: The A4DS mode allows dynamic time-resolved scanning of areas larger than the detector width by continuous periodic table Scan range movement between two end positions. The temporal sampling of ----------- the scan range is equidistant in the central region (empty circles) Continuous periodic table movement and non-equidistant in the peripheral regions (filled circles). 6 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis A different approach to extend the CTP scan range is the Since wider coverage is associated with a higher “toggling table” technique, where the table moves back radiation dose and can result in direct irradiation of the and forth between two adjacent positions doubling the eye lenses, the optimal coverage should be selected coverage (e.g., from 4 to 8 cm or from 8 to 16 cm). At based on clinical needs of an individual patient, with the each position a conventional axial CTP acquisition is maximum coverage being applied only when justified16. performed allowing temporal sampling rates of 3-4 s. This approach helps avoid unnecessary radiation and, The jolts from the table motion affect patient comfort. hence, better complies with the ALARA (As Low As If these critically ill patients are unable to remain Reasonably Achievable) principle. A VPCT scan range of perfectly still, the image quality is also adversely ~10 cm is usually considered adequate for stroke imaging affected. An added drawback with this technique is the as it allows an acceptable prediction of tissue outcomes17 inability to perform 3D motion correction. Another and covers the whole supratentorial brain while avoiding approach to increase the CTP scan range is to use extra direct irradiation of the eye lenses. wide detectors. However, systems with very wide detectors (16 cm) suffer from considerably more scatter Neuro VPCT protocols on Siemens scanners are set to be radiation which reduces low contrast detectability and performed either at 70 or 80 kVp, as these settings have makes them less dose efficient (about 20% noise the lowest radiation dose for a specific iodine contrast to increase15). In order to compensate for the higher dose noise ratio (CNR). Since iodine CNR is the most relevant required by the extra wide detectors their advocates have parameter for a perfusion scan, the kVp should not be suggested a variety of heterogeneous sampling schemes raised to higher values. This might lead to unacceptable that reduce the sampling rate down to 5s in later phases high dose values. of the acquisition. Unfortunately, these protocols might not work for every patient in clinical settings. In case of Using the default protocol settings, a typical VPCT scan of a substantial contrast delay (e.g., patient with weak the whole supratentorial brain with a 11.4 cm coverage cardiac output or extracranial bypass) relevant phases on the Force scanner (70 kVp, 200 mAs, 45 s) results in a of the regional time attenuation curves might be CTDIvol of 147.7 mGy. This is well below any potential sampled insufficiently, compromising the accuracy of skin reaction, and the stochastic radiation risk corresponds the calculation. to about 2 years of natural background radiation. The Siemens Healthineers’ approach with A4DS and F4DS avoids both the abrupt motion associated with the “toggling table” technique and dose inefficiency of extra wide detectors while still achieving wider coverage. Injection flow rate of 5–6 ml/s or higher. Pre-heat the contrast medium to decrease viscosity and enable high flow rates. 18 g needle (green), or larger, into right antecubital vein. Recommendation for Injection duration lower than 8 seconds. injection protocol: A contrast medium volume not too small, to ensure detectable enhancement changes. Saline flush at the same flow rate. Short delay between injection and scan (~ 4 seconds), unless using test bolus to determine delay. 7 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Postprocessing Being confident that motion can be properly accounted for, Siemens Healthineers syngo.CT Neuro Perfusion uses For the most accurate analysis of VPCT data acquired in a DC model18 as default. Within syngo.via, all relevant the A4DS and F4DS modes, Siemens Healthineers perfusion parameters can be displayed in one view recommends using the syngo.CT Neuro Perfusion software (Figure 3). The MS model is also included in the software that has several important features. Volume coverage package. This model is less sensitive to a delayed bolus or provided by these spiral acquisition modes helps achieve a shortened scan time. For both models, the perfusion better motion correction in 3D which can be insufficient parameters to be displayed can be selected according to with the conventional 2D approach. Since it is quite user preference in syngo.CT Neuro Perfusion (Figure 5). common for stroke patients to move during the acquisition, proper motion correction is crucial for The sensitivity of CTP algorithms to delayed contrast accurate perfusion analysis. This is especially true for DC arrival is also very important for perfusion analysis. models which are very sensitive to the accurate shape of A vendor cross comparison study conducted by Kudo et the arterial input function (AIF). Reconstructions at 5mm al.19 showed that perfusion maps derived from delay- thickness and 3mm increment or at 1.5mm thickness and sensitive algorithms overestimate the final infarct size. 1mm increment are recommended. Thicker slices and This study also showed the delay insensitivity of the larger increments may limit the effectiveness of the 3D MS model, which has been commercially available on motion correction, i.e., it might be impossible to correct Siemens products since 1998. This fact was also patient motion properly with too thick slices. The 50% favorably reviewed in a corresponding editorial by overlap of the reconstructed images is deliberate to Konstas and Lev20. The DC model used by syngo.CT Neuro improve detection of small objects, e.g., the collaterals. Perfusion is delay-insensitive by its design because it includes the local bolus arrival time as one of the fitting parameters. A study by Abels et al.18 demonstrated that, when the same source data and preprocessing steps were used, both models yielded comparable qualitative CT Neuro Perfusion Configuration ? X and quantitative results which would have led to the same therapy decision. Template: Stroke Create New Delete The availability of two models for perfusion analysis Common Calculation Visualization Results Penumbra adds more flexibility to syngo.CT Neuro Perfusion and Archive Format . CT Grayscale Enhanced CT Color RGB results in a robust performance for patients, even in Standard Volumes Window Value Archive suboptimal conditions. Temporal MIP 80 Temporal Average 80 Baseline 80 Deconvolution Window Value Archiv Cerebral Blood Flow 100 Cerebral Blood Volume DI Mean Transit Time 10 Time to Drain 15 Time to Start 10 TMax 12 Flow Extraction Product 20 Maximum Slope Window Value Archive Cerebral Blood Flow 100 Cerebral Blood Volume 6 Time to Peak 20 Time to Start 10 of max. 9 volumes activated OK Cancel Figure 5: CT Perfusion parameter selection on syngo.CT Neuro Perfusion 8 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Another important feature of syngo.CT Neuro Perfusion The periodic table movement during the dynamic scan is the Siemens Healthineers’ exclusive 4D noise reduction acquisition results in an equidistant temporal sampling algorithm which utilizes a spatiotemporal multi-band in the central slice of the VPCT scan range and filtering approach. In this approach, images from every non-equidistant temporal sampling in the peripheral time frame in the dynamic series are decomposed into slices (Figure 4). Since conventional brain perfusion uses multiple (spatial) frequency bands. The lowest frequency equidistant sampling (between 1 – 4 s), it has been band predominately includes information about the questioned if the dynamic spiral acquisition approach smooth image content (i.e., image contrast), while the can allow an accurate calculation of the quantitative higher frequency bands predominantly contain perfusion parameters. However, the non-uniformity of information about the edge details and noise. After the A4DS and F4DS modes with the dynamic spiral averaging different bands with different weighting acquisition sampling scheme is explicitly taken into functions in the temporal domain (i.e., a very narrow account in the dedicated algorithms used by the syngo. function for the lowest frequency and broader functions CT Neuro Perfusion software. The accurate shape of the for the higher frequencies), all bands are recombined to arterial input function (AIF) can be obtained from the produce the final image. This final image contains the central slice which has the equidistant sampling of 1.5 s, unchanged information about iodine enhancement (i.e., even in case of a substantial contrast delay. The the time attenuation curves are not modified) but has perfusion parameters can be reliably estimated for the reduced noise since the temporal averaging of the higher time-attenuation curves of brain tissue with the shape- (spatial) frequency bands is equivalent to collecting more based DC model and the AIF, even with the x-ray photons. The 4D noise reduction can be used either non-equidistant temporal sampling in the peripheral to improve the quality of the perfusion maps (i.e., fewer slices. The accuracy of the dynamic spiral volume areas where the model fails due to insufficient signal-to- perfusion technique has been validated in the study by noise ratio as shown in Figure 6) or reduce the radiation Haberland et al.21. The results of this work have shown dose while maintaining the same image quality. Keeping that the performance of this technique is equivalent to dose at a low level is a major concern for brain perfusion the performance of standard dynamic modes with since a dynamic acquisition at multiple time points can equidistant sampling. result in radiation dose levels higher than routine diagnostic CT exams. Perfusion 25cc@5cc/sec 1 AH Hospital Perfusion 25cc@25cc/sec 1 AM Hospital 001 '03.Jan-47. M. 57Y syngo 001 VE20A SL08P62 403-Jon-47, M, 57Y Syngo VE20A SL08P62 16-Ju-04 H-SP-CR 16-Jul-04 H-SP-CR 18:06 20.36 18.06:29.36 SP 209.2 PAR 17 80 SP 209.2 KV 80 KV 80 MAS 75 MAS 75 TIOS TI 0.5 GT -17.5 GT -17,5 SL 12.0 SL 12.0 203 MP Perfusion CT 203 HJJOT H301 Flow Perfusion CT < N > Perfusion 25cc@5cc/sec 1 AH Hospital Perfusion 25cc@@5cc/sec 1 AH Hospital 001 001 '03.Jan-47. M. 57Y syngo VE20A SL08P62 *03.Jan-47. M. 57Y Syngo OA SL08PS2 16-Jul-04 H-SP-CR 16-Ju-04 H-SP-CR 18:06:29.36 18:06:29:36 MP 17 PAR 17 SP 209.2 SP 209. Figure 6: An example of how the 4D noise reduction algorithm improves the quality of the MIP (left column) and CBF (right column) images. The CBF image with the 4D noise reduction (bottom row) has fewer areas where KV 80 the model fails due to insufficient signal-to-noise ratio, MAS 75 110.5 MAS 75 TI05 GT -17.5 GT -17.5 SL. 12.0 compared to the image without 4D noise reduction SL 12.0 MIP Perfusion CT 203 H301 Flow Perfusion CT (top row). 9 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Perfusion analysis by syngo.CT Neuro thresholds for the core and penumbra must be defined Perfusion (VB20 or higher) can be by the user according to their respective institution performed in a fully automated fashion guidelines. Studies have shown that there is a large using the Auto Stroke feature. overlap of perfusion values in the infarcted and surviving areas. The optimal threshold maximally predicts the final infarct with the least amount of over or under With whole-brain coverage, the full extent of the disease estimation. Some suggestions for model dependent can be evaluated and perfusion parameters can be thresholds can be found in Abels et al.18 If desired, visualized in 3D with axial, coronal and sagittal views. the core and penumbra thresholds can be configured Moreover, using the appropriate configurable threshold to match the settings employed in the DAWN and values for different perfusion parameters (e.g., CBV and DEFUSE 3 trials2,3. CBF), both the infarct core and penumbra regions can be identified and color coded to facilitate the analysis of the core/penumbra mismatch (Figure 7). Compared to the Auto Stroke, in combination with Siemens qualitative assessment frequently used, this approach is Healthineers’ Rapid Results technology can auto- more objective for the determination of core/penumbra archive the automatically generated results (e.g., mismatch. It should be noted, however, that the actual perfusion maps, core and penumbra volumes, etc.) to PACS without user interaction. H H TTTTTTTTTTTTTTTTTTTTTTTTTT Force_Perf_VPCT_Stroke4 Force Perf VPCT Stroke4 Force Perf VPCT Stroke4 ANON 16 ANON 1,6 ANON 3/15/2018 3/15/2018 3/15/2018 SP L28.7 SP H172.0 SP A234.9 R R 5cm 5cm 5cm LLLLLLL F A. 80 80 80 Manip MPR 39 Temporal MIP Manip MPR 39 Temporal MIP Manip MPR nz Temporal MIP MIP / HU MIP / HU MIP / HU Force Perf VPCT Force_Perf_VPCT_Stroke TAC TAR/NVT ANON 2,7 ANON 3,7 3/15/2018 00.00 3/15/2018 6.00 HU SP H175.0 SP H175:0 .TAR R 5cm 5cm IF 10 15 20 0.00 25 0.00 30 100 6. 0 sec C M Relative Manip MPR Cerebral Blood Flow (d) 49 Manip MPR 2. 9 Cerebral Blood Volume (d) CBFD / (mL/100mL/min) CBVD / (mL/100mL) A A Curves Statistics TAR/NV Force Perf VPCT_Stroke4 Force Perf VPCT_Stroke4 ANON ANON 5,7 3/15/2018 3/15/2018 5.00 ' SP H175.0 Region Legend Show SP H175.0 TAC Summa Total Penumbra 6.6cm R R TAR M Infarct 3.88cm3 NVT PRR 62.98 % K 5cm 5cm Rest Calculated on basis of Temporal MIP volume F 0.00 15.0 Manip MPR . SurmartyMean Value Standard Dev. Manip MPR Volume / cm3 TMAXD >6s Time to Drain (d) relativeCBFD <30% MAXD / s TTDD / s Figure 7: With the user defined perfusion parameters and threshold values, a 3D evaluation of brain tissue for the mismatch between the infarct core (red) and the penumbra (yellow) can be performed demonstrating the full extent of ischemic damage. Figure shows the results for the case presented in Figure 3. 10 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Perfusion analysis with syngo.CT Neuro Perfusion (VB20 SIEMENS or higher) can be performed in a fully automated fashion Healthineers using the Auto Stroke feature. Auto stroke performs the Motion Correction, Segmentation, and Vessel Definition steps automatically with no user interactions. The results CT Neuro Perfusion Q + can then be reviewed by scrolling through the data before confirming the analysis (Figure 8). Auto Stroke, in CT Neuro Perfusion combination with Siemens Healthineers’ Rapid Results technology can auto-archive the automatically generated Stroke Reset results (e.g., perfusion maps, core and penumbra volumes, etc.) to PACS without user interaction. 8.68s Customized parameter settings and penumbra analysis parameters must be predefined based on the user 1: Motion Correction preferences within syngo.CT Neuro Perfusion software 2: Segmentation configuration. Auto Stroke and Rapid Results have made 3: Vessel Definition post-processing neuro perfusion data a seamless and user-friendly workflow 24 hours a day. It is important to : Results Preview note though, in cases with suboptimal or poor-quality Check result images. Click Confirm to save and start the evaluation. Unsaved perfusion data acquisition (e.g., severe patient motion, results will be deleted. Confirm inadequate contrast enhancement, etc.), fully automated processing may fail and produce inaccurate perfusion 5: Results maps. Therefore, Auto Stroke results should be checked Perfusion Evaluation for quality assurance and the data re-processed if necessary, using the manual workflow option. (Please refer to syngo.CT Neuro Perfusion manual). Figure 8: Auto Stroke performs the Motion Correction, Segmentation, and Vessel Definition steps automatically with no user interactions. Before confirming, the results can be reviewed by scrolling through the dataset. Patient Motion Check the shape of the AIF. Patient motion can be inferred from jumps in the AIF or the reference vessel venous output function (VOF). Patient motion is also indicated Helpful checks to by unusually thick bones in the tMIP as well as blurry vessels. Violet areas close to the ensure the accuracy skull in the vessel masks are also indicative of patient motion. of perfusion analysis in the presence of Insufficient cardiac output suboptimal Check the position of the AIF. Insufficient cardiac output is reflected in a delayed AIF peak. acquisition: Delayed contrast bolus Check the AIF and specifically the extent of the downslope of the curve that has been obtained. If the downslope is not captured, the MS model would be a better alternative to the default DC model Choose a different registration base image or delete a time point if it does not align Measures to salvage with the other volumes. Note that volumes close to the bolus peak are critical, and if these are deleted, results might be unreliable (due to an incorrect approximation of a CTP scan in case of the AIF shape). failed automatic evaluation: Place the VOF manually if the auto detection fails. Place the AIF manually if the auto detection fails. 11 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Conclusion suboptimal conditions. The syngo.CT Neuro perfusion Auto Stroke and Rapid Results technology enable a In recent years we have seen a significant evolution in streamlined workflow for processing and auto archiving the management and treatment for ischemic stroke the perfusion results to PACS seamlessly. (Figure 9). Advanced neuroimaging techniques like CTP are invaluable tools in evaluating the extent of the stroke Time is brain – Optimal stroke care relies on quick and making informed decisions regarding treatment. imaging, diagnosis and treatment with interactions Siemens Healthineers’ dynamic spiral acquisition across the healthcare continuum. The Siemens techniques (A4DS and F4DS) with 4D noise reduction Healthineers’ CT imaging solutions allow for a timely algorithm allow whole brain perfusion imaging with near and accurate response to ischemic stroke and have the isotropic resolution. Robust motion correction and the potential to help reduce the door to needle time, save availability of two different delay insensitive models for brain tissue and improve stroke outcomes. perfusion analysis offer diagnostic results even in 2. Triaging patients within hospital upon arrival, quick imaging (NCT, CCTA, CTP) and diagnosis along with determining treatment plan. 1. Pre-hospital testing/ evaluations and triaging patients to appropriate facility. Imaging (NCT, CTA) with a Mobile Stroke 3. Administer tPA and prep for further treatment. Unit (MSU) where available could save time on the next 2 steps. 4. Transport to Angio suite for Endovascular treatment. 5. Comprehensive pathways to help improve your patients outcomes. 27. Figure 9: Example Stroke Pathway for management and treatment of ischemic stroke. 12 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Appendix SOMATOM go.All siemens-healthineers.us/somatom-go-all Acquisition Scan mode Flex 4D Spiral Scan length 8.47 cm Scan time 47.54 sec Tube voltage 70 kV Tube current 133 mAs Rotation time 0.33 sec Pitch 1.0 Slice collimation 32 x 0.7 Reconstruction Slice thickness/increment 5 mm/3.4 mm Reconstruction kernel Hr36 Dose CTDI vol 177.64 mGy DLP 1787.7 mGy*cm SOMATOM go.Top siemens-healthineers.us/somatom-go-top Acquisition Scan mode Flex 4D Spiral Scan length 8.49 cm Scan time 47.38 sec Tube voltage 70 kV Tube current 133 mAs Rotation time 0.33 sec Pitch 0.5 Slice collimation 64 x 0.6 Reconstruction Slice thickness/increment 5 mm/3 mm Reconstruction kernel Hr36 Dose CTDI vol 133.73 mGy DLP 1470.8 mGy*cm 13 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Appendix (continued) SOMATOM X.cite siemens-healthineers.us/somatom-xcite Acquisition Scan mode Flex 4D spiral Scan length 10 cm Scan time 47.49 sec Tube voltage 70 kV Tube current 149 mAs Rotation time 0.3 sec Pitch 0.5 Slice collimation 64 x 0.6 Reconstruction Slice thickness/increment 5 mm/3 mm Reconstruction kernel Hr36 Dose CTDI vol 173.73 mGy DLP 1865.3 mGy*cm SOMATOM Definition Edge siemens-healthineers.us/somatom-definition-edge Acquisition Scan mode Adaptive 4D Spiral Scan length 10 cm Scan time 46.35 sec Tube voltage 70 kV Tube current 200 mAs Rotation time 0.285 sec Pitch 0.5 Slice collimation 32 x 1.2 Reconstruction Slice thickness/increment 5 mm/3 mm or 1.5 mm/1 mm Reconstruction kernel Hr35 Dose CTDI vol 139.74 mGy DLP 1667.11 mGy*cm 14 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Appendix (continued) SOMATOM Edge Plus siemens-healthineers.us/somatom-edge-plus Acquisition Scan mode Adaptive 4D Spiral Scan length 10 cm Scan time 46.35 sec Tube voltage 70 kV Tube current 200 mAs Rotation time 0.285 sec Pitch 0.5 Slice collimation 32 x 1.2 Reconstruction Slice thickness/increment 5 mm/3 mm or 1.5 mm/1 mm Reconstruction kernel Hr35 Dose CTDI vol 139.74 mGy DLP 1667.11 mGy*cm SOMATOM Drive siemens-healthineers.us/somatom-drive Acquisition Scan mode Adaptive 4D Spiral Scan length 10 cm Scan time 46.35 sec Tube voltage 70 kV Tube current 200 mAs Rotation time 0.285 sec Pitch 0.5 Slice collimation 32 x 1.2 Reconstruction Slice thickness/increment 5 mm/3 mm or 1.5 mm/1 mm Reconstruction kernel Hr35 Dose CTDI vol 139 mGy DLP 1636.05 mGy*cm 15 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis Appendix (continued) SOMATOM Force siemens-healthineers.us/somatom-force Acquisition Scan mode Adaptive 4D Spiral Scan length 11.4 cm Scan time 45.45 Tube voltage 70 kV Tube current 200 mAs Rotation time 0.25 sec Pitch 0.5 Slice collimation 48 x 1.2 Reconstruction Slice thickness/increment 5 mm/3 mm or 1.5 mm/1 mm Reconstruction kernel Hr36 Dose CTDI vol 147.7 mGy DLP 2183.19 mGy*cm 16 Whitepaper · CT Neuro Perfusion in ischemic stroke management: whole brain dynamic imaging with automated perfusion analysis References 1Campbell BCV, Khatri P. 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Acad Radiol. 2019;26(11):1565-1579. doi:10.1016/j. acra.2018.12.013 17 At Siemens Healthineers, our purpose is to enable On account of certain regional limitations of sales rights healthcare providers to increase value by empowering and service availability, we cannot guarantee that all them on their journey toward expanding precision products included in this brochure are available through medicine, transforming care delivery, and improving the Siemens Healthineers sales organization worldwide. patient experience, all enabled by digitalizing healthcare. Availability and packaging may vary by country and is subject to change without prior notice. 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For the most current information, please contact your local sales The outcomes and statements provided by customers representative from Siemens Healthineers. of Siemens Healthineers are unique to each customer’s setting. Since there is no “typical” hospital and many Note: Any technical data contained in this document may variables exist (e.g., hospital size, case mix, and level of vary within defined tolerances. Original images always service/technology adoption), there can be no guarantee lose a certain amount of detail when reproduced. that others will achieve the same results. Siemens Healthineers Headquarters USA Siemens Healthcare GmbH Siemens Medical Solutions USA, Inc. 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