Renal cell carcinoma: magnetic resonance imaging and computerized tomography

Summary Surgical data of eight patients who underwent nephrectomy for renal cell carcinoma were compared with the findings of magnetic resonance imaging (MRI) and, in five of these, with those of computerized tomography (CT) as well. In another three patients, only CT and MRI were available, since the presence of metastases precluded surgery. In general, MRI and CT accurately displayed local tumor extension, whereas magnetic resonance was superior to computed tomography in demonstrating tumor involvement of large venous structures.     

Comparison of magnetic resonance imaging and computed tomography in the local assessment of osteosarcoma

Summary We have compared the value of magnetic resonance imaging (MRI) with computed tomography (CT) in assessing the extent and the localization of osteosarcomas. Twenty patients were examined by both systems, and the results related to the clinical and histological findings. While both investigations are valuable, MRI may be more useful for defining the local extent of an osteosarcoma.

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Résumé Le but de cette étude est d'évaluer la capacité de l'imagerie par résonance magnétique (IRM) à préciser le siège et le degré d'extension des ostéosarcomes et d'en comparer les résultats à ceux de la tomodensitométrie (TDM). Nous avons examiné 20 patients atteints d'ostéosarcome par IRM (Siemens MRI scanner 1.5 tesla) ainsi que par TDM (CT/T CT scanner Yokokawa). Un examen anatomopathologique de la pièce chirurgicale a été effectué et ses résultats comparés à ceux de l'IRM et de la TDM. La taille de la tumeur mesurée par l'IRM était très comparable à celle de la pièce opératoire: la différence était en moyenne de 3.3 mm±1.6. L'appréciation par la TDM de l'atteinte corticale a été la même que celle de l'IRM dans 15 cas, mais supérieure dans les 5 autres. L'IRM a été supérieure à la TDM chez 5 patients dont les lésions atteignaient l'articulation et identique chez les 12 autres. L'IRM a été supérieure à la TDM en ce qui concerne l'évaluation de l'extension dans les parties molles dans 9 cas et égale dans les 11 autres. L'IRM s'est montrée supérieure à la TDM pour estimer l'atteinte neuro-vasculaire dans 9 cas et égale dans les 11 autres. Ces résultats montrent que l'IRM définit mieux le degré d'extension locale des ostéosarcomes que la TDM.

     

Magnetic resonance imaging for assessment of vena caval tumor thrombi: a comparative study with venacavography and computerized tomography scanning

We assessed the accuracy of magnetic resonance imaging in demonstrating the presence and extent of vena caval tumor thrombi. The study group included 20 patients with vena caval thrombi from renal cell carcinoma (18), renal pelvic transitional cell carcinoma (1) and adrenal pheochromocytoma (1). Preoperative diagnostic studies included magnetic resonance imaging in all patients, inferior venacavography in 16 and computerized tomography scanning in 15. All patients underwent an operation in which the presence and extent of the vena caval thrombus were confirmed. Magnetic resonance imaging accurately delineated the presence and extent of the thrombus in all 20 patients (100%). Venacavography was accurate in 15 patients (94%) but 8 (50%) required a retrograde and antegrade study. Computerized tomography scanning demonstrated the presence of a tumor thrombus in all 15 patients but accurately delineated the cephalad extent of the thrombus in only 5 (33%). In patients with vena caval tumor thrombi magnetic resonance imaging can provide accurate information regarding the extent of vena caval involvement while avoiding the need for an invasive contrast imaging study.     

Postoperative magnetic resonance imaging after acoustic neuroma surgery: influence of packing materials in the drilled internal auditory canal on assessment of residual tumor

Serial magnetic resonance (MR) images taken after acoustic neuroma surgery were analyzed to evaluate the pattern and timing of postoperative contrast enhancement in 22 patients who underwent acoustic neuroma removal via the suboccipital transmeatal approach. The opened internal auditory canal (IAC) was covered with a muscle piece in nine patients and with fibrin glue in 13. A total of 56 MR imaging examinations were obtained between days 1 and 930 after surgery. MR imaging showed linear enhancement at the IAC within the first 2 days after surgery, and revealed nodular enhancement on day 3 or later in patients with a muscle piece. MR imaging tended to show linear enhancement at the IAC, irrespective of the timing of the examination in the patients with fibrin glue. Postoperative MR imaging on day 3 or later showed the incidence of nodular enhancement in patients with muscle was significantly higher than in patients with fibrin glue. The results illustrate the difficulty in differentiating nodular enhancement on a muscle piece from tumor by a single postoperative MR imaging study. Therefore, fibrin glue is generally advocated as a packing material of the IAC because it rarely shows masslike enhancement on postoperative MR imaging. When a muscle piece is used in patients at high risk for postoperative cerebrospinal fluid leaks, MR imaging should be obtained within the first 2 days after surgery, since benign enhancement of muscle will not occur and obscure the precise extent of tumor resection.     

Convective distribution of macromolecules in the primate brain demonstrated using computerized tomography and magnetic resonance imaging

OBJECT: Convection-enhanced delivery (CED), the delivery and distribution of drugs by the slow bulk movement of fluid in the extracellular space, allows delivery of therapeutic agents to large volumes of the brain at relatively uniform concentrations. This mode of drug delivery offers great potential for the treatment of many neurological disorders, including brain tumors, neurodegenerative diseases, and seizure disorders. An analysis of the treatment efficacy and toxicity of this approach requires confirmation that the infusion is distributed to the targeted region and that the drug concentrations are in the therapeutic range. METHODS: To confirm accurate delivery of therapeutic agents during CED and to monitor the extent of infusion in real time, albumin-linked surrogate tracers that are visible on images obtained using noninvasive techniques (iopanoic acid [IPA] for computerized tomography [CT] and Gd-diethylenetriamine pentaacetic acid for magnetic resonance [MR] imaging) were developed and investigated for their usefulness as surrogate tracers during convective distribution of a macromolecule. The authors infused albumin-linked tracers into the cerebral hemispheres of monkeys and measured the volumes of distribution by using CT and MR imaging. The distribution volumes measured by imaging were compared with tissue volumes measured using quantitative autoradiography with [14C]bovine serum albumin coinfused with the surrogate tracer. For in vivo determination of tracer concentration, the authors examined the correlation between the concentration of the tracer in brain homogenate standards and CT Hounsfield units. They also investigated the long-term effects of the surrogate tracer for CT scanning, IPA-albumin, on animal behavior, the histological characteristics of the tissue, and parenchymal toxicity after cerebral infusion. CONCLUSIONS: Distribution of a macromolecule to clinically significant volumes in the brain is possible using convection. The spatial dimensions of the tissue distribution can be accurately defined in vivo during infusion by using surrogate tracers and conventional imaging techniques, and it is expected that it will be possible to determine local concentrations of surrogate tracers in voxels of tissue in vivo by using CT scanning. Use of imaging surrogate tracers is a practical, safe, and essential tool for establishing treatment volumes during high-flow interstitial microinfusion of the central nervous system.     

Cerebellar encephalomalacia on magnetic resonance imaging after removal of acoustic tumor.

MRI is widely used for postoperative surveillance of patients undergoing surgery for removal of acoustic neuroma. The purpose of this study was to investigate the frequency and pattern of postoperative changes in the cerebellum and brain stem on MRI after removal of acoustic neuroma. A retrospective study was conducted in 30 consecutive patients who underwent postoperative MRI between 1994 and 1995. The timing of the scans after surgery ranged from 12 months to 10 years. T2 -weighted turbo spin-echo images revealed cerebellar encephalomalacia in 17 of 30 cases. Cerebellar encephalomalacia was found more consistently in patients who had large tumors and was more frequent after the suboccipital approach. Encephalomalacia is largely caused by gliotic changes in the adjacent cerebellar tissues after tumor removal.     

Retroperitoneal cystic lymphangioma diagnosed by computerized tomography,magnetic resonance imaging and thin needle aspiration

We report a case of retroperitoneal cystic lymphangioma presenting with right back pain. Although preoperative diagnosis is usually difficult in such a rare condition, we could make the preoperative diagnosis on usually difficult in such a rare condition, we could make the preoperative diagnosis on grounds of the peculiar findings obtained by computerized tomography (CT), magnetic resonance imaging (MRI) and needle aspiration.     

Growing blood clot mimicking an aneurysm on postoperative computerized tomography and magnetic resonance imaging studies. Case report and review of the literature.

The authors describe the case of a 15-year-old boy who underwent resection of a large left temporal tumor. During a normal postoperative course, computerized tomography (CT) scanning demonstrated a spherically hyperdense structure near the internal carotid artery, enlarging on a control CT scan. A suspected false aneurysm was confirmed on magnetic resonance imaging; angiographic studies were negative. The authors believed they were dealing with a thrombosed false aneurysm and they performed operative revision. Intraoperatively the "aneurysm" could be dissected off the internal carotid artery and no lesion of the arterial wall was obvious. Histological findings showed a fresh blood clot. This case demonstrates that a blood clot may mimic an aneurysm on CT and magnetic resonance studies, which has not been described earlier. The origin of the blood clot remains unclear.     

Anaesthesia for magnetic resonance imaging/computed tomography

The need for general anaesthesia for magnetic resonance imaging/computed tomography investigations can be reduced by the implementation of structured sedation programmes supervised by anaesthetists. Despite its side-effects, chloral hydrate is still the drug most widely used. Rectal thiopental or intravenous propofol are suggested anaesthetic agents for pre-school children and uncooperative or claustrophobic individuals. Spiral computed tomography scans and ultrafast magnetic resonance imaging shorten immobilization times further. However, functional magnetic resonance imaging and intervention techniques in neuroradiology depend on a motionless patient. A useful strategy for testing anaesthesia equipment has been outlined.     

Comparison of computed tomography and magnetic resonance imaging in the diagnosis of parotid tumors

OBJECTIVE: The role of computed tomography (CT) and magnetic resonance imaging (MRI) in the diagnosis of parotid tumors was investigated. METHODS: Forty patients with the clinical suspicion of a parotid mass underwent both CT and MRI of the parotid region. Two radiologists independently assessed the CT and MRI results with respect to tumor localization, tumor margin characteristics, and infiltration of surrounding tissue. Histopathologic specimens were obtained in all cases and correlated with the radiologic findings. RESULTS: The sensitivity and specificity of CT and MRI were nearly the same for tumor location, tumor margin, and tumor infiltration. CONCLUSION: The 2 imaging techniques provided the same information with respect to the presurgical planning and contribute to the diagnosis and therapy planning of parotid tumors.     

Comparison of magnetic resonance imaging and computed tomography in the evaluation of head injury

Thirty-five patients who had incurred head trauma were studied with computed tomography (CT) and magnetic resonance imaging (MRI). CT was performed using a General Electric 8800 scanner. MRI was conducted with a Technicare Teslacon system using a 5.0 kG (0.5 T) magnetic field. Clinically, patients varied from those with mild concussions without focal neurological signs to those with severe neurological dysfunction including posttraumatic coma. MRI was superior to CT in imaging 23 of 41 extracerebral fluid collections, both in estimating the size of the collections and in diagnosing small collections. MRI was also superior to CT in distinguishing chronic subdural hematomas from hygromas. Further, MRI was superior to CT in visualizing nonhemorrhagic contusion in 15 of 21 lesions. Because of the potential failure of MRI to diagnose acute subarachnoid or acute parenchymal hemorrhage, CT remains the procedure of choice in diagnosing head injury less than 72 hours old.     

Efficacy of gadolinium-diethylenetriaminepentaacetic acid-enhanced magnetic resonance imaging for differentiation between superficial and muscle-invasive tumor of the bladder: a comparative study with computerized tomography and transurethral ultrasonography

Gadolinium-labeled diethylenetriaminepentaacetic acid (Gd-DTPA)-enhanced magnetic resonance imaging (MRI) was evaluated in an effort to clarify whether MRI could replace or be proved to be superior to computerized tomography (CT) and/or transurethral ultrasonography. A total of 57 bladder cancer patients was evaluated. MRI was performed with a superconducting magnet operating at 1.5 Tesla. The images acquired were multisections, having a fast spin-echo pulse sequence of less than a 14-second breath holding. Serial scans were performed before and immediately after Gd-DTPA venous injection. The findings on different imaging techniques were compared with the histological stagings. A proper diagnosis was made in 42 of 57 cases (73.7%) by Gd-DTPA-enhanced MRI, in 27 of 57 (47.4%) by CT and in 31 of 57 (54.4%) by transurethral ultrasonography when comparing the histological findings. The sensitivity and specificity for differentiating superficial and muscle-invasive tumor of each imaging method were, respectively, 96.2 and 83.3% in Gd-DTPA-enhanced MRI, 96.0 and 58.3% in CT, and 88.0 and 66.7% in transurethral ultrasonography. These data suggest that the staging of bladder cancer by Gd-DTPA-enhanced MRI appears to be superior and more accurate than the staging obtained by CT and transurethral ultrasonography.     

Comparison of magnetic resonance imaging and computed tomography in the preoperative staging of rectal cancer

Nineteen patients with middle and lower rectal carcinomas were operated on, with abdominoperineal resection in 10 patients, lower anterior resection with coloanal anastomosis in 6 patients, and colorectal anastomosis in 3 patients. The distance of the lower margin of the tumor to insertion of the levator ani on the rectal wall was correctly evaluated by computed tomography in 12 (63%) of 19 patients and by magnetic resonance imaging in 13 (68%) of 19 patients, while digital examination correctly assessed the distance in 15 (79%) of 19 patients. Computed tomography and magnetic resonance imaging were unable to assess extension through the rectal wall. No significant difference was observed between computed tomography and magnetic resonance imaging in assessing extension to the perivesical fat, adjacent organs, pelvic side wall, or lymph nodes. According to the TNM classification, magnetic resonance imaging correctly staged 74% (14/19) of carcinomas, while computed tomography correctly staged 68% (13/19).     

Comparison of magnetic resonance imaging and computed tomography in the preoperative evaluation of pituitary adenomas

Twenty surgically verified pituitary adenomas were imaged in a systematic comparative fashion with high field strength magnetic resonance imaging (MRI) and computed tomography (CT) before operation. The study group included 11 microadenomas, 4 macroadenomas, 2 recurrent microadenomas, and 3 recurrent macroadenomas. The MRI and CT examinations were evaluated for lesion detection, pituitary stalk displacement, cavernous sinus displacement or invasion, hemorrhage, cystic degeneration within the adenoma, bony erosion, detection of suprasellar extension, and displacement of suprasellar structures. T1 and T2 relaxation characteristics of the adenomas were evaluated on MRI examinations, and contrast enhancement characteristics were evaluated on CT examinations. MRI was superior to CT for detecting the extrasellar extent of tumor. Within the sella turcica, MRI and CT were equivalent with regard to lesion detection, except for 1 patient in whom CT was able to detect a surgically confirmed 3-mm microadenoma that was not visualized on the MRI examination.     

Nuclear magnetic resonance and computerized tomography in meniscus injuries of the knee joint

In a prospective study we evaluated the use of CAT scan and MRI in 53 patients with chronic symptoms and acute injuries of the knee joint. All these patients subsequently underwent surgery. A total of 21 patients had acute or chronic meniscus ruptures. The sensitivity of MRI was 86% (medial: 88%, lateral: 75%), its specificity, 95% (medial: 92%, lateral: 98%), its accuracy 93% (medial: 91%, lateral: 96%), its positive predictive value of 82% (medial: 83%, lateral: 75%), and its negative predictive value 96% (medial: 94%, lateral: 98%); CAT scan had a sensitivity of 86% (medial: 88%, lateral: 75%), a specificity of 97% (medial: 94%, lateral: 98%), an accuracy of 94% (medial: 93%, lateral: 96%), a positive predictive value of 86% (medial: 88%, lateral: 75%), and a negative predictive value of 97% (medial: 94%, lateral: 98%). In this study CAT scan and MRI proved to have a very high negative predictive value in the diagnostic of meniscal lesions. A negative result with one of these imaging techniques means that a rupture of a meniscus is highly unlikely. This may avoid unnecessary invasive procedures such as arthrotomies or arthroscopic examinations.     

Bladder outlet obstruction due to pelvic lipoma: computerized tomography, magnetic resonance imaging and radiographic evaluation

We report an unusual case of long-standing bladder outlet obstruction due to pelvic lipoma in a 31-year-old white man. The mass was evaluated by plain film, computerized tomography and magnetic resonance imaging. The differential diagnosis of fat-containing extraperitoneal pelvic masses is discussed.     

Computed tomography and magnetic resonance imaging of the inner ear

The majority of temporal bone radiographic studies are obtained either for middle ear and mastoid disease or in the evaluation of retrocochlear pathology. With recent technologic advances, diagnostic imaging of the inner ear has developed an increasing role in the evaluation and management of diseases that affect the cochlea, semicircular canals, and the vestibular and cochlear aqueducts. High-resolution computed tomography (CT) provides excellent detail of the osseous labyrinth, whereas magnetic resonance imaging (MRI) generates images derived from the membranous labyrinth and its associated neural elements. Optimal techniques for obtaining high quality CT and MRI images of the normal and diseased inner ear are presented. CT has proved useful in the evaluation of inner ear malformations, cochlear otosclerosis, labyrinthine fistulization from cholesteatoma, translabyrinthine fractures, otic capsule osteodystrophies, in the assessment of cochlear patency before cochlear implantation, and in the localization of prosthetic devices such as stapes wires and cochlear implants. While MRI produces discernible images of the soft tissue and fluid components of the inner ear, it has yet to demonstrate any unique advantages in the evaluation of inner ear disease. However, MRI produces excellent and highly useful images of the audiovestibular and facial nerves, cerebellopontine angle, and brain.     

Computed tomography and magnetic resonance imaging of the acute abdomen

CT is a noninvasive investigation that in many instances is more sensitive in elucidating intra-abdominal and retroperitoneal disease than is conventional radiography. With modern scanners, the procedure is rapid and efficient and suitable for the most severely ill and infirm. The scans are easily interpretable, and the anatomic and morphologic depiction of disease is readily understood by those with surgical training. Information regarding the state of the bowel wall, mesentery, and intraperitoneal and retroperitoneal structures is displayed in greater detail than by any other diagnostic imaging modality. The use of intravenous contrast medium is rarely essential. The concentration of iodinated contrast needed for opacification of the bowel is no greater than 2 per cent to 5 per cent and will not complicate bowel surgery, as would standard upper gastrointestinal or barium enema studies. Abscess, free air, calcium, and intraperitoneal fluid are very sensitively detected. CT is extremely useful in aiding surgical decision making in the acute abdomen and is complementary to or has replaced conventional studies.