Diffusion tensor trace mapping in normal adult brain using single-shot epi technique: A methodological study of the aging brain

Purpose: To quantify age-related changes of the average diffusion coefficient value in normal adult brain using orientation-independent diffusion tensor trace mapping and to address the methodological influences on diffusion quantification.

Material and Methods: Fifty-four normal subjects (aged 20-79 years) were studied on a 1.5-T whole-body MR medical unit using a diffusion-weighted single-shot echo-planar imaging technique. Orientation-independent diffusion tensor trace maps were constructed for each subject using diffusion-weighted MR measurements in four different directions using a tetrahedral gradient combination pattern. The global average (including cerebral spinal fluid) and the tissue average of diffusion coefficients in adult brains were determined by analyzing the diffusion coefficient distribution histogram for the entire brain. Methodological influences on the measured diffusion coefficient were also investigated by comparing the results obtained using different experimental settings.

Results: Both global and tissue averages of the diffusion coefficient are significantly correlated with age ( p<0.03). The global average of the diffusion coefficient increases 3% per decade after the age of 40, whereas the increase in the tissue average of diffusion coefficient is about 1% per decade. Experimental settings for self-diffusion measurements, such as data acquisition methods and number of b-values, can slightly influence the statistical distribution histogram of the diffusion tensor trace and its average value.

Conclusion: Increased average diffusion coefficient in adult brains with aging are consistent with findings regarding structural changes in the brain that have been associated with aging. The study also demonstrates that it is desirable to use the same experimental parameters for diffusion coefficient quantification when comparing between different subjects and groups of interest.

Positron Emission Tomography Compared with Magnetic Resonance Imaging and Computed Tomography in Supratentorial Gliomas Using Multiple Stereotactic Biopsies as Reference

Ten patients with findings at computed tomography (CT) suggesting intracranial supratentorial glioma were investigated to compare the diagnostic efficacy of this technique with that of positron emission tomography (PET) using 11C-methionine and exminations with magnetic resonance (MR). The findings were related to histopathologic examination of serial stereotactic biopsies, which were guided by the appearance of the lesions on PET examination. To obtain corresponding slice orientation with the different examination techniques, an individually shaped helmet fixation was used. However, in 3 cases this fixation device could not be used for MR. Histopathologic diagnosis, obtained in all cases from multiple target stereotactic biopsies, included glioma in 9 patients and reactive gliosis in one case. A detailed comparison of the three imaging techniques and the findings at stereotactic biopsies was possible in 7 patients, while in 3 patients comparison with MR was less exact due to the patient's refusal to wear the helmet during this examination. MR was the most accurate method for outlining the total extent of a lesion, i.e. the tumor and the edema surrounding it. Four lesions had homogeneous signal characteristics and in 6 lesions two (or more) compartments could be distinguished with MR. In 5 cases the MR findings were in complete agreement with the histopathologic findings. However, a thorough correlation between signal characteristics and histology was not possible. Using PET the occurrence and the extent of tumor tissue was correctly predicted in 7 patients. The PET was normal in one case. Findings at CT were in agreement with the histopathologic diagnosis in 5 patients. MR was the most sensitive method for the detection of lesions. PET using methionine appeared to have a somewhat higher capacity to outline correctly the true extent of a tumor. The combination of CT and PET was superior to MR for determining the type and grade of the tumors.

MR Imaging of Adult Colo-Rectal Intussusception

MR imaging of an intussuscepted sigmoid cancer misinterpreted as a rectal carcinoma is described. High-resolution technique with pelvic-phased array coils and fast spin-echo was used. The diagnosis is discussed in relation to the MR findings.

The nervous system in early HIV infection: a prospective study through 7 years

In this study 28 patients with early stage HIV infection (CD4 >280 x 10(6)/l) were subjected to yearly examinations of the nervous system up to 7 years in order to detect any deterioration. Clinical neurological as well as neuropsychological performance was evaluated. The patients also underwent yearly neurophysiological tests (digital EEG, visual evoked potentials, somatosensory evoked potentials, auditory evoked potentials P300 and electroneurography). Every other year, SPECT with (99m)Tc-D,L-hexamethylpropylene amine oxime and brain MRI were performed. Originally, 38 patients were included in the study but only the results of 28 patients who complied with three of more yearly check-ups are presented. The results of yearly investigations of cerebrospinal fluid (CSF) have been presented earlier [Eur J Neurol4 (1997) 1]. All the patients showed signs of HIV in the CSF. Yet, no major deterioration in the neurological, psychological performance, neurophysiological or neuroimaging examinations could be discerned.

Assessment of hepatic iron content using magnetic resonance imaging

Numerous studies over the past decade have shown that magnetic resonance imaging (MRI) has great potential for detecting and quantifying the distribution of iron in the body. With MRI, tissue iron is indirectly identified by the paramagnetic effects of iron on the shortening of water proton MR relaxation times. However, these effects are complex and involve a number of factors, such as tissue hydration, distribution of iron and water within the tissue, and the amount of iron loading within the iron storage molecules. A coherent understanding of how these factors influence the MRI signal is still lacking. The dependence on experimental conditions, such as magnet field strength, pulse sequences, and data acquisition parameters, further complicates iron quantification with MRI. To date, there is no generally accepted MRI approach available for clinical application. In this review, we first explain the basic MR relaxation mechanisms underlying the detection of iron with MRI. We then review the literature on empirical MRI studies of hepatic iron. Finally, we summarize the critical issues that need to be addressed to develop MRI techniques for non-invasive iron detection in the body.

Diffusion tensor trace mapping in normal adult brain using single-shot EPI technique. A methodological study of the aging brain

PURPOSE

To quantify age-related changes of the average diffusion coefficient value in normal adult brain using orientation-independent diffusion tensor trace mapping and to address the methodological influences on diffusion quantification.

MATERIAL AND METHODS

Fifty-four normal subjects (aged 20-79 years) were studied on a 1.5-T whole-body MR medical unit using a diffusion-weighted single-shot echo-planar imaging technique. Orientation-independent diffusion tensor trace maps were constructed for each subject using diffusion-weighted MR measurements in four different directions using a tetrahedral gradient combination pattern. The global average (including cerebral spinal fluid) and the tissue average of diffusion coefficients in adult brains were determined by analyzing the diffusion coefficient distribution histogram for the entire brain. Methodological influences on the measured diffusion coefficient were also investigated by comparing the results obtained using different experimental settings.

RESULTS

Both global and tissue averages of the diffusion coefficient are significantly correlated with age (p<0.03). The global average of the diffusion coefficient increases 3% per decade after the age of 40, whereas the increase in the tissue average of diffusion coefficient is about 1% per decade. Experimental settings for self-diffusion measurements, such as data acquisition methods and number of b-values, can slightly influence the statistical distribution histogram of the diffusion tensor trace and its average value.

CONCLUSION

Increased average diffusion coefficient in adult brains with aging are consistent with findings regarding structural changes in the brain that have been associated with aging. The study also demonstrates that it is desirable to use the same experimental parameters for diffusion coefficient quantification when comparing between different subjects and groups of interest.

Local recurrence of rectal cancer: MR imaging before and after oral superparamagnetic particles vs contrast-enhanced computed tomography

The aim of this study was to compare three imaging strategies for the diagnosis of local recurrence of rectal cancer: (a) MR imaging; (b) MR imaging after administration of enteral superparamagnetic particles (Ferristene); and (c) contrast-enhanced CT. Seventeen patients with previous surgery for rectal cancer were examined, 12 patients with local tumour recurrence in the pelvis and 5 patients with postoperative changes. Pelvic multi-coil MR imaging before and after oral administration of superparamagnetic contrast medium [Abdoscan (Ferristene USAN), Nycomed-Amersham, Lidingö, Sweden] as well as abdominal and pelvic CT was performed in all patients. The examinations were independently evaluated by three different radiologists. The general effect of the oral MR contrast medium, the delineation of normal and pathological structures as well as confidence in the diagnosis were registered on a visual analog scale (VAS). The diagnosis according to MR before and after oral contrast medium, and CT, was compared, in 16 patients, with the final diagnosis which was verified by biopsy (n = 3), surgery (n = 6), clinical follow-up (n = 4) and by follow-up with MR or CT (n = 3). No significant improvement in MR image quality was found after enteral contrast medium. The post-contrast MR diagnosis was not changed in any of the patients. The diagnosis on MR correlated with the final diagnosis in 12 of 16 patients (sensitivity 91%, accuracy 62%) and the diagnosis on CT in 11 of 16 patients (sensitivity 82 %, accuracy 56 %). The radiologists' "confidence" in the diagnosis and the degree of accordance with the final diagnosis did not score higher on MR after than before oral contrast administration; however, the accordance with the final diagnosis scored better on MR than on CT. No advantages of orally administered superparamagnetic contrast medium were observed in the examined patient group. Magnetic resonance is preferable to CT in diagnosing local tumour recurrence.

Quantification of cerebral blood flow by bolus tracking and artery spin tagging methods

This study deals with perfusion quantification in healthy volunteers using two types of dynamic magnetic resonance imaging (MRI) methods. Absolute cerebral blood flow (CBF) measurements were performed in 11 subjects by applying both bolus tracking of exogenous contrast agent and non-invasive arterial spin labeling MRI techniques. Both methods produced CBF images with good tissue contrast and CBF values are in good agreement with literature data. The correlation between cerebral blood volume (CBV) and CBF is also discussed.

The effect of sodium citrate in arterial catheters on acid-base and electrolyte measurements

OBJECTIVE

To compare the effects of heparin or sodium citrate used to anticoagulate indwelling arterial catheters on acid-base and electrolyte measurements.

DESIGN

Randomized controlled trial.

SETTING

Medical-surgical university-affiliated intensive care unit.

SUBJECTS

Twenty patients with indwelling arterial catheters.

INTERVENTIONS

Patients were randomly allocated to have ten 1-mL aliquots of blood sampled serially from an arterial catheter maintained with either heparin or sodium citrate. A sample then obtained by arterial puncture provided true measurement values. Acid-base and electrolyte measurements of whole blood were obtained from each sample by means of a Coming 860 analyzer.

MEASUREMENTS AND MAIN RESULTS

Contamination with sodium citrate lowered ionized calcium and pH but increased glucose and Pco2. Heparin produced negligible effects on those measurements. When sodium citrate was used, reliable measurements were not obtained for ionized calcium, pH, and glucose, even after 9 mL of blood had been discarded. However, reliable P(CO2) measurements were obtained after 2 mL of blood was discarded.

CONCLUSIONS

Sodium citrate used to maintain arterial catheters can contaminate blood samples. The result of that contamination can mimic severe hypocalcemia, metabolic acidosis, and mild hyperglycemia. Failure to recognize the effects of sodium citrate on acid-base and electrolyte measurements may lead to changes in treatment that could affect patient outcome adversely.

Increased extracellular brain water after coronary artery bypass grafting is avoided by off-pump surgery

OBJECTIVE

To determine if coronary artery bypass graft (CABG) surgery without cardiopulmonary bypass (CPB) avoids the brain swelling known to occur after CPB, to quantify these brain water compartment changes, and to identify the water shifts as due to intracellular or extracellular water.

DESIGN

Prospective, controlled, and blinded.

SETTING

Cardiac surgical unit in a university teaching hospital.

SUBJECTS

Patients scheduled for CABG who were assigned to conventional (n = 10) or off-pump (n = 7) surgery according to their coronary anatomy.

INTERVENTIONS

Magnetic resonance imaging (MRI) examinations were performed 1 day before surgery and 1 hour and 1 week after CABG surgery.

MAIN OUTCOME MEASURES

Extracellular and intracellular water homeostasis was described quantitatively by calculating the averaged apparent diffusion coefficient of brain water using diffusion-weighted MRI. Blinded visual ordering of the images from the three examinations was performed according to brain size using conventional MRI.

RESULTS

The average diffusion coefficient of brain water increased 4.7%+/-1.5% immediately after CABG with CPB and normalized after 1 week but did not change after CABG without CPB. No focal ischemic changes were seen in either group, and no gross neurologic deficits were observed. Visual analysis showed consistent brain swelling after CPB and variable changes in those operated without CPB.

CONCLUSION

Changes consistent with increased extracellular brain water seen after CABG with CPB were not observed in patients undergoing CABG without CPB. The clinical significance of brain water changes and increased brain water content after surgery with CPB remains undefined.

High numbers of perforin mRNA expressing CSF cells in multiple sclerosis patients with gadolinium-enhancing brain MRI lesions

Enhanced expression of pro- and anti-inflammatory cytokines is a common finding in MS, but attempts to correlate cytokine expression with disease activity have produced conflicting results. In this paper, gadolinium-(Gd-)enhancing lesions on brain MRI were used as markers for active inflammation in patients with MS not treated with any immunomodulatory drugs. In parallel, in situ hybridization was used to detect blood and cerebrospinal fluid (CSF) mononuclear cells (MNC) expressing cytokine mRNA. An association was observed between numbers of perforin mRNA expressing CSF MNC and numbers of Gd-enhancing brain MRI lesions. Perforin mRNA expressing CSF MNC were not detected in any of the patients lacking active lesions on brain MRI. The expression of tumor necrosis factor-alpha, interleukin-10 (IL-10) and IL-12 mRNA in CSF MNC did not differ between MS patients with and without active MRI lesions. Based on the present finding, a role for perforin in the disruption of the blood-brain barrier in MS can be hypothesized.

Diffusion MRI studies of experimental animal models and patients with stroke

PURPOSE

This overview summarises the diffusion magnetic resonance imaging (MRI) results both from the experimental animal model studies and clinical investigations in acute cerebral ischemic stroke.

DATA SOURCES

An English literature searched using MEDLINE (1990-1997).

STUDY SELECTION

Over 80 papers and reviews published in the last eight years and our partial results were selected.

RESULTS AND CONCLUSIONS

Diffusion weighted magnetic resonance imaging (DWI) has been extensively used to study acute cerebral ischemia both in experimental animal models and in patients. DWI yields signal intensity contrast modulated by water molecular self-diffusion. By recording a series of DWI with different amplitudes of the displacement encoding gradient, the apparent diffusion coefficient (ADC) can be quantitatively mapped. DWI combined with quantitative ADC mapping can provide earlier and more precise evaluation of the ischemic zones. However, the biophysical mechanisms behind the decreased ADC in acute cerebral ischemia are still not fully understood.

Rectal adenocarcinoma: assessment of tumour involvement of the lateral resection margin by MRI of resected specimen

The aim of the present study was to investigate whether MRI could predict tumour involvement of the lateral resection margin on resected rectal cancer specimens. 26 specimens obtained after total mesorectal excision were examined in the sagittal and axial plane on a clinical 1.5 T MR system using phased-array surface coils. The shortest distance between the deepest point of tumour penetration and the lateral resection margin was measured. This distance is referred to as LRM. The results were correlated to measurements on digital images of giant histopathological sections. The total number of lymph nodes and lymph node metastases was also counted. LRM was less than or equal to 1 mm (a distance considered for non-radically excised tumours) in eight of the histopathological specimens. On MR images of the resected specimen, LRM was less than or equal to 1 mm in seven of these specimens. LRM was shorter in MR examinations than in histopathological giant sections in 11 specimens. The sensitivity, specificity, positive and negative predictive values for prediction of tumour involvement of the lateral resection margin (LRM < or = 1 mm) by MR of the resected specimen were 88%, 78%, 64% and 93%, respectively. Presence of lymph node metastases could not accurately be predicted by MR. However, it is concluded that the presence of a tumour free lateral resection margin can be predicted by MRI of resected rectal specimens when this exceeds 1 mm.

ADC mapping by means of a single-shot spiral MRI technique with application in acute cerebral ischemia

Diffusion-weighted MRI based on single-shot echo planar imaging (EPI) has been established as a useful tool to study acute cerebral ischemia. However, EPI is prone to spatial distortion and ghosting artifacts. In this study, a pulse sequence for diffusion-weighted imaging (DWI) based on a single-shot spiral readout is presented. Using this technique, multislice apparent diffusion coefficient (ADC) mapping can be performed in an interleaved fashion with the same temporal resolution as EPI. Other advantages associated with ADC mapping by the single-shot spiral method include minimal ghosting artifacts, reduced spatial distortion, and capability to scan in arbitrary planes. This technique has been successfully tested in five normal volunteers and three stroke patients. It has been demonstrated that the single-shot spiral technique is capable of producing high quality DWI and ADC trace maps (128 x 128) in the axial, sagittal, and coronal planes, which facilitate clinical diagnosis.

[Alcohol-induced cognitive impairment is reversible. Neuropsychological tests but not MRT show improvement after abstinence]

Of alcoholic patients who underwent MRI (magnetic resonance imaging) of the brain and neuropsychological tests shortly after discontinuation of heavy drinking, a subgroup underwent repeat MRI scans and neuropsychological assessment one year later. The reduction in drinking habits was associated with cognitive improvement but no significant difference in MRI variables including T1-relaxation time.

Diffusion-weighted MR imaging of acute cerebral ischemia

Diffusion-weighted MR imaging has been used in studies on experimental animal models and on patients with acute cerebral ischemia. Compared with CT and conventional MR techniques, diffusion-weighted imaging can provide earlier and more precise detection of the location and the extent of an ischemic lesion during the critical first few hours after the onset of stroke. Quantitative apparent diffusion coefficient (ADC) mapping of the brain water can also be carried out by recording a series of diffusion-weighted images with different amplitudes of the displacement encoding gradients. ADC maps can provide important information about the extra- and intracellular water homeostasis. ADC reduction of the tissue water is one of the early signals of the pathophysiological cascade resulting from ischemic tissue injury. Diffusion MR imaging has become a valuable tool in stroke research. It may also prove a valuable tool in monitoring the efficiency of therapeutic effects in stroke patients. It is our intention to provide an overview of the recent development in this area with emphasis on the diffusion-weighted MR techniques, and to discuss the possible underlying biophysical mechanisms responsible for the contrast of diffusion-weighted imaging.

The pelvis after surgery and radio-chemotherapy for rectal cancer studied with Gd-DTPA-enhanced fast dynamic MR imaging

The aim of this work was to study the gadolinium-enhancement of malignant and benign pathology in the pelvis after surgery for rectal cancer. Thirty patients with either local recurrence (n = 17) or benign changes related to treatment for rectal cancer (n = 13) were studied with pelvic MR imaging. T2-weighted fast spin-echo as well as T1-weighted spin- or gradient-echo imaging before and after intravenous contrast was performed and referred to as contrast-enhanced MRI (CEMRI). In addition, between the pre- and postcontrast images, dynamic contrast-enhanced MRI (DCEMRI) was performed using a single-slice, multi-phase, contrast-enhanced T1-weighted fast spoiled gradient-echo sequence. The time between the start of contrast injection to the beginning of enhancement, the duration and rate of enhancement as well as enhancement amplitude were recorded. The data were compared with the clinical diagnosis according to biopsy in 8 patients and surgery in 6 patients. In the remaining 16 patients, the clinical diagnosis was obtained by clinical or radiological follow-up. DCEMRI did not improve the diagnostic information compared with CEMRI. None of the examined parameters were found to help discriminating malignant from benign changes. Characterisation of lesions in the pelvis after rectal cancer surgery was not improved by a dynamic gadolinium-enhanced sequence.

Magnetocardiographic localization of arrhythmia substrates: a methodology study with accessory pathway ablation as reference

In magnetocardiographic (MCG) localization of arrhythmia substrates, a model of the thorax as volume conductor is a crucial component of the calculations. In this study, we investigated different models of the thorax, to determine the most suitable to use in the computations. Our methods and results are as follows. We studied 11 patients with overt Wolff-Parkinson-White syndrome, scheduled for catheter ablation. The MCG registrations were made with a 37-channel "superconducting quantum interference device" system. The underlying equivalent current dipole was computed for the delta-wave. Three models of the thorax were used: the infinite halfspace, a sphere and a box. For anatomical correlation and to define the suitable sphere and box, magnetic resonance images were obtained. As reference we used the position of the tip of the catheter, at successful radio-frequency-ablation, documented by cine-fluoroscopy. Nine patients could be evaluated. The mean errors (range) when using the infinite halfspace, the sphere and the box were 96 (49-125), 21 (5-39), and 36 mm (20-58 mm), respectively (p < 0.0001). In conclusion, the sphere was significantly better suited than the other models tested in this study, but even with this model the accuracy of MCG localization must further improve to be clinically useful. More realistic models of the thorax are probably required to achieve this goal.

[Magnetic resonance tomography of the lesser pelvis. Clinical application in disparity with technology]

Technological innovations which change diagnostic routines are continually being introduced in medical care, as exemplified by magnetic resonance imaging (MRI) with its advanced diagnostic capacity, now considered indispensible for the investigation of many disorders of the central nervous system. The article consists in an outline of applications of MRI in the investigation of the lower abdomen, a field characterised by substantial technical improvements in recent years, and a brief review of subject literature. Based on their experience of pelvic MRI, the authors advocate its more frequent use in investigating disorders of the lesser pelvis.

Radiosurgical lesions in the normal human brain 17 years after gamma knife capsulotomy

OBJECTIVE

To our knowledge, this is the first long-term follow-up study of high-dose single-session irradiation to the human brain and provides new data concerning late tissue reactions after irradiation to small target volumes. The long-term lesional brain changes in 14 patients subjected to bilateral gamma knife capsulotomy for otherwise intractable anxiety disorders were retrospectively analyzed by magnetic resonance imaging.

METHODS

The prototype gamma unit was used for the radiosurgical procedure, and the collimators provided rectangular cross-sectional fields with an anteroposterior diameter of 3 mm and a transverse diameter of 5 or 11 mm. Maximum target doses were 120 to 180 Gy. Magnetic resonance imaging was performed 15 to 18 years (mean, 17 yr) after treatment, and dose-volume histograms were calculated for the dose distributions.

RESULTS

One patient had been irradiated twice on one side. In all but one of the remaining 27 targets, lesions with a volume of less than 100 mm3 were revealed by magnetic resonance imaging. The volumes of the lesions were confined within the volume corresponding to a minimum dose of approximately 110 Gy, with one exception. In one of three targets receiving a maximum dose of 120 Gy, no lesion was detected. There were no late radiation effects such as cyst formations, telangiectasias, hemorrhagic infarctions, or neoplasms.

CONCLUSION

This investigation indicates that a minimum dose of 110 Gy, with the currently used 4-mm collimator, to the edge of the target volume is required to create a lesion. The results prove that gamma knife surgery can be used in functional neurosurgery for producing small permanent lesions in the normal human brain.

Experimental correlation between T2* and ultimate compressive strength in lumbar porcine vertebrae

RATIONALE AND OBJECTIVES

The authors used magnetic resonance (MR) imaging to investigate the correlation between T2* measurements of trabecular bone and the ultimate compressive strength of lumbar porcine vertebrae.

METHODS

Five pigs that weighted 25-32 kg were sacrificed and imaged with a 1.5-T MR system. T2* of the lumbar vertebrae was measured from gradient-echo images. The vertebrae were individually compressed at a fixed speed in the direction of the spine until crushed. The maximum load a vertebra could resist was recorded.

RESULTS

T2* ranged from 7.1 to 14.5 msec. T2* determined from 5-mm coronal sections differed from that determined from axial and sagittal sections (P < .05). Between 2.9 and 5.4 kN of force (296-550 kg) was needed to crush a vertebra. A linear correlation between the ultimate compressive strength and T2* of all vertebrae was observed for all imaging planes and section thicknesses (P < .001, except for 10-mm sagittal images, for which P < .002). The T2* determined for the axial plane showed the best correlation with the ultimate compressive strength (r = -0.83).

CONCLUSION

The correlation between T2* values and vertebral strength indicates that MR imaging may potentially be used to predict fracture risks in patients.

Global cerebral blood flow during infusion of adenosine in humans: assessment by magnetic resonance imaging and positron emission tomography

Adenosine, an endogenous vasodilator, induces a cerebral vasodilation at hypotensive infusion rates in anaesthetized humans. At lower doses (< 100 micrograms kg-1 min-1), adenosine has shown to have an analgesic effect. This study was undertaken to investigate whether a low dose, causing tolerable symptoms of peripheral vasodilation affects the global cerebral blood flow (CBF). In nine healthy volunteers CBF measurements were made using axial magnetic resonance (MR) phase images of the internal carotid and vertebral arteries at the level of C2-3. Quantitative assessment of CBF was also obtained with positron emission tomography (PET) technique, using intravenous bolus [15O]butanol as tracer in four of the subject at another occasion. During normoventilation (5.4 +/- 0.2 kPa, mean +/- s.e.m.), the cerebral blood flow measured by magnetic resonance imaging technique, as the sum of the flows in both carotid and vertebral arteries, was 863 +/- 66 mL min-1, equivalent to about 64 +/- 5 mL 100 g-1 min-1. The cerebral blood flow measured by positron emission tomography technique, was 59 +/- 4 mL 100 g-1 min-1. All subjects had a normal CO2 reactivity. When adenosine was infused (84 +/- 7 micrograms kg-1 min-1.) the cerebral blood flow, measured by magnetic resonance imaging was 60 +/- 5 mL 100 g-1 min-1. The end tidal CO2 level was slightly lower (0.2 +/- 0.1 kPa) during adenosine infusion than during normoventilation. In the subgroup there was no difference in cerebral blood flow as measured by magnetic resonance imaging or positron emission tomography. In conclusion, adenosine infusion at tolerable doses in healthy volunteers does not affect global cerebral blood flow in unanaesthetized humans.

Rectal tumours--MR imaging with endorectal and/or phased-array coils, and histopathological staging on giant sections. A comparative study

OBJECTIVE

To investigate the accuracy of MR imaging in the preoperative staging of patients with clinically resectable rectal tumours.

MATERIAL AND METHODS

Forty-eight consecutive patients with rectal tumours were examined, 29 with a pelvic phased-array coil and 19 with a multi-coil arrangement including a pelvic phased-array coil and an endorectal coil. MR images and histopathological specimens and sections were reviewed independently and tumours were staged according to the TNM classification.

RESULTS

A more complete visualisation of the various layers of the rectal wall was achieved on the endorectal MR images than on the pelvic phased-array images. The sensitivity of MR in correctly staging T3 tumours compared with histopathology was 81% with a specificity of 82%. Penetration of the rectal wall was predicted with a sensitivity of 82% and a specificity of 87%. Sensitivity and specificity in predicting lymph node metastases was 83% and 74% respectively.

CONCLUSION

MR imaging with both pelvic phased-array and endorectal coils allowed the preoperative staging of rectal tumours with a high degree of accuracy.

Functional magnesium deficiency in critically ill patients identified using a magnesium-loading test

OBJECTIVE

To determine the feasibility of the magnesium-loading test in the critically ill and to validate serum ionized magnesium assay using the magnesium-loading test as a reference in this same patient population.

DESIGN

Double-blind, randomized, controlled clinical investigation.

SETTING

Tertiary level intensive care unit.

PATIENTS

Forty-four consecutive critically ill patients without evidence of renal insufficiency.

INTERVENTION

Patients were randomly allocated to receive 30 mmol (7.5 g) of magnesium sulfate daily for 3 days, or an equivalent amount of normal saline.

MEASUREMENTS AND MAIN RESULTS

We recorded baseline characteristics, and serial serum biochemical measurements included creatinine, glucose, sodium, potassium, phosphate, total calcium, ionized calcium, total magnesium, and ionized magnesium. Serum assays were accompanied by 24-hr urine collections of creatinine and magnesium over the 3-day period. Baseline characteristics were comparable in both groups. In patients receiving magnesium, serum ionized magnesium and total magnesium concentrations were increased by 43% (p = .0001) and 59% (p = .0002), respectively, on day 1 as compared with the control group. Magnesium excretion in the control group averaged 4.8 +/- 2.3 mmol/day during the 3-day study period, while the magnesium excretion in the magnesium-loaded group was significantly increased to 22.7 +/- 10.9 mmol/day (p < .0001). Following day 1 magnesium loading, patients who excreted < 70% of the total magnesium (30 mmol infused magnesium plus 4.8 mmol basal excretion) were termed as functionally magnesium-deficient retainers (n = 12), and patients who excreted > 70% of the total magnesium were termed as nonretainers (n = 7). In addition, magnesium retainers on day 2 (nine of ten patients) and day 3 (five of six patients) excreted > 70% of the total magnesium, indicating a replenishment of body magnesium stores. In contrast, nonretainers on day 2 (four of five patients), and day 3 (four of four patients) continued to excrete excess amounts of magnesium. In the retainer group, only two patients had a low serum ionized magnesium concentration, while two other patients had low total serum magnesium values. In addition, magnesium retention was associated with low ionized calcium and high phosphate values.

CONCLUSIONS

The magnesium-loading test is feasible and appears to be valid based on its performance during the 3-day evaluation. Using the magnesium-loading test as a reference, serum ionized magnesium appears to be an insensitive biochemical marker of functional hypomagnesemia. Larger cohort studies using the magnesium-loading test will help establish the true prevalence of magnesium deficiency and its associated risk factors in critically ill patients.

A new view on the CSF-circulation with the potential for pharmacological treatment of childhood hydrocephalus

A new model of the cerebrospinal fluid (CSF) circulation is proposed, implying that the main absorption of CSF occurs through the brain capillaries. This model is based on recent observations of CSF dynamics using radionuclide cisternography and cardiac gated magnetic resonance imaging. Magnetic resonance imaging of communicating hydrocephalus has demonstrated a highly significant decrease of CSF flow through the foramen magnum, which is explained by decreased expansion of the intracranial arteries. This invariable finding in combination with the new view of the CSF-circulation makes a hemodynamic pathogenesis of hydrocephalus very probable. Communicating hydrocephalus may be caused by any process that restricts the arterial pulsations and is therefore termed restricted arterial pulsation hydrocephalus. In obstructive hydrocephalus, the ventricular dilatation leads to a compression of the cortical veins and consequently is termed venous congestion hydrocephalus. Based on these considerations, a new concept of pharmacological treatment of hydrocephalus is proposed by using a selective venous constrictor.

MR imaging of adult colo-rectal intussusception. A case report

MR imaging of an intussuscepted sigmoid cancer misinterpreted as a rectal carcinoma is described. High-resolution technique with pelvic-phased array coils and fast spin-echo was used. The diagnosis is discussed in relation to the MR findings.

Haemorrhagic pituitary tumours

In a group of 69 patients with pituitary tumours, 12 were found to have evidence of intratumoral haemorrhage on MRI, characterized by high signal intensity on short TR/TE sequences. This was verified in all but 1 patient. The majority of the bleedings occurred in macroadenomas. Five (42%) were prolactinomas and 4 (33%) were non-functioning adenomas. There were 2 GH- and 1 ACTH-secreting tumours. All 5 patients with prolactinomas were on bromocriptine medication. Two of the patients had a clinical picture of pituitary apoplexy. The haemorrhage was not large enough to prompt surgery in any of the patients. However, surgical verification of the diagnosis was obtained in 5 cases, while 6 patients were examined with follow-up MRI.

Carcinoma of the cervix: predictive value of clinical and magnetic resonance (MR) imaging assessment of prognostic factors

PURPOSE

This retrospective study assesses the predictive value of magnetic resonance imaging (MRI) to identify high risk cervical cancer patients.

METHODS AND MATERIALS

The MRI evaluation of morphologic risk factors in patients with invasive cervical carcinoma treated with definitive radiation therapy were correlated with clinical factors and with complete tumor regression (CTR) at 6 months, tumor local control (TLC), and patient outcome at 12 months after irradiation. Sixty-six patients, median age 44.5 years, with bulky Stage I or greater disease were included in the study.

RESULTS

In univariate analysis, clinical International Federation of Gynecology and Obstetrics (FIGO) stage had significant correlation with patient outcome, but it correlated poorly with complete tumor regression and tumor local control. In contrast, MRI stage showed significant correlation with complete tumor regression, tumor local control, and disease-free survival at 12 months. When each stage was analyzed separately, the greatest difference was demonstrated between clinical and MRI assignment of stage Ib disease. MRI Stage Ib disease significantly correlated with all three categories analyzed, while clinical Stage Ib did not. Superiority of MRI assessment of low stage disease was also evident in the detection of lymph node metastasis. Significant risk for nodal metastasis was related to tumor size greater than 4 cm, invasion of the parametria and urinary bladder, and stage of the disease.

CONCLUSION

The multivariate analysis demonstrated that the most related variables in order of significance were the presence of juxta-regional and paraaortic lymph nodes, patient age, tumor size, and MRI tumor stage. This study demonstrates the value of MR imaging as an adjunct to clinical assessment of bulky invasive cervical cancer, rendering more complete assessment of morphologic risk factors important in patient prognosis.

Effects of alfentanil on the hemodynamic and catecholamine response to tracheal intubation

A randomized, placebo-controlled study was conducted in 60 ASA Class I, II, and III patients to determine the dose response of alfentanil in moderating the cardiovascular and catecholamine response to tracheal intubation (INT). Patients were randomly allocated into one of four groups to receive either 15 micrograms/kg alfentanil (A15), 30 micrograms/kg alfentanil (A30), 45 micrograms/kg alfentanil (A45), or normal saline (control), given intravenously (i.v.) before induction of anesthesia. One minute after administration of 4.0 mg/kg thiopental and 1.5 mg/kg succinylcholine i.v., tracheal intubation was performed using direct laryngoscopy. In response to INT, increases in heart rate, systolic blood pressure, and systemic vascular resistance occurred in the control group. These changes were significantly more than corresponding changes of heart rate, systolic blood pressure, and systemic vascular resistance in all three alfentanil groups (P < 0.05). In contrast, cardiac index and ejection fraction decreased moderately in every group during the study period, but there were no differences among groups with respect to either cardiac index or ejection fraction at corresponding times following INT. In the control group, epinephrine and norepinephrine serum concentrations increased by 152 +/- 52% and 58 +/- 62%, respectively, following INT (different from A30 and A45, P < 0.05). However, up to a dose of 30 micrograms/kg (A30), a dose-dependent decrease in the maximum percent changes of both epinephrine and norepinephrine occurred in response to INT. A larger dose of alfentanil was no more efficacious as the catecholamine response to tracheal intubation was not significantly different when comparing the A45 and A30 groups.(ABSTRACT TRUNCATED AT 250 WORDS)

PET analysis of [11C]flumazenil binding to benzodiazepine receptors in chronic alcohol-dependent men and healthy controls

Benzodiazepine (BZ) receptor binding in the brain was determined in five chronic alcohol-dependent men and in five healthy male control subjects using [11C]flumazenil (Ro 15-1788) and positron emission tomography (PET). Magnetic resonance imaging was used to evaluate brain anatomy and pathology, and to define regions of interest in the brain. [11C]Flumazenil binding was quantified by applying a saturation procedure with two PET experiments, the first with high (400-3400 Ci/mmol) and the second with low (approximately 1 Ci/mmol) specific radioactivity. Radioactivity in the pons was taken as an estimate of free and nonspecifically bound radioligand. Equilibrium was defined to prevail when the derivative of specific binding (dCb(t)/dt) was equal to zero. The values were used in a Scatchard analysis for determination of the maximum density of binding sites (Bmax) and the equilibrium binding constant (Kd). The mean values of Bmax and Kd were about the same in the two groups, but the Bmax variance for the alcoholics was significantly greater for all regions of interest as compared with the healthy volunteers. The results may indicate that chronic alcohol consumption has multiple effects on the BZ receptor complex.

Magnetic resonance imaging of the brain before and after open heart operations

Magnetic resonance imaging of the brain was performed in 29 adult male patients before and 1 week after elective coronary artery bypass grafting to study the cerebral effect of cardiopulmonary bypass. The mean age of the patients was 60 years (range, 45 to 69 years). During cardiopulmonary bypass, either a bubble oxygenator without an arterial line filter (n = 9), a bubble oxygenator with a depth adsorption filter (n = 10), or a flat-sheet membrane oxygenator without a filter (n = 10) was used. The mean bypass time was 88 minutes (standard deviation, 31 minutes) and did not differ significantly between the three groups. Preoperative magnetic resonance imaging revealed high signal intensity foci on T2-weighted images (white matter abnormalities) in 17 (59%; 95% confidence limits, 39% to 76%) of the 29 patients, all of which were nonspecific and of the common type considered to be related to aging, and all were unchanged at the postoperative examination. Preoperative and postoperative frontal horn indices, bicaudate diameters, and third ventricle widths did not differ significantly regardless of oxygenator type or whether or not an arterial line filter was used during cardiopulmonary bypass. Two patients (7%; 95% confidence limits, 1% to 23%), both receiving bubble oxygenation (1 without a filter and 1 with an arterial line filter) sustained a cerebral infarction during cardiopulmonary bypass.

[The value of magnetic resonance scanning in the diagnosis of small acoustic neurinomas]

This article describes three cases of acustic neurinoma in which both clinical examination and audiovestibular investigations raised strong suspicions of acustic neurinoma but no tumours could be demonstrated by CT. Magnetic resonance scanning employing gadolinium-DTPA revealed small intrameatal acustic neurinomas in all three cases. Attention is drawn to the fact that magnetic resonance scanning provides a new diagnostic possibility for acustic neurinoma and is a valuable supplement to the established diagnostic procedures in suspected acustic neurinoma even although CT reveals normal anatomical conditions in the internal auditory meatus.

Central nervous system malformations and white matter changes in pseudo-neonatal adrenoleukodystrophy

Clinical, biochemical and morphological findings in a 16-month-old infant girl with pseudo-neonatal adrenoleukodystrophy are reported. The parents were first cousins and the baby was born at term, small for gestational age. The neonatal period was characterized by convulsions resistant to treatment, generalized, severe muscle hypotonus, feeding difficulties and poor weight gain. Developmentally she remained at a neonatal level. A CT-scan showed low density of cerebral white matter and MR examination white matter changes, a thin corpus callosum, cerebellar malformation and dorsal displacement of the brainstem. There was an accumulation of very long chain fatty acids (VLCFA) in serum lipids and cultured skin fibroblasts but plasmalogen and phytanic acid levels were normal. A liver biopsy revealed enlarged peroxisomes staining for catalase. Three similar cases have been reported previously; in two of these there was a deficiency of acyl-CoA oxidase. MR evidence of leukodystrophy combined with gross cerebral and cerebellar morphologic changes have not been reported earlier.

Positron emission tomography compared with magnetic resonance imaging and computed tomography in supratentorial gliomas using multiple stereotactic biopsies as reference

Ten patients with findings at computed tomography (CT) suggesting intracranial supratentorial glioma were investigated to compare the diagnostic efficacy of this technique with that of positron emission tomography (PET) using 11C-methionine and examinations with magnetic resonance (MR). The findings were related to histopathologic examination of serial stereotactic biopsies, which were guided by the appearance of the lesions on PET examination. To obtain corresponding slice orientation with the different examination techniques, an individually shaped helmet fixation was used. However, in 3 cases this fixation device could not be used for MR. Histopathologic diagnosis, obtained in all cases from multiple target stereotactic biopsies, included glioma in 9 patients and reactive gliosis in one case. A detailed comparison of the three imaging techniques and the findings at stereotactic biopsies was possible in 7 patients, while in 3 patients comparison with MR was less exact due to the patient's refusal to wear the helmet during this examination. MR was the most accurate method for outlining the total extent of a lesion, i.e. the tumor and the edema surrounding it. Four lesions had homogeneous signal characteristics and in 6 lesions two (or more) compartments could be distinguished with MR. In 5 cases the MR findings were in complete agreement with the histopathologic findings. However, a thorough correlation between signal characteristics and histology was not possible. Using PET the occurrence and the extent of tumor tissue was correctly predicted in 7 patients. The PET was normal in one case. Findings at CT were in agreement with the histopathologic diagnosis in 5 patients. MR was the most sensitive method for the detection of lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of improved drinking habits on brain atrophy and cognitive performance in alcoholic patients: a 5-year follow-up study

In the period 1977-1979, a sample of consecutively admitted alcoholic in-patients was studied with CT scan of the brain and neuropsychological tests. A subsample of 52 patients met the following criteria: age less than 46 years, no history of severe head injury or focal signs of traumatic brain damage, and no history of liver disease, drug abuse, or long-lasting anticonvulsant therapy. However, 72% of the patients showed brain atrophy and 49% intellectual impairment as compared to 16% and 13%, respectively, in an age-matched sample of men from the general population. Five years later, after excluding patients with head trauma, serious alcoholic liver disease and drug abuse, 37 patients were reinvestigated. Sixteen patients were abstinent or had greatly improved drinking habits during the 5-year follow-up period and 21 were still drinking. Alcohol abstinence was found to be associated with a regress of cortical atrophy and central atrophy as assessed by the width of the 3rd ventricle. However, the recovery was not complete as compared with the prevalence of atrophy in the sample from the general population. Among the patients a significant improvement in one cognitive test and a trend to improvement in some other tests associated with improved drinking habits was observed. Regression of central atrophy as assessed by a decreased diameter of the 3rd ventricle was associated with improvement in the very same cognitive tests. The results suggest that both atrophy of the brain and cognitive ability can improve in alcoholics who give up drinking.(ABSTRACT TRUNCATED AT 250 WORDS)

Magnetic resonance images related to clinical outcome after psychosurgical intervention in severe anxiety disorder

Postoperative verification of radiosurgical lesions in white matter has been difficult to obtain with CT. With magnetic resonance (MR) imaging, however, lesions could be demonstrated in patients undergoing a psychosurgical procedure, gamma capsulotomy, for anxiety disorder. The appearance and location of the lesions were related to the irradiation dose and to the long-term clinical outcome studied prospectively by two independent evaluators who had not been involved in the selection or the treatment of the patients. Seven consecutive cases were examined. CT was also included for comparison reasons. Lesions were clearly visible with MR in patients who improved after surgery. Conversely, lesions were inadequate in cases who did not benefit. MR proved to be more accurate than CT both in detecting the lesions and in defining their configuration. The observations argue for the use of MR for post-operative verification of radiosurgical lesions. MR may facilitate the determination of a clinically effective radiation threshold estimate for radiosurgical lesions, which should be of value for the planning of studies of this type of limbic system surgery.

Does successful interferon treatment of tumor patients require life-long treatment?

Case histories of 5 tumor patients treated with natural leukocyte interferon-alpha (IFN-alpha) are presented. One patient with juvenile laryngeal papillomatosis responded well to interferon treatment, but the disease recurred when therapy was withdrawn. Upon reinstitution of treatment, the patient once again responded well. Another patient with myelomatosis also responded well to interferon therapy and in this case, too, the tumor recurred when interferon treatment was withdrawn. Reinstitution of interferon therapy was, however, unsuccessful. One patient with generalized giant cell tumor of bone responded with regression after more than 5 years of interferon treatment. Another patient with pulmonary osteosarcoma metastases, having received irradiation and interferon combination therapy followed by sole interferon treatment, responded well with a lasting stationary radiogram after 6 years of interferon treatment. One patient with malignant glioma, showing signs of tumor growth during the first few months of interferon therapy, eventually responded, and became disease-free after 6 years. The latter 3 patients are continuously receiving interferon therapy although more than 5 years have elapsed since their interferon therapy was initiated. It is suggested that interferon therapy for malignant tumors be given for life (or to progression of disease) in responding patients. Such a concept entails biological implications for interferon therapy in general and for antitumor action of interferons in particular. Other possible clinical schedules should only be constructed within the framework of controlled clinical trials.

A comparison of computed tomography and myelography in the diagnosis of lumbar disc herniation

Ninety patients suspected to have a herniated lumbar disc were examined by myelography and computed tomography (CT). Of these, 37 were subjected to surgery. The surgical findings were in agreement in 21 patients (57%) with the myelograms and in 28 patients (76%) with the CT examinations. False-positive CT examinations were found in only one patient. CT is as reliable as myelography in the primary diagnosis of disc herniation.

Radiation therapy of ovarian carcinoma: presentation of a six-field technique

A new technique for radiotherapy in ovarian carcinoma is presented. The aim was to deliver a homogeneous radiation dose to the entire abdominal cavity. The whole abdomen, except for 20% of the upper compartment, received a homogeneous dose of 40 Gy, while 2/3 of the kidneys and the posterior part of the liver received a dose ranging from 40 to 20 Gy. No clinically significant impairment of liver function was seen during follow-up.