Magnetic resonance imaging of renal transplants

Nineteen patients were examined to determine the clinical potential of magnetic resonance imaging (MRI) for evaluation of renal transplants. A 0.6-T cryogenic magnet and spin-echo technique with varying pulsing factors were used. T1-weighted images were best for differentiating the cortical and medullary parts of the transplanted kidney. Of the six living-related transplants with good renal function that were imaged, five demonstrated good corticomedullary differentiation (CMD) and one faint CMD. Three transplants with acute rejection were imaged, and all demonstrated a decrease in CMD and decrease in overall signal intensity compared with baseline. No CMD was seen in the three chronically rejecting transplants imaged. The appearance of cadaveric transplants and acute tubular necrosis was quite variable. All perinephric fluid collections were well depicted by MRI. Lymphoceles could be distinguished from hematomas. MRI may prove to be a useful adjunct in the evaluation of renal transplants and perinephric fluid collections.     

Magnetic resonance imaging of experimental renal hemorrhage

Experimental renal hemorrhage was induced by injecting autologous blood into the left kidney of 13 rats. To investigate the magnetic resonance (MR) characteristics of acute renal hemorrhage and subsequent stages of resolution, repetitive MR images were obtained using a 0.35 Tesla imager during a period of 21 days postinduction. A dual spin-echo imaging (TR 500 and 2,000 msec, TE 28 and 56 msec) was used to calculate the relaxation times and record the intensities in the renal medulla and cortex. Histologic examination (n = 9) indicated that blood was dispersed intrarenally, and no encapsulated hematoma developed. The signal intensity on the T1- and T2-weighted images, as well as the relaxation times in the hemorrhagic renal parenchyma were unchanged during 21 days when compared with intact kidney values. Subcapsular fresh blood had a high signal intensity on T2-weighted images. A marked overlap of the relaxation parameters between intact kidney parenchyma and diffuse intrarenal hemorrhage was observed. Detection of dispersed intrarenal blood using spin echo MR imaging may be difficult.     

Magnetic resonance imaging in the complications of kidney transplantation

Kidney transplantation is currently the treatment of choice in most patients with end-stage chronic renal failure owing to the excellent results in terms of both graft and patient survival. However, surgical complications are still very frequent. Although urological (stricture, urinary fistulas, vesico-ureteral reflux) and lymphatic complications (lymphocoele) have a high incidence, they only rarely lead to graft loss. By contrast, vascular complications (stenosis, arterial and venous thrombosis, arterio-venous fistulas, pseudoaneurysms) are relatively rare, but potentially serious and may affect graft survival. Finally, medical complications such as acute tubular necrosis (ATN), rejection and de novo neoplasms may also arise in kidney transplantation. The purpose of this pictorial review is to illustrate the increasingly significant contribution of magnetic resonance angiography (MRA) in the management of complications of kidney transplantation, and emphasise how this method should now be considered a mandatory step in the diagnostic workup of selected cases. Moreover, the application and role in this setting of new magnetic resonance imaging (MRI) techniques, such as diffusion-weighted and blood oxygen level-dependent (BOLD) MRI, are also discussed.     

Magnetic resonance imaging in staging of renal cell carcinoma

From this preliminary study, the authors conclude that MRI adds little to the diagnosis of renal cell carcinoma, but may be very helpful in staging it.     

Magnetic resonance imaging of papillary renal cell carcinoma

The authors report magnetic resonance (MR) studies in a case of papillary renal cell carcinoma. The preoperative ultrasound and computed tomographic scans suggested either a hemorrhagic cyst or a carcinoma, but the angiogram demonstrated avascularity. The magnetic resonance scan was more consistent with carcinoma than complicated cyst. We report the MR findings with pathologic correlation.     

Magnetic resonance imaging of papillary renal cell carcinoma

The authors report magnetic resonance (MR) studies in a case of papillary renal cell carcinoma. The preoperative ultrasound and computed tomographic scans suggested either a hemorrhagic cyst or a carcinoma, but the angiogram demonstrated avascularity. The magnetic resonance scan was more consistent with carcinoma than complicated cyst. We report the MR findings with pathologic correlation.     

Magnetic resonance imaging in the staging of renal cell carcinoma

A prospective study has been carried out to examine the role of magnetic resonance imaging (MRI) in the investigation of renal cell carcinoma in 24 patients. In all cases the inferior vena cava (IVC) was well demonstrated with MRI. In 14 out of 15 patients where surgical correlation was available, the MRI and operative staging were in agreement. Magnetic resonance imaging and computed tomographic (CT) staging were in agreement in 16 out of the 17 patients where both were performed. In one case, CT suggested hepatic invasion but this was found not to be present on MRI and at operation. Magnetic resonance imaging also provided substantial additional information in three patients, including two cases where MRI demonstrated a patent IVC that appeared occluded on CT (one of which also had vertebral metastases seen on MRI but missed on CT) and one case where CT failed to demonstrate minimal involvement of the IVC. Magnetic resonance imaging is an accurate means of staging renal cell carcinoma with clear advantages over CT. In no case in this series was inferior vena cavography found to be necessary.     

Magnetic resonance imaging of renal transplants: initial experience

Magnetic resonance imaging (MRI) was used in 45 renal transplant investigations (38 patients) using a Picker 0.15 T resistive system and a localized surface coil. An attempt was made to define optimal sequences in the evaluation of both normal and pathological transplants. Three sequences were found to be of value; a T1 weighted sequence (IR2180/700/40) to assess corticomedullary differentiation and its loss in acute rejection and acute tubular necrosis, a T2 weighted sequence (SE2000/80) for assessment of renal vessels and disturbances in blood supply, and a STIR (short tau inversion recovery) sequence (IR800/100/40) to define further the distended collecting system in obstruction and the presence of any perirenal collection. Encouraging results have been obtained, particularly in cases of acute rejection. It is suggested that the MRI scan is a useful screening test in cases of clinical doubt and may even obviate biopsy in some cases.     

Magnetic resonance imaging of renal masses at 0.02 tesla

To determine the usefulness of extremely low field magnetic resonance imaging (MRI) in the evaluation of renal masses 19 patients with 15 tumors (13 renal and 2 renal pelvic carcinomas) and 8 cysts were examined in a 0.02 tesla MRI unit. The findings were compared with results of computed tomography (CT) and ultrasound. Cavography was performed in 6 patients. MRI enabled differentiation between cysts and solid tumors. Tumor extension into the inferior vena cava could be demonstrated in one case and liver metastases in two patients. The image quality was inferior to that reported at higher field strengths and the tumors were more precisely staged by CT and ultrasound. At present, it is unlikely that low field MRI will play any substantial role in the evaluation of renal masses.     

Magnetic resonance imaging of large chromophobe renal cell carcinomas

Purpose  

The objective of this study was to clarify the magnetic resonance imaging (MRI) findings of large chromophobe renal cell carcinomas.     

Magnetic resonance imaging in hemifacial hyperplasia.

We describe a case of hemifacial hyperplasia due to a combination of lipoma and lipomatosis. The contribution of MRI to the diagnosis of hemifacial hyperplasia and to monitoring growth and development in this condition is demonstrated.     

Magnetic resonance imaging in carotid dissection.

Magnetic Resonance Imaging was performed in two cases of suspected internal carotid artery dissection. In both cases it was possible to demonstrate the dissection. It is suggested that magnetic resonance imaging (MRI) could replace more invasive techniques in the diagnosis of this condition.     

Magnetic resonance imaging of renal abscess in an experimental animal model

The value of magnetic resonance imaging (MRI) in the diagnosis of renal abscess was investigated in an experimental animal model. MRI is capable of depicting the location and extent of the inflammatory process using T1 weighted scans because of relatively long T1 relaxation values which were significantly longer than T1 relaxation times of adjacent normal renal parenchyma.     

Magnetic resonance imaging in chronic Achilles tendinopathy.

The main objective of this thesis was to evaluate and monitor the morphological response following treatment interventions in patients with chronic Achilles tendinopathy by using different MRI techniques. For this purpose, we investigated different types of sequences, including gadolinium contrast medium-enhanced T1-WI images (CME T1-WI), and developed a precise method to measure tendon volume and mean intratendinous signal of the Achilles tendon. Study I aimed at evaluating 15 patients with chronic, painful Achilles tendinosis, before and 2 years after surgical treatment. There was marked regression of the intratendinous signal postoperatively. The most sensitive sequence for depicting an intratendinous lesion in this study was CME T1-WI images. They showed a regression of the intratendinous signal abnormality from 13/15 patients preoperatively to 4/15 postoperatively. The clinical outcome was excellent in eight, good in five, fair in one and poor in one patient. In study II, the early contrast agent enhancement in the dynamically enhanced MRI signal (DEMRI) was correlated with the histopathologic findings in 15 patients with chronic Achilles tendinopathy. Early contrast enhancement (within the first 72s) was seen in DEMRI in the symptomatic Achilles tendons, with a significant difference compared to the asymptomatic contralateral tendons. Increased severity of tendon changes, including fiber structure abnormality, increased vascularity, rounding of nuclei, and increased amount of glycosaminoglycans, correlated to CME. In study III, we developed a computerized 3-D seed-growing MRI technique to measure tendon volume and mean intratendinous signal. This technique showed an excellent inter- and intra-observer reliability. The technique was also used to follow up prospectively the tendon adaptation and healing described in studies IV-VI. In study IV, using serial MRI during a period of 1 year, we evaluated the biological effect of tendon repair following iatrogenic tendon injury by five transversal ultrasound-guided core biopsies employing a needle technique in chronic Achilles tendinopathy. Alterations found during healing, such as tendon volume and intratendinous reactive changes, could be monitored by MR imaging, and subsided as noted in the 7- and 12-month follow-ups. In study V, we evaluated the effect of treatment with a 3-month, daily performed, heavy-loaded calf-muscle strength training program in 25 patients who had been suffering from chronic, painful Achilles tendinopathy. Tendon volume decreased by 14%, and the mean intratendinous signal by 23%. The clinical outcome was improved. In study VI, we revealed tendon adaptation immediately following calf-muscle strength training. An MRI examination within 30min of the performed exercises resulted in increased total tendon volume (12%) and mean intratendinous signal (31%). CONCLUSION: MRI techniques can be used as an adjunct to clinical evaluation by monitoring morphological effects following different treatment interventions, thereby adding evidence in clinical studies on patients with chronic Achilles tendinopathy.     

Magnetic resonance imaging in occult spinal dysraphism.

A prospective study was carried out in 100 cases of suspected occult spinal dysraphic anomalies with Magnetic Resonance Imaging in order to determine its diagnostic efficacy as the initial imaging modality. MR imaging provided accurate preoperative information in 91 out of 92 cases (98.9%). Some of the unusual and interesting findings in the series were: presence of intrinsic cord abnormality in 19 out of 21 cases (90.4%) with a normal plain radiograph, 4 cases of diastematomyelia with a dermoid in the dorsal and lumbar region associated with syringohydromyelia, intradural fibrous/glial bands, syringohydromyelia/myelomalacia of the conus with tethered cord syndrome having a normally placed conus, and myelocystocele. It is concluded that MRI is an excellent primary diagnostic tool, together with a plain radiograph, for complete preoperative evaluation of mid-line spinal anomalies.     

Magnetic resonance imaging findings in tuberculous meningoencephalitis.

OBJECTIVE: To evaluate the efficacy of magnetic resonance imaging (MRI) for distinguishing tuberculosis from other types of meningoencephalitis. PATIENTS AND METHODS: MRIs of 100 patients with tuberculous (50), pyogenic (33), viral (14), or fungal (3) meningoencephalitis were analyzed independently by 2 radiologists. Number, size, location, signal characteristics, surrounding edema, and contrast enhancement pattern of nodular lesions; location and pattern of meningeal enhancement; extent of infarct or encephalitis and hydrocephalus were evaluated. RESULTS: Contrast-enhancing nodular lesions were detected in patients with tuberculous (43 of 50 patients), pyogenic (9 of 33), and fungal (3 of 3) infections. No nodules were detected in patients with viral meningoencephalitis. Using the criteria of 1 or more solid rim or homogeneously enhancing nodules smaller than 2 cm, the sensitivity, specificity and accuracy for diagnosing tuberculous meningitis were 86.0%, 90.0% and 88.0%, respectively. CONCLUSION: Magnetic resonance imaging is useful in distinguishing tuberculous from pyogenic, viral and fungal meningoencephalitis.     

Magnetic resonance imaging in sports medicine--an overview.

As more Britons become health conscious and are involved in a variety of sporting events, sports-related injuries are a daily occurrence. Although evaluation of bony abnormalities resulting from acute and chronic sports injury by conventional radiography and bone scintigraphy has been satisfactory, the assessment of soft tissue and tendinous injury is more difficult and imprecise. Due to its superior contrast sensitivity and multiplanar imaging capability, magnetic resonance imaging has already shown great promise in delineating soft-tissue and tendinous abnormalities. In addition, marrow pathology is exquisitely displayed.     

Magnetic resonance in renal transplants

The authors report their experience in the study of renal transplant recipients by MR, in order to determine its clinical potentials. The main purpose of this work is to focus on MR patterns in relation to clinical findings of rejected or normally functioning kidney. Twenty-four patients were examined with a 0.5 T superconductive magnet, body coil, spin-echo pulse sequence (SE) and inversion-recovery (IR). MRI patterns could be seen in normally functioning kidneys and transplant rejections, while variable MRI findings were observed in transplants with acute tubular necrosis (ATN). In the normally functioning transplanted kidney there is a clear corticomedullary differentiation (CMD), and the extent of vascular penetration into the renal parenchyma is clearly seen. In transplant rejection, CMD is either diminished or absent, and there is no vascular penetration into the parenchyma; to differentiate acute from chronic rejections, the increase/decrease in renal size and the change in renal shape (spherical shape in acute transplant rejection) respectively must be observed. MRI proves thus to be useful in the study of renal transplants, even in case of questionable clinical findings, and in patients in whom renal biopsy is contraindicated.