Editor’s Choices

Responses of the Human Brain to Mild Dehydration and Rehydration Explored In Vivo by 1H-MR Imaging and Spectroscopy

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Serial T1WI and 1H-MR spectroscopy data were acquired in 15 healthy individuals at normohydration, at 12 hours of dehydration, and during 1 hour of oral rehydration. Osmotic challenges were monitored by serum measures, including osmolality and hematocrit. With dehydration, serum osmolality increased by 0.67% and brain tissue fluid decreased by 1.63%. MR imaging morphometry demonstrated corresponding decreases of cortical thickness and volumes of the whole brain, cortex, white matter, and hypothalamus/thalamus. These changes reversed during rehydration. The authors conclude that it is essential to control for hydration levels in studies on brain morphometry and metabolism in order to avoid confounding the findings.

Abstract

Cortical thickness analysis. Local changes of cortical thickness (A, red-to-yellow: for thinning on dehydration; blue-to-light blue: for thickening on rehydration). Dehydration primarily induces cortical thinning (upper row), which reverses on rehydration (bottom row). Note that these prevailing changes are not uniformly distributed over the cerebral surface. Changes on the mesial surface (not shown) were slightly less pronounced but similar. The corresponding statistical significance (B, red-to-yellow: for thinning on dehydration; blue-to-light blue: for thickening upon rehydration) is expressed by increasingly lower false-positive probabilities across subjects.

BACKGROUND AND PURPOSE

As yet, there are no in vivo data on tissue water changes and associated morphometric changes involved in the osmo-adaptation of normal brains. Our aim was to evaluate osmoadaptive responses of the healthy human brain to osmotic challenges of de- and rehydration by serial measurements of brain volume, tissue fluid, and metabolites.

MATERIALS AND METHODS

Serial T1-weighted and 1H-MR spectroscopy data were acquired in 15 healthy individuals at normohydration, on 12 hours of dehydration, and during 1 hour of oral rehydration. Osmotic challenges were monitored by serum measures, including osmolality and hematocrit. MR imaging data were analyzed by using FreeSurfer and LCModel.

RESULTS

On

Diagnostic Accuracy of PET, SPECT, and Arterial Spin-Labeling in Differentiating Tumor Recurrence from Necrosis in Cerebral Metastasis after Stereotactic Radiosurgery

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The authors retrospectively reviewed patients treated between 2007–2010 and identified 14 patients with cerebral metastasis who had clinical or radiographic progression following stereotactic radiosurgery and were imaged with arterial spin-labeling (ASL), FDG-PET, and thallium SPECT before stereotactic biopsy. FDG-PET and ASL were equally sensitive in detecting tumor progression (83%). The specificity of ASL was superior to that of the other modalities (100%, 75%, and 50%, respectively). A combination of modalities did not augment the sensitivity, specificity, positive predictive value, or negative predictive value of ASL.

Abstract

CE-MR imaging, thallium SPECT, FDG-PET, and ASL-MR images from case 1 (A) with metastatic renal cell carcinoma to periventricular white matter of the posterior left lateral horn. CE-MR imaging shows new enhancement in the region treated. SPECT was positive while PET and ASL were negative for tumor recurrence. Biopsy of the target region indicated radiation necrosis in case 2 (B) with metastatic breast cancer to the right cerebellum. CE-MR imaging shows new enhancement in the region treated. PET (SUV = 6.6) and ASL were positive for tumor recurrence. Biopsy of the target region indicated tumor recurrence in case 3 (C) with metastatic melanoma to the right inferior frontal cortex. Only PET was positive for tumor recurrence (SUV = 10.7). Biopsy of the target region indicated tumor recurrence.
CE-MR imaging, thallium SPECT, FDG-PET, and ASL-MR images from case 1 (A) with metastatic renal cell carcinoma to periventricular white matter of the posterior left lateral horn. CE-MR imaging shows new enhancement in the region treated. SPECT was positive while PET and ASL were negative for tumor recurrence. Biopsy of the target region indicated radiation necrosis in case 2 (B) with metastatic breast cancer to the right cerebellum. CE-MR imaging shows new enhancement in the region treated. PET (SUV = 6.6) and ASL were positive for tumor recurrence. Biopsy of the target region indicated tumor recurrence in case 3 (C) with metastatic melanoma to the right inferior frontal cortex. Only PET was positive for tumor recurrence (SUV = 10.7). Biopsy of the target region indicated tumor recurrence.

BACKGROUND AND PURPOSE

Radiographic assessment of cerebral metastasis after stereotactic radiosurgery remains a major challenge in neuro-oncology. It is often difficult to distinguish tumor progression from radiation necrosis in this setting using conventional MR imaging. The objective of this study was to compare the diagnostic sensitivity and specificity of different functional imaging modalities for detecting tumor recurrence after stereotactic radiosurgery.

MATERIALS AND METHODS

We retrospectively reviewed patients treated between 2007 and 2010 and identified 14 patients with cerebral metastasis who had clinical or

The Contribution of Common Surgically Implanted Hardware to Functional MR Imaging Artifacts

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The authors calculated the BOLD-dependent MR imaging artifact impact arising from surgically implanted hardware through a retrospective analysis of fMRIs acquired from 2006–2014. Mean artifact volume associated with intracranial hardware was 4.3 cubic centimeters. The mean artifact volume from extracranial hardware in patients with cerebrovascular disease was 28.4 cubic centimeters. Artifacts had no-to-mild effects on clinical interpretability in all patients with intracranial implants. Extracranial hardware artifacts had no-to-moderate impact on clinical interpretability. The exceptions to interpretability in the face of hardware were ventriculoperitoneal shunts, particularly those with programmable valves and siphon gauges, and large numbers of KLS-Martin maxDrive screws.

Abstract

A representative patient (patient 3) with an intracranial implant. Signal drop-out from a left MCA Pharos Vitesse stent (Codman Neurovascular) is apparent on the magnitude BOLD fMRI image (A, white arrow), resulting in a total artifact volume of 2.1 cm3, which only mildly affected clinical interpretation of the examination. The patient was evaluated 2 years following implantation of the Pharos Vitesse stent in a stenosed left MCA. DSA (B) shows in-stent restenosis (black arrow), with corresponding decreased cerebrovascular reactivity (normalized CVR: voxel CVR normalized to cerebellar CVR) in the left MCA territory (C). In contrast, there is relative symmetry of the temporal signal-to-noise ratio (tSNR) map (D), suggesting that the asymmetric hemodynamic findings are not attributable to artifacts.
A representative patient (patient 3) with an intracranial implant. Signal drop-out from a left MCA Pharos Vitesse stent (Codman Neurovascular) is apparent on the magnitude BOLD fMRI image (A, white arrow), resulting in a total artifact volume of 2.1 cm3, which only mildly affected clinical interpretation of the examination. The patient was evaluated 2 years following implantation of the Pharos Vitesse stent in a stenosed left MCA. DSA (B) shows in-stent restenosis (black arrow), with corresponding decreased cerebrovascular reactivity (normalized CVR: voxel CVR normalized to cerebellar CVR) in the left MCA territory (C). In contrast, there is relative symmetry of the temporal signal-to-noise ratio (tSNR) map (D), suggesting that the asymmetric hemodynamic findings are not attributable to artifacts.

BACKGROUND AND PURPOSE

Blood oxygenation level–dependent MR imaging is increasingly used clinically to noninvasively assess cerebrovascular reactivity and/or language and motor function. However, many patients have metallic implants, which will induce susceptibility artifacts, rendering the functional information uninformative. Here, we calculate and interpret blood oxygenation level–dependent MR imaging artifact impact arising from surgically implanted hardware.

MATERIALS AND METHODS

A retrospective analysis of all blood oxygenation level–dependent MRIs (n = 343; B0 = 3T; TE = 35 ms; gradient …

Ultra-High-Field MRI Visualization of Cortical Multiple Sclerosis Lesions with T2 and T2*: A Postmortem MRI and Histopathology Study

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At 7T, 2D multiecho spin-echo T2WI and 3D gradient-echo T2*WI were acquired from 27 formalin-fixed coronal hemispheric brain sections of 15 patients and 4 healthy controls. Proteolipid-stained tissue sections were matched to the corresponding MR images, and lesions were manually scored on both MR imaging sequences and tissue sections. The T2WI sequence detected slightly more lesions than the T2*WI sequence (28% and 16%). When histopathologic information (type, location) was revealed to the reader, the sensitivity went up to 84%. Many lesions are still missed prospectively.

Abstract

Section stained with anti-proteolipid protein antibodies (A), matched with T2*WI (B) and T2WI (C and D). Note that the histologic section corresponds with multiple slices of the MR image; the top part of image B and D corresponds to the top part of image A, and the bottom part of image C corresponds to the bottom part of image A. The border between successive MR imaging slices is depicted by the blue dotted line. Lesions are indicated with arrows (WML is blue; GML is red). The type of GM lesion is indicated by I–IV. Also indicated is whether histologic lesions were retrospectively seen on MR imaging (asterisk) or missed on MR imaging (number sign). All other histologic lesions were prospectively detected. Degree of magnification: 50×.
Section stained with anti-proteolipid protein antibodies (A), matched with T2*WI (B) and T2WI (C and D). Note that the histologic section corresponds with multiple slices of the MR image; the top part of image B and D corresponds to the top part of image A, and the bottom part of image C corresponds to the bottom part of image A. The border between successive MR imaging slices is depicted by the blue dotted line. Lesions are indicated with arrows (WML is blue; GML is red). The type of GM lesion is indicated by I–IV. Also indicated is whether histologic lesions were retrospectively seen on MR imaging (asterisk) or missed on MR imaging (number sign). All other histologic lesions were prospectively detected. Degree of magnification: 50×.

BACKGROUND AND PURPOSE

At 7T MR imaging, T2*-weighted gradient echo has been shown to provide high-resolution anatomic images of gray matter lesions. However, few studies have verified T2*WI lesions histopathologically or compared them with more standard techniques at ultra-high-field strength. This study aimed to determine the sensitivity of T2WI and T2*WI sequences for detecting cortical GM lesions in MS.

MATERIALS AND METHODS

At 7T, 2D multiecho spin-echo T2WI and 3D gradient-echo T2*WI were acquired from 27 formalin-fixed coronal hemispheric brain sections of 15 patients and …

Nigrosome 1 Detection at 3T MRI for the Diagnosis of Early-Stage Idiopathic Parkinson Disease: Assessment of Diagnostic Accuracy and Agreement on Imaging Asymmetry and Clinical Laterality

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Nigrosomes are calbindin-poor zones within the substantia nigra pars compacta, and are the primary subregion where dopaminergic cells are lost in Parkinson disease. High-resolution 3D multiecho imaging was performed at 3T in 13 healthy subjects and 24 patients with idiopathic Parkinson disease confirmed by 18F-FP-CIT PET. Diagnostic sensitivity, specificity, and accuracy of the nigrosome 1 detection at 3T MR imaging was 100%, 84.6%, and 94.6%, respectively. Further, the clinical laterality was in high concordance with the laterality of the nigrosome 1 detection.

Abstract

Visual assessment of nigrosome 1 in MR imaging. On the oblique axial MEDIC imaging, the evaluation of nigrosome 1 (arrows) was performed on 3 sections: an upper section at the lower tip of the red nucleus and the 2 successive sections (A). The oblique coronal MEDIC imaging was also assessed on 3 sections: an anterior section at the anterior tip of the red nucleus and the 2 consecutive sections (B). In this particular 71-year-old woman, the nigrosome 1 appears normal on both sides.
Visual assessment of nigrosome 1 in MR imaging. On the oblique axial MEDIC imaging, the evaluation of nigrosome 1 (arrows) was performed on 3 sections: an upper section at the lower tip of the red nucleus and the 2 successive sections (A). The oblique coronal MEDIC imaging was also assessed on 3 sections: an anterior section at the anterior tip of the red nucleus and the 2 consecutive sections (B). In this particular 71-year-old woman, the nigrosome 1 appears normal on both sides.

BACKGROUND AND PURPOSE

In the early stages of idiopathic Parkinson disease, motor symptoms are usually asymmetric. We aimed to assess the feasibility of nigrosome 1 detection at 3T MR imaging to analyze the agreement of its asymmetry and clinical laterality.

MATERIALS AND METHODS

High-resolution 3D multiecho imaging was performed at 3T MR imaging in 13 healthy subjects and 24 patients with idiopathic Parkinson disease confirmed by N-3-fluoropropyl-2-β-carbomethoxy-3-β-(4-iodophenyl) nortropane (18F-FP-CIT) PET. The nigrosome 1 detection findings by using the MR imaging data were rated as “normal,” “possibly abnormal,” and “abnormal” by 2 independent reviewers. The degree of 18F-FP-CIT binding was visually assessed in the caudate nucleus and putamen on PET images. Clinical laterality was evaluated by scores of the Unified Parkinson Disease Rating Scale, Part III. Asymmetry of the affected nigrosome …

Progressive versus Nonprogressive Intracranial Dural Arteriovenous Fistulas: Characteristics and Outcomes

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Of 579 patients with intracranial dural arteriovenous fistulas, 545 had 1 fistula and 34 (5.9%) had enlarging, de novo, multiple, or recurrent fistulas. Of those 34 patients, 19 had progressive dural arteriovenous fistulas with de novo fistulas or fistula enlargement. Angioarchitectural correlates to chronically elevated intracranial venous pressures, such as venous sinus dilation and pseudophlebitic cortical venous pattern, were more common in progressive disease. Three young patients died despite endovascular, surgical, and radiosurgical treatments.

Abstract

Multiple and progressive DAVFs. Same patient as in Fig 3. DSA images before treatment at our institution but 4 years after initial proximal coil embolization of external carotid artery feeders below the skull base at an outside institution demonstrate multiple skull base fistulas associated with venous hypertension, cortical venous reflux, venous sinus dilation, and a jugular bulb outflow stenosis (between white arrows). (Upper row: right vertebral artery lateral, right vertebral artery lateral, left vertebral artery anteroposterior; lower row: left ICA anteroposterior, left external carotid artery anteroposterior, left external carotid artery lateral). A middle meningeal artery to the torcular fistula indicated by the white arrows is shown in greater detail in Fig 5.
Multiple and progressive DAVFs. Same patient as in Fig 3. DSA images before treatment at our institution but 4 years after initial proximal coil embolization of external carotid artery feeders below the skull base at an outside institution demonstrate multiple skull base fistulas associated with venous hypertension, cortical venous reflux, venous sinus dilation, and a jugular bulb outflow stenosis (between white arrows). (Upper row: right vertebral artery lateral, right vertebral artery lateral, left vertebral artery anteroposterior; lower row: left ICA anteroposterior, left external carotid artery anteroposterior, left external carotid artery lateral). A middle meningeal artery to the torcular fistula indicated by the white arrows is shown in greater detail in Fig 5.

BACKGROUND AND PURPOSE

A minority of intracranial dural arteriovenous fistulas progress with time. We sought to determine features that predict progression and define outcomes of patients with progressive dural arteriovenous fistulas.

MATERIALS AND METHODS

We performed a retrospective imaging and clinical record review of patients with intracranial dural arteriovenous fistula evaluated at our hospital.

RESULTS

Of 579 patients with intracranial dural arteriovenous fistulas, 545 had 1 fistula (mean age, 45 ± 23 years) and 34 (5.9%) had enlarging, de novo, multiple, or recurrent fistulas (mean age, 53 ± 20 years; P = .11). Among these 34 patients, 19 had progressive dural arteriovenous fistulas with de novo fistulas or fistula

Meta-Analysis of CSF Diversion Procedures and Dural Venous Sinus Stenting in the Setting of Medically Refractory Idiopathic Intracranial Hypertension

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The authors performed a PubMed search of all peer-reviewed articles from 1988–2014 for patients who underwent a procedure for medically refractory idiopathic intracranial hypertension. The CSF diversion procedure analysis included 435 patients. Postprocedure in this group, there was improvement of vision in 54%, headache in 80%, and papilledema in 70%. The dural venous sinus stenting analysis included 136 patients. In this group, after intervention, there was improvement of vision in 78%, headache in 83%, and papilledema in 97% of patients. The current clinical paradigm of CSF diversion first should be re-examined given the good technical success and low complication rates of stenting.

Abstract

BACKGROUND AND PURPOSE

In medically refractory idiopathic intracranial hypertension, optic nerve sheath fenestration or CSF shunting is considered the next line of management. Venous sinus stenosis has been increasingly recognized as a treatable cause of elevated intracranial pressure in a subset of patients. In this article, we present the results of the largest meta-analysis of optic nerve sheath fenestration, CSF shunting, and dural venous sinus stenting. This is the only article that compares these procedures, to our knowledge.

MATERIALS AND METHODS

We performed a PubMed search of all peer-reviewed articles from 1988 to 2014 for patients who underwent a procedure for medically refractory idiopathic intracranial hypertension.

RESULTS

Optic nerve sheath fenestration analysis included 712 patients. Postprocedure, there was improvement of vision in 59%, headache in 44%, and papilledema in 80%; 14.8% of patients required a repeat procedure with major and minor complication rates of 1.5% and 16.4%, respectively. The CSF diversion procedure analysis included 435 patients. Postprocedure, there was improvement of vision in 54%, headache in 80%, and papilledema in 70%; 43% of patients required at least 1 additional surgery. The major and minor complication rates were 7.6% and 32.9%, respectively. The dural

Seizure Frequency Can Alter Brain Connectivity: Evidence from Resting-State fMRI

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Resting-state fMRI data from 36 patients with hot-water epilepsy (18 with infrequent seizures) and 18 healthy age- and sex-matched controls were analyzed for seed-to-voxel connectivity. Patients in the frequent-seizure group had increased connectivity within the medial temporal structures and widespread areas of poor connectivity, including the default mode network. Seizure frequency can alter functional brain connectivity, which can be visualized by resting-state fMRI.

Abstract

Whole-brain cluster-correlation maps of seed-to-voxel–based resting-state functional connectivity for the PCC seed region (FDR-corrected P < .001). Shown is DMN connectivity using PCC seed at 3 different axial levels: at the level of ventricles in the top row, midbrain in the middle row, and the cerebellum in the bottom row for healthy controls (A), the infrequent-seizure group (B), the frequent-seizure group (C), the infrequent-seizure group versus healthy controls (D), the frequent-seizure group versus healthy controls (E), and the infrequent-seizure group versus the frequent-seizure group (F). The colors represent the significance of connectivity; red indicates an increase in connectivity, and blue indicates a decrease in connectivity.
Whole-brain cluster-correlation maps of seed-to-voxel–based resting-state functional connectivity for the PCC seed region (FDR-corrected P < .001). Shown is DMN connectivity using PCC seed at 3 different axial levels: at the level of ventricles in the top row, midbrain in the middle row, and the cerebellum in the bottom row for healthy controls (A), the infrequent-seizure group (B), the frequent-seizure group (C), the infrequent-seizure group versus healthy controls (D), the frequent-seizure group versus healthy controls (E), and the infrequent-seizure group versus the frequent-seizure group (F). The colors represent the significance of connectivity; red indicates an increase in connectivity, and blue indicates a decrease in connectivity.

BACKGROUND AND PURPOSE

The frequency of seizures is an important factor that can alter functional brain connectivity. Analysis of this factor in patients with epilepsy is complex because of disease- and medication-induced confounders. Because patients with hot-water epilepsy generally are not on long-term drug therapy, we used seed-based connectivity analysis in these patients to assess connectivity changes associated with seizure frequency without confounding from antiepileptic drugs.

MATERIALS AND METHODS

Resting-state fMRI data from 36 patients with hot-water epilepsy (18 with frequent seizures [>2 per month] and 18 with infrequent seizures [≤2 per month]) and 18 healthy age- and sex-matched controls were analyzed for seed-to-voxel connectivity by using 106 seeds. Voxel wise paired t-test analysis (P < .005, corrected for false-discovery rate) was used to identify

Repeatability of Standardized and Normalized Relative CBV in Patients with Newly Diagnosed Glioblastoma

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Relative CBV estimates were calculated from dynamic susceptibility contrast MR imaging in double-baseline examinations of 33 patients with treatment-naïve and pathologically proved glioblastoma multiforme. Normalized and standardized relative CBV were calculated by using 6 common postprocessing methods. The ΔR2* estimation method that incorporates leakage correction offers the best repeatability for rCBV, with standardized rCBV being less variable.

Abstract

Visual comparison of nRCBV and sRCBV. Methods 1–6 (across) for visit 1 (top 2 rows) and visit 2 (bottom 2 rows) in the same subject in approximately the same section for visits 1 and 2. All data are presented with the same respective scale for nRCBV or sRCBV and are in arbitrary units.
Visual comparison of nRCBV and sRCBV. Methods 1–6 (across) for visit 1 (top 2 rows) and visit 2 (bottom 2 rows) in the same subject in approximately the same section for visits 1 and 2. All data are presented with the same respective scale for nRCBV or sRCBV and are in arbitrary units.

Background and Purpose

For more widespread clinical use advanced imaging methods such as relative cerebral blood volume must be both accurate and repeatable. The aim of this study was to determine the repeatability of relative CBV measurements in newly diagnosed glioblastoma multiforme by using several of the most commonly published estimation techniques.

Materials and Methods

The relative CBV estimates were calculated from dynamic susceptibility contrast MR imaging in double-baseline examinations for 33 patients with treatment-naïve and pathologically proved glioblastoma multiforme (men = 20; mean age = 55 years). Normalized and standardized relative CBV were calculated by using 6 common postprocessing methods. The repeatability of both normalized and standardized relative CBV, in both tumor and contralateral brain, was examined for each method with metrics of repeatability, including the repeatability coefficient and within-subject coefficient of variation. The minimum sample size required to detect a parameter change of 10% or 20% was also determined for both normalized relative CBV and standardized relative CBV for each estimation method.

Results

When ordered by the repeatability coefficient, methods using postprocessing leakage correction and ΔR2*(t) techniques offered superior repeatability. Across processing techniques, …

Aqueductal Stroke Volume: Comparisons with Intracranial Pressure Scores in Idiopathic Normal Pressure Hydrocephalus

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Phase-contrast MR imaging was performed in 21 patients with probable idiopathic normal pressure hydrocephalus. Patients were selected for shunting on the basis of pathologically increased intracranial pressure pulsatility. Patients with shunts were offered a second MR imaging after 12 months. Ventricular volume and transverse aqueductal area were calculated. No correlations between aqueductal stroke volume and preoperative scores of mean intracranial pressure or mean wave amplitudes were observed. Aqueductal stroke volume does not reflect intracranial pressure pulsatility or symptom score, but rather aqueduct area and ventricular volume.

Abstract

ASV (A) and ventricular volume (B) are presented for patients with shunts and iNPH before (n = 17) and after (n = 12) shunting (surgery group) and for conservatively managed patients with iNPH (conservative group, n = 4) before management. Significance levels are presented in the plots.
ASV (A) and ventricular volume (B) are presented for patients with shunts and iNPH before (n = 17) and after (n = 12) shunting (surgery group) and for conservatively managed patients with iNPH (conservative group, n = 4) before management. Significance levels are presented in the plots.

Background and Purpose

Aqueductal stroke volume from phase-contrast MR imaging has been proposed for predicting shunt response in normal pressure hydrocephalus. However, this biomarker has remained controversial in use and has a lack of validation with invasive intracranial monitoring. We studied how aqueductal stroke volume compares with intracranial pressure scores in the presurgical work-up and clinical score, ventricular volume, and aqueduct area and assessed the patient’s response to shunting.

Materials and Methods

Phase-contrast MR imaging was performed in 21 patients with probable idiopathic normal pressure hydrocephalus. Patients were selected for shunting on the basis of pathologically increased intracranial pressure pulsatility. Patients with shunts were offered a second MR imaging after 12 months. Ventricular volume and transverse aqueductal area were calculated, as well as clinical symptom score.

Results

No correlations between aqueductal stroke volume and preoperative scores of mean intracranial pressure or mean wave amplitudes were observed. Preoperative aqueductal stroke volume was not different between patients with …