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Biomedical subjects

P D Griffiths

Publications and source records attributed to P D Griffiths.

At least 55 records · Page 3Linked to original sources
PubMed2004

Comparison of ultrasound and magnetic resonance imaging in 100 singleton pregnancies with suspected brain abnormalities.

OBJECTIVE: To compare the diagnostic accuracy of the current reference standard-ultrasound with in utero magnetic resonance imaging, in a selected group of patients. DESIGN: Prospective study. SETTING: Five fetal maternal tertiary referral centres and an academic radiology unit. SAMPLE: One hundred cases of fetuses with central nervous system abnormalities where there has been diagnostic difficulties on ultrasound. In 48 cases the women were less than 24 weeks of gestation and in 52 cases later in pregnancy. METHODS: All women were imaged on a 1.5 T clinical system using a single shot fast spin echo technique. The results of antenatal ultrasound and in utero magnetic resonance were compared. MAIN OUTCOME MEASURES: The definitive diagnosis was made either at autopsy or by postmortem magnetic resonance imaging, in cases that went to termination of pregnancy, or a combination of postnatal imaging and clinical follow up in the others. RESULTS: In 52 of cases, ultrasound and magnetic resonance gave identical results and in a further 12, magnetic resonance provided extra information that was judged not to have had direct effects on management. In 35 of cases, magnetic resonance either changed the diagnosis (29) or gave extra information that could have altered management (6). In 11 of the 30 cases where magnetic resonance changed the diagnosis, the brain was described as normal on magnetic resonance. CONCLUSIONS: In utero magnetic resonance imaging is a powerful tool in investigating fetal brain abnormalities. Our results suggest that in selected cases of brain abnormalities, detected by ultrasound, antenatal magnetic resonance may provide additional, clinically useful information that may alter management.

Brain↗
PubMed2004

How well do we investigate patients with suspected subarachnoid haemorrhage? The continuing need for cerebrospinal fluid investigations.

OBJECTIVE: To demonstrate the extent of compliance with established guidelines for the investigation of suspected subarachnoid haemorrhage (SAH) and the implications of non-compliance. DESIGN: Prospective observational study of practice in three hospitals in the Trent region. SETTING: One teaching hospital with a tertiary neuroscience referral centre and two large district general hospitals. PARTICIPANTS: 50 consecutive patients from each centre referred for suspected SAH with negative computed tomography. MAIN OUTCOME MEASURES: Diagnosis of SAH confirmed or excluded according to guidelines. RESULTS: When the data from the three centres were combined (n = 150 computed tomography negative cases) cerebrospinal fluid (CSF) investigation was not performed in 60/150 (40%). In the 90 cases where CSF studies were performed SAH was confirmed in 11 (12%). CONCLUSION: There is significant non-compliance in following the established guidelines for the investigation of SAH at the centres studied. As the primary cause of non-traumatic SAH is ruptured aneurysm, which is associated with high morbidity and mortality from second haemorrhage, this highlights a major source of concern for clinical governance.

Adolescent↗
PubMed2004

Distribution and quantification of human herpesvirus 6 in multiple sclerosis and control brains.

Multiple sclerosis (MS) is thought to be precipitated by environmental factors, potentially including viruses, in genetically susceptible individuals and recently human herpesvirus 6 (HHV-6) has been associated with the disease. We have analysed post mortem brain for the presence, variant type and quantity of HHV-6 by PCR. A total of 124 samples from seven anatomically defined regions of brain were tested from MS cases and controls. HHV-6 DNA was detected in 41% and 44% of MS case and control samples. The median viral loads were 11 and 9 genome copies/microg DNA in cases and controls respectively and the viral load was not increased in lesions. Except in one instance, the HHV-6 DNA detected was variant B. There was no apparent difference in the distribution of HHV-6 DNA in the brains of MS cases versus controls, nor between normal appearing and lesional tissue in MS cases. Periventricular regions of the brain were more frequently positive for HHV-6 DNA in both MS cases and controls, although this difference was not statistically significant. These studies confirm the neurotropism of HHV-6 but do not demonstrate differences in the distribution, variant type or quantity of HHV-6 in brains from patients with MS versus controls.

Aged↗
PubMed2004

Intracranial MR venography in children: normal anatomy and variations.

BACKGROUND AND PURPOSE: Little information is available regarding the anatomy of the intracranial veins and sinuses that can be shown on MR venograms of children. The aim of this study was to determine the normal venous anatomy and anatomic variants. METHODS: Fifty children who were referred for investigation of developmental delay and who had normal results of MR imaging of the brain were recruited into the study. The cerebral veins and sinuses, including the occipital sinuses, were assessed by using 2D time-of-flight venography. Particular attention was paid to the anatomy of the venous confluence. RESULTS: Twenty-seven cases had dominant right transverse sinuses, 18 had dominant left transverse sinuses, four had co-dominant transverse sinuses, and one had absence of both transverse sinuses. In 21 (51%) of 41 cases without occipital sinuses, absent or hypoplastic transverse sinuses were found. Nine patients had occipital sinuses. Five (56%) of nine patients with occipital sinuses were younger than 2 years, and patients younger than 2 years accounted for 24% of all patients (12 of 50 patients) in the study. In six (67%) of nine patients with occipital sinuses, absent or hypoplastic transverse sinuses were shown. Two patients had bulbous prominence of the vein of Galen. One had foreshortened superior sagittal sinus, which in turn is drained by two paramedian cortical veins. CONCLUSION: Understanding the normal anatomy of the cerebral venous system and its variants by using MR venography in children provided the background to future studies on anomalous venous structure in malformations of the brain.

Adolescent↗
PubMed2003

Neurovascular MRI with dynamic contrast-enhanced subtraction angiography.

The first generation of digital subtraction MR angiography using thick-slab contrast-enhanced 2D projection techniques has confirmed the potential of MRI to produce noninvasive subsecond angiograms of the craniocervical circulation. As time-resolved techniques become more sophisticated and 3D acquisitions can be obtained with high isotropic spatial resolution we may start to see the demise of catheter angiography as a diagnostic procedure.

Angiography, Digital Subtraction↗
PubMed2003

Choice of cross size in stereology--a cautionary note.

The stereological method of cross-counting based on the Cavalieri principle is widely used in neuroimaging to estimate the volume of cerebral structures. Although superficially simple, the stereological technique is validated by arcane mathematical proofs, so the cross size is determined by most investigators on a pragmatic basis with the assumption that the volume calculated is independent of the cross size used. We used three cross sizes (8x8, 5x5 and 3x3 voxels) to estimate the brain volume of six healthy control subjects. The volume estimate using a cross size of 3x3 was 9% larger than with a cross size of 5x5 and the latter was 15% larger than with a cross size of 8x8. We conclude that cross size significantly affects whole brain volume estimates and this result is presumably applicable to other structures whose cross-sectional areas form complex shapes. Investigators should be aware of this fact, especially when trying to make direct comparisons between volume estimates derived from the stereological method using different cross sizes.

Adolescent↗
PubMed2003

Magnetic resonance imaging with stepped B(0) fields.

This paper introduces the concept of imaging with stepped magnetic fields within the main B(0) field. The resonance frequency within each step is separated from the next by an amount greater than the imaging bandwidth. Each step thus gives rise to a separate imaging region enabling simultaneous imaging over multiple slices without aliasing. The auxiliary magnetic field regions are produced by coil inserts. The principle is illustrated using simple coil designs which introduce up to two steps into the main B(0) field. Phantoms placed in each uniform region were successfully imaged simultaneously with no aliasing.

Calibration↗
PubMed2003

Magnetic resonance spectroscopic abnormalities in sporadic and variant Creutzfeldt-Jakob disease.

AIM: To study the proton MR spectroscopic findings in Creutzfeldt-Jakob disease (CJD) (sporadic and variant). MATERIALS AND METHODS: MR imaging and proton MR spectra were acquired in two patients with sporadic CJD (biopsy proven) and one patient with variant CJD. RESULTS: The two patients with sporadic CJD demonstrated MR signal change within the basal ganglia and thalami and reduced N-acetylaspartate (NAA):creatine ratios. The patient with variant CJD showed characteristic signal change within the pulvinar of the thalami and a markedly reduced N-acetylaspartate:creatine ratio. CONCLUSION: All three patients with CJD demonstrated evidence of reduced N-acetylaspartate: creatine ratios on MR spectroscopy. These changes imply that neuronal loss and/or dysfunction is a consistent finding in established CJD.

Adult↗
PubMed2003

Neuroimaging for non-accidental head injury in childhood: a proposed protocol.

Non-accidental head injury (NAHI) is a major cause of neurological disability and death during infancy. Radiological imaging plays a crucial role in evaluating craniospinal injury, both for guiding medical management and the forensic aspects of abusive trauma. The damage sustained is varied, complex and may be accompanied by an evolving pattern of brain injury secondary to a cascade of metabolic and physiological derangements. Regrettably, many cases are poorly or incompletely evaluated leading to diagnostic errors and difficulties in executing subsequent child care or criminal proceedings. It is evident, from cases referred to the authors, that imaging protocols for NAHI are lacking (or only loosely adhered to, if present) in many centres throughout the U.K. Future research in this field will also be hampered if there is a lack of consistent and reliable radiological data. There is no nationally agreed protocol for imaging NAHI. We propose such a protocol, based upon a wide experience in the medical management of child abuse and extensive involvement in the medicolegal aspects of NAHI.

Child↗
PubMed2003

Ultrafast MR imaging in pediatric neuroradiology.

PURPOSE: To compare the diagnostic information obtained from ultrafast MR imaging with standard MR imaging techniques in pediatric neuroradiology. The goal was to judge whether ultrafast methods can be used to replace standard methods and reduce the need for sedation or general anesthesia as a result of the considerably shorter scan times. MATERIAL AND METHODS: Our prospective study involved 125 patients. Routine clinical imaging was performed along with two ultrafast methods. Single shot fast spin echo (SSFSE) was used to give T2-weighted images and an echo planar imaging (EPI) sequence to provide a T1-weighted images. The ultrafast images were presented to an experienced neuroradiologist who was also given the information present on the initial referral card. These reports based on the ultrafast images were then compared with the formal radiologic report made solely on the basis of the standard imaging. RESULTS: The overall sensitivity and specificity for ultrafast imaging when compared to the reference standard were 78% and 98% with positive and negative predictive values of 98% and 76%. Pathologies characterized by small areas of subtle T2 prolongation were difficult or impossible to see on the ultrafast images but otherwise they provided reliable information. CONCLUSIONS: This paper demonstrates that ultrafast MR imaging can diagnose many pediatric intracranial abnormalities as well as standard methods. Anatomic resolution limits its capacity to define subtle developmental anomalies and contrast resolution limitations of the ultrafast methods reduce the detection of pathology characterized by subtle T2 prolongation.

Brain Diseases↗
PubMed2003

Low field strength magnetic resonance imaging of the neonatal brain.

BACKGROUND: Magnetic resonance (MR) imaging of the neonate has been restricted by the need to transport the sick baby to the large magnetic resonance scanners and often the need for sedation or anaesthesia in order to obtain good quality images. Ultrasound is the reference standard for neonatal imaging. OBJECTIVE: To establish a dedicated neonatal MR system and compare the clinical usefulness of MR imaging with ultrasound imaging. DESIGN: Prospective double blind trial. SETTING: Neonatal intensive care unit, Sheffield. MAIN OUTCOME MEASURES: Imaging reports. PATIENTS: 134 premature and term babies. RESULTS: In 56% of infants with pathology suspected on clinical grounds, MR provided additional useful clinical information over and above that obtained with ultrasound. CONCLUSION: Infants can be safely imaged by dedicated low field magnetic resonance on the neonatal intensive care unit without the need for sedation at a cost equivalent to ultrasound.

Brain↗
PubMed2003

Motor functional MRI for pre-operative and intraoperative neurosurgical guidance.

Functional MRI (fMRI) may provide a means of locating areas of eloquent cortex that can be used to guide neurosurgeons in their quest to maximize intracerebral tumour resection whilst minimizing post-procedural neurological deficits. This work aimed to develop and provide an initial assessment of such a technique. 19 patients with mass lesions close to the primary motor cortex underwent fMRI at 1.5T. A single shot echo planar technique was used to acquire data corresponding to right and left hand movement. Resultant activation maps were used to aid pre-surgical planning. Data was used in conjunction with an intraoperative navigation system in 13 cases. Activation was attributed to primary motor, primary somatosensory or supplementary motor cortex in 17 of 19 subjects. No permanent changes in motor deficit were detected post surgery. The additional information provided by fMRI, particularly when incorporated into a neuronavigation guided craniotomy, was deemed highly valuable to the neurosurgeon as it enabled safe resection of tumour in anatomical locations previously deemed to be too high risk for safe resection using conventional (non-fMRI-guided) technique. This observation is reinforced by the fact that no patients suffered permanent neurological deficit after radical tumour debulking (surgical estimates >90% tumour resection).

Adolescent↗
PubMed2003

MR imaging of the fetal brain and spine: a maturing technology.

INTRODUCTION: We describe the background and refinements to a 3-year research study designed to evaluate the role of magnetic resonance (MR) imaging in detecting and defining abnormalities of the fetal central nervous system in utero. METHODS: We describe our experience of using ultra-fast MR imaging methods (specifically single-shot fast spin echo) in 250 fetuses at various gestational ages. All fetuses had known or suspected brain or spine abnormalities based on antenatal ultrasound imaging. We describe the ethical issues raised by this type of work and the differences in diagnostic accuracy between ultrasound and MR imaging. RESULTS: We show that MR imaging can be performed in a clinical environment with a high degree of success: only 2 women out of 250 could not be examined (1 was claustrophobic and the other was too large for our scanner). In the 100 cases of singleton pregnancies, where detailed follow-up is available, there is a > 40% improvement in diagnostic accuracy when MR imaging is included in the fetal assessment compared to ultrasound alone. CONCLUSION: We conclude that in utero MR imaging is a powerful tool in the assessment of fetal brain and spine abnormalities, and suggest that further work be undertaken to provide a widely available clinical service.

Brain↗
PubMed2002

Temozolomide in malignant gliomas of childhood: a United Kingdom Children's Cancer Study Group and French Society for Pediatric Oncology Intergroup Study.

PURPOSE: To determine the response rate of the malignant gliomas of childhood to an oral, daily schedule of temozolomide. PATIENTS AND METHODS: A multicenter, phase II evaluation of an oral, daily schedule of temozolomide (200 mg/m(2) on 5 consecutive days) was undertaken in children with relapsed or progressive, biopsy-proven, high-grade glioma (arm A) and progressive, diffuse, intrinsic brainstem glioma (arm B). Evidence of activity was defined by radiologic evidence of a sustained reduction in tumor size on serial magnetic resonance imaging scans. RESULTS: Fifty-five patients were recruited (34 to arm A and 21 to arm B) and received 215 cycles of chemotherapy. Grade 3/4 thrombocytopenia was the most frequent toxic event (7% of cycles). Prolonged myelosuppression resulted in significant treatment delays and dose reductions (17% and 22% of cycles, respectively). Two toxic deaths were documented and were related to myelosuppression and sepsis in one patient and pneumonia in a second. The overall (best) response rate was 12% for arm A (95% confidence interval [CI], 3 to 28 in the study cohort, and 2 to 31 for eligible patients) and 5% and 6%, respectively, for arm B (95% CI, 0 to 26 in the study cohort, and 0 to 27 for eligible patients). Stabilization of disease was also documented and was most noteworthy for brainstem gliomas, where two patients achieved both radiologic static disease and discontinued steroid medication. CONCLUSION: Despite moderate toxicity, objective response rates to temozolomide have been low, indicating that temozolomide has minimal activity in the high-grade gliomas of childhood.

Adolescent↗
PubMed2002

MR imaging of the lungs with hyperpolarized helium-3 gas transported by air.

Hyperpolarized noble gas MRI shows promise in the functional imaging of the pulmonary air spaces. The production of hyperpolarized (HP) gas requires specialized laser optical pumping apparatus, which is not likely to be home built in the majority of clinical MRI radiology centres. There are two routes through which HP gas will be made available to hospitals for clinical use: either the apparatus will be installed locally at a considerable expense to the centre, or a central facility will produce the gas and then deliver it to remote MRI sites as and when required. In this study, the feasibility of transporting large quantities of HP gas for in vivo MR imaging from a remote production facility in Mainz, Germany, by airfreight to Sheffield, UK, was successfully demonstrated.

Air↗
PubMed2002

Image-based EPI ghost correction using an algorithm based on projection onto convex sets (POCS).

This work describes the use of a method, based on the projection onto convex sets (POCS) algorithm, for reduction of the N/2 ghost in echo-planar imaging (EPI). In this method, ghosts outside the parent image are set to zero and a model k-space is obtained from the Fourier transform (FT) of the resulting image. The zeroth- and first-order phase corrections for each line of the original k-space are estimated by comparison with the corresponding line in the model k-space. To overcome problems of phase wrapping, the first-order phase corrections for the lines of the original k-space are estimated by registration with the corresponding lines in the model k-space. It is shown that applying these corrections will result in a reduction of the ghost, and that iterating the process will result in a convergence towards an image in which the ghost is minimized. The method is tested on spin-echo EPI data. The results show that the method is robust and remarkably effective, reducing the N/2 ghost to a level nearly comparable to that achieved with reference scans.

Algorithms↗