xml: <clinical_study>
    <!-- This xml conforms to an XML Schema at:
      https://clinicaltrials.gov/ct2/html/images/info/public.xsd -->
    <required_header>
      <download_date>ClinicalTrials.gov processed this data on September 20, 2023</download_date>
      <link_text>Link to the current ClinicalTrials.gov record.</link_text>
      <url>https://clinicaltrials.gov/ct2/show/NCT06028802</url>
    </required_header>
    <id_info>
      <org_study_id>AC23097</org_study_id>
      <secondary_id>MRC/IAA/003</secondary_id>
      <secondary_id>330583</secondary_id>
      <nct_id>NCT06028802</nct_id>
    </id_info>
    <brief_title>CT Clock Tool Feasibility Study</brief_title>
    <official_title>Feasibility Study of the CT Clock Tool for Estimating Onset Time of Ischaemic Stroke</official_title>
    <sponsors>
      <lead_sponsor>
        <agency>University of Edinburgh</agency>
        <agency_class>Other</agency_class>
      </lead_sponsor>
      <collaborator>
        <agency>NHS Lothian</agency>
        <agency_class>Other</agency_class>
      </collaborator>
    </sponsors>
    <source>University of Edinburgh</source>
    <oversight_info>
      <has_dmc>No</has_dmc>
      <is_fda_regulated_drug>No</is_fda_regulated_drug>
      <is_fda_regulated_device>No</is_fda_regulated_device>
    </oversight_info>
    <brief_summary>
      <textblock>
        Interruption of blood supply to the brain from a blocked blood vessel causes ischaemic&#xD;
        stroke. This leads to symptoms relating to the areas of brain affected. For example, people&#xD;
        with stroke may suddenly have trouble moving their arms, legs or face, and may find it hard&#xD;
        to speak or lose consciousness. There are treatments available to open up the blocked blood&#xD;
        vessel:&#xD;
  &#xD;
          -  Thrombolysis involves injecting a medicine to break down the blood clot causing the&#xD;
             blockage.&#xD;
  &#xD;
          -  Thrombectomy means pulling the blood clot out through a tiny tube placed within the&#xD;
             blood vessel.&#xD;
  &#xD;
        Both treatments can help restore blood supply to the brain and reverse the symptoms caused by&#xD;
        stroke. These treatments are usually only offered when there is a clear onset time for stroke&#xD;
        symptoms. However, for around 20% of strokes, the time of onset is unknown. Patients may wake&#xD;
        up with symptoms, be confused or be found collapsed.&#xD;
  &#xD;
        So that treatment can be available to more people, the investigators have developed a method&#xD;
        to estimate when an ischaemic stroke began, the CT Clock Tool. This method involves taking&#xD;
        measurements from the brain imaging that most patients with stroke routinely get on arrival&#xD;
        at hospital (CT or CAT scanning). In other words, no extra tests are needed to use the&#xD;
        method; the investigators seek to make better use of existing tests.&#xD;
  &#xD;
        In this study, the aim is to understand whether it is feasible to use the CT Clock Tool&#xD;
        method in the real world. For example, can doctors correctly use the tool during their normal&#xD;
        work to produce accurate estimates for the onset time of stroke? The results of this study&#xD;
        will be used to plan a future clinical trial for testing the safety of the CT Clock Tool when&#xD;
        it is used to treat patients.&#xD;
      </textblock>
    </brief_summary>
    <detailed_description>
      <textblock>
        Background&#xD;
  &#xD;
        Stroke is a major health concern worldwide causing high rates of disability and death. Most&#xD;
        strokes (approximately 85%) are cause by ischaemia following blockage to an arterial blood&#xD;
        vessel. Two effective treatments are available that can remove the vessel blockage and thus&#xD;
        reduce the rates of both disability and death after stroke. However, both treatments have&#xD;
        time-limits for safe delivery. Thrombolysis uses an injected medicine to break down the blood&#xD;
        clot and must be used within 4.5 hours of stroke onset (the European licensing time limit for&#xD;
        alteplase). Thrombectomy is a surgical procedure that involves pulling the clot out using a&#xD;
        catheter placed inside the artery and is usually limited to 6 hours from stroke onset.&#xD;
  &#xD;
        Unfortunately, for approximately 20% of patients with ischaemic stroke, the time of symptom&#xD;
        onset is not known, usually because patients wake with symptoms or are found collapsed. Such&#xD;
        patients have traditionally been denied treatment, but recent research has shown that&#xD;
        advanced brain imaging methods (for example CT perfusion or MRI) can be used to identify&#xD;
        patients who can still safely be treated in the absence of a known onset time for stroke.&#xD;
        However, these advanced imaging methods are not widely available for acute stroke assessment,&#xD;
        especially outside major treatment centres in developed nations. For example, it remains&#xD;
        difficult in Scotland to offer advanced brain imaging to all who might need it. Plain&#xD;
        (non-enhanced) CT is much more widely available and is the standard immediate assessment&#xD;
        method for most patients with stroke worldwide.&#xD;
  &#xD;
        As ischaemic stroke progresses, injured brain slowly begins to change on plain CT and the&#xD;
        ischaemic lesion becomes more and more pronounced with greater oedema and swelling. These&#xD;
        changes are seen as a darkening of tissue, indicating a decrease in CT attenuation.&#xD;
  &#xD;
        The investigators have developed a method for estimating time of ischaemic stroke onset for&#xD;
        individual patients that uses only attenuation measurements of plain CT brain imaging, the CT&#xD;
        Clock Tool.&#xD;
  &#xD;
        Rationale&#xD;
  &#xD;
        The proposed CT Clock Tool method for estimating the time of stroke onset (and thus&#xD;
        clarifying individual patient eligibility for effective treatment) is significantly simpler&#xD;
        to use in the acute setting than the advanced methods currently available (CT perfusion or&#xD;
        MRI).&#xD;
  &#xD;
        The CT Clock Tool can provide specific time estimates for a given patient. These estimates&#xD;
        are derived from simple measurements of brain that can be manually acquired from non-enhanced&#xD;
        CT scans within seconds, no other imaging or specialist viewing software is required.&#xD;
        Specifically, users (for example stroke clinicians or radiologists) measure the attenuation&#xD;
        of any visible ischaemic lesion and of the equivalent normal brain to derive a CT attenuation&#xD;
        ratio (attenuation of ischaemic brain ÷ attenuation of normal brain).&#xD;
  &#xD;
        Initial testing shows that an attenuation ratio greater than 0.82 is highly predictive of a&#xD;
        stroke onset to CT time less than 4.5 hours (i.e. within the European time limit for&#xD;
        thrombolysis with alteplase). At this threshold, the CT Clock Tool is 97% sensitive and 83%&#xD;
        specific for correctly classifying patients who are within 4.5 hours of stroke symptom onset.&#xD;
        In addition, the investigators have tested associations between the appearances of&#xD;
        non-enhanced CT and CT perfusion (CTP) when both are acquired at the same time. The CT&#xD;
        attenuation ratio was compared with CTP appearances that indicate affected brain tissue is&#xD;
        likely to remain viable. In other words, and in the absence of CTP, a CT attenuation ratio&#xD;
        greater than 0.87 is 86% sensitive and 91% specific for identifying brain tissue that remains&#xD;
        viable (and is therefore most likely to benefit from treatment).&#xD;
  &#xD;
        The longer-term aim is to incorporate the CT Clock Tool into routine clinical care,&#xD;
        especially in centres that cannot provide alternative or advanced methods to assess patient&#xD;
        eligibility for acute treatment.&#xD;
  &#xD;
        This current study seeks to provide a first prospective clinical feasibility evaluation to&#xD;
        assess the practicalities of using the method in real time and to evaluate the potential&#xD;
        impact on clinical care. The results of the present analysis will inform the design of a&#xD;
        future randomised-controlled trial to evaluate whether the CT Clock Tool can safely be used&#xD;
        to determine the eligibility of patients for treatment with thrombolysis and/or thrombectomy&#xD;
        where time of stroke onset is unknown or is delayed.&#xD;
      </textblock>
    </detailed_description>
    <overall_status>Not yet recruiting</overall_status>
    <start_date type="Anticipated">September 4, 2023</start_date>
    <completion_date type="Anticipated">October 2024</completion_date>
    <primary_completion_date type="Anticipated">September 3, 2024</primary_completion_date>
    <study_type>Observational</study_type>
    <has_expanded_access>No</has_expanded_access>
    <study_design_info>
      <observational_model>Case-Only</observational_model>
      <time_perspective>Prospective</time_perspective>
    </study_design_info>
    <primary_outcome>
      <measure>Feasibility of front-line clinicians (stroke clinicians and radiologists) using the CT Clock Tool method during routine care</measure>
      <time_frame>CT Clock Tool measurements to be acquired on the day of patient admission (baseline)</time_frame>
      <description>Proportion of cases where a front-line clinician successfully uses the CT Clock Tool method in the acute setting, i.e. acquires CT measurements (regardless of result)</description>
    </primary_outcome>
    <secondary_outcome>
      <measure>Comparison of stroke onset time estimates provided by front-line clinicians using the CT Clock Tool with actual elapsed time</measure>
      <time_frame>Baseline</time_frame>
      <description>Accuracy of stroke onset time estimates - absolute error of time estimates, proportion over versus under calling time</description>
    </secondary_outcome>
    <secondary_outcome>
      <measure>Diagnostic accuracy of these time estimates for determining treatment eligibility relative to standard thrombolysis and thrombectomy limits (4.5 and 6 hours, respectively)</measure>
      <time_frame>Baseline</time_frame>
      <description>Sensitivity, specificity, positive and negative predictive values for the CT Clock Tool with reference to thrombolysis and thrombectomy time limits. Including sensitivity analyses for those with and without visible lesions, with differing stroke severity, and with and without advanced imaging at baseline.</description>
    </secondary_outcome>
    <secondary_outcome>
      <measure>Whether estimates of brain tissue viability correlate with equivalent CTP findings</measure>
      <time_frame>Baseline</time_frame>
      <description>Proportion of cases where tissue viability estimates of the CT Clock Tool agree with CTP indicators for tissue viability</description>
    </secondary_outcome>
    <secondary_outcome>
      <measure>User experience of the CT Clock Tool on a (Likert) satisfaction scale</measure>
      <time_frame>Baseline</time_frame>
      <description>Ease of use for finding/estimating the location of lesions and making measurements. Each assessed on a scale from 1 (easy) to 5 (hard), i.e. lower scores are better.</description>
    </secondary_outcome>
    <secondary_outcome>
      <measure>Inter-rater agreement</measure>
      <time_frame>Baseline</time_frame>
      <description>For CT attenuation measurements and the respective time and tissue viability estimates derived from different front-line clinician measurements of the same CT</description>
    </secondary_outcome>
    <number_of_groups>2</number_of_groups>
    <enrollment type="Anticipated">60</enrollment>
    <condition>Ischemic Stroke, Acute</condition>
    <arm_group>
      <arm_group_label>Visible lesion</arm_group_label>
      <description>Patients where an ischaemic lesion is visible on non-enhanced CT acquired at baseline.</description>
    </arm_group>
    <arm_group>
      <arm_group_label>Non-visible lesion</arm_group_label>
      <description>Patients where an ischaemic lesion is not visible on non-enhanced CT acquired at baseline.</description>
    </arm_group>
    <intervention>
      <intervention_type>Diagnostic Test</intervention_type>
      <intervention_name>CT Clock Tool measurement</intervention_name>
      <description>Ratio of CT attenuation measurements acquired from within the visible ischaemic lesion (or estimated location if not visible) ÷ CT attenuation measurements acquired from within the equivalent normal brain.</description>
      <arm_group_label>Non-visible lesion</arm_group_label>
      <arm_group_label>Visible lesion</arm_group_label>
    </intervention>
    <eligibility>
      <study_pop>
        <textblock>
          Investigators will recruit adult patients presenting acutely to the emergency department&#xD;
          with symptoms of stroke, where non-enhanced brain CT excludes haemorrhage and other&#xD;
          structural causes for symptoms (i.e. ischaemic stroke is the most likely diagnosis).&#xD;
        </textblock>
      </study_pop>
      <sampling_method>Non-Probability Sample</sampling_method>
      <criteria>
        <textblock>
          Inclusion Criteria:&#xD;
  &#xD;
            -  With and without a known time of stroke onset.&#xD;
  &#xD;
            -  With a stroke severity score (NIHSS) &gt;4&#xD;
  &#xD;
            -  With suspected anterior or posterior circulation ischaemic stroke.&#xD;
  &#xD;
            -  Over 18 years of age with no upper limit.&#xD;
  &#xD;
            -  Patients with and without concurrently acquired CTP imaging (acquired only for&#xD;
               potential thrombectomy candidates, approximately 20%)&#xD;
  &#xD;
            -  Patients able to provide informed consent (including witnessed consent when loss of&#xD;
               functional ability is evident, e.g. upper limb weakness in dominant hand or visual&#xD;
               loss).&#xD;
  &#xD;
          Exclusion Criteria:&#xD;
  &#xD;
            -  With a suspected lacunar syndrome (i.e. pure motor stroke, pure sensory stroke, mixed&#xD;
               sensorimotor stroke [without cortical signs], ataxic hemiparesis, dysarthria-clumsy&#xD;
               hand syndrome).&#xD;
  &#xD;
            -  Where CT brain imaging demonstrates a non-ischaemic cause for stroke symptoms, e.g.&#xD;
               brain haemorrhage, tumour or other relevant structural abnormality.&#xD;
        </textblock>
      </criteria>
      <gender>All</gender>
      <minimum_age>18 Years</minimum_age>
      <maximum_age>N/A</maximum_age>
      <healthy_volunteers>No</healthy_volunteers>
    </eligibility>
    <overall_official>
      <last_name>Grant Mair, MD</last_name>
      <role>Principal Investigator</role>
      <affiliation>University of Edinburgh</affiliation>
    </overall_official>
    <overall_contact>
      <last_name>Grant Mair, MD</last_name>
      <phone>+44 131 465 9563</phone>
      <email>grant.mair@ed.ac.uk</email>
    </overall_contact>
    <location>
      <facility>
        <name>Royal Infirmary of Edinburgh</name>
        <address>
          <city>Edinburgh</city>
          <zip>EH16 4SA</zip>
          <country>United Kingdom</country>
        </address>
      </facility>
      <contact>
        <last_name>Allan MacRaild</last_name>
        <email>allan.macraild@nhslothian.scot.nhs.uk</email>
      </contact>
    </location>
    <location_countries>
      <country>United Kingdom</country>
    </location_countries>
    <link>
      <url>https://ctclock.net</url>
      <description>Study website, will include results when available.</description>
    </link>
    <reference>
      <citation>Mair G, Alzahrani A, Lindley RI, Sandercock PAG, Wardlaw JM. Feasibility and diagnostic accuracy of using brain attenuation changes on CT to estimate time of ischemic stroke onset. Neuroradiology. 2021 Jun;63(6):869-878. doi: 10.1007/s00234-020-02591-w. Epub 2020 Oct 30.</citation>
      <PMID>33128140</PMID>
    </reference>
    <reference>
      <citation>Alzahrani A, Zhang X, Albukhari A, Wardlaw JM, Mair G. Assessing Brain Tissue Viability on Nonenhanced Computed Tomography After Ischemic Stroke. Stroke. 2023 Feb;54(2):558-566. doi: 10.1161/STROKEAHA.122.041241. Epub 2023 Jan 5.</citation>
      <PMID>36601950</PMID>
    </reference>
    <verification_date>August 2023</verification_date>
    <study_first_submitted>August 25, 2023</study_first_submitted>
    <study_first_submitted_qc>August 31, 2023</study_first_submitted_qc>
    <study_first_posted type="Actual">September 8, 2023</study_first_posted>
    <last_update_submitted>August 31, 2023</last_update_submitted>
    <last_update_submitted_qc>August 31, 2023</last_update_submitted_qc>
    <last_update_posted type="Actual">September 8, 2023</last_update_posted>
    <responsible_party>
      <responsible_party_type>Sponsor</responsible_party_type>
    </responsible_party>
    <condition_browse>
      <!-- CAUTION:  The following MeSH terms are assigned with an imperfect algorithm            -->
      <mesh_term>Stroke</mesh_term>
      <mesh_term>Ischemic Stroke</mesh_term>
    </condition_browse>
    <patient_data>
      <sharing_ipd>Yes</sharing_ipd>
      <ipd_description>Anonymised non-imaging data (demographics, stroke severity, stroke subtype, CT imaging features, final diagnosis) will be made openly available using the University of Edinburgh's DataShare platform, https://datashare.ed.ac.uk/.</ipd_description>
      <ipd_info_type>Study Protocol</ipd_info_type>
      <ipd_info_type>Clinical Study Report (CSR)</ipd_info_type>
      <ipd_time_frame>Available within 12 months of study end, available in perpetuity.</ipd_time_frame>
      <ipd_access_criteria>Open access.</ipd_access_criteria>
    </patient_data>
    <!-- Results have not yet been posted for this study                                          -->
  </clinical_study>
  
  
text: download date: ClinicalTrials.gov processed this data on September 20, 2023
  link text: Link to the current ClinicalTrials.gov record.
  url: https://clinicaltrials.gov/ct2/show/NCT06028802
  org study id: AC23097
  secondary id: MRC/IAA/003
  secondary id: 330583
  nct id: NCT06028802
  lead sponsor: 
  collaborator: 
  has dmc: No
  is fda regulated drug: No
  is fda regulated device: No
  Interruption of blood supply to the brain from a blocked blood vessel causes ischaemic
        stroke. This leads to symptoms relating to the areas of brain affected. For example, people
        with stroke may suddenly have trouble moving their arms, legs or face, and may find it hard
        to speak or lose consciousness. There are treatments available to open up the blocked blood
        vessel:
  
          -  Thrombolysis involves injecting a medicine to break down the blood clot causing the
             blockage.
  
          -  Thrombectomy means pulling the blood clot out through a tiny tube placed within the
             blood vessel.
  
        Both treatments can help restore blood supply to the brain and reverse the symptoms caused by
        stroke. These treatments are usually only offered when there is a clear onset time for stroke
        symptoms. However, for around 20% of strokes, the time of onset is unknown. Patients may wake
        up with symptoms, be confused or be found collapsed.
  
        So that treatment can be available to more people, the investigators have developed a method
        to estimate when an ischaemic stroke began, the CT Clock Tool. This method involves taking
        measurements from the brain imaging that most patients with stroke routinely get on arrival
        at hospital (CT or CAT scanning). In other words, no extra tests are needed to use the
        method; the investigators seek to make better use of existing tests.
  
        In this study, the aim is to understand whether it is feasible to use the CT Clock Tool
        method in the real world. For example, can doctors correctly use the tool during their normal
        work to produce accurate estimates for the onset time of stroke? The results of this study
        will be used to plan a future clinical trial for testing the safety of the CT Clock Tool when
        it is used to treat patients.
  Background
  
        Stroke is a major health concern worldwide causing high rates of disability and death. Most
        strokes (approximately 85%) are cause by ischaemia following blockage to an arterial blood
        vessel. Two effective treatments are available that can remove the vessel blockage and thus
        reduce the rates of both disability and death after stroke. However, both treatments have
        time-limits for safe delivery. Thrombolysis uses an injected medicine to break down the blood
        clot and must be used within 4.5 hours of stroke onset (the European licensing time limit for
        alteplase). Thrombectomy is a surgical procedure that involves pulling the clot out using a
        catheter placed inside the artery and is usually limited to 6 hours from stroke onset.
  
        Unfortunately, for approximately 20% of patients with ischaemic stroke, the time of symptom
        onset is not known, usually because patients wake with symptoms or are found collapsed. Such
        patients have traditionally been denied treatment, but recent research has shown that
        advanced brain imaging methods (for example CT perfusion or MRI) can be used to identify
        patients who can still safely be treated in the absence of a known onset time for stroke.
        However, these advanced imaging methods are not widely available for acute stroke assessment,
        especially outside major treatment centres in developed nations. For example, it remains
        difficult in Scotland to offer advanced brain imaging to all who might need it. Plain
        (non-enhanced) CT is much more widely available and is the standard immediate assessment
        method for most patients with stroke worldwide.
  
        As ischaemic stroke progresses, injured brain slowly begins to change on plain CT and the
        ischaemic lesion becomes more and more pronounced with greater oedema and swelling. These
        changes are seen as a darkening of tissue, indicating a decrease in CT attenuation.
  
        The investigators have developed a method for estimating time of ischaemic stroke onset for
        individual patients that uses only attenuation measurements of plain CT brain imaging, the CT
        Clock Tool.
  
        Rationale
  
        The proposed CT Clock Tool method for estimating the time of stroke onset (and thus
        clarifying individual patient eligibility for effective treatment) is significantly simpler
        to use in the acute setting than the advanced methods currently available (CT perfusion or
        MRI).
  
        The CT Clock Tool can provide specific time estimates for a given patient. These estimates
        are derived from simple measurements of brain that can be manually acquired from non-enhanced
        CT scans within seconds, no other imaging or specialist viewing software is required.
        Specifically, users (for example stroke clinicians or radiologists) measure the attenuation
        of any visible ischaemic lesion and of the equivalent normal brain to derive a CT attenuation
        ratio (attenuation of ischaemic brain ÷ attenuation of normal brain).
  
        Initial testing shows that an attenuation ratio greater than 0.82 is highly predictive of a
        stroke onset to CT time less than 4.5 hours (i.e. within the European time limit for
        thrombolysis with alteplase). At this threshold, the CT Clock Tool is 97% sensitive and 83%
        specific for correctly classifying patients who are within 4.5 hours of stroke symptom onset.
        In addition, the investigators have tested associations between the appearances of
        non-enhanced CT and CT perfusion (CTP) when both are acquired at the same time. The CT
        attenuation ratio was compared with CTP appearances that indicate affected brain tissue is
        likely to remain viable. In other words, and in the absence of CTP, a CT attenuation ratio
        greater than 0.87 is 86% sensitive and 91% specific for identifying brain tissue that remains
        viable (and is therefore most likely to benefit from treatment).
  
        The longer-term aim is to incorporate the CT Clock Tool into routine clinical care,
        especially in centres that cannot provide alternative or advanced methods to assess patient
        eligibility for acute treatment.
  
        This current study seeks to provide a first prospective clinical feasibility evaluation to
        assess the practicalities of using the method in real time and to evaluate the potential
        impact on clinical care. The results of the present analysis will inform the design of a
        future randomised-controlled trial to evaluate whether the CT Clock Tool can safely be used
        to determine the eligibility of patients for treatment with thrombolysis and/or thrombectomy
        where time of stroke onset is unknown or is delayed.
  observational model: Case-Only
  time perspective: Prospective
  measure: Feasibility of front-line clinicians (stroke clinicians and radiologists) using the CT Clock Tool method during routine care
  time frame: CT Clock Tool measurements to be acquired on the day of patient admission (baseline)
  description: Proportion of cases where a front-line clinician successfully uses the CT Clock Tool method in the acute setting, i.e. acquires CT measurements (regardless of result)
  measure: Comparison of stroke onset time estimates provided by front-line clinicians using the CT Clock Tool with actual elapsed time
  time frame: Baseline
  description: Accuracy of stroke onset time estimates - absolute error of time estimates, proportion over versus under calling time
  measure: Diagnostic accuracy of these time estimates for determining treatment eligibility relative to standard thrombolysis and thrombectomy limits (4.5 and 6 hours, respectively)
  time frame: Baseline
  description: Sensitivity, specificity, positive and negative predictive values for the CT Clock Tool with reference to thrombolysis and thrombectomy time limits. Including sensitivity analyses for those with and without visible lesions, with differing stroke severity, and with and without advanced imaging at baseline.
  measure: Whether estimates of brain tissue viability correlate with equivalent CTP findings
  time frame: Baseline
  description: Proportion of cases where tissue viability estimates of the CT Clock Tool agree with CTP indicators for tissue viability
  measure: User experience of the CT Clock Tool on a (Likert) satisfaction scale
  time frame: Baseline
  description: Ease of use for finding/estimating the location of lesions and making measurements. Each assessed on a scale from 1 (easy) to 5 (hard), i.e. lower scores are better.
  measure: Inter-rater agreement
  time frame: Baseline
  description: For CT attenuation measurements and the respective time and tissue viability estimates derived from different front-line clinician measurements of the same CT
  arm group label: Visible lesion
  description: Patients where an ischaemic lesion is visible on non-enhanced CT acquired at baseline.
  arm group label: Non-visible lesion
  description: Patients where an ischaemic lesion is not visible on non-enhanced CT acquired at baseline.
  intervention type: Diagnostic Test
  intervention name: CT Clock Tool measurement
  description: Ratio of CT attenuation measurements acquired from within the visible ischaemic lesion (or estimated location if not visible) ÷ CT attenuation measurements acquired from within the equivalent normal brain.
  arm group label: Non-visible lesion
  arm group label: Visible lesion
  study pop: 
  sampling method: Non-Probability Sample
  criteria: 
  gender: All
  minimum age: 18 Years
  maximum age: N/A
  healthy volunteers: No
  last name: Grant Mair, MD
  role: Principal Investigator
  affiliation: University of Edinburgh
  last name: Grant Mair, MD
  phone: +44 131 465 9563
  email: grant.mair@ed.ac.uk
  facility: 
  contact: 
  country: United Kingdom
  url: https://ctclock.net
  description: Study website, will include results when available.
  citation: Mair G, Alzahrani A, Lindley RI, Sandercock PAG, Wardlaw JM. Feasibility and diagnostic accuracy of using brain attenuation changes on CT to estimate time of ischemic stroke onset. Neuroradiology. 2021 Jun;63(6):869-878. doi: 10.1007/s00234-020-02591-w. Epub 2020 Oct 30.
  PMID: 33128140
  citation: Alzahrani A, Zhang X, Albukhari A, Wardlaw JM, Mair G. Assessing Brain Tissue Viability on Nonenhanced Computed Tomography After Ischemic Stroke. Stroke. 2023 Feb;54(2):558-566. doi: 10.1161/STROKEAHA.122.041241. Epub 2023 Jan 5.
  PMID: 36601950
  responsible party type: Sponsor
  mesh term: Stroke
  mesh term: Ischemic Stroke
  sharing ipd: Yes
  ipd description: Anonymised non-imaging data (demographics, stroke severity, stroke subtype, CT imaging features, final diagnosis) will be made openly available using the University of Edinburgh's DataShare platform, https://datashare.ed.ac.uk/.
  ipd info type: Study Protocol
  ipd info type: Clinical Study Report (CSR)
  ipd time frame: Available within 12 months of study end, available in perpetuity.
  ipd access criteria: Open access.