Three-dimensional reformations of computed tomography in the assessment of facial trauma

Three-dimensional (3D) computed tomography (CT) reformations were obtained in 15 patients presenting with facial injuries of differing severity. The 3D images were compared with standard radiographs and high resolution CT, including multiplanar reformations, and assessed under the headings of fracture detection, extent and displacement using a simple scoring system. 3D was valuable in severe trauma with multiple fractures, providing a clear demonstration of fraction extent and fragment displacement. 3D was much less useful in minor trauma in which little or no fragment displacement had occurred, and demonstrated fewer fractures overall than either radiography or CT in all categories of facial injury. When used as part of a high resolution CT examination 3D imaging can provide useful information to both radiologist and surgeon in cases of severe facial trauma.

Detection of myocardial infarction in the mini-pig using NMR imaging

Spin-echo images of 10 myocardial infarcts in nine mini-pigs were obtained at 30 h, 3 days, and approximately 10 days postinfarction. Infarcts were not detected at all at 30 h in five out of five cases examined. At 3 days postembolization (six cases) one infarct was certainly detected, whilst at 10 days (nine cases) all infarcts were seen as high-signal areas in long TE spin-echo sequences. After 2 weeks no further infarct signal change was detected (three cases), but myocardial thinning became more evident. Using techniques similar to those reported here, early postinfarct changes in the dog have been detected by other authors. Possible reasons for this difference between pig and dog are discussed.

Quantitative magnetic resonance imaging in rectal carcinoma

T1 and T2 relaxation times have been calculated in 30 patients with rectal carcinoma and seven patients with a fibrotic pelvic mass. The relaxation times were calculated using a multipoint iterative method with data from seven total saturation recovery and six spin-echo sequences. The results show that the calculated T1 relaxation value is a useful discriminant between carcinoma and pelvic fibrosis and should improve the detection of early tumour recurrence.

Identification of intracardiac thrombus: comparison of computed tomography and cross-sectional echocardiography

Thirty-eight patients with conditions predisposing to intracardiac thrombus have been studied by computed tomography and cross-sectional echocardiography. Computed tomography identified 22 cases of intracardiac thrombus (13 left ventricular, eight left atrial and one right atrial). Cross-sectional echocardiography identified five of these left ventricular thrombi and the right atrial thrombus, but none of the left atrial thrombi. In addition, measurements of thrombus density on computed tomography identified a significant difference (p less than 0.02) between the density of a new compared with an organized thrombus.

Three-dimensional CT reformations in the assessment of congenital and traumatic cranio-facial deformities

Standard radiography and computed tomography (CT) produce two-dimensional representations of anatomical structures under investigation. Recent developments in computer software now enable the production, from a series of conventional CT sections, of three-dimensional images of complex anatomical structures thus providing an opportunity for improved diagnosis and treatment planning.

Quantitative tissue characterisation in pancreatic disease using magnetic resonance imaging

Twenty-nine patients, 27 of whom had either inflammatory disease of the pancreas or pancreatic tumour, were studied by magnetic resonance imaging (MRI) and computed tomography (CT). Six healthy volunteers were studied by MRI alone. The pancreatic T1 and T2 relaxation times were calculated using a multipoint iterative method with data from seven total saturation recovery and six spin echo sequences. Magnetic resonance imaging can demonstrate the normal pancreas and a variety of pathological processes greater than 1-2 cm in size, but with less spatial resolution than CT. The relaxation-time results indicated no significant discrimination between chronic pancreatitis and pancreatic tumour. A significant elevation in the relaxation times was observed, however, in those patients with calcific chronic pancreatitis compared with the non-calcific chronic pancreatitic group and normal controls, suggesting a different pathophysiology for the two subgroups of chronic pancreatitis. The active phase of acute pancreatitis was associated with significantly elevated relaxation times, which returned to normal levels during the resolved phase of the disease. Associated extrapancreatic fluid collections were characterised by their very long relaxation times. The problems associated with spatial resolution, respiratory motion and lack of quantitative tissue characterisation suggest that MRI of the pancreas, using present methods, is unlikely to contribute to the overall management of patients with exocrine pancreatic disease.

Three-dimensional computed tomographic reformations of sellar and para-sellar lesions

The purpose of this study was to determine whether diagnostically useful three-dimensional (3D) reformations could be obtained from unmodified high resolution pituitary CT scans. Twelve CT examinations in 9 patients in whom an enhancing tumour or extensive bone destruction was identified around the sella, were studied using 3D images obtained on soft tissue and bone thresholds. 3D images were considered superior to conventional CT sections and reformations for the assessment of the vascular relations of tumours with large supra-sellar components, and in cases of extensive bone erosion. In selected cases, 3D CT imaging may facilitate a faster and more comprehensive appraisal of high resolution CT studies by clarifying otherwise complex spatial relationships.

Analysis of magnetic resonance images from normal and degenerate lumbar intervertebral discs

Degenerate discs can be identified quantitatively by measurement of magnetic resonance (MR) relaxation times. MR images have been recorded from 16-year-old and 82-year-old cadaveric L3-4 discs at the highest resolution attainable with a Picker International MR Imaging System operating at 0.26 Tesla. By recording images with a series of spin-echo and/or saturation-recovery sequences of differing time intervals, the values for sample magnetization, M infinity, and the T1 and T2 relaxation times, have been calculated from each pixel in the MR image. The distribution of M infinity values shows the relative degrees of hydration in different regions of the disc while the corresponding T1 and T2 values are sensitive to the chemical environment of the water molecules. Images from cadaveric discs allowed the nucleus pulposus and annulus fibrosus to be distinguished clearly, and the laminated structure of the annulus could be seen. Loss of water from the nucleus during aging was demonstrated by a reduction and change in the distribution of the M infinity values for an 82-year-old disc, as compared with a 16-year-old disc. Values of T1 and T2 indicated a difference in the chemical environment of water molecules in the nucleus pulposus and annulus fibrosus; the extent of this difference was much greater for younger than for older discs. High-resolution MR images from discs of living subjects showed almost as much detail as those from experimental specimens, but in the latter, the laminated structure of the annulus was resolved.(ABSTRACT TRUNCATED AT 250 WORDS)

A method for the clinical measurement of relaxation times in magnetic resonance imaging

A method for the determination of relaxation times in clinical magnetic resonance images is described. Three components are measured: the spin-lattice (T1) and spin-spin (T2) relaxation times and the proton density (M infinity). These components are separated in the algorithm to give increased tissue discrimination. Multiple data points are used to minimise error and increase reproducibility. Errors that arise in imaging data because of the short sequence repetition periods are considered and a technique for their reduction described. Clinical results obtained using the method are reviewed. These results demonstrate the clinical utility of the technique.

In vivo evaluation of myocardial infarction by computed tomography: an experiment with electrocardiographic gating

Retrospectively gated and ungated images of normal and 24 h post-infarction mini-pig hearts were obtained. The 11 imaged infarcts were transcatheter embolisation of the branches of the left anterior descending coronary artery. Using a contrast infusion technique and scanning during infusion, four infarcts were clearly detected as low-attenuation areas in the myocardium, one of these showing adjacent contrast enhancement. Two other infarcts showed as enhancing regions. Two small infarcts (0.8-1.0 cm3) were not detected and three others were in doubt. Streaking and other artefacts presented difficulties in image interpretation, which were sometimes resolved by gating. A comparison is made of these findings with those obtained from experiments with dogs, of comparable methodology. Differences are considered to result from anatomical differences between the two species, more particularly in the collateral blood supply to the myocardium.

A method for increasing the resolution of scanned projection radiography and other digital X-ray systems

A method for increasing the sampling frequency of digital X-ray systems is described. The method employs discrete, stepwise magnetic deflection of the focal spot and the recombination of the resulting displaced images. The technique was applied to a GE CT/T 8800 scanner operating in "Scout View" mode. The hardware and software modifications were minor. The transverse resolution was shown to improve from 0.63 to 0.9 line pairs per mm, using a test phantom. The effect of the improvement in resolution is also illustrated in the human. The possibility of further improving the resolution of the system is discussed.

Accuracy of area measurements made from MR images compared with computed tomography

The accuracy of area measurements made on magnetic resonance (MR) and CT images with clinical general purpose scanners was compared using automatic boundary detection. Both backprojection and two-dimensional Fourier transform reconstruction were used with several pulse sequences for the MR images. Several phantoms were scanned with different receiver coils and image matrices. Errors caused by grey level variation in MR images can be reduced using local edge detection. The estimated values varied with the sequence, reconstruction algorithm, and the area under investigation. Magnetic resonance area measurements should be interpreted with caution.

Magnetic resonance (MR) cine imaging of the human heart

A novel approach has been developed for MR cine imaging of the human heart by a modified ECG-gated 2DFT method. A pulse sequence has been devised to minimise the effects of saturation which can be anticipated in sequences that require rapid pulsing. Five frames are produced at the same anatomical level at predetermined intervals during the cardiac cycle. The total time taken to achieve this data is 8 minutes. Additional frames can be interleaved by repeating the sequence with an ECG-gated delay. The anatomical sections, which can be in any orthogonal plane, are then displayed as a cine loop. Cine display in the coronal plane has been used to examine 10 volunteers and 12 patients. In addition to the morphological feature displayed in single slice ECG-gated imaging, areas of dyskinesia can be detected and subjective estimates have been made of left ventricular function.

MR imaging of the intervertebral disc: a quantitative study

The T1 and T2 relaxation times and the proton density of the nucleus pulposus have been measured in 107 normal and 18 surgically proven degenerate intervertebral discs. Data from total saturation recovery and spin echo sequences have been utilised in a robust multi-point method and relaxation times and proton density calculated. The results show that both the T1 and T2 values of the normal nucleus pulposus decrease with age. There was no significant correlation between proton density and age in normal discs. At all ages there was a highly significant difference between the T1 values of normal and degenerate discs. With T2 a highly significant difference in the younger age groups reduced to no distinction in the seventh decade. The observed change in the T1 and T2 values of the nucleus is in agreement with the reduction of water content known to occur with age. Our results indicate that quantitative MR imaging may assist in the diagnosis of intervertebral disc degeneration.

Computed tomographic assessment of left ventricular aneurysms

Twenty patients with left ventricular aneurysms were studied by left ventricular angiography and computed tomography. Measurements of left ventricular short axis, percentage of non-aneurysmal myocardium, and size of aneurysm were determined by both techniques. Qualitative assessments of left ventricular size together with the anatomical relation of the aneurysm to the ventricle were also made. The aneurysm was assessed for resectability by both techniques using these criteria. In all cases there was a distinct and diagnostic change in the contour of the ventricle on computed tomography. Computed tomography indicated eight aneurysms to be unresectable, and this agreed with the angiographic assessment. Of the remaining 12 aneurysms, seven were considered to be resectable on angiography. Computed tomography appears to be a reliable non-invasive technique for identifying left ventricular aneurysms and a useful screening method for identifying unresectable aneurysms.

Computed tomographic assessment of coronary artery bypass grafts

Twenty four patients with 65 coronary artery bypass grafts were studied by computed tomography and angiogrphy within a 10 day period in order to assess graft patency and graft flow. In the assessment of graft patency computed tomography had an accuracy of 93% and in that of graft flow one of 91%. These results indicate that computed tomography is an accurate method for assessing graft patency and flow and is useful in the investigation of certain groups of patients who have had coronary artery bypass graft surgery.