Preoperative portal vein embolisation for primary and metastatic liver tumours: volume effects, efficacy, complications and short-term outcome.

BACKGROUND: The aim of portal vein embolisation is to induce hyperplasia of normal tissue when resection of a cancerous portion of the liver is contraindicated only by the volume of liver that would remain following operation. METHODS: Eight patients with inoperable liver tumours (3 women and 5 men, median age 69.5 years, 3 colorectal hepatic metastasts, 2 choloangiocarcinomas and 3 hepatocellular cancers) were selected for portal vein embolisation. Selected portal branches were occluded with microparticles and coils. Liver volumes were determined by magnetic resonance imaging (MRI) before embolisation and again before operation. RESULTS: Embolisation was successfully performed in all 8 patients, 7 by the percutaneous-transhepatic route, while one patient required open cannulation of a mesenteric vein. Management was altered in 6 patients who proceded to 'curative' resection; projected remaining liver volumes increased (Wilcoxon's matched pairs test p=0.02) from a median of 361 cc to a median of 550 cc; two patients had disease progression such that operation was no longer indicated. In one patient a misplaced coil unintentionally occluded a portal branch to normal liver. CONCLUSIONS: Portal vein embolisation produced appreciable hyperplasia of the normal liver and extended the option of 'curative' operation to 6 out of the 8 cases attempted. Complications can occur. The long-term results following operation are unknown.

Giant ancient schwannoma of the pelvis.

A 43-year-old man with a large ancient schwannoma of the pelvis, presenting with varicose veins, is reported. Ancient schwannoma (neurilemmoma) is a benign tumour of nerve sheath origin characterised histologically by features of severe degeneration and which rarely can grow to a large size. Malignant transformation, though reported, is extremely rare.

MRI screening for acoustic neuroma: a comparison of fast spin echo and contrast enhanced imaging in 1233 patients.

Gadolinium enhanced MRI is the gold standard investigation for the detection of acoustic neuroma. Non-contrast MRI sequences have been suggested as an alternative for screening examinations. In order to determine the utility of fast spin echo imaging, both gadolinium enhanced T1 weighted images and fast spin echo T2 weighted images were acquired in 1233 consecutive patients referred for exclusion of acoustic neuroma. Two radiologists independently recorded their findings. Fast spin echo T2 weighted images were evaluated with respect to the visibility of nerves within the internal auditory canals and allocated a confidence score for the presence or absence of acoustic neuroma. 33 acoustic neuromas were identified. Only 56% were confidently identified on fast spin echo T2 weighted images alone; gadolinium enhanced T1 weighted images were required to confirm the diagnosis in 44% of the cases, including 9 of the 10 intracanalicular tumours. However, when identification of two normal intracanalicular nerves is employed as the criterion of normality, the single fast spin echo T2 weighted sequence excluded acoustic neuroma in 59% of this screened population. It is concluded that an imaging strategy intended to identify small intracanalicular acoustic neuromas cannot rely on fast spin echo T2 weighted imaging alone. Gadolinium enhanced T1 weighted imaging could be restricted to patients where fast spin echo images do not exclude acoustic neuroma but this strategy requires continuous supervision by an experienced radiologist. In most practices the screening examination should continue to include a gadolinium enhanced sequence in order to optimize the detection of small acoustic neuromas.

Correlation between spiral computed tomography, endoscopic ultrasonography and findings at operation in pancreatic and ampullary tumours.

BACKGROUND: Spiral computed tomography (CT) allows high-resolution examination of the pancreas, surrounding vascular structures, lymph nodes and liver. Endoscopic ultrasonography (EUS) also allows high-resolution imaging of the pancreas and adjacent structures but is an invasive procedure. With the availability of spiral CT, the role of EUS in the investigation of patients with suspected pancreatic or ampullary tumours is unclear. METHODS: Forty-eight patients with clinical suspicion of a pancreatic or ampullary tumour underwent both spiral CT and EUS. Thirty-four patients had surgical exploration, of whom 17 underwent pancreatic resection and 17 had biliary and gastric bypass. The results of spiral CT and EUS were compared with the operative findings. RESULTS: The final histological diagnosis was ductal adenocarcinoma (24 patients), ampullary carcinoma (six), serous cystadenoma (two) and chronic pancreatitis (two). EUS demonstrated 33 and spiral CT 26 of the 34 primary lesions. EUS was particularly useful in the assessment of small resectable tumours missed by spiral CT. The sensitivity and specificity of EUS and spiral CT for detecting involvement by the tumour of the superior mesenteric vein, portal vein and lymph nodes were similar, but EUS was less effective at evaluating the superior mesenteric artery. CONCLUSION: EUS is an important additional investigation after spiral CT in patients with a suspected pancreatic or ampullary tumour.

Anatomy of the arterial supply to the liver demonstrated by MRI.

The aim of this study was to establish the accuracy of dynamic contrast-enhanced magnetic resonance imaging (DCEMRI) in assessing the site of origin and the patency of the hepatic arteries. Sixty-one patients were examined with serial DCEMRI. MRI was performed at 1.0 T with a rapid multi-section breath-hold fast low-angle shot (FLASH) technique in the coronal oblique plane before and at 10, 40 and 70 s after a bolus of gadolinium-DTPA. The hepatic, left gastric, gastroduodenal, splenic and superior mesenteric arteries were examined. The main portal vein, its right and left intrahepatic divisions, and the splenic and superior mesenteric veins were also assessed. The common hepatic artery was occluded in one patient. The right hepatic artery was seen in 59 patients, left hepatic in 54, left gastric in 43, gastroduodenal in 54, splenic in 60 and superior mesenteric artery in 61. Results were concordant with surgery in 38 of 39 cases and with X-ray angiography in 21 of 22 cases. In the detection of aberrant vessels DCEMRI had a sensitivity of 89 %, a specificity of 100 % and an accuracy of 97 %. All five veins were occluded in 1 patient. The main portal vein was patent in 56 patients, occluded in 2 and narrowed in 2. Thirty-two patients had upper abdominal varices. It is concluded that DCEMRI with sequential imaging provides a non-invasive demonstration of hepatic arterial and venous structures.

A comparison of fast and conventional T2 weighted spin-echo sequences in the detection of focal liver lesions at 1.0T.

Conventional and fast T2-weighted spin-echo scans obtained at 1.0T were compared in 29 patients undergoing magnetic resonance imaging of the liver, 25 of whom had focal liver lesions. Conventional spin-echo (CSE) detected 49 of 50 lesions (98%), fast spin-echo (FSE) 45 of 50 lesions (90%). Qualitative assessment of lesion conspicuity, artefact level, and overall image quality by two radiologists showed conventional spin-echo was preferred to fast spin-echo. Lesion conspicuity was graded moderate or good in 84% of lesions on CSE compared to 73% on FSE. Artefact level was higher on FSE in 34%, equal in 61% and higher on CSE in 5%. Overall, CSE was preferred to FSE in 76% of cases. Mean lesion to liver contrast to noise ratio was significantly higher on conventional spin-echo than fast spin-echo: CSE mean 5.9, FSE mean 4.9 P < 0.05. This difference in contrast to noise ratio remained for malignant lesions, but no significant difference was present for cysts and haemangiomas. We advise careful assessment of new sequences before conventional T2-weighted spin-echo is replaced by fast T2-weighted spin-echo in the detection of focal liver lesions.

Magnetic resonance imaging in the detection of focal liver lesions: comparison of dynamic contrast-enhanced TurboFLASH and T2 weighted spin echo images.

In a previous study using dynamic contrast-enhanced TurboFLASH (DCETF) for demonstration of the portal venous system we found that this technique showed more liver lesions than T2 weighted spin echo (T2WSE) imaging in the same patients. In this study we have formally compared axial T2WSE images (TR 2000, TE 45/90) with TurboFLASH images (TR 135, TE 4, FA 80 degrees) acquired immediately after bolus injection of Gd-DTPA (0.1 mmol kg-1) in 41 patients referred for hepatic magnetic resonance imaging (MRI) prior to surgery for liver lesions. The images of each sequence were independently reviewed by two observers. The lesions were counted and each sequence was scored for conspicuity, level of artefact and subjective image quality. Contrast-to-noise ratios using user defined regions of interest were calculated. Significantly more lesions were seen on DCETF (n = 186) images than on T2WSE (n = 123) images (p < 0.001). Lesion conspicuity was equal in 53% of cases, better on DCETF in 36% and better on T2WSE in 11%. Contrast-to-noise ratios were significantly higher on DCETF images (p < 0.05). DCETF imaging provided a substantial improvement in lesion detection compared with T2WSE imaging.

Potential for increasing conspicuity of short-T1 lesions in the brain using magnetisation transfer imaging.

We investigated the feasibility of using T1-weighted magnetisation transfer sequences to generate tissue contrast and increase the conspicuity of short-T1 areas within the brain. We imaged two normal volunteers with and without saturating off-resonance radiofrequency irradiation at a range of repetition times (TR 200-760 ms). T1 values and magnetisation transfer ratios for white matter and deep grey matter were calculated. We studied eight patients with intracranial lesions showing short-T1 areas, using mildly T1-weighted sequences with and without magnetisation transfer contrast. Lesion numbers, areas and signal intensities were measured and lesion-to-background contrast was calculated. Comparison was made with conventional T1-weighted spin-echo images. In the normal volunteers, contrast between the thalamus, caudate and lentiform nuclei and white matter showed striking visual differences, with magnetisation transfer weighing, with decreasing TR. In all patients, short-T1 lesions were seen more clearly on magnetisation transfer-weighted images, with significant increase in lesion number, area and contrast, when compared with conventional T1-weighted scans.

Dynamic contrast-enhanced MR imaging of the portal venous system: comparison with x-ray angiography.

PURPOSE: To compare dynamic contrast material--enhanced multisection magnetic resonance (MR) imaging with x-ray angiography in the evaluation of the portal venous system. MATERIALS AND METHODS: Eighteen patients underwent preoperative x-ray angiography and dynamic contrast-enhanced MR imaging. MR imaging was performed at 1.0 T with a multisection breath-hold fast low-angle shot (FLASH) technique in the coronal-oblique plane, before and after injection of a bolus of gadopentetate dimeglumine. The portal vein, its right and left intrahepatic branches, the splenic veins, and the superior mesenteric veins were examined. The presence of varices was also assessed. RESULTS: Of the 84 vessels evaluated with both techniques, appearances were similar in 76 (90%). Both examinations showed the main portal vein to be patent in nine patients, occluded in five, and patent but abnormal in two. Findings in the main portal vein were discordant in two patients. In one patient, surgical follow-up helped confirm the findings at MR imaging. CONCLUSION: MR imaging can replace x-ray angiography in the preoperative evaluation of portal vein patency in most patients.

Imaging of human brain activity at 0.15 T using fluid attenuated inversion recovery (FLAIR) pulse sequences.

A 3-4% change in signal intensity correlated with visual stimulation was observed in the occipital lobes of three normal volunteers examined with MRI at 0.15 T using fluid attenuated inversion recovery pulse sequences. Similar results were observed at 1.0 T. A double difference technique in which difference images are themselves opposed provided an increase in sensitivity.

MRI diffusion-weighted imaging of the brain: contributions to image contrast from CSF signal reduction, use of a long echo time and diffusion effects.

The contributions of CSF signal reduction, use of a long echo time and diffusion weighting to the appearance of pulsed gradient spin echo (PGSE) images are analysed by reference to T2-weighted spin echo and T2-weighted fluid attenuated inversion recovery (FLAIR) pulse sequences. Both PGSE and T2-weighted FLAIR sequences reduce CSF signal and produce very heavy T2 weighting allowing the specific additional contribution produced by the diffusion weighting of PGSE sequences to be recognized. Considerable advantage accrues from CSF suppression with both PGSE and FLAIR sequences through reduction in partial volume effects and artefacts. The very heavy T2 weighting with both these pulse sequences highlights certain white matter tracts and provides high sensitivity to disease. The additional diffusion weighting with PGSE sequences can enhance or reduce white matter tract signals and may enhance or reduce lesion conspicuity relative to the FLAIR sequences. Many of the benefits attributed to the diffusion-weighted PGSE sequence may result from the reduction of the CSF signal and the heavy T2 weighting of the sequence without a contribution from diffusion effects. However, additional anatomical detail, sensitivity to myelination and increased lesion conspicuity may result from the diffusion weighting.

Proton MR spectroscopy of the brain in AIDS dementia complex.

Proton MR spectroscopy of the brain has been undertaken in 8 healthy volunteers and in 11 patients with human immunodeficiency virus infection and varying stages of AIDS dementia complex (ADC). Spectral appearances in patients with no ADC or early ADC were not significantly different from normal volunteers. Spectra from patients with moderate to severe ADC exhibited significant reductions in levels of N-acetyl aspartate (NAA) relative to creatine (Cr) and also showed elevations in choline containing compounds (relative to Cr). Because NAA is though to be a metabolic marker for normally functioning neurons, these findings suggest the presence of neuronal injury or loss in moderate to severe ADC. The significance of these findings is discussed.

High signal regions in normal white matter shown by heavily T2-weighted CSF nulled IR sequences.

Inversion recovery (IR) sequences with an inversion time (TI) designed to markedly reduce or null the signal from CSF (TI of approximately 2,100 ms at 1.0 T) and a very long echo time (TE) of 240 ms were used to image the brain of two normal adult volunteers, one 34-year-old man with an intrinsic tumor, and one 3-month-old infant with an infarct. Using these very heavily T2-weighted pulse sequences, adult gray and white matter showed similar signal intensity in many areas of the brain, but normal white matter in regions of the centrum semiovale, posterior internal capsule, parietopontile tract, occipitothalamic radiation, and brain stem showed a much higher signal intensity than surrounding gray or white matter. The infant displayed a low signal intensity in myelinated regions in the internal capsule and occipitothalamic radiation and a high signal in unmyelinated white matter. In many of the images there were strong similarities to the distribution of high signal within white matter seen with pulsed gradient spin echo sequences (TE 130 ms) designed to demonstrate effects due to anisotropic diffusion. Arguments are advanced to support the view that the high signal intensity in white matter tracts is due to one or more long T2 components that may be associated with unmyelinated or sparsely myelinated fibres within white matter. The resemblance to diffusion weighted images may reflect the fact that both employ long TEs and both produce a low signal from CSF. If myelin possessed a different susceptibility from axoplasm so that magnetic field gradients were generated around nerve fibres when their orientation was not parallel to B0, diffusion of water might then produce the observed dependence on fibre direction. The high signal regions in white matter are a potential source of confusion in image interpretation, and measurements of T2 in white matter need to be made with these regional variations in mind. The concept of normal appearing white matter also needs to be applied with a knowledge of these differences. The IR sequences used in this study provide a very high T2 dependence with a low signal from CSF and may be useful for detecting disease in the CNS of adults and children.

Magnetic resonance imaging of the uterine cervix using an intravaginal coil.

Cylindrical receiver coils designed for intravaginal use were utilized to image the uterine cervix. Good quality images of the cervix, vaginal wall, and parametrium were obtained and patient tolerance of the procedure was good.

Fat suppression in magnetic resonance imaging at low field strength using binomial pulse sequences.

The use of binomial pulse sequences for fat suppression in MRI at low field strength (0.15 T) was investigated. Both spin-echo and inversion-recovery sequences were used and images obtained of the limbs, head and neck, and pelvis of volunteers and patients. Good fat suppression was seen particularly in small fields of view. Despite technical problems, chemical shift selective techniques can be applied at low field strength.

Design and implementation of magnetization transfer pulse sequences for clinical use.

The transfer of magnetization between a free and a bound pool of spins is described in terms of the respective longitudinal relaxation times and the life times of spins in each pool. The effect of an off resonance radiofrequency (RF) pulse in producing saturation in the bound pool and a consequent decrease in both the available longitudinal magnetization and the T1 of spins in the free pool is described. The effects of increasing duration of the saturating RF pulse on image pixel signal intensity were used to determine values for the decrease in both T1 and the available magnetization in gray and white matter of the brain as well as in muscle, fat, and CSF. At 0.15 T the available magnetization of muscle was reduced by approximately 60% and its T1 was decreased from 350 to 150 ms. The available magnetization of white and gray matter was reduced by 40% and their values of T1 were reduced by 80-110 ms. The reduction in available magnetization was used to increase contrast on proton density weighted or T2-weighted SE pulse sequences. These changes were also used to design inversion recovery (IR) pulse sequences with particular contrast properties. A short inversion time (TI) magnetization transfer (MT) IR (MT-STIR) pulse sequence was used to reduce the signal from normal muscle to zero to produce an angiographic effect in the leg. Increased tissue contrast was observed with a T2-weighted (MT-SE) sequence in a patient with bilateral cerebral infarction and with an MT-IR pulse sequence in a patient who had an intracranial hematoma. Three patients with cerebral tumors showed high lesion contrast with MT-STIR sequences. Components within two tumors were changed to different degrees by MT and in one case change in the brain attributable to recent radiotherapy treatment was only identified with an MT-STIR sequence. Magnetization transfer can be used to manipulate both the available longitudinal magnetization and the T1 of normal and abnormal tissues. The changes in tissue contrast produced by this can be very substantial and are likely to be of importance in clinical imaging.

Ultrasound, computed tomography and magnetic resonance imaging in patellar tendinitis.

This prospective study describes the ultrasound, computerized tomography and magnetic resonance imaging findings in 16 cases of patellar tendinitis. In all cases tendon enlargement and reduced echogenicity were visible on ultrasound. Computerized tomography demonstrated enlargement of the tendon with reduced attenuation of the central portion. Magnetic resonance imaging showed focal tendon enlargement in all patients with high signal lesions in 88% of cases. This study has shown that patellar tendinitis may be identified with all three modalities. Ultrasound is recommended as the initial investigation in the assessment of patients with this condition.

Proton MR spectroscopy and imaging of the brain in AIDS: evidence of neuronal loss in regions that appear normal with imaging.

Central nervous system involvement is increasingly being recognised as a common manifestation of the acquired immunodeficiency syndrome (AIDS), either as a direct effect of the human immunodeficiency virus, or as a result of secondary infection or malignancy. A subset of patients with clinical or psychometric evidence of CNS involvement have normal appearances on imaging. This report describes proton magnetic resonance spectroscopy (1H MRS) in two patients with AIDS and discusses the role of 1H MRS in providing a marker of neuronal loss in patients with normal or borderline imaging.