MRI of fistula-in-ano: a comparison of endoanal coil with external phased array coil techniques

PURPOSE

The objective of our study was to compare MRI of fistulas-in-ano using an endoanal coil with that using a pelvic phased array coil and to assess the value of a combined approach by correlating the findings with those at surgery.

METHOD

Twenty consecutive patients with clinical suspicion of perianal sepsis were studied using an endoanal coil immediately followed by a phased array coil. T1 weighted and STIR images in transverse and coronal planes were made with each coil and analysed by noting the presence and site of a collection and primary track, the position of any internal opening, and subcutaneous or supralevator extension. Operative findings were similarly recorded.

RESULTS

Of 20 patients with suspected fistulas, 8 had simple fistulas, 8 had complex fistulas, and 4 had no current evidence of infection. The concordance between MR and surgery for identifying the presence and site of the collection, the primary track, and the internal opening in both simple and complex cases was superior using the endoanal coil as compared with the phased array. Both coils together reflected the findings of the endoanal coil used alone. However, for supralevator/subcutaneous extension, concordance was superior using the phased array compared with the endoanal coil, and a combined approach reflected the values of the phased array coil used alone.

CONCLUSION

Endoanal MRI is highly sensitive in the delineation of fistulas-in-ano. In combination with phased array techniques, it provides valuable preoperative assessment in both simple and complex cases.

Magnetic resonance imaging of spinal cord in multiple sclerosis by fluid-attenuated inversion recovery

Magnetic resonance imaging examination of the upper spinal cord was done in sixteen adult patients with clinically definite multiple sclerosis (MS) by T2 weighted fluid attenuated inversion recovery (FLAIR) scanning in which the signal from cerebrospinal fluid was suppressed. These scans were compared with matched images obtained with conventional T1 and T2 weighted pulse sequences (including contrast enhancement). 6 lesions (five patients) were seen with the conventional scans and 37 lesions (fourteen patients) were seen with the FLAIR scans. The FLAIR sequence considerably improves the ability of MRI to demonstrate spinal involvement in MS.

Ultrasound, CT, and MRI comparison in primary and secondary tumors of the liver

Thirty-five patients with surgically removed or percutaneous biopsy-proven tumors were examined by ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI). This retrospective study describes the appearance of the primary tumors and metastases and compares the sensitivity and specificity of the 3 imaging methods. Ultrasound, CT, and MRI examinations as well as clinical, operative, and/or histologic data were available for all 35 patients. Paramagnetic contrast agent gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) was used in 23 patients and a short TI inversion recovery MRI sequence was used in 23 patients, in addition to various spin echo MRI sequences. Thirteen patients were examined using both Gd-DTPA and the short TI inversion recovery sequence. Our comparative study--based on the following criteria: detection, size, location of the tumor, and portal vein involvement and bile duct dilatation--demonstrated an advantage of MRI over ultrasound in 16 of 35 cases, equal results in 17 of 35 cases and a disadvantage of MRI compared to ultrasound in 2 of 35 cases. With the identical criteria, MRI proved to be more informative than CT in 10 of 35 cases, equal in 21 of 35 cases, and less informative in 4 of 35 cases.

The MR contribution after CT demonstration of supratentorial mass effect without additional localising features

The contribution of magnetic resonance (MR) imaging was retrospectively evaluated in 24 patients in whom CT demonstrated a supratentorial mass effect without significant additional localising features. Using a combination of T1-weighted inversion recovery (IR) and T2-weighted spin echo sequences, the MR images localised the lesion with greater precision than CT in 80% of cases. Areas of contrast enhancement were visible on the IR images in five of nine (56%) patients assessed after intravenous gadolinium-diethylenetriamine pentaacetic acid, where no comparable enhancement was seen on CT. Twenty of the 24 patients subsequently underwent surgery; eight had biopsies and 12 had resections. Magnetic resonance accurately predicted the site of the tumour in all these patients. Three of the remaining four cases were treated with radiotherapy on the basis of the MR findings without a tissue diagnosis being sought. Magnetic resonance produces better localization than CT and provides a sound basis for further diagnostic and therapeutic procedures.

Magnetic resonance imaging of the solitary hepatic mass: direct correlation with pathology and computed tomography

Magnetic resonance images (MRI) of the liver were obtained using a combination of short time inversion recovery (STIR) and spin echo (SE) sequences. These were correlated with comparable tissue slices generated from resected specimens obtained at partial hepatectomy. All 10 cases appeared to have solitary masses on contrast enhanced computed tomography (CT). Histological examination revealed five primary tumours (two hepatocellular carcinomas, two haemangiomas and one cholangiocarcinoma) and five metastatic tumours. The STIR images demonstrated a high signal intensity in all areas of viable tumour involvement and reduced signal intensity in regions of confluent necrosis with superimposed haemorrhage or calcification. This sequence also demonstrated additional areas of high signal intensity adjacent to several lesions which were not visible on CT. Microscopy of these regions in the specimens demonstrated no tumour involvement or steatosis and their precise cause remains obscure. All the lesions demonstrated on the CT images were visible on MRI and no additional lesions were discovered on detailed microscopical examination of the specimens. Delineation of the extent of the cholangiocarcinoma was a problem with both techniques. MRI showed no major advantage over CT except for a higher contrast of the lesion compared with normal liver and also a better delineation of the tumour mass.

Bone marrow in leukemia and aplastic anemia: MR imaging before, during, and after treatment

Serial magnetic resonance (MR) studies of the cervical bone marrow were performed in five patients undergoing bone marrow transplantation for chronic granulocytic leukemia and in four patients with aplastic anemia who were treated with antilymphocytic globulin. Findings were compared with those from a group of healthy volunteers. Chemical shift imaging techniques were used to exploit the presence of protons in fat and water in the red marrow. Characteristic changes were seen in aplastic anemia before treatment, but derivation of images representing fat and water fractions was necessary to distinguish leukemic marrow. Acute changes during the treatment of leukemia may reflect the effects of chemotherapy and radiation therapy, whereas changes in the chronic phase of both diseases may prove useful in predicting treatment outcome. MR studies are likely to be useful in the assessment and treatment of hematologic disorders.

Contrast-enhanced magnetic resonance imaging of tumours of the central nervous system: a clinical review

The clinical application of the intravascular paramagnetic contrast agent gadolinium-DTPA for magnetic resonance imaging (MRI) imaging of tumours of the central nervous system (CNS) has been assessed over the past 3 years. Various patterns of contrast enhancement were observed, and situations in MRI where the administration of contrast medium may be useful have been defined. These include lesions which are isointense with normal brain matter, the separation of tumour from surrounding oedema, evaluation of the degree of blood-brain barrier breakdown, delineation of tumours obscured by overlying calcification on computed tomography (CT) and in the investigation of lesions in anatomical areas where CT has known limitations (brain stem, cervical spine). Changes in relaxation times in normal and abnormal tissues following contrast medium, toxicity and dosage of gadolinium-DTPA, and MRI pulse sequence techniques are reviewed.

Magnetic resonance imaging of the retroperitoneum

The results of magnetic resonance imaging (MRI) examinations in 50 patients with histological or clinical diagnoses of retroperitoneal disorders and 20 normal volunteers are presented. An increase in relaxation time (T1) was recognised in most pathological conditions except for four liposarcomas and one adrenal cortical neoplasm and one metastatic lesion of the same gland. Inversion recovery (IR) provided the best tissue contrast, enabling the detection of small lesions. Flow-dependent sequences and sagittal imaging planes were particularly helpful in the evaluation of aortic aneurysms. Ferric ammonium citrate used as an oral paramagnetic contrast agent and a short T1 inversion recovery sequence gave encouraging initial results in recognising bowel loops. Gadolinium-DTPA injected intravenously provided tumour enhancement, indicating vascular perfusion and demarcating tumour margins. An attempt to eliminate motion artefacts was carried out in 15 volunteers and six patients either by a new software system (respiratory ordered phase encoding) or by using short T1 inversion-recovery to suppress the high signal from fat. The same pulse sequence results were useful in demonstrating subcutaneous fistulous tracts by eliminating the adjacent fat. The actual role of MRI in the investigation of the retroperitoneum in view of current technical developments is discussed.

Nuclear magnetic resonance imaging of the heart

Satisfactory NMR images of the heart can now be obtained using ECG gated inversion recovery and spin-echo sequences. The images obtained provide good anatomical information in the transverse, coronae, and sagittal planes, particularly of the myocardium and some intracardiac structures, such as cardiac valves and papillary muscle. The pericardium can be visualized, and so can the large vessels arising from the heart. Myocardial disease, in particular ischemia and infarction, is discussed in some detail, and mention is made of the cardiac aneurysms and various types of cardiomyopathy. Congenital heart disease and pericardial pathology are also briefly discussed.

Present and future clinical position of magnetic resonance imaging

Following the appearance of the first clinical reports on magnetic resonance imaging (MRI) five years ago, stock is now taken of the clinical value of this new imaging technique and its future potential is assessed. Contrast and spatial resolution as well as specificity of CT and MRI are compared and the multiplicity of sequences, multiplanar facility, and flexibility of MRI over CT are analyzed. The dominant role of MRI over CT in the study of some disorders of the central nervous system is assessed and so are the limitations. In this context the usefulness of paramagnetic contrast media is also evaluated. The difficulties of body imaging are discussed. The solutions of overcoming cardiac and respiratory motions artifacts are evaluated and areas where MRI has already achieved a high level of clinical application are identified. Mention is made of additional information obtainable by MRI as, for example, sodium imaging, blood flow measurements, and the combination of imaging with spectroscopy. Possible future prospects are analyzed, for example, high-resolution imaging, alternative sequences to those commonly used in particular the short TI IR sequence (STIR), chemical shift imaging, and the possibility of utilizing susceptibility for imaging purposes. The problem of radiofrequency receiver coil design is approached and so is the choice of magnetic fields. The future relationship of MRI with established noninvasive techniques is stressed.

Periventricular leukomalacia: evaluation with MR imaging

We reviewed 24 magnetic resonance (MR) images of 12 infants diagnosed as having periventricular leukomalacia based on ultrasound results. Abnormalities were identified on the MR images of every patient and were divided into three categories: distribution of low-signal-intensity areas within the cerebral white matter, degree of ventriculomegaly and brain atrophy, and extent of myelination. Follow-up examinations on six patients were also compared for significant changes. Abnormalities noted on MR images that most consistently related to poor outcome for the patient were low-signal-intensity lesions involving all four cerebral lobes, moderate to severe delays in myelination, lack of progression of myelination, and moderate to severe cortical atrophy. MR imaging was able to depict the extent and progression of myelination, and it may be used to continue follow-up of these patients beyond the time of fontanel closure.

Gadolinium-DTPA in the assessment of liver tumours by magnetic resonance imaging

The effect of gadolinium-DTPA (Gd-DTPA, Schering AG) as a magnetic resonance imaging (MRI) contrast agent was studied in 15 patients with liver tumours. A dose of 0.1 mmol/kg was used. An analysis of the time-course of enhancement, a comparison of four different pulse sequences, and a dose-comparison study were carried out with monitoring of haematological and biochemical parameters before and after injection of Gd-DTPA. Maximum enhancement, that is, increase in signal intensity, was noted on IR1400/400/13 between 10 and 20 min after injection while on SE580/40 and SE580/80 maximum enhancement was noted 30 min after injection. In some cases enhancement was noted up to 120 minutes after injection. SR1000/13f sequences showed very little enhancement. On comparison with contrast-enhanced X-ray computed tomography (CT), enhancement was greater on MRI in seven cases, equal in six and less in two, as assessed subjectively. Additional lesions were shown in one case using Gd-DTPA compared to precontrast enhanced MRI scans. However, no additional lesions were seen on contrast-enhanced MRI scans compared to contrast-enhanced CT scans. Gd-DTPA is capable of enhancing liver tumours on MRI and may have a place in the assessment of the operability of such lesions.

The role of magnetic resonance imaging techniques in the evaluation of orbital and ocular disease

Technical developments have resulted in a great improvement in the quality of magnetic resonance imaging (MRI) of the orbit. With surface coil data acquisition spatial resolution of less than a millimetre can now be achieved, and contrast discrimination is such that the cortex and nucleus of the lens can be distinguished. The application of MRI to the diagnosis of orbital and ocular pathology was studied in a group of 51 patients with a wide range of pathology. Advantages of MRI over computed tomography (CT) included the avoidance of ionising radiation, the direct multiplanar facility and the use of flow-dependent sequences to identify pathological vessels without the need for contrast medium; although CT was superior in showing bone detail. Only a limited discrimination between different tumour types is possible by assessment of their MRI characteristics. Research is currently being directed towards achieving thinner slices, shorter data acquisition times and removal of the high signal from retrobulbar fat.

Total stabilization of the cervical spine in patients with cervical spondylotic myelopathy

Certain patients with cervical spondylotic myelopathy demonstrate instability in the upper cervical vertebral column associated with marked narrowing of the vertebral canal in the neighboring lower cervical segments. This combination of causative mechanisms creates difficulty in using routine surgical procedures, especially in elderly and severely debilitated patients. We present three cases that typify this situation and illustrate marked resolution of debilitating myelopathy through total posterior fusion of the cervical spine usually incorporating the occiput.