Acute Kidney Injury and Abnormalities on Brain Magnetic Resonance Imaging or Death in Infants with Hypoxic-Ischemic Encephalopathy: A Case-Control Study

OBJECTIVE

 This study aimed to analyze the association between acute kidney injury (AKI) and abnormalities on brain magnetic resonance imaging (MRI) or death in neonates treated with therapeutic hypothermia for hypoxic-ischemic encephalopathy (HIE).

STUDY DESIGN

 This is a retrospective case-control analysis of 380 neonates born at ≥35 weeks' gestation treated with therapeutic hypothermia for HIE. Death or abnormal brain MRI using the basal ganglia watershed scoring system was compared between neonates with and without AKI.

RESULTS

 A total of 51 (13.4%) neonates had AKI. Infants with AKI had higher rates of the composite of death or abnormal brain MRI (74.5 vs. 38.3%; p < 0.001). Rate of death (21.6 vs. 5.5%; p < 0.001) and severe abnormalities on MRI or death (43.1 vs. 19.1%; p < 0.001) were also higher in neonates with AKI.

CONCLUSION

 AKI is strongly associated with abnormalities on brain MRI or death in neonates with HIE. Identification of AKI in this patient population may be helpful in guiding clinical management and predicting potential neurodevelopmental impairment.

KEY POINTS

· Neonates with HIE are at increased risk for AKI.. · AKI is associated with hypoxic-ischemic injury on brain MRI or death among neonates with HIE.. · Identification of AKI in infants with HIE may help predict neurodevelopmental impairment..

Automated subfield volumetric analysis of amygdala, hippocampus, and thalamic nuclei in mesial temporal lobe epilepsy

Purpose

Identifying relationships between clinical features and quantitative characteristics of the amygdala-hippocampal and thalamic subregions in mesial temporal lobe epilepsy (mTLE) may offer insights into pathophysiology and the basis for imaging prognostic markers of treatment outcome. Our aim was to ascertain different patterns of atrophy or hypertrophy in mesial temporal sclerosis (MTS) patients and their associations with post-surgical seizure outcomes. To assess this aim, this study is designed in 2 folds: (1) hemispheric changes within MTS group and (2) association with postsurgical seizure outcomes.

Methods and materials

27 mTLE subjects with mesial temporal sclerosis (MTS) were scanned for conventional 3D T1w MPRAGE images and T2w scans. With respect to 12 months post-surgical seizure outcomes, 15 subjects reported being seizure free (SF) and 12 reported continued seizures. Quantitative automated segmentation and cortical parcellation were performed using Freesurfer. Automatic labeling and volume estimation of hippocampal subfields, amygdala, and thalamic subnuclei were also performed. The volume ratio (VR) for each label was computed and compared between (1) between contralateral and ipsilateral MTS using Wilcoxon rank-sum test and (2) SF and not seizure free (NSF) groups using linear regression analysis. False Discovery rate (FDR) with significant level of 0.05 were used in both analyses to correct for multiple comparisons.

Results

Amygdala: The medial nucleus of the amygdala was the most significantly reduced in patients with continued seizures when compared to patients who remained seizure free. Hippocampus: Comparison of ipsilateral and contralateral volumes with seizure outcomes showed volume loss was most evident in the mesial hippocampal regions such as CA4 and hippocampal fissure. Volume loss was also most explicit in the presubiculum body in patients with continued seizures at the time of their follow-up. Ipsilateral MTS compared to contralateral MTS analysis showed the heads of the ipsilateral subiculum, presubiculum, parasubiculum, dentate gyrus, CA4, and CA3 were more significantly affected than their respective bodies. Volume loss was most noted in mesial hippocampal regions. Thalamus: VPL and PuL were the most significantly reduced thalamic nuclei in NSF patients. In all statistically significant areas, volume reduction was observed in the NSF group. No significant volume reductions were noted in the thalamus and amygdala when comparing ipsilateral to contralateral sides in mTLE subjects.

Conclusions

Varying degrees of volume loss were demonstrated in the hippocampus, thalamus, and amygdala subregions of MTS, especially between patients who remained seizure-free and those who did not. The results obtained can be used to further understand mTLE pathophysiology.

Clinical relevance/application

In the future, we hope these results can be used to deepen the understanding of mTLE pathophysiology, leading to improved patient outcomes and treatments.

Case report: Utilizing diffusion-weighted MRI on a patient with chronic low back pain treated with spinal cord stimulation

Diffusion-weighted magnetic resonance imaging (dwMRI) has increasingly demonstrated greater utility in analyzing neuronal microstructure. In patients with chronic low back pain (cLBP), using dwMRI to observe neuronal microstructure can lead to non-invasive biomarkers which could provide clinicians with an objective quantitative prognostic tool. In this case report, we investigated dwMRI for the development of non-invasive biomarkers by conducting a region-based analysis of a 55-year-old male patient with failed back surgery syndrome (FBSS) treated with spinal cord stimulation (SCS). We hypothesized that dwMRI could safely generate quantitative data reflecting cerebral microstructural alterations driven by neuromodulation. Neuroimaging was performed at 6- and 12- months post-SCS implantation. The quantitative maps generated included diffusion tensor imaging (DTI) parameters; fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD) computed from whole brain tractography. To examine specific areas of the brain, 44 regions of interest (ROIs), collectively representing the pain NeuroMatrix, were extracted and registered to the patient's diffusion space. Average diffusion indices were calculated from the ROIs at both 6- and 12- months. Regions with >10% relative change in at least 3 of the 4 maps were reported. Using this selection criterion, 8 ROIs demonstrated over 10% relative changes. These ROIs were mainly located in the insular gyri. In addition to the quantitative data, a series of questionnaires were administered during the 6- and 12-month visits to assess pain intensity, functional disability, and quality of life. Overall improvements were observed in these components, with the Pain Catastrophizing Scale (PCS) displaying the greatest change. Lastly, we demonstrated the safety of dwMRI for a patient with SCS. In summary, the results from the case report prompt further investigation in applying dwMRI in a larger cohort to better correlate the influence of SCS with brain microstructural alterations, supporting the utility of dwMRI to generate non-invasive biomarkers for prognostication.

Resting-State fMRI Can Detect Alterations in Seizure Onset and Spread Regions in Patients with Non-Lesional Epilepsy: A Pilot Study

Introduction

Epilepsy is defined as non-lesional (NLE) when a lesion cannot be localized via standard neuroimaging. NLE is known to have a poor response to surgery. Stereotactic electroencephalography (sEEG) can detect functional connectivity (FC) between zones of seizure onset (OZ) and early (ESZ) and late (LSZ) spread. We examined whether resting-state fMRI (rsfMRI) can detect FC alterations in NLE to see whether noninvasive imaging techniques can localize areas of seizure propagation to potentially target for intervention.

Methods

This is a retrospective study of 8 patients with refractory NLE who underwent sEEG electrode implantation and 10 controls. The OZ, ESZ, and LSZ were identified by generating regions around sEEG contacts that recorded seizure activity. Amplitude synchronization analysis was used to detect the correlation of the OZ to the ESZ. This was also done using the OZ and ESZ of each NLE patient for each control. Patients with NLE were compared to controls individually using Wilcoxon tests and as a group using Mann-Whitney tests. Amplitude of low-frequency fluctuations (ALFF), fractional ALFF (fALFF), regional homogeneity (ReHo), degree of centrality (DoC), and voxel-mirrored homotopic connectivity (VMHC) were calculated as the difference between NLE and controls and compared between the OZ and ESZ and to zero. A general linear model was used with age as a covariate with Bonferroni correction for multiple comparisons.

Results

Five out of 8 patients with NLE showed decreased correlations from the OZ to the ESZ. Group analysis showed patients with NLE had lower connectivity with the ESZ. Patients with NLE showed higher fALFF and ReHo in the OZ but not the ESZ, and higher DoC in the OZ and ESZ. Our results indicate that patients with NLE show high levels of activity but dysfunctional connections in seizure-related areas.

Discussion

rsfMRI analysis showed decreased connectivity directly between seizure-related areas, while FC metric analysis revealed increases in local and global connectivity in seizure-related areas. FC analysis of rsfMRI can detect functional disruption that may expose the pathophysiology underlying NLE.

Case report: The promising application of dynamic functional connectivity analysis on an individual with failed back surgery syndrome

Failed back surgery syndrome (FBSS), a chronic neuropathic pain condition, is a common indication for spinal cord stimulation (SCS). However, the mechanisms of SCS, especially its effects on supraspinal/brain functional connectivity, are still not fully understood. Resting state functional magnetic resonance imaging (rsfMRI) studies have shown characteristics in patients with chronic low back pain (cLBP). In this case study, we performed rsfMRI scanning (3.0 T) on an FBSS patient, who presented with chronic low back and leg pain following her previous lumbar microdiscectomy and had undergone permanent SCS. Appropriate MRI safety measures were undertaken to scan this subject. Seed-based functional connectivity (FC) was performed on the rsfMRI data acquired from the FBSS subject, and then compared to a group of 17 healthy controls. Seeds were identified by an atlas of resting state networks (RSNs), which is composed of 32 regions grouped into 8 networks. Sliding-window method and k-means clustering were used in dynamic FC analysis, which resulted in 4 brain states for each group. Our results demonstrated the safety and feasibility of 3T MRI scanning in a patient with implanted SCS system. Compared to the brain states of healthy controls, the FBSS subject presented very different FC patterns in less frequent brain states. The mean dwell time of brain states showed distinct distributions: the FBSS subject seemed to prefer a single state over the others. Although future studies with large sample sizes are needed to make statistical conclusions, our findings demonstrated the promising application of dynamic FC to provide more granularity with FC changes associated with different brain states in chronic pain.

DTI of chronic spinal cord injury in children without MRI abnormalities (SCIWOMR) and with pathology on MRI and comparison to severity of motor impairment

STUDY DESIGN

This investigation was a cohort study that included: 36 typically developing (TD) children and 19 children with spinal cord lesions who underwent spinal cord MRI.

OBJECTIVES

To investigate diffusion tensor imaging (DTI) cervical and thoracic spinal cord changes in pediatric patients that have clinically traumatic and non-traumatic spinal cord injury (SCI) without MR (SCIWOMR) abnormalities.

SETTING

Thomas Jefferson University, Temple University, Shriners Hospitals for Children all in Philadelphia, USA.

METHODS

36 TD children and 19 children with spinal cord lesions that represent either a chronic traumatic acquired SCI or chronic non-traumatic SCI (≥6 months post injury), age range, 6-16 years who underwent cervical and thoracic spinal cord MRI in 2014-2017. Additionally DTI was correlated to clinical American Spinal Injury Association Impairment Scale (AIS).

RESULTS

Both SCIWOMR and MRI positive (+) groups showed abnormal FA and RD DTI values in the adjacent MRI-normal appearing segments of cephalad and caudal spinal cord compared to TD. The FA values demonstrated perilesional abnormal DTI findings in the middle and proximal segments of the cephalad and caudal cord in the SCIWOMR AIS A/B group compared to SCIWOMR AIS C/D group.

CONCLUSIONS

We found DTI changes in children with SCIWOMR with different causes of spinal lesions. We also investigated the relationship between DTI and clinical AIS scores. This study further examined the potential diagnostic value of DTI and should be translatable to adults with spinal cord lesions.

Phase Ib Clinical Trial of IGV-001 for Patients with Newly Diagnosed Glioblastoma

PURPOSE

Despite standard of care (SOC) established by Stupp, glioblastoma remains a uniformly poor prognosis. We evaluated IGV-001, which combines autologous glioblastoma tumor cells and an antisense oligonucleotide against IGF type 1 receptor (IMV-001), in newly diagnosed glioblastoma.

PATIENTS AND METHODS

This open-label protocol was approved by the Institutional Review Board at Thomas Jefferson University. Tumor cells collected during resection were treated ex vivo with IMV-001, encapsulated in biodiffusion chambers with additional IMV-001, irradiated, then implanted in abdominal acceptor sites. Patients were randomized to four exposure levels, and SOC was initiated 4-6 weeks later. On the basis of clinical improvements, randomization was halted after patient 23, and subsequent patients received only the highest exposure. Safety and tumor progression were primary and secondary objectives, respectively. Time-to-event outcomes were compared with the SOC arms of published studies.

RESULTS

Thirty-three patients were enrolled, and median follow-up was 3.1 years. Six patients had adverse events (grade ≤3) possibly related to IGV-001. Median progression-free survival (PFS) was 9.8 months in the intent-to-treat population (vs. SOC, 6.5 months; P = 0.0003). In IGV-001-treated patients who met Stupp-eligible criteria, PFS was 11.6 months overall (n = 22; P = 0.001) and 17.1 months at the highest exposure (n = 10; P = 0.0025). The greatest overall survival was observed in Stupp-eligible patients receiving the highest exposure (median, 38.2 months; P = 0.044). Stupp-eligible patients with methylated O⁶-methylguanine-DNA methyltransferase promoter (n = 10) demonstrated median PFS of 38.4 months (P = 0.0008). Evidence of immune activation was noted.

CONCLUSIONS

IGV-001 was well tolerated, PFS compared favorably with SOC, and evidence suggested an immune-mediated mechanism (ClinicalTrials.gov: NCT02507583).

Abstract B71: Phase 1b/2 prospective randomized trial of four autologous cell vaccine dose cohorts for initial treatment of glioblastoma

Introduction: We present a novel autologous cell vaccine therapy designed to treat patients with newly diagnosed glioblastoma (Trial Registration: IND 14379, NCT01550523).

Methods: This phase 1b trial has a phase 2 design with 4 randomized vaccine dose cohorts in 33 patients with the objective being safety assessment but also including clinical, radiographic, and immune analyses. Eligibility criteria included age &gt; 18 and Karnofsky score of &gt; 60; neither bihemispheric disease nor extent of resection were exclusion criteria but autoimmune diseases were. During craniotomy for tumor resection, if frozen section confirmed GBM, incisions were made in the lower abdomen through the rectus sheath and pockets created between the sheath and the muscle and the wounds closed with a temporary three-layer closure. Tumor resection involved an aspirator that collected morselized viable tumor tissue in sterile traps. The tissue was processed by overnight culture with 0.2 mg of an IGF-1R antisense oligodeoxynucleotide/gm. The next (first postoperative) day, treated tumor cells were harvested, encapsulated in either ten or twenty small biodiffusion chambers along with 4 micrograms of the IGF-1R antisense, irradiated and then implanted at bedside in the abdominal acceptor sites as previously described (1). Chambers were explanted 24 or 48 hours later, depending on randomization. Standard of care according to Stupp (2) was initiated at 6 weeks. Studies included 3T MRI imaging and analysis of serial blood samples for T cell function and cytokine levels. Disease progression was assessed using RANO (3) and iRANO (4) criteria with a data cutoff of March 1 (N=30) used for this analysis.

Results: The trial opened September 1, 2015 and completed accrual on March 1, 2018. A midpoint interim analysis revealed significantly more robust cytokine responses at the highest vaccine dose. Randomization was therefore stopped at subject 23 and amended to treat using only the highest dose. Progression-free survival (PFS) was compared to three historic SOC comparators (Stupp [2], Kong [5], and an antecedent cohort of 37 consecutive patients treated with SOC at our institution [TJUH]). PFS was significantly improved at 10.5 mo v. SOC comparators: 6.9 mo (Stupp, p = .003), 5.3 mo (Kong, p = .002) and 7 mo (TJUH, p = .013). Seventy-five percent of the 14 patients in the highest-dose cohort had robust proinflammatory and early evidence of sustained immune reactivity associated with tumor regression or no recurrence after surgery.

Conclusion: These data reflect a therapeutic benefit defined as significant improvement in PFS without increased safety risk compared to three different SOC cohorts. Since GBM remains one of the most challenging solid tumors, this treatment design invites investigator collaboration in a multicenter phase 2 trial.

References: 1. Andrew et al. J Clin Oncol 19:2189-2200; 2. Stupp et al. NEJM 352:987-96; 3. Wen et al. J Clin. Oncol 28:1963-72; 4. Okada et al. Lancet Oncol 16:534-42; 5. Kong et al. Oncotarget 8:7003-13.

Citation Format: Kevin D. Judy, David W. Andrews, Larry Harshyne, Lawrence Kenyon, Kiran Talekar, Kofi-Buaku Atsina, Lyndon Kim, Wenyin Shi, Maria Werner-Wasik, Rhonda Kean, Samantha Garcia, Kara Pigott, Charles B. Scott, D. Craig Hooper. Phase 1b/2 prospective randomized trial of four autologous cell vaccine dose cohorts for initial treatment of glioblastoma [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B71.

Abstract CT038: Results of a Phase Ib trial of an autologous cell vaccine for newly diagnosed glioblastoma

Background: We evaluated an autologous cell vaccine, a combination of GBM tumor cells and an antisense molecule against insulin-like growth factor type 1 receptor DNA/mRNA (IGF-1R AS ODN), in adults with newly diagnosed GBM (NCT02507583).

Methods: Tumor cells collected during resection were treated ex vivo with IGF-1R AS ODN, encapsulated in biodiffusion chambers with IGF-1R AS ODN, irradiated, then implanted in an abdominal acceptor site on the first post-operative day. Four vaccine exposures were evaluated: lowest (10 chambers implanted for 24 hours); lower (10 / 48 hours); higher (20 / 24 hours); and highest (20 / 48 hours). Standard of care (SOC; ie, radiotherapy and temozolomide) was initiated after 4-6 weeks. Randomization was halted after patient 23 and subsequent patients received the highest exposure. Evaluation of safety and tumor responses were the primary and secondary objectives, respectively. Exploratory objectives included assessment of progression-free survival (PFS) and overall survival (OS). The SOC comparator group was an antecedent cohort of 35 newly diagnosed, GBM patients treated at the same center.

Results: Thirty-three patients were enrolled between September 1, 2015 and March 1, 2018. Six, 5, 5, and 17 patients received the lowest, lower, higher, and highest exposures. Median (range) follow-up was 13 (4-39) months. As of the January 1, 2019 cutoff, no vaccine-related adverse events were observed. Seventeen of 33 (51.5%) remained progression-free, 12 of whom are alive and functioning well. The autologous cell vaccine significantly prolonged PFS and OS vs. SOC (Table). Survival advantages were conferred by the highest exposure to the autologous cell vaccine and good T cell function prior to surgery.

Conclusions: This vaccine was well-tolerated and prolonged PFS and OS when compared with SOC alone.

Table.Survival outcomes in patients receiving vaccine vs. SOC aloneTreatment group2 yr OS estimateMedian OS (mo)p-value v. SOC for OS1 yr PFS estimateMedian PFS estimatep-value v. SOC for PFSVaccine highest dose (N=17)34%21.9.04141%10.4.031Vaccine all (ITT, N=33)31%17.3.01642%9.8.018SOC (n=35)14%12.128%6.9

Citation Format: David W. Andrews, Samantha Garcia, Kevin D. Judy, Larry A. Harshyne, Sanjana Govindarajan, Lawrence Kenyon, Kiran Talekar, Adam Flanders, Kofi-Buaku Atsina, Lyndon Kim, Nina L. Martinez, Wenyin Shi, Maria Werner-Wasik, Mikhail Prosniak, Mark T. Curtis, Rhonda Kean, Emily Bongiorno, Sami Sauma, Kara Pigott, Charles B. Scott, D Craig Hooper. Results of a Phase Ib trial of an autologous cell vaccine for newly diagnosed glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT038.

Apgar Scores at 10 Minutes and Outcomes in Term and Late Preterm Neonates with Hypoxic-Ischemic Encephalopathy in the Cooling Era

OBJECTIVE

To determine the short-term outcomes (abnormal brain magnetic resonance imaging [MRI]/death) in infants born with a 10-minute Apgar score of 0 who received therapeutic hypothermia and compare them with infants with higher scores.

STUDY DESIGN

This is a retrospective review of 293 neonates (gestational age ≥ 35 weeks) born between November 2006 and October 2015 admitted with hypoxic-ischemic encephalopathy who received therapeutic hypothermia. Results of brain MRIs were assessed by the basal ganglia/watershed scoring system. Short-term outcomes were compared between infants with Apgar scores of 0, 1 to 4, and ≥5 at 10 minutes.

RESULTS

Eight of 17 infants (47%) with an Apgar of 0 at 10 minutes survived, having 4 (24%) without abnormalities on the brain MRI and 7 (41%) without severe abnormalities. There was no significant difference in the combined outcomes of "death/abnormal MRI" and "death/severe abnormalities on the MRI" between infants with Apgar scores of 0 and 1 to 4. Follow-up data were available for six of eight surviving infants, and none had moderate or severe neurodevelopmental impairment.

CONCLUSION

In the cooling era, 47% of infants with no audible heart rate at 10 minutes and who were admitted to the neonatal intensive care unit survived; 24% without abnormalities on the brain MRI and 41% without severe abnormalities.

Advanced magnetic resonance imaging in glioblastoma: a review

Glioblastoma, the most common and most rapidly progressing primary malignant tumor of the central nervous system, continues to portend a dismal prognosis, despite improvements in diagnostic and therapeutic strategies over the last 20 years. The standard of care radiographic characterization of glioblastoma is magnetic resonance imaging (MRI), which is a widely utilized examination in the diagnosis and post-treatment management of patients with glioblastoma. Basic MRI modalities available from any clinical scanner, including native T1-weighted (T1w) and contrast-enhanced (T1CE), T2-weighted (T2w), and T2-fluid-attenuated inversion recovery (T2-FLAIR) sequences, provide critical clinical information about various processes in the tumor environment. In the last decade, advanced MRI modalities are increasingly utilized to further characterize glioblastomas more comprehensively. These include multi-parametric MRI sequences, such as dynamic susceptibility contrast (DSC), dynamic contrast enhancement (DCE), higher order diffusion techniques such as diffusion tensor imaging (DTI), and MR spectroscopy (MRS). Significant efforts are ongoing to implement these advanced imaging modalities into improved clinical workflows and personalized therapy approaches. Functional MRI (fMRI) and tractography are increasingly being used to identify eloquent cortices and important tracts to minimize postsurgical neuro-deficits. A contemporary review of the application of standard and advanced MRI in clinical neuro-oncologic practice is presented here.

Imaging of Spinal Cord Injury: Acute Cervical Spinal Cord Injury, Cervical Spondylotic Myelopathy, and Cord Herniation

We review the pathophysiology and imaging findings of acute traumatic spinal cord injury (SCI), cervical spondylotic myelopathy, and briefly review the much less common cord herniation as a unique cause of myelopathy. Acute traumatic SCI is devastating to the patient and the costs to society are staggering. There are currently no "cures" for SCI and the only accepted pharmacologic treatment regimen for traumatic SCI is currently being questioned. Evaluation and prognostication of SCI is a demanding area with significant deficiencies, including lack of biomarkers. Accurate classification of SCI is heavily dependent on a good clinical examination, the results of which can vary substantially based upon the patient׳s condition or comorbidities and the skills of the examiner. Moreover, the full extent of a patients׳ neurologic injury may not become apparent for days after injury; by then, therapeutic response may be limited. Although magnetic resonance imaging (MRI) is the best imaging modality for the evaluation of spinal cord parenchyma, conventional MR techniques do not appear to differentiate edema from axonal injury. Recently, it is proposed that in addition to characterizing the anatomic extent of injury, metrics derived from conventional MRI and diffusion tensor imaging, in conjunction with the neurological examination, can serve as a reliable objective biomarker for determination of the extent of neurologic injury and early identification of patients who would benefit from treatment. Cervical spondylosis is a common disorder affecting predominantly the elderly with a potential to narrow the spinal canal and thereby impinge or compress upon the neural elements leading to cervical spondylotic myelopathy and radiculopathy. It is the commonest nontraumatic cause of spinal cord disorder in adults. Imaging plays an important role in grading the severity of spondylosis and detecting cord abnormalities suggesting myelopathy.

Sources of variability in computed tomography perfusion: implications for acute stroke management

Object

Although dynamic, first-pass cerebral CT perfusion is used in the evaluation of acute ischemic stroke, a lack of standardization restricts the value of this imaging modality in clinical decision-making. The purpose of this study was to comprehensively review the reported sources of variability and error in cerebral CT perfusion results.

Methods

A systematic literature review was conducted, 120 articles were reviewed, and 23 published original research articles were included. Sources of variability and error were thematically categorized and presented within the context of the 3 stages of a typical CT perfusion study: data acquisition, postprocessing, and results interpretation.

Results

Seven factors that caused variability were identified and described in detail: 1) contrast media, the iodinated compound injected intravascularly to permit imaging of the cerebral vessels; 2) data acquisition rate, the number of images obtained by CT scan per unit time; 3) user inputs, the subjective selections that operators make; 4) observer variation, the failure of operators to repeatedly measure a perfusion parameter with precision; 5) software operational mode, manual, semiautomatic, or automatic; 6) software design, the mathematical algorithms used to perform postprocessing; and 7) value type, absolute versus relative values.

Conclusions

Standardization at all 3 stages of the CT perfusion study cycle is warranted. At present, caution should be exercised when interpreting CT perfusion results as these values may vary considerably depending on a variety of factors. Future research is needed to define the role of CT perfusion in clinical decision-making for acute stroke patients and to determine the clinically acceptable limits of variability in CT perfusion results.