Quantitative volumetric MRI study of the cerebellum and vermis in schizophrenia: clinical and cognitive correlates

OBJECTIVE

Recent evidence suggests that the cerebellum may play a role in higher cognitive functions and, therefore, may play an important role in schizophrenia.

METHOD

The authors used magnetic resonance imaging to measure cerebellum and vermis volume in 15 patients with schizophrenia and 15 normal comparison subjects.

RESULTS

They found that 1) vermis volume was greater in patients with schizophrenia than in normal subjects, 2) greater vermis white matter volume in the patients with schizophrenia significantly correlated with severity of positive symptoms and thought disorder and with impairment in verbal logical memory, and 3) patients with schizophrenia showed a trend for more cerebellar hemispheric volume asymmetry (left greater than right).

CONCLUSIONS

These data suggest that an abnormality in the vermis may contribute to the pathophysiology of schizophrenia.

Subgenual cingulate cortex volume in first-episode psychosis

OBJECTIVE

Gray matter volume and glucose utilization have been reported to be reduced in the left subgenual cingulate of subjects with familial bipolar or unipolar depression. It is unclear whether these findings are secondary to recurrent illness or are part of a familial/genetic syndrome. The authors' goal was to clarify these findings.

METHOD

Volumetric analyses were performed by using magnetic resonance imaging in 41 patients experiencing their first episode of affective disorder or schizophrenia and in 20 normal comparison subjects.

RESULTS

The left subgenual cingulate volume of the patients with affective disorder who had a family history of affective disorder was smaller than that of patients with affective disorder with no family history of the illness and the normal comparison subjects. Patients with schizophrenia did not differ from comparison subjects in left subgenual cingulate volume.

CONCLUSIONS

Left subgenual cingulate abnormalities are present at first hospitalization for psychotic affective disorder in patients who have a family history of affective disorder.

Effects of creatine supplementation on the energy cost of muscle contraction: a 31P-MRS study

Five women and 3 men (29.8 +/- 1.4 yr) performed dynamic knee-extension exercise inside a magnetic resonance system (means +/- SE). Two trials were performed 7-14 days apart, consisting of a 4- to 5-min exhaustive exercise bout. To determine quadriceps cost of contraction, brief static and dynamic contractions were performed pre- and postexercise. (31)P spectra were used to determine pH and relative concentrations of P(i), phosphocreatine (PCr), and betaATP. Subjects consumed 0.3 g. kg(-1). day(-1) of a placebo (trial 1) or creatine (trial 2) for 5 days before each trial. After creatine supplementation, resting DeltaPCr increased from 40.7 +/- 1.8 to 46. 6 +/- 1.1 mmol/kg (P = 0.04) and PCr during exercise declined from -29.6 +/- 2.4 to -34.1 +/- 2.8 mmol/kg (P = 0.02). Muscle static (DeltaATP/N) and dynamic (DeltaATP/J) costs of contraction were unaffected by creatine supplementation as well as were ATP, P(i), pH, PCr resynthesis rate, and muscle strength and endurance. DeltaATP/J and DeltaATP/N were greatest at the onset of the exercise protocol (P < 0.01). In summary, creatine supplementation increased muscle PCr concentration, which did not affect muscle ATP cost of contraction.

Schizotypal personality disorder and MRI abnormalities of temporal lobe gray matter

BACKGROUND

Structural MRI data indicate schizophrenics have reduced left-sided temporal lobe gray matter volumes, especially in the superior temporal gyrus (STG) and medial temporal lobe. Our data further suggest a specificity to schizophrenia spectrum disorders of STG volume reduction. Interpretation of research studies involving schizophrenics may be complicated by the effects of exposure to neuroleptics and chronic illness. Sharing the same genetic diathesis of schizophrenics, subjects with schizotypal personality disorder (SPD) offer a unique opportunity to evaluate commonalities between schizophrenia and SPD, particularly as SPD subjects are characterized by cognitive and perceptual distortions, an inability to tolerate close friendships, and odd behavior, but they are not psychotic and so have generally not been prescribed neuroleptics nor hospitalized. Evaluation of brain structure in SPD may thus offer insight into the "endophenotype" common to both disorders. In addition, differences between groups may suggest which are the brain structures of schizophrenics that contribute to the development of psychosis.

METHODS

To test the hypothesis of whether SPD subjects might show similar STG abnormalities, STG and medial temporal lobe regions of interest (ROI) were manually drawn on high resolution coronal MRI 1.5 mm thick slices. Images were derived from 16 right-handed male SPD subjects, without regard to family history, and 14 healthy, right-handed, comparison males who did not differ from the SPD group on parental socio-economic status, age, or verbal IQ.

RESULTS

As predicted, SPD subjects showed a reduction in left STG gray matter volume compared with age and gender matched comparison subjects. SPD subjects also showed reduced parahippocampal left/right asymmetry and a high degree of disordered thinking. Comparisons with chronic schizophrenics previously studied by us showed the SPD group had a similarity of left STG gray matter volume reduction, but fewer medial temporal lobe abnormalities.

CONCLUSIONS

These abnormalities strengthen the hypothesis of a temporal lobe abnormality in SPD, and the similarity of STG findings in schizophrenia and SPD suggest that STG abnormalities may be part of the spectrum "endophenotype." It is also possible that presence of medial temporal lobe abnormalities may help to differentiate who will develop schizophrenia and who will develop the less severe schizophrenia spectrum disorder, SPD.

The postmigrational development of polymicrogyria documented by magnetic resonance imaging from 31 weeks' postconceptional age

We report the case of a 27-week premature infant in whom magnetic resonance imaging (MRI) at 4 postnatal weeks (postconceptional age, 31 weeks), term, and 6 months of age documented the postnatal postmigrational evolution of bilateral perisylvian polymicrogyria. The polymicrogyria was readily detected by ultrafine 1.5-mm coronal slices on three-dimensional, Fourier-transformed, spoiled gradient-recalled and T2-weighted MRI sequences. These MRI sequences provide the first in vivo documentation of the postmigrational evolution of polymicrogyria. The likelihood that the polymicrogyria was related to an ischemic encephaloclastic mechanism is supported by the simultaneous occurrence of periventricular leukomalacia.

Partial wavelet encoding: a new approach for accelerating temporal resolution in contrast-enhanced MR imaging

We propose a new approach using wavelet encoding to improve temporal resolution in contrast-enhanced magnetic resonance (MR) imaging. Exploiting the unique property of wavelets localized in space and frequency, we construct an efficient encoding scheme to capture signal changes due to contrast agent uptake, which in general is spatially localized with low- and mid-range frequency components. On the basis of space-frequency analysis, we describe mathematical formulations of our method and discuss its theoretical advantages over Fourier-based phase-encoding methods (the keyhole and reduced-encoding imaging by generalized-series reconstruction [RIGR] techniques). The results obtained in computer simulations and a phantom study demonstrate the feasibility and practical advantages of our approach.

Determination of the optimal delay between sonications during focused ultrasound surgery in rabbits by using MR imaging to monitor thermal buildup in vivo

PURPOSE

To use magnetic resonance (MR) imaging to monitor thermal buildup and its effects in treated tissues during sequentially delivered sonications in vivo to optimize the intersonication delay for any set of ultrasound and tissue parameters.

MATERIALS AND METHODS

Sequential sonications were delivered next to each other in both thighs in 10 male New Zealand white rabbits. The time between sonications was 11-60 seconds. Phase-difference MR imaging was used to monitor temperature rise, which was used to estimate the thermal dose delivered to the tissue. T2-weighted and contrast agent-enhanced T1-weighted imaging were used to gauge the extent of tissue coagulation.

RESULTS

With a short intersonication delay (11-40 seconds), the estimated temperature rise and the extent of tissue coagulation increased dramatically in subsequent sonications. However, when the delay was long (50-60 seconds), the size and shape of the destroyed tissue with subsequent sonications was uniform, and the temperature buildup was substantially lower.

CONCLUSION

MR imaging can be used to monitor thermal buildup and its effects due to sequential, neighboring sonications in vivo to produce evenly shaped regions of tissue coagulation. The temperature information obtained from the monitoring can be used to optimize the intersonication delay for any set of ultrasound and tissue parameters.

Intraoperative MR imaging guidance for intracranial neurosurgery: experience with the first 200 cases

PURPOSE

To review preliminary experience with an open-bore magnetic resonance (MR) imaging system for guidance in intracranial surgical procedures.

MATERIALS AND METHODS

A vertically oriented, open-configuration 0.5-T MR imager was housed in a sterile procedure room. Receive and transmit surface coils were wrapped around the patient's head, and images were displayed on monitors mounted in the gap of the magnet and visible to surgeons. During 2 years, 200 intracranial procedures were performed.

RESULTS

There were 111 craniotomies, 68 biopsies, 12 intracranial cyst evaluations, four subdural drainages, and five transsphenoidal pituitary resections performed with the intraoperative MR unit. In each case, the intraoperative MR system yielded satisfactory results by allowing the radiologist to guide surgeons toward lesions and to assist in treatment. In two patients, hyperacute hemorrhage was noted and removed. The duration of the procedure and the complication rate were similar to those of conventional surgery.

CONCLUSION

Intraoperative MR imaging was successfully implemented for a variety of intracranial procedures and provided continuous visual feedback, which can be helpful in all stages of neurosurgical intervention without affecting the duration of the procedure or the incidence of complications. This system has potential advantages over conventional frame-based and frameless stereotactic procedures with respect to the safety and effectiveness of neurosurgical interventions.

Early detection of periventricular leukomalacia by diffusion-weighted magnetic resonance imaging techniques

Periventricular leukomalacia (PVL), the principal form of brain injury in the premature infant, is characterized by overt focal necrotic lesions in periventricular white matter and less prominent, more diffuse cerebral white matter injury. The early detection of the latter, diffuse component of PVL is not consistently possible with conventional brain imaging techniques. We demonstrate the early detection of the diffuse component of PVL by diffusion-weighted magnetic resonance imaging (DWI). In a premature infant with no definite cerebral abnormality detectable by cranial ultrasonography or conventional magnetic resonance imaging, DWI showed a striking bilateral decrease in water diffusion in cerebral white matter. The DWI abnormality (ie, decreased apparent diffusion coefficient) was similar to that observed with acute cerebral ischemic lesions in adults. At 10 weeks of age, conventional magnetic resonance imaging and ultrasonography showed striking changes consistent with PVL, including the presence of small cysts. The observations indicate the importance of DWI in the early identification of the diffuse component of PVL and also perhaps the role of ischemia in the pathogenesis of the lesion.

Quantitative follow-up of patients with multiple sclerosis using MRI: reproducibility

The reproducibility of an automated method for estimating the volume of white matter abnormalities on brain magnetic resonance (MR) images of multiple sclerosis (MS) patients was evaluated. Twenty MS patients underwent MR imaging twice within 30 minutes. Measurement variability is introduced mainly by MRI acquisition and image registration procedures, which demonstrate significantly worse reproducibility than the image segmentation. The correction of partial volume artifacts is essential for sensitive measurements of overall lesion burden. The average lesion volume difference (bias) between two MR exams of the same MS patient (N = 20) was 0.05 cm3, with a 95% confidence interval between -0.17 and +0.28 cm3, suggesting that the proposed measurement system is suitable for clinical follow-up trials, even in relatively small patient cohorts. The limits of agreement for lesion volume were between -1.3 and +1.5 cm3, implying that in individual patients changes in lesion load need to be at least this large to be detected reliably. This automated method for estimating lesion burden is a reliable tool for the evaluation of MS progression and exacerbation in patient cohorts and potentially also in individual patients.

Quantitative follow-up of patients with multiple sclerosis using MRI: technical aspects

A highly reproducible automated procedure for quantitative analysis of serial brain magnetic resonance (MR) images was developed for use in patients with multiple sclerosis (MS). The intracranial cavity (ICC) was identified on standard dual-echo spin-echo brain MR images using a supervised automated procedure. MR images obtained from one MS patient at 24 time points in the course of a 1-year follow-up were aligned with the images of one of the time points. Next, the contents of the ICC in each MR exam were segmented into four tissues, using a self-adaptive statistical algorithm. Misclassifications due to partial voluming were corrected using a combination of morphologic operators and connectivity criteria. Finally, a connectivity detection algorithm was used to separate the tissue classified as lesions into individual entities. Registration, classification of the contents of the ICC, and identification of individual lesions are fully automatic. Only identification of the ICC requires operator interaction. In each MR exam, the program estimated volumes for the ICC, gray matter (GM), white matter (WM), white matter lesions (WML), and cerebrospinal fluid (CSF). The reproducibility of the system was superior to that of supervised segmentation, as evidenced by the coefficient of variation: CSF supervised 45.9% vs. automated 7.7%, GM 16.0% vs. 1.4%, WM 15.7% vs. 1.3%, and WML 39.5% vs 52.0%. Our results demonstrate that this computerized procedure allows routine reproducible quantitative analysis of large serial MRI data sets.

Left planum temporale volume reduction in schizophrenia

BACKGROUND

The planum temporale, located on the posterior and superior surface of the temporal lobe, is a brain region thought to be a biological substrate of language and possibly implicated in the pathophysiology of schizophrenia. To investigate further the role of planum temporale abnormalities in schizophrenia, we measured gray matter volume underlying the planum temporale from high spatial resolution magnetic resonance imaging techniques.

METHODS

Sixteen male patients with chronic schizophrenia and 16 control subjects were matched for age, sex, handedness, and parental socioeconomic status. Magnetic resonance imaging images were obtained from a 1.5-T magnet.

RESULTS

Gray matter volume was significantly reduced in the left planum temporale (28.2%) in schizophrenic patients compared with normal controls. Schizophrenic patients showed a reversal of the left greater than right planum temporale asymmetry found in normal controls. Heschl's gyrus (primary auditory cortex) showed no differences between the left and right sides in either group. Of note, the Suspiciousness/Persecution subscale score of the Positive and Negative Syndrome Scale was associated with reduced left planum temporale volume in schizophrenic patients.

CONCLUSIONS

Patients with schizophrenia have reduced left planum temporale gray matter and a reversal of planum temporale asymmetry, which may underlie an impairment in language processing and symptoms of suspiciousness or persecution characteristic of schizophrenia.

Multi-component apparent diffusion coefficients in human brain

The signal decay with increasing b-factor at fixed echo time from brain tissue in vivo has been measured using a line scan Stejskal-Tanner spin echo diffusion approach in eight healthy adult volunteers. The use of a 175 ms echo time and maximum gradient strengths of 10 mT/m allowed 64 b-factors to be sampled, ranging from 5 to 6000 s/ mm2, a maximum some three times larger than that typically used for diffusion imaging. The signal decay with b-factor over this extended range showed a decidedly non-exponential behavior well-suited to biexponential modeling. Statistical analyses of the fitted biexponential parameters from over 125 brain voxels (15 x 15 x 1 mm3 volume) per volunteer yielded a mean volume fraction of 0.74 which decayed with a typical apparent diffusion coefficient around 1.4 microm2/ms. The remaining fraction had an apparent diffusion coefficient of approximately 0.25 microm2/ms. Simple models which might explain the non-exponential behavior, such as intra- and extracellular water compartmentation with slow exchange, appear inadequate for a complete description. For typical diffusion imaging with b-factors below 2000 s/mm2, the standard model of monoexponential signal decay with b-factor, apparent diffusion coefficient values around 0.7 microm2/ms, and a sensitivity to diffusion gradient direction may appear appropriate. Over a more extended but readily accessible b-factor range, however, the complexity of brain signal decay with b-factor increases, offering a greater parametrization of the water diffusion process for tissue characterization.

MR imaging of pelvic floor continence mechanisms in the supine and sitting positions

OBJECTIVE

Our goal was to determine the anatomic differences in pelvic floor anatomy for continent women and women with stress incontinence using MR imaging and to assess whether these anatomic differences depend on the position of the subject during imaging.

SUBJECTS AND METHODS

Eight continent volunteers and eight women with stress incontinence underwent MR imaging in the supine and sitting positions. For imaging, we used an open-configuration 0.5-T magnet. T2-weighted images were obtained in the midline sagittal plane with subjects at rest and at maximal pelvic floor strain in 5 sec using a modified fast spin-echo sequence. In the axial plane, thin-section T2-weighted images were obtained with subjects at rest using a standard fast spin-echo technique. Images were evaluated for mobility of the urethra and bladder neck and for integrity of the vagina, levator ani, and supporting fascia.

RESULTS

Pelvic floor laxity and abnormalities of the supporting fascia were more common in incontinent women than in continent women. Both descent of the bladder neck when subjects strained and the posterior urethrovesical angle were not significantly greater when subjects were measured in the sitting position (p < .1).

CONCLUSION

Changes of pelvic floor laxity related to incontinence can be seen with subjects in both the supine and the sitting positions but are increased in the sitting position.

A simple method of scalp localization using multiplanar reconstruction of MR images

BACKGROUND

Image-based scalp localization methods currently used are complex and not standardized. The authors have developed a simple yet accurate method for craniotomy localization using multiplanar reconstruction (MPR) algorithms.

METHODS

In this method, the goal is to localize a projected point (defined as T) of the center of the lesion on the scalp. An oblique coronal plane is reformatted using a patient's magnetic resonance (MR) images with MPR algorithms to include both the center of the lesion and bilateral external auditory meati. Then the distance between T and the ipsilateral external auditory meatus or sagittal suture (defined as S) is measured along the scalp contour in the plane. The distance between the bregma and S is also measured. These distances are used for scalp localization, using a tape measure in the operating room.

RESULTS

We have had successful scalp localization in six clinical cases. It took about 3 min to measure each distance on the MR console.

CONCLUSION

This method for craniotomy planning using MPR algorithms is simple and sufficiently accurate.

MRI monitoring of laser ablation using optical flow

The optical flow method is used for visualizing and quantifying the dynamics of tissue changes observed by MRI during thermal ablations. An approach was implemented for parallel two-dimensional optical flow calculations including the replacement of spurious velocities. Velocity magnitude results were found to be accurate in low-noise cases in tests using series of synthetic images. Optical flow results are presented from thermal ablation experiments utilizing a homogeneous polyacrylamide gel phantom and heterogeneous rabbit liver tissue in vivo, exhibiting heating and cooling with the accompanying quantitative characterization of the dilation and contraction of the thermally affected region. Results demonstrate that optical flow is capable of noninvasive real-time monitoring and control of interstitial laser therapy (ILT).

Endoscopic sinus surgery with magnetic resonance imaging guidance: initial patient experience

We report the first endoscopic surgeries performed with patients under general anesthesia using intraoperative guidance with MRI. The procedures were experimental and intended to test (1) the unusual working environment of a unique new "open-configuration" MRI unit for head and neck surgery, and (2) real-time image guidance. Twelve patients underwent endoscopic sinus surgery while under general anesthesia in a new open MRI unit that provides the surgeon with access to the patient while imaging is performed. Eleven patients had chronic sinusitis (eight of them had bilateral disease), and one had a right nasoethmoid and antral tumor. All 12 surgeries were performed without complications. Both the endoscopic view and the MRI scans were available at the surgical field. The image plane was surgeon controlled, and the MRI updated images in as little as 14 seconds. MRI provided adequate visualization of both the disease and the related anatomy and allowed the surgeon to navigate during the procedure. The intraoperative data reflect the tissue changes during surgery and provide optimum feedback for surgical guidance. Although the operating environment poses some limitations, it has become apparent that intraoperative MRI has a role in the treatment of head and neck disorders and warrants further study.

Microstructural development of human newborn cerebral white matter assessed in vivo by diffusion tensor magnetic resonance imaging

Alterations of the architecture of cerebral white matter in the developing human brain can affect cortical development and result in functional disabilities. A line scan diffusion-weighted magnetic resonance imaging (MRI) sequence with diffusion tensor analysis was applied to measure the apparent diffusion coefficient, to calculate relative anisotropy, and to delineate three-dimensional fiber architecture in cerebral white matter in preterm (n = 17) and full-term infants (n = 7). To assess effects of prematurity on cerebral white matter development, early gestation preterm infants (n = 10) were studied a second time at term. In the central white matter the mean apparent diffusion coefficient at 28 wk was high, 1.8 microm2/ms, and decreased toward term to 1.2 microm2/ms. In the posterior limb of the internal capsule, the mean apparent diffusion coefficients at both times were similar (1.2 versus 1.1 microm2/ms). Relative anisotropy was higher the closer birth was to term with greater absolute values in the internal capsule than in the central white matter. Preterm infants at term showed higher mean diffusion coefficients in the central white matter (1.4 +/- 0.24 versus 1.15 +/- 0.09 microm2/ms, p = 0.016) and lower relative anisotropy in both areas compared with full-term infants (white matter, 10.9 +/- 0.6 versus 22.9 +/- 3.0%, p = 0.001; internal capsule, 24.0 +/- 4.44 versus 33.1 +/- 0.6% p = 0.006). Nonmyelinated fibers in the corpus callosum were visible by diffusion tensor MRI as early as 28 wk; full-term and preterm infants at term showed marked differences in white matter fiber organization. The data indicate that quantitative assessment of water diffusion by diffusion tensor MRI provides insight into microstructural development in cerebral white matter in living infants.

Optimization of chemical shift selective suppression of fat

Strategies to optimize flip angles for chemical shift selective fat suppression are discussed. Mathematical models for fat suppression in spoiled gradient recalled acquisition, spin echo, and RARE, which incorporate steady state conditions and multiple spectral components of fat, are developed. The optimal suppression flip angle is found to be larger than that determined with a single fat component model by more than 10 degrees due to contributions from unflipped components such as olefinic and glycerol protons that lie outside the suppression band.

Creatine supplementation and age influence muscle metabolism during exercise

Young [n = 5, 30 +/- 5 (SD) yr] and middle-aged (n = 4, 58 +/- 4 yr) men and women performed single-leg knee-extension exercise inside a whole body magnetic resonance system. Two trials were performed 7 days apart and consisted of two 2-min bouts and a third bout continued to exhaustion, all separated by 3 min of recovery. 31P spectra were used to determine pH and relative concentrations of Pi, phosphocreatine (PCr), and beta-ATP every 10 s. The subjects consumed 0.3 g . kg-1 . day-1 of a placebo (trial 1) or creatine (trial 2) for 5 days before each trial. During the placebo trial, the middle-aged group had a lower resting PCr compared with the young group (35.0 +/- 5.2 vs. 39.5 +/- 5.1 mmol/kg, P < 0.05) and a lower mean initial PCr resynthesis rate (18.1 +/- 3.5 vs. 23.2 +/- 6.0 mmol . kg-1 . min-1, P < 0.05). After creatine supplementation, resting PCr increased 15% (P < 0.05) in the young group and 30% (P < 0.05) in the middle-aged group to 45.7 +/- 7.5 vs. 45.7 +/- 5.5 mmol/kg, respectively. Mean initial PCr resynthesis rate also increased in the middle-aged group (P < 0.05) to a level not different from the young group (24.3 +/- 3.8 vs. 24.2 +/- 3.2 mmol . kg-1 . min-1). Time to exhaustion was increased in both groups combined after creatine supplementation (118 +/- 34 vs. 154 +/- 70 s, P < 0.05). In conclusion, creatine supplementation has a greater effect on PCr availability and resynthesis rate in middle-aged compared with younger persons.

Digital wavelet-encoded MRI: a new wavelet-encoding methodology

A new digital wavelet-encoding method for MRI is described. The method differs from previously described wavelet-encoding approaches, because the point-spread function is made independent of the wavelet basis used. This has a significant practical advantage, because wavelet bases can now be considered that would otherwise be excluded due to the difficulty of precisely exciting wavelet-shaped RF profiles. The method has been implemented on a clinical MRI system, and human images are presented.