A blinded clinical comparison of MR imaging and CT in neuroradiology

Migraine and MRI: uncovering potential associations

OBJECTIVE

This study aims to investigate the association between patients with migraine headaches and brain magnetic resonance imaging (MRI) findings.

BACKGROUND

Migraine is a frequently encountered primary headache disorder with a disproportionate female predominance. Diagnosis is usually based on the patient's clinical history with neuroimaging reserved for severe or atypical presentations to exclude other pathologies. Migraine patients often experience a profound impact on their quality of life.

METHODS

A retrospective study was conducted at King Abdullah University Hospital, Jordan, involving patients with a clinical diagnosis of migraine who had undergone MRI brain imaging between January 2021 to March 2023. Descriptive data were documented, with two independent neuro-radiologists interpreting MRI findings.

RESULTS

Our study included 670 migraine patients (510 females; mean age, 40.3 years). White matter hyperintensity lesions were found in 309 patients (46.1%), significantly affecting older age groups with a mean age of 46.8 years (p > 0.001). Additionally, gender played a role, with a higher prevalence of these lesions in female migraine patients, accounting for 79.6% (p = 0.05). Multiple logistic regression analysis proved age to be an independent risk factor for the presence of white matter hyperintensity lesions (OR: 1.0688, 95% CI: 1.0546-1.0831, p > 0.001).

CONCLUSION

White matter hyperintensity lesions were seen in the MRI imaging of a subset of migraine patients. Patients with these lesions tend to be older and of female gender. However, the clinical significance of these findings remains unclear.

Magnetic resonance imaging in chronic headache: our experiences and perspectives

Background

Headache is a common symptomatology necessitating hospital consultations. Despite the prohibitive cost to patients in Nigeria, Magnetic resonance imaging (MRI) has become an evaluating tool for headache.

Objectives

To determine the yield of cranial MRI and frequency of significant intracranial lesions among patients with chronic headache.

Methods

A three-year retrospective analysis of cranial MR images and records of patients referred to Medicaid Diagnostic Centre in Abuja, Nigeria on account of chronic headache was done. Data was analyzed using SAS software version 9.3.

Results

150 patients aged 9 to 73 years (mean= 39.5 years) with chronic headache were studied. There were 54 males and 96 females with a ratio of 1:1.8. 48% and 52% had normal and abnormal MRI findings respectively. Although the number with abnormal MRI was higher than those with normal exams, this difference was not significant (p=0.624). The commonest neoplastic and non-neoplastic abnormalities were pituitary macroadenoma (4%) and sinusitis (21.3%) respectively.

Conclusion

In our study, MRI had a low diagnostic yield in patients with chronic headache. Therefore, it is expedient that physicians stratify patients with chronic headache based on red flag signs to determine the need for cranial MRI in view of financial burden.

Brain Metastases — Comparison of Gadodiamide Injection-Enhanced MR Imaging at Standard and High Dose, Contrast-Enhanced CT and Non-Contrast-Enhanced MR Imaging

The aim was to compare the abilities of contrast-enhanced CT, non-contrast-enhanced MR imaging and contrast-enhanced MR imaging using standard (0.1 mmol/kg b.w.) and high (0.3 mmol/kg b.w.) doses of Gadodiamide injection to detect brain metastases (i.e. blood-brain barrier damage). Sixteen patients with at least 2 metastases found by CT were evaluated by MR imaging using non-contrast-enhanced spin-echo, T1-weighted, T2-weighted sequences, and contrast-enhanced spin-echo T1-weighted sequences at 2 dose levels. Gadodiamide injection was first given at the dose of 0.1 mmol/kg b.w. After imaging, another 0.2 mmol/kg b.w. was given, yielding a cumulative dose of 0.3 mmol/kg b.w. No contrast media-related adverse events were recorded. The images were evaluated openly by one and blindly by 2 investigators and the number of metastases, size, delineation (open study) and diagnostic certainty (blind study) of each individual metastasis noted. High-dose MR imaging showed significantly more and smaller metastases than any other examination, and gave a higher diagnostic certainty. All high-dose images were superior to those with the standard dose MR imaging when compared blindly in pairs. We conclude that spin-echo MR imaging with a high dose of Gadodiamide injection is an efficient way to improve the detection of brain metastases, in particular of small ones.

Magnetic Resonance Imaging of Intracranial Neoplasms at 0.02 Tesla

Sixty-five patients with single or multiple intracranial neoplasms were examined with an MR imager operating at 0.02 tesla. In 56 patients the diagnosis was histologically confirmed. All patients had an abnormal CT finding. MR images were positive in 59 cases, while the lesion remained undetected or equivocal in 6 cases (2 pituitary adenomas and 4 meningiomas). The MR signal intensity of several meningiomas was equal to that of normal brain tissue. Some astrocytomas were better delineated on MRI than on CT. For the study of pituitary lesions, the spatial resolution was unsatisfactory. The ultralow field MR imager was found to be sensitive for the detection of other intracranial neoplasms.

Agreement between low-field MRI and CT for the detection of suspected intracranial lesions in dogs and cats

OBJECTIVE

To assess the agreement between CT and MRI for enabling detection of intracranial lesions in cats and dogs.

DESIGN

Evaluation study.

ANIMALS

51 dogs and 7 cats with suspected intracranial lesions.

PROCEDURES

During a 2-year-period, dogs and cats with suspected intracranial pathological changes underwent MRI and CT (single slice) of the head. Radiologists evaluated images produced with both techniques without awareness of subject identity. Agreement between methods was assessed for allowing detection of solitary or multiple lesions, selected lesion characteristics (via the Cohen κ statistic), and lesion dimensions (via Bland-Altman plots).

RESULTS

CT and MRI had substantial agreement for allowing detection of lesions and identification of whether the lesions were solitary or multiple. The techniques agreed almost perfectly for allowing identification of a mass effect and contrast medium enhancement, which were considered principal diagnostic imaging signs. A lower degree of agreement was attained for allowing identification of enhancement patterns and aspects of lesion margins. Agreement was substantial to almost perfect for lesion visualization in most anatomic brain regions but poor for identification of lesion dimensions.

CONCLUSIONS AND CLINICAL RELEVANCE

Degrees of agreement between CT and MRI for allowing the detection and characterization of intracranial lesions ranged from poor to almost perfect, depending on the variable assessed. More investigation is needed into the relative analytic sensitivity and possible complementarities of CT and MRI in the detection of suspected intracranial lesions in dogs and cats.

MRI in headache

Headaches are described as primary, where no contributing cause is found, or secondary, where a discrete lesion or other condition has triggered the phenotype. Primary headache is a common condition; migraine causes much of the morbidity in this population, at great personal and economic cost. The decision to use MRI is a common dilemma facing clinicians, particularly as primary headache phenotypes can be triggered by secondary causes. Studies demonstrate that there is no appreciable difference in the frequency of pathological and incidental findings in common headache populations compared with the general community. Imaging is therefore not routinely required where a primary headache diagnosis can be made. Clinicians must be aware of the risk of manufacturing morbidity in uncovering incidental and nonsignificant imaging changes. However, patients demonstrating 'red flags' on medical history and examination do require imaging to help exclude a secondary cause of symptoms. Other headache phenotypes, such as the trigeminal autonomic cephalalgias, also generally require MRI.

MR Imaging in the Evaluation of Chronic or Recurrent Headache

PURPOSE

To evaluate ability of magnetic resonance (MR) imaging to depict an abnormality in patients with chronic or recurrent headache without neurologic abnormality.

MATERIALS AND METHODS

Institutional review board approval and patient informed consent were not required. A total of 306 patients with normal neurologic findings and chronic or recurrent headache were examined with MR imaging. Patients were divided into three groups: those with no abnormality, those with minor abnormality, and those with clinically important intracranial abnormality, which may result in chronic or recurrent headache. Literature review was also performed. Upper 99.5% confidence bound for frequency of abnormal MR findings was calculated.

RESULTS

A total of 169 patients (55.2%) were placed in the first group, 135 (44.1%) were placed in the second group, and two (0.7%) were placed in the third group because they had a clinically important abnormality at MR imaging. Neither contrast material enhancement (n = 195) nor repeated MR imaging (n = 23) contributed to the diagnosis. Literature review revealed two previous studies concerning unspecified headache (in addition to the current study), including a total of 1036 MR imaging results and 22 (2.1%) clinically important results (upper 99.5% confidence bound, 3.4%). Twelve studies of migraine headache were found, with a total of 790 MR imaging examinations. Excluding the 19 patients with complicated migraine, the 99.5% confidence bound of the frequency of clinically important abnormality at MR imaging was estimated as 0.68%. Clinically important infarctions were noted on MR images in five (26.3%) of 19 patients with complicated migraine.

CONCLUSION

MR imaging is an unrewarding technique in the evaluation of patients with chronic or recurrent headache and normal neurologic findings. Neither contrast enhancement nor repeated MR imaging contributed to diagnosis, although the number of patients in the latter category was small.

Adults and children with headache: evidence-based diagnostic evaluation

Headache represents one of the most common complaints in the outpatient and emergency room setting [1]. Most causes of headache are benign and do not require emergent imaging or intervention. The authors' review of the diagnostic tests does not offer absolute indications for neuroimaging because most of the evidence is based on studies that are not randomized controlled trials. Imaging guidelines for adults and children, however, have emerged based on the available level 2 and 3 literature. CT imaging remains the initial test of choice for new-onset headache in adults and headache suggestive of SAH. Most of the available literature also recommends performing lumbar puncture when CT is equivocal in ruling out SAH [1]. The sensitivity of MR imaging appears to be less than CT for SAH [1]. Newer MR imaging techniques need to be tested and developed to determine if they have higher sensitivity than CT or lumbar puncture in the detection of SAH. In adults with suspected brain metastatic disease, contrast-enhanced MR imaging is the imaging study of choice [38,39]. Contrast-enhanced MR imaging is the examination of choice for brain metastatic lesions less than 2 cm [39]. CT angiography and MR angiography have sensitivities greater than 85% for brain aneurysms larger than 5 mm [43]. If clinically warranted, aneurysms smaller than 5 mm may require digitally subtracted angiography because of the low sensitivity of MR and CT angiography. In children, the choice of diagnostic test strategy depends on the risk group. In high-risk patients, MR imaging is the test of choice whereas in low-risk patients, close clinical observation with periodic reassessment is the best strategy [44]. Clinical diagnosis will always play a key role in the evaluation of headache disorders; however, for the small subset of patients who present with headache secondary to an intracranial space-occupying lesion, bleeding, or SAH, making the diagnosis is crucial to decreasing morbidity and mortality. CT, MR imaging, and lumbar puncture play important roles in the assessment of headache disorders, but their future roles will continue to evolve as the technology becomes more sophisticated and robust, and physicians become more expert with their use [1].

Children with headache suspected of having a brain tumor: a cost-effectiveness analysis of diagnostic strategies

OBJECTIVE

To assess the clinical and economic consequences of 3 diagnostic strategies-magnetic resonance imaging (MRI), computed tomography followed by MRI for positive results (CT-MRI), and no neuroimaging with close clinical follow-up-in the evaluation of children with headache suspected of having a brain tumor. Three risk groups based on clinical variables were evaluated.

MATERIALS AND METHODS

A decision-analytic Markov model and cost-effectiveness analysis was performed incorporating the risk group prior probability, MRI and CT sensitivity and specificity, tumor survival, progression rates, and cost per strategy. Outcomes were based on quality-adjusted life year (QALY) gained and incremental cost per QALY gained.

RESULTS

For low-risk children with chronic nonmigraine headaches of >6 months' duration as the sole symptom (prior probability of brain tumor 0.01%), no neuroimaging with close clinical follow-up was less costly and more effective than the 2 neuroimaging strategies. For the intermediate-risk children with migraine headache and normal neurologic examination (prior probability of brain tumor 0.4%), CT-MRI was the most effective strategy but cost >$1 million per QALY gained compared with no neuroimaging. For high-risk children with headache of <6 months' duration and other clinical predictors of a brain tumor such as an abnormal neurologic examination (prior probability of brain tumor 4%), the most effective strategy was MRI, with cost-effectiveness ratio of $113 800 per QALY gained compared with no imaging.

CONCLUSION

Our analysis suggests that MRI maximizes QALY gained at a reasonable cost-effectiveness ratio in children with headache at high risk of having a brain tumor. Conversely, the strategy of no imaging with close clinical follow-up is cost saving in low-risk children. Although the CT-MRI strategy maximizes QALY gained in the intermediate-risk patients, its additional cost per QALY gained is high. In children with headache, appropriate selection of patients and diagnostic strategy may maximize quality-adjusted life expectancy and decrease costs of medical workup.

Spatial characteristics of cerebral polyopia: a case study

A 41-year-old woman showed bilateral monocular polyopia and an incomplete, right-sided homonymous hemianopia following bilateral cerebral strokes confirmed by neuroimaging. She was tested with briefly-presented visual stimuli to determine whether her polyopic images varied with visual field position of stimuli which evoked them. Stimuli close to her scotoma elicited polyopic images at shorter latency and higher probability than did stimuli more distant from it. RS could maintain stable fixation on small stimuli, suggesting that eye movements were not responsible for her polyopia. We discuss the possibility that cerebral polyopia is due to recoding of visual receptive fields in primary visual cortex and that bilateral occipital lesions are a causative factor in the genesis of the disorder.

Cost effectiveness and outcome assessment of magnetic resonance imaging in diagnosing cord compression

BACKGROUND

This study was designed to investigate the costs associated with the use of magnetic resonance imaging (MRI) in the workup of spinal cord compression caused by metastatic disease, an area in which it has proven to be diagnostically useful.

METHODS

The study was divided into two parts. Part 1 consisted of a retrospective review of the hospital charts of 46 patients, half of whom were diagnosed with cord compression in the pre-MRI era and the other half diagnosed after MRI availability; costs for these two groups were compared. Part 2 consisted of a review of several major studies comparing the sensitivities and specificities of MRI with alternative imaging techniques, usually myelography. Cost effectiveness and cost/cost ratios were derived for diagnostic usefulness using prevalence, sensitivity, specificity, and cost estimates of MRI and its alternatives, including costs of false-negative and false-positive testing.

RESULTS

Our hospital-based experience yielded an average cost of $ 3664 per patient without MRI and $ 2283 per patient when MRI was available (1991 dollar amounts). The cost of diagnosis was 65% more expensive without MRI. Use of the literature-based experience demonstrated that the cost of diagnosis was at least 82% more costly without MRI than when it was available. However, when key variables were altered during sensitivity analysis, this difference of increased cost of diagnosis without MRI ranged from 25% to 98%.

CONCLUSION

This work suggests that MRI may result in significant economic benefits in diagnosing metastatic cord compression, but further work is needed on physician behavior and referral patterns with MRI versus myelography as is long term follow-up for potential reductions in patient debility using MRI.

Health care technology as a policy issue

Health care technology has become an increasingly visible issue in many countries, primarily because of the rising costs of health care. In addition, many questions concerning quality of care are being raised. Health care technology assessment has been seen as an aid in addressing questions concerning technology, including benefits and costs. A number of industrialized countries have developed active programs of health care technology assessment during the past two decades. Eight countries at similar levels of socio-economic and health development--Australia, Canada, France, Germany, the Netherlands, Sweden, the United Kingdom and the United States--have been examined to gain insights into how they manage health care technology and what place technology assessment has in such management. In addition to seeking general information, specific cases--treatment for coronary artery disease, medical imaging, laparoscopic surgery, treatment of end-stage renal disease, neonatal intensive care, and breast cancer screening--were examined in each country.

Spin-spin relaxation in experimental allergic encephalomyelitis. Analysis of CPMG data using a non-linear least squares method and linear inverse theory

We have used the CPMG pulse sequence to measure proton T2 values and water content in spinal cord and brain samples from Hartley guinea pigs inoculated to produce experimental allergic encephalomyelitis (EAE). Relaxation data were fitted using minuit, a non-linear curve fitting routine. Three exponentials provided the best fit to spinal cord data (10 ms (13%), 76 ms (57%), 215 ms (30%)) and two exponentials for brain tissue (10 ms (4%), 92 ms (96%)). Least squares algorithms were also used to analyse the spinal cord data in terms of discrete and smooth distributions of relaxation times. The discrete least squares solutions consisted of three to five isolated spikes between 0.010 and 0.300 s. This type of solution was difficult to interpret in terms of water reservoirs. Smooth solutions consisted of two broad peaks, a small peak with a T2 near 0.010 s and a larger peak near 0.100 s. The integral ratio of the larger to the smaller peak was 7.092 +/- 1.782 for normal tissue, and increased to a maximum of 16 with increasing parenchymal cellular infiltration and demyelination. The short T2 peak has been assigned to water in the hydration layers of the myelin sheath. The width of the longer T2 peak was sensitive to tissue heterogeneity. The least squares and smooth distribution analysis models could be used to distinguish samples with extensive parenchymal infiltration from normal tissue, even though only a maximum of 60% of the tissue was affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Economic assessment of magnetic resonance imaging for inpatients: is it still too early?

This economic assessment of the implementation of magnetic resonance imaging (MRI) in a French hospital examines data on the diagnostic resources used in neurology and neurosurgery before and after MRI was available. Given a similar patient population and case mix, there was no change in the resources used other than the addition of MRI. So far, MRI appears to be a complement to, and not a substitute for, other imaging techniques used in neuroradiology. The focus of this work is purely economic; its conclusions do not challenge the major scientific contributions of MRI.

Magnetic resonance imaging. Diffusion of technology in an ambulatory setting

To better understand technology diffusion in an ambulatory care setting, we analyzed adult outpatients' use of magnetic resonance (MR) and computed tomography (CT) imaging in a group-model HMO between 1986 and 1989. The use of MR, but not CT, increased at a rapid pace with only a small proportion of the scans being accounted for by primary care physicians.

Magnetic resonance imaging in minor head injury

STUDY OBJECTIVES

To investigate the role of cranial magnetic resonance (MR) imaging in evaluating patients discharged from the emergency department after minor head injury.

DESIGN

A prospective blinded cohort study.

SETTING

University hospital ED.

TYPE OF PARTICIPANTS

Fifty-eight patients with minor head injury who were discharged from the ED with written head injury instructions. Patients admitted to the hospital were excluded.

INTERVENTIONS

Ultra-low-field cranial MR scans were performed on patients within 24 hours of discharge. Scans were read blindly by two radiologists.

MEASUREMENTS AND MAIN RESULTS

Fisher's exact test was used to compare symptoms in patients with abnormal and normal MR scans. There was no significant difference in symptoms between patients with abnormal and those with normal scans (P greater than .10). The proportion of abnormal MR scans was analyzed using the binomial distribution. Six of the 58 patients (10.3%) had traumatic intracranial abnormalities (proportion, 0.103; SD, 0.04; 95% CI, 0.04-0.21). Three had cortical contusions, and three had small subdural hematomas. Two of the six patients with abnormal MR scans, both with small subdural hematomas, had normal computed tomography scans.

CONCLUSION

Ten percent of patients discharged from the ED after minor head injury had abnormal ultra-low-field cranial MR scans. Additional research is needed to establish the clinical importance of this unexpected observation.

The investigation of acoustic neuroma

Gadolinium-enhanced magnetic resonance (GdMR) is the long awaited, easy and definitive investigation for imaging or excluding small acoustic neuromas. However, on the grounds of cost alone it is unrealistic to submit every patient with mild unilateral sensorineural deafness to GdMR. A screening regime is described which combines simple but effective imaging studies of the internal auditory meatus with clinical testing of vestibular function and objective audiometry. The 'two out of three positive' approach based on these tests has proved to be a reliable screening regime for selecting patients for GdMR.

Intracranial meningiomas: how frequent are indicative findings in CT and MRI?

Frequencies of CT and MRI findings characteristic of meningiomas were compared in 50 cases. Plain and contrast enhanced examinations with CT and MRI were evaluated retrospectively regarding 12 criteria known to be indicative of the diagnosis of meningiomas. CT proved to be superior in demonstrating calcifications and a typical tumor density. On the other hand. MRI was better suited for identifying the extraaxial location of tumors, the broad contact of tumors to the meninges, tumor capsules and meningeal contrast enhancement adjacent to the tumor. Both methods provided nearly equal results in demonstrating mass effects, hyperostoses, intensive and homogeneous contrast enhancement, and smooth tumor contours after contrast administration. On the whole, neither of the two methods demonstrated a universal superiority for the diagnosis of intracranial meningiomas. Rather, each method displayed distinct advantages.

Targeting assessments of magnetic resonance imaging in suspected multiple sclerosis

Decision-analytic methods can be valuable for targeting research in technology assessment. They can indicate whether further evaluation of a technology is warranted, and if so, which variables are key determinants of its clinical utility and cost-effectiveness. This approach was tested on a salient issue--whether magnetic resonance imaging (MR) should be used in evaluating patients with mild neurologic symptoms who might have multiple sclerosis (MS). The authors developed a decision-analytic model to assess the expected utility and costs associated with immediately using MR in this situation, compared with waiting for further symptoms to emerge before testing. Sensitivity analyses demonstrated that priorities for technology assessment research include estimating the value of information to patients in resolving uncertainty, evaluating the impact on patients of being labeled with a diagnosis of MS, and measuring the test characteristics of MR.

Intracranial meningiomas. Comparison of plain and contrast-enhanced examinations in CT and MRI

Fifty patients with intracranial meningiomas underwent plain and contrast-enhanced examinations with CT and MRI. Each of the MR studies consisted of three plain (T1, proton density and T2-weighted) and a post-contrast series (0.1 mmol Gd-DTPA/kg body weight). All techniques (plain CT, plain MRI, contrast-enhanced CT, contrast-enhanced MRI) proved to be highly efficient as regards tumour detection: depending on the technique, an intracranial lesion was demonstrated in 47-50 cases. The image contrast was assessed as good or excellent in 21 cases having plain CT and in 33 cases having plain MRI, but in 46 and 50 of the contrast-enhanced CT and MRI studies respectively. Adequate tumour delineation was achieved in 18 cases with plain CT, in 35 cases with plain MRI and in 46 and 50 cases of the contrast-enhanced CT and MRI examinations. The contrast-enhanced studies proved to be superior to the plain CT and MRI studies as regards image contrast and tumor delineation. Because of the methodological advantages of the MRI technique, contrast-enhanced MRI was judged to be slightly superior to contrast-enhanced CT.

Imaging of brain metastases. Comparison of computerized tomography (CT) and magnetic resonance imaging (MRI)

For the demonstration of brain metastases both CT and MRI are available as diagnostic modalities. To compare both imaging methods as to their sensitivity in detecting brain metastases CT scans and MR images of 60 patients with suspected brain metastases were evaluated. Comparing contrast-enhanced CT and plain MRI neither modality was found to be clearly superior in this respect.

Comparison of magnetic resonance imaging and computed tomography in suspected lesions in the posterior cranial fossa

OBJECTIVE

To compare computed tomography and magnetic resonance imaging in investigating patients suspected of having a lesion in the posterior cranial fossa.

DESIGN

Randomised allocation of newly referred patients to undergo either computed tomography or magnetic resonance imaging; the alternative investigation was performed subsequently only in response to a request from the referring doctor.

SETTING

A regional neuroscience centre serving 2.7 million.

PATIENTS

1020 Patients recruited between April 1986 and December 1987, all suspected by neurologists, neurosurgeons, or other specialists of having a lesion in the posterior fossa and referred for neuroradiology. The groups allocated to undergo computed tomography or magnetic resonance imaging were well matched in distributions of age, sex, specialty of referring doctor, investigation as an inpatient or an outpatient, suspected site of lesion, and presumed disease process; the referring doctor's confidence in the initial clinical diagnosis was also similar.

INTERVENTIONS

After the patients had been imaged by either computed tomography or magnetic resonance (using a resistive magnet of 0.15 T) doctors were given the radiologist's report and a form asking if they considered that imaging with the alternative technique was necessary and, if so, why; it also asked for their current diagnoses and their confidence in them.

MAIN OUTCOME MEASURES

Number of requests for the alternative method of investigation. Assessment of characteristics of patients for whom further imaging was requested and lesions that were suspected initially and how the results of the second imaging affected clinicians' and radiologists' opinions.

RESULTS

Ninety three of the 501 patients who initially underwent computed tomography were referred subsequently for magnetic resonance imaging whereas only 28 of the 493 patients who initially underwent magnetic resonance imaging were referred subsequently for computed tomography. Over the study the number of patients referred for magnetic resonance imaging after computed tomography increased but requests for computed tomography after magnetic resonance imaging decreased. The reason that clinicians gave most commonly for requesting further imaging by magnetic resonance was that the results of the initial computed tomography failed to exclude their suspected diagnosis (64 patients). This was less common in patients investigated initially by magnetic resonance imaging (eight patients). Management of 28 patients (6%) imaged initially with computed tomography and 12 patients (2%) imaged initially with magnetic resonance was changed on the basis of the results of the alternative imaging.

CONCLUSIONS

Magnetic resonance imaging provided doctors with the information required to manage patients suspected of having a lesion in the posterior fossa more commonly than computed tomography, but computed tomography alone was satisfactory in 80% of cases...

A comparative study of CT and MRI in midline tumors of childhood and adolescence

In order to compare the validity of CT and MRI, we evaluated results of these studies in 40 children and adolescents suffering from supratentorial and infratentorial midline tumors. Plain and enhanced CT scans were compared with MRI for sensitivity, specificity and capacity to delineate the tumor. These parameters were evaluated by three independent investigators on a scale with four grades of accuracy. The results demonstrate greater sensitivity and better delineation of the tumor with MRI, but greater specificity in diagnosis of tumors with CT studies.

Computed tomography versus magnetic resonance imaging of the brain. A collaborative interinstitutional study

A retrospective study (1983-1984) of magnetic resonance imaging (MRI) and computed tomography (CT) examinations in 471 patients with known pathology in the brain and craniocervical junction was conducted in order to determine the relative efficacy of MRI versus CT. All MRI examinations involved slice thickness greater than 10 mm, and only single-slice single-echo or multislice single-echo imaging techniques were available. These studies were evaluated independently by two neuroradiologists from a panel of six for anatomic abnormalities, lesion contrast, and radiologist's impression. Results, which excluded microadenomas of the pituitary and approximately 9% of studies in which consensus was not achieved by the readers, were as follows: (1) 14% of the studies were positive on MRI but normal on CT; (2) in 55% of the studies, MRI was better than CT; (3) MRI was equal or better than CT in 95% of the studies; and (4) CT was better than MRI in 5% (21/421) of the examinations. There were no patients in this series where CT was positive but MRI missed the abnormality.

The relevance of socioeconomic and health policy issues to clinical research. The case of MRI and neuroradiology

Magnetic resonance imaging (MRI) is a high-cost, new technology with great potential for improving patient care. The lack of a coherent public policy for MRI, or its predecessor computed tomography (CT), has caused considerable problems. Lack of an enunciated public policy has led to inconsistent reimbursement and reimbursement levels that develop in haphazard ways. Furthermore, diffusion has been unpredictable and has led to geographical excesses and deficiencies. Technology assessments of MRI, although numerous, have used inconsistent criteria to rate MRI's clinical efficacy. The lack of methodologically sound studies of MRI severely hampered early evaluation. This article examines these problems and suggests that the medical profession take a stronger leadership role in developing policies for expensive, promising new diagnostic technologies. The profession should promote, demand, and perform rigorous clinical evaluations of new technologies, and help develop a consensus regarding the criteria for what constitutes a clinically valuable advance in diagnostic technology.

Magnetic resonance imaging of acoustic neuromas: the role of gadolinium-DTPA

Magnetic resonance imaging (MRI) was performed in 20 patients with evidence on computed tomography (CT) of 21 acoustic neuromas before and after intravenous administration (0.1-0.2 mmol/kg body weight) of gadolinium-diethylene-triamine-pentaacetic acid (Gd-DTPA). Multi-section spin-echo (SE) sequences of varying repetition (TR) and echo (TE) times were performed in the transverse and coronal planes with a section thickness of 10 mm. All acoustic neuromas displayed marked enhancement on the T1-weighted (short TR/TE) SE sequence post-Gd-DTPA. The intrameatal component was particularly well demonstrated compared with non-enhanced magnetic resonance (MR) images and contrast-enhanced CT. Identification of intrameatal tumour was difficult on T2-weighted SE images and one tumour was not identified on the T1-weighted SE sequence prior to Gd-DTPA. Four of five intrameatal tumours measuring less than 8 mm could only be demonstrated on CT by using CT air meatography. Extrameatal tumour extension was demonstrated on contrast-enhanced CT, although the assessment of brain-stem involvement and displacement was not as clearly seen as on coronal MR images. In two patients with large acoustic neuromas and a cyst, the true relationship of the cyst to the tumour could only be identified on the post-Gd-DTPA scan. Magnetic resonance imaging with gadolinium-DTPA is a relatively quick, safe, well tolerated and effective method for the diagnosis of acoustic neuroma.

The value of CT and very low field MRI in the etiological diagnosis of dizziness

A total of 79 dizziness patients were examined by either computed tomography (CT), or very low field magnetic resonance imaging (MRI), or both. In most cases, the patients were selected for the neuroimaging because preliminary clinical examination had suggested central nervous system (CNS) involvement. Abnormal CT or MRI findings with probable clinical relevance to the etiology of dizziness were obtained in 34%. The most common abnormalities were atrophy, infarction, and demyelination.; 29% of the CT scans and 40% of the MRI showed relevant abnormalities. The present results emphasize the diagnostic usefulness of head CT and MRI when dizziness of CNS etiology is suspected.

Gadolinium-DTPA as a contrast agent in magnetic resonance imaging of the brain

One hundred patients with CT-proven intracranial disease have been studied by magnetic resonance imaging (MRI) before and after intravenous injection with Gadolinium-DTPA (Gd-DTPA), in order to assess the role and clinical efficacy of Gd-DTPA. T2-weighted spin echo sequences, although sensitive to the detection of intracranial disease, in general fail to differentiate macroscopic tumor from oedema. Following Gd-DTPA, T1-weighted spin echo sequences in primary tumours demonstrated a variable degree of contrast enhancement unrelated to histological type. Small tumours, especially acoustic neuromas and meningiomas in the posterior fossa, were rendered more conspicuous. Optimum time for scanning was between five and 25 min following injection for all lesions except those adjacent to normal enhancing structures such as nasal/sinus mucosa and pituitary gland when delayed scans up to 45 min were necessary. No differences were observed between the 0.1 and 0.2 mmol/kg Gd-DTPA concentrations used and no complications attributable to Gd-DTPA were detected. Clinical advantages of Gd-DTPA include shorter scan times, macroscopic tumour/oedema separation and improved detection of certain tumours, particularly acoustic neuromas.

Magnetic resonance imaging of the brain and spine

The efficacy of magnetic resonance imaging (MRI) in the diagnosis of diseases of the central nervous system is reviewed. MRI, computed tomography (CT) and certain radionuclide studies are compared in the evaluation of intracranial tumours, cerebral vascular disease, multiple sclerosis and other white matter diseases, dementia, head injury, infection, epilepsy, spinal lesions and in paediatric central nervous system disorders. The measurement of cerebrospinal fluid volumes and dynamics by MRI is discussed. MRI most clearly has advantages where CT is degraded by bone hardening and streak artefacts (spine, skull base, posterior and temporal fossa, sella and parasellar regions) and in diseases in which the X-ray attenuation of the suspected lesion differs little from normal parenchyma (paediatric brain disorders, demyelination and dysmyelination, early oedema associated with infarction, infection or low-grade infiltrating neoplasm, subacute and chronic haemorrhage and lesions in the spinal subarachnoid space and cord). Elsewhere MRI and CT should be seen as complementary rather than competitive methods of imaging. In spite of an absence of information about the contribution of MRI to management decisions and a lack of rigorous, prospective controlled trials, MRI will play an increasing role in the diagnosis of diseases of the central nervous system.