Martyn Paley

Frequency and natural history of subdural haemorrhages in babies and relation to obstetric factors

BACKGROUND Subdural haematomas are thought to be uncommon in babies born at term. This view is mainly based on findings in symptomatic neonates and babies in whom subdural haemorrhages are detected fortuitously. We aimed to establish the frequency of subdural haemorrhages in asymptomatic term neonates; to study the natural history of such subdural haematomas; and to ascertain which obstetric factors, if any, are associated with presence of subdural haematoma. METHODS We did a prospective study in babies who were born in the Jessop wing of the Central Sheffield University Hospitals between March, 2001, and November, 2002. We scanned neonates with a 0.2 T magnetic resonance machine. FINDINGS 111 babies underwent MRI in this study. 49 were born by normal vertex delivery without instrumentation, 25 by caesarean section, four with forceps, 13 ventouse, 18 failed ventouse leading to forceps, one failed ventouse leading to caesarean section, and one failed forceps leading to caesarean section. Nine babies had subdural haemorrhages: three were normal vaginal deliveries (risk 6.1%), five were delivered by forceps after an attempted ventouse delivery (27.8%), and one had a traumatic ventouse delivery (7.7%). All babies with subdural haemorrhage were assessed clinically but no intervention was needed. All were rescanned at 4 weeks and haematomas had completely resolved. INTERPRETATION Presence of unilateral and bilateral subdural haemorrhage is not necessarily indicative of excessive birth trauma.

Detection of subarachnoid haemorrhage with magnetic resonance imaging

OBJECTIVES To measure the sensitivity and specificity of five MRI sequences to subarachnoid haemorrhage. METHODS Forty one patients presenting with histories suspicious of subarachnoid haemorrhage (SAH) were investigated with MRI using T1 weighted, T2 weighted, single shot fast spin echo (express), fluid attenuation inversion recovery (FLAIR), and gradient echo T2* sequences, and also by CT. Lumbar puncture was performed in cases where CT was negative for SAH. Cases were divided into acute (scanned within 4 days of the haemorrhage) and subacute (scanned after 4 days) groups. RESULTS The gradient echo T2* was the most sensitive sequence, with sensitivities of 94% in the acute phase and 100% in the subacute phase. Next most sensitive was FLAIR with values of 81% and 87% for the acute and subacute phases respectively. Other sequences were considerably less sensitive. CONCLUSIONS MRI can be used to detect subacute and acute subarachnoid haemorrhage and has significant advantages over CT in the detection of subacute subarachnoid haemorrhage. The most sensitive sequence was the gradient echo T2*.

Combined helium-3/proton magnetic resonance imaging measurement of ventilated lung volumes in smokers compared to never-smokers.

To use a combination of helium‐3 (3‐He) magnetic resonance imaging (MRI) and proton single‐shot fast spin echo (SSFSE) to compare ventilated lung volumes in groups of “healthy” smokers, smokers diagnosed with moderate chronic obstructive pulmonary disease (COPD), and never‐smokers.

Diffusion tensor imaging for the assessment of upper motor neuron integrity in ALS

Background: High angular resolution diffusion tensor imaging (HARD) is an MRI technique that exploits the mobility of water molecules to yield maps of structural order and directionality of white matter tracts with greater precision than six-direction diffusion tensor imaging (DTI) schemes. Objective: To assess whether HARD is more sensitive than conventional MRI or neurologic assessment in detecting the upper motor neuron (UMN) pathology of patients with ALS. Methods: Twenty-five patients with definite UMN clinical signs and 23 healthy volunteers underwent conventional MRI. HARD datasets were collected from a subset of these participants plus four patients with isolated lower motor neuron (LMN) signs. ALS symptom severity was assessed by a neurologist, the conventional MR images were reviewed by neuroradiologists, and the DTI maps were subject to quantitative region of interest analysis. Results: Motor cortex hypointensity on T2-weighted images and corona radiata hyperintensity on proton density-weighted images distinguished patients with UMN involvement from volunteers with 100% specificity, but only 20% sensitivity. Fractional anisotropy (FA) was reduced in the posterior limb of the internal capsule in patients with UMN involvement compared to volunteers. A FA threshold value with a sensitivity of 95% to detect patients with ALS (including those with isolated LMN signs) had a specificity of 71%. Conclusions: High angular resolution diffusion tensor imaging may be more sensitive than conventional MRI or neurologic assessment to the upper motor neuron (UMN) pathology of ALS, but it lacks the specificity required of a diagnostic marker. Instead, it is potentially useful as a quantitative tool for monitoring the progression of UMN pathology.

Dynamic radial projection MRI of inhaled hyperpolarized 3He gas.

A radial projection sliding‐window sequence has been developed for imaging the rapid flow of 3He gas in human lungs. The short echo time (TE) of the radial sequence lends itself to fast repetition times, and thus allows a rapid update in the image when it is reconstructed with a sliding window. Oversampling in the radial direction combined with angular undersampling can further reduce the time needed to acquire a complete image data set, without significantly compromising spatial resolution. Controlled flow phantom experiments using hyperpolarized 3He gas exemplify the temporal resolution of the method. In vivo studies on three healthy volunteers, one patient with chronic obstructive pulmonary disease (COPD), and one patient with hemiparalysis of the right diaphragm demonstrate that it is possible to accurately resolve the passage of gas down the trachea and bronchi and into the peripheral lung. Magn Reson Med 49:991–997, 2003.

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.

Post-mortem MRI as an adjunct to fetal or neonatal autopsy

CONTEXT Understanding what was wrong with a dead fetus or why a newborn child died can help the parents to grieve, while any findings can be used to inform the parents if there is a risk to future pregnancies and the level of risk. This information is mainly obtained from autopsies, but the number of parents agreeing to autopsy has dropped, which has prompted the search for adjuncts to autopsy. STARTING POINT The UKs Chief Medical Officer outlined the rationale for exploring alternatives to autopsy in 2000 and 2001. After wide consultation, MRI was deemed to offer the most realistic chance of making a contribution. Results so far are promising, but of insufficient depth and quality to make firm recommendations about providing a service in the future. In 2004, the UK Department of Health therefore tendered for this research to be done in fetal and neonatal (and adult) cases, and this work is due to start in 2005. WHERE NEXT? High-quality anatomical information about the brain and spine of fetuses and neonates can be easily obtained with standard MRI scanners. Most developmental and acquired abnormalities can be seen on post-mortem MRI. More work needs to be done on organs not in the central nervous system, and heart malformations, in particular, might present diagnostic problems. A possible outcome could be whole-body MRI plus targeted biopsies of abnormalities taken under image guidance as an adjunct to formal autopsy.

3D volume-localized pO2 measurement in the human lung with 3He MRI

A method for 3D volume‐localized quantification of pO2 in the lungs is presented that uses repetitive frame 3D gradient‐echo imaging of 3He. The method was demonstrated by experiments on 3He phantoms containing known concentrations of O2 and in vivo on a group of three healthy human volunteers. The results were compared with those obtained by equivalent 2D thin‐slice and 2D projection methodologies, and were found to be consistent with published results from the 2D projection methodologies (pO2 = 0.09–0.18 bar). Studies performed on the same subject, on three separate occasions, demonstrated a repeatability of pO2 measurement to within 14% using the 3D technique. Experimental differences between the 2D and 3D methods were substantiated with theoretical and numerical analyses of the signal decay, which took into account the effects of out‐of‐slice diffusion as a source of error in the thin‐slice 2D experiments. It is shown that the 2D thin‐slice technique systematically underestimates pO2 when there is significant gas diffusion (factor of 4 underestimate for D = 0.9 cm2s−1 representative of free 3He in air). Magn Reson Med 53:1055–1064, 2005.

MRI of Helium-3 Gas in Healthy Lungs: Posture Related Variations of Alveolar Size

To probe the variation of alveolar size in healthy lung tissue as a function of posture using diffusion‐weighted helium‐3 hyperpolarized gas imaging.

Quantitative analysis of regional airways obstruction using dynamic hyperpolarized 3He MRI—Preliminary results in children with cystic fibrosis

To investigate regional airways obstruction in patients with cystic fibrosis (CF) with quantitative analysis of dynamic hyperpolarized (HP) 3He MRI.