Degree Of Contrast Enhancement Research Articles

Uterine cervical carcinoma: evaluation of pelvic lymph node metastasis with MR imaging.

To assess accuracy of magnetic resonance (MR) imaging in detection of pelvic node metastasis from uterine cervical carcinoma. In 136 patients (aged 26-71 years [mean, 49 years]) with uterine cervical carcinoma seen between October 1990 and July 1992, maximum axial diameter (MAAD), minimum axial diameter (MIAD), and signal intensity enhancement ratio of positive nodes were measured. With MAAD of 1.0 cm, MR imaging had an accuracy of 90.4%, sensitivity of 62.2%, and specificity of 94.9% in detection of pelvic node metastasis. Mean MAAD and MIAD were 1.43 and 1.30 cm for true-positive nodes and 1.18 and 0.75 cm for false-positive nodes, respectively. Mean MAAD/MIAD was 1.09 for true-positive and 1.76 for false-positive nodes. With MIAD of 1.0 cm, MR imaging had an accuracy of 93.0% with 62.2% sensitivity and 97.9% specificity. No significant differences were noted in the degree of contrast enhancement between true-positive and false-positive nodes. The accuracy of MR imaging was fairly high in detection of pelvic node metastasis from uterine cervical carcinoma, and MIAD was a more accurate size criterion than MAAD.

The management of histologically unverified presumed cerebral gliomas with radiotherapy

Purpose : To define the natural history, and prognostic factors of patients with histologically unverified presumed gliomas diagnosed on CT or MR imaging, and treated with external beam radiotherapy. Methods and Materials : Retrospective review of 111 adults with histologically unverified presumed cerebral glioma treated with radiotherapy between 1974 and 1990. Using CT or MRI criteria alone 41 were presumed low grade, 63 high grade gliomas and 7 were unclassified. Survival results were compared to a cohort of 82 adults with histologically verified low grade gliomas treated over the same period with surgery and radiotherapy. Results : The 5 year survival probability of the whole cohort was 31%. Age, performance status, and the degree of contrast enhancement were independent prognostic factors for survival. Patients with presumed low grade glioma had a 5 year survival of 41% compared to 52% for patients with verified low grade glioma. After correction for prognostic factors no significant difference was found in the survival between patients with verified and unverified low grade tumors. One of 15 cases with subsequent histology, obtained at autopsy or salvage surgery, had nonglial pathology. Conclusion : Patients diagnosed on the basis of clinical features and imaging as having presumed glioma have similar natural history and clinical behavior after treatment with radiotherapy to those with histologically confirmed gliomas. However, the results should not be taken as justification for avoiding biopsy. A proportion of patients may have nonglial pathology and new more effective treatment strategies for patients with glial tumors can only evolve on the basis of full diagnostic information including pathology.

Astrocytic gliomas: MRI and pathological grade.

The relationship between MR configuration and pathological grade was studied in 41 histologically verified supratentorial astrocytic gliomas with a 0.5T superconductive MR system. The gliomas included 13 low-grade astrocytomas (LGAs), 14 anaplastic astrocytomas (AAs) and 14 glioblastoma multiformes (GBMs). MRI configurations were classified into nine criteria which were scored and statistically analyzed. The mean values of LGAs, AAs and GBMs were 0.45 +/- 0.31, 1.18 +/- 0.20 and 1.47 +/- 0.22. In each grade, MRI score increased as pathological grades increased (p < 0.01-0.001). LGAs had significantly lower values than AAs in five of the nine criteria (55.6%); heterogeneity, cyst or necrosis, edema or mass effect, border definition, and the degree of contrast enhancement, and lower values than GBMs in eight criteria (88.9%) except for hemorrhage. Three criteria (33.3%), heterogeneity, cyst or necrosis, and flow void sign were significantly higher in GBMs than AAs. The four variables, heterogeneity, cyst or necrosis, edema or mass effect and border definition, proved to be important factors related to the pathological grade in a multiple regression analysis.

Nerve sheath tumors: evaluation with CT and MR imaging : Verstraete KL, Achten E, De Schepper A, et al. (Dienst Radiologie en Medische Beeldvorming, Universitair Ziekenhuis Gent, De Pintelaan 185, B-9000, Gent, Belgium). J Belge Radiol 1992;75:311–320

Tumors of nerves are classified into benign (schwannoma and neurofibroma) and malignant nerve sheath tumors. Schwannomas almost always occur as solitary lesions, whereas neurofibromas may occur alone or in a greater number, especially in patients with the peripheral form of von Recklinghausen's disease. Benign nerve sheath tumors often present as asymptomatic, slowly growing soft tissue masses. Although malignant nerve sheath tumors are relatively rare, a sudden increase in the size of a lesion, in particular in a patient with neurofibromatosis, should raise the suspicion of malignant change. On computed tomography (CT) and magnetic resonance imaging (MR) a benign nerve sheath tumor usually appears as a well-defined, oval, spherical or fusiform mass with smooth borders and distinct outlines, located in the subcutaneous tissue or centered at the expected anatomic location of a nerve, with displacement of adjacent soft tissues. Generally nerve sheath tumors have a low density on unenhanced CT scans. On MR they are isointense to muscle on T1-weighted images, whereas on T2-weighted images the signal intensity is high. Both on CT and MR the degree of contrast enhancement is moderate to marked and may be homogeneous or inhomogeneous. MR has become the method of choice for evaluating the anatomic location, contour, and relation of a nerve sheath tumor to adjacent neural, vascular, and muscular structures. The imaging criteria for malignant nerve sheath tumors are not specific enough to distinguish them from other malignant soft tissue tumors, so that neither CT nor MR can establish a definite diagnosis.

CT arterial portography of the abdomen: effect of injecting papaverine into the mesenteric artery on hepatic contrast enhancement.

The purpose of this study was to determine the effect of precontrast injection of papaverine hydrochloride into the superior mesenteric artery on the degree of contrast enhancement of the hepatic parenchyma during CT arterial portography (CTAP, CT with injection of contrast material into the superior mesenteric artery). Twenty-two patients were included in this study. All patients had a baseline unenhanced CT scan and then had CTAP performed with transcatheter injection of 150 ml of nonionic iodinated contrast material (30 g iodine/100 ml) at a rate of 2 ml/sec. Eleven patients received a precontrast injection of 40 mg of papaverine hydrochloride via catheter into the superior mesenteric artery, and 11 patients had CTAP without papaverine hydrochloride. Attenuation of the liver was measured before and after contrast administration in both groups of patients. For each CTAP section, the absolute hepatic enhancement (postcontrast attenuation--precontrast attenuation) and the relative hepatic enhancement ([absolute hepatic enhancement/precontrast attenuation] x 100) were calculated. Also, the mean absolute enhancement and the mean relative enhancement for the entire liver were calculated for each patient. The mean relative enhancement (+/- SD) of hepatic parenchyma was 192 +/- 54% with papaverine hydrochloride and 146 +/- 26% without papaverine hydrochloride. Relative enhancement was significantly higher when papaverine hydrochloride was used (p < .02). The mean absolute enhancement (+/- SD) of hepatic parenchyma was 123 +/- 25 H with papaverine hydrochloride and 91 +/- 19 H without papaverine hydrochloride. Absolute enhancement was significantly higher in patients who had papaverine hydrochloride (p < .01). The results show that precontrast transcatheter infusion of papaverine hydrochloride increases the degree of contrast enhancement of the liver during CTAP.

Uses and limitations of spoiled gradient-refocused imaging in the evaluation of suspected intracranial tumors

This article describes the use of a radiofrequency-spoiled gradient-recalled (SPGR) imaging pulse sequence in the evaluation of intracranial masses. This pulse sequence provides excellent anatomic detail with T1-weighted image contrast. Rapid, sequential, single-slice (two-dimensional) images of the brain can be obtained in patients who are unable to hold still for long periods of time. In addition, volumetric (three-dimensional) image data sets can be obtained that provide extremely thin (1- to 2-mm) sections of high detail and good signal-to-noise ratio for selected critical structures within the brain. Finally, because SPGR is also utilized for time-of-flight angiography, parenchymal information can be obtained simultaneously with cerebral blood vessel definition. One potential pitfall that the magnetic resonance radiologist must be aware of is the fact that, in many patients, the degree of contrast enhancement is greatly diminished on postgadolinium SPGR images compared with conventional spin-echo T1-weighted images. Comparison with a set of standard spin-echo postcontrast images or, potentially, the use of higher doses of gadolinium may solve this problem. In spite of this limitation, the selective utilization of SPGR imaging can yield additional useful information for evaluation and preoperative planning in patients with intracranial masses.

Peyronie's disease: MR findings in 28 patients.

Induratio penis plastica (Peyronie's disease) is a chronic fibrotic process involving the penis. Proper treatment of the disease requires assessment of the degree of inflammation preceding or accompanying the fibrous Peyronie's plaques. Owing to its high tissue contrast and its multiplanar capability, MR imaging offers excellent visualization of penile anatomy. To determine the usefulness of MR imaging in the diagnosis and staging of Peyronie's disease, we used MR imaging with a surface coil to examine 28 consecutive patients with clinical evidence of the disease. Eighteen patients had contrast-enhanced MR imaging with gadopentetate dimeglumine. In seven patients who subsequently had surgery or biopsy, MR findings were correlated with histopathologic findings. On unenhanced images, fibrous plaques were shown in 20 patients. Enhanced MR images showed focal contrast enhancement around or within the plaques in seven patients. Images in three patients with plaques showed no enhancement. Images in five patients showed focal areas of contrast enhancement without evidence of plaques. Histologic studies demonstrated that the degree of contrast enhancement correlated with the extent of inflammatory cell infiltration. In two patients with unenhancing plaques on MR, histology confirmed the absence of inflammation. Our results suggest that MR imaging not only depicts the localization and extent of fibrous plaques in patients with Peyronie's disease but also reveals the presence of inflammation. This makes MR imaging the technique of choice for planning therapy and for evaluating the response to conservative treatment.

Adaptive contrast enhancement and de-enhancement

Two different interpolative schemes for adaptive contrast enhancement have been presented for speeding up the contrast enhancement algorithm proposed by Beghdadi and Negrate. To reduce the enhancement of noise in relatively flat regions present in the image, an adaptive power variation technique is used in which the degree of contrast enhancement is varied depending on the severity of brightness change in a region. A contrast transformation function is proposed which can be used for adaptive enhancement as well as de-enhancement of images.

The value of paramagnetic contrast agent gadolinium-DTPA in the diagnosis of pituitary adenomas.

The purpose of this study was to assess the role of MR imaging and the paramagnetic contrast agent Gadolinium-DTPA(Gd-DTPA) in the diagnosis of pituitary macroadenomas. 44 macroadenomas were examined with MRI before and after intravenous application of Gd-DTPA. Gd-DTPA produced excellent enhancement of solid adenoma. The best contrast between adenoma and surrounding structures could be gained on post-Gd T1-weighted images. Post-Gd images were equivalent to pre-Gd images in the evaluation of supra- and infrasellar extensions of macroadenomas. Post-Gd images had advantages in the evaluation of cavernous sinus invasion by adenoma. The difference in degree of contrast enhancement between adenoma and cavernous sinus facilitated the exact evaluation of lateral extension by adenoma in 18 cases. Almost equal degree of enhancement of both structures impaired tumor-sinus contrast in 2 cases. In the other 24 cases the tumor filled the cavernous sinus completely. It is our opinion that Gd-DTPA can be used on a widespread basis because of its excellent capability to highlight and delineate pituitary adenomas.

Hepatic tumors: dynamic MR imaging.

Thirty-six patients with hepatic tumors (28 hepatocellular carcinomas, seven cavernous hemangiomas, one metastatic tumor) were examined with serial magnetic resonance (MR) imaging, after a bolus intravenous injection of 0.05 mmol/kg gadolinium-diethylenetriaminepentaacetic acid. A typical MR imaging pattern for hemangiomas (present in five of seven cases [71.4%]) was a lesion of diminished signal intensity on precontrast images, peripheral contrast enhancement during the bolus dynamic phase, and complete fill-in of high signal intensity on delayed scan images. Twenty-eight hepatocellular carcinomas showed a variety of contrast enhancement patterns during the dynamic phase. In 21 patients (75%), there was no area of high signal intensity within the tumor on the delayed phase. A peripheral halo with delayed enhancement was noticed in 12 patients (42.8%) Histologic correlation in hepatocellular carcinomas showed that the degree of contrast enhancement corresponded to tumor vascularity and that the peripheral halo corresponded to fibrous capsular structure.

Supratentorial ependymomas. Neuroimaging and clinicopathological correlation.

In 10 patients with supratentorial ependymomas, the tumors exhibited hyperdensity on computerized tomography (CT) scanning prior to contrast infusion and, with one exception, all tumors were mixed lesions with the low densities suggesting cystic or necrotic portions. Eighty percent of the tumors contained small calcifications. Characteristically, the tumors were well demarcated and demonstrated moderate to marked enhancement after the intravenous administration of contrast material. Angiograms obtained in some patients showed mild hypervascular tumor staining and absence of large feeding arteries. The degree of contrast enhancement, angiographic vascularity, and tumor stain was compared to the pathological anaplasia of the tumors. No correlation was observed. Of four patients who were still alive during a follow-up period of 4 years or longer, three had recurrences with inoperable tumors; the remaining patient is without recurrence after craniospinal radiation. This same patient belonged to a group of five patients with a diagnosis of high-grade ependymoma, four of whom had recurrence. Follow-up CT accurately recorded the clinical course of each patient. Annual routine follow-up examinations are proposed for patients with low-grade ependymomas, and for those with high-grade ependymomas follow-up CT should be performed every 6 months. The characteristic appearance and behavior of these tumors include several distinctive features on angiographic and CT images.

Intravenous administration of contrast medium during computed tomography (CT) of the operated lumbar spine

In 35 patients with recurrent radicular complaints which occurred 4 weeks to 38 months after operation for lumbar disc herniation, the degree of contrast enhancement of hypertrophic scar tissue was examined. All patients were scanned before and immediately after intravenous contrast application (volume: 1.5-2.0 ml/kg body weight, flow rate: 0.35 ml/sec). In 83% of the cases hypertrophic scar tissue did show definite contrast enhancement, whereas disc herniation remained unenhanced. Comparison between contrast enhancement and age of scar tissue produced poor correlation (r = 0.3012) with older scarring showing a trend towards lower enhancement levels. In cases where morphologic and topographic criteria in plain CT examination fail to yield a diagnosis, intravenous contrast application is recommended. Our data indicate that even those patients might benefit from the procedure who have been operated upon for disc herniation several months or years ago.

Contrast enhancement of LED, vaccum fluorescent and plasma displays with circular polarizing filters

Filters are widely used for contrast enhancement of active electronic displays. This paper considers the application of circular polarizers to LED, vacuum fluorescent and plasma displays under a variety of ambient illumination situations. Relevant parameters controlling contrast enhancement have been identified. The degree of contrast enhancement obtained with appropriate circular polarizing filters under different ambient illumination values is reported for each display type. These values are compared with those obtained using non-polarizing chromatic filters. In general, when contrast is being degraded by specular reflections of ambient light, the circular polarizing filters improve contrast to a much greater extent than the non-polarizing filters.

Short term, high dose corticosteroids in computed tomographic staging of experimental brain abscess.

A short term, high dose corticosteroid treatment protocol was investigated to determine its clinical utility in staging an experimental brain abscess. Corticosteroids were shown to decrease the degree of contrast enhancement of brain abscess 12 h after administration but the magnitude of the effect was not consistent enough to be clinically useful in staging. The corticosteroid effect progressively diminished as the inflammatory lesion encapsulated over time. This effect emphasized that a decreasing ring diameter and not diminished contrast enhancement should be the CT criterion for brain abscess resolution.

Pathological correlation of CT ring in recurrent, previously treated gliomas.

The meaning of the enhancing ring commonly seen on computerized tomographic (CT) scans in patients with recurrent, treated glioblastoma has long been of concern. Does the ring represent radiation necrosis, pseudocapsule formation, compressed adjacent brain, or, in fact, a peripheral zone of viable tumor? We employed a multiple intratumoral biopsy technique at the time of reoperation to investigate this ring. Pathological evidence is presented documenting the content of the ring to the viable tumor. It is suggested that perhaps treatment failure may be determined on sequential CT examinations by comparing the volume and degree of contrast enhancement.

Image processing and quantitative assessment in computer tomography for non-surgical treatment of brain tumours.

Using the EMI computer tomographic (CT) system, EMI-1010, a series of new programmes were developed for the digital analysis of the CT images in order to make a more objective and quantitative assessment possible of two non-surgical methods of treatment of brain tumours such as irradiation and chemotherapy. Amongst the various therapeutic effects demonstrable from the Ct data, a reduction of the mass effect was found to lower the average CT number, with a dilatation of the cisterns and ventricles. In contrast, an improvement in the amount of perifocal oedema increased the average CT number of the region, however the changes in CT number of the tumour itself may be variable. The separate evaluation of these factors, therefore, gives more information about the results of the treatment than a simple analysis of the histogram of the region. Circumscribed tumours are fairly well evaluated with our programme for the statistical analysis of the volume and the CT weight of tumours and the degree of contrast enhancement using histograms and subtraction scans. For the digital analysis of the ventricular system, the subarachnoid space, perifocal oedema, and irregularly shaped infiltrating tumours, our programmes for the character-image print-out and edge correction for the partial-volume effect of skull and air are much more useful than the CRT display for data extraction and geographic-pattern recognition.

High-dose, few fractions radiotherapy for brain metastases

From November 1976 through September 1981, 28 patients with brain metastases received the conventional therapy and 9 patients received a high-dose, few fractions radiotherapy. There were two types of deaths—neurological and systemic death. In the conventional therapy group, neurological death occurred in 61% of all cases, but no neurological death was observed in the high dose radiotherapy group. Sequential computerized tomography (CT) scans were performed to estimate the therapeutic effect in 6 patients who received the conventional therapy and in 6 patients who received the high dose radiotherapy. Therapeutic effect was estimated by palliative indices which rated changes in the volume of the contrastenhanced area and of the perifocal low density area, and changes in the degree of contrast-enhancement of the tumor on CT scan. Many patients who received the high dose rediotherapy showed a reduction in tumor size and in the degree of contrast-enhancement, necrotic tumor tissue surrounded by lipid-laden macrophages on pathology, and a few months of neurological improvement. Preliminary results of this study suggest that high-dose, few fractions radiotherapy is effective for brain metastasis treatment.

CT of meningiomas on the Posterior surface of the petrous bone.

A detailed analysis of the CT findings in 16 surgically verified cases of meningioma of the posterior surface of the petrous bone is presented. The results indicate that a correct preoperative diagnosis is possible in almost every case. Frequently occurring specific CT criteria for meningioma of the posterior surface of the petrous bone include: hyperdense, homogeneously enhancing, extra-axial, CPA mass; inverse relationship between precontrast attenuation value and degree of contrast enhancement of the tumor; oval shape; obtuse angle between lateral tumor border and posterior surface of petrous bone, and evidence of transcisternal supratentorial tumor extension. Infrequently occurring specific CT criteria include: tumor calcification; hyperostosis or exostosis of the posterior surface of the petrous bone; a comma-shaped tumor configuration in cases with transcisternal tumor extension and evidence of transtentorial tumor extension. Oxygen CT cisternography is the most sensitive and reliable technique for detecting small tumors. The CT differential diagnosis of meningioma of the posterior surface of the petrous bone is discussed.

Computed tomography of supratentorial astrocytoma

In a group of 40 astrocytomas the C.T. appearance was correlated with the grade of malignancy. On the plain scan the majority presented an irregular, nonhomogeneous low density lesion, better demarcatable in high than in low grade astrocytomas. Contrast enhancement was seen in 28 of the 32 high grade astrocytomas, 50% of the annular, 25% of the nodular and 25% of the mixed type. Six of the 8 low grade astrocytomas showed no contrast enhancement and 1 showed an annular type lesion. A relationship was found between the degree of contrast enhancement and the vascularity. Mass effect was observed in all but 1 patient, but more pronounced in high grade astrocytomas. At the first interpretation 98% were recognized as a lesion, 93% as a tumor and 68% as an astrocytoma. One false negative and no false postive C.T.scans were obtained. In review, high and low grade malignancies were correctly differentiated in 90%. As a screening method, the combination of EEG and echo equalled C.T.; in establishing a definite diagnosis angiography was inferior to C.T. Solely on the basis of the C.T. appearance, astrocytomas can hardly be differentiated from the other malignant brain tumors, but the grade of malignancy can be predicted reliably.