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Background Contrast-enhanced spectral mammography (CESM) may help to determine the malignancy potential of lesions according to the degree of enhancement. Purpose To investigate the correlation between the degree of contrast enhancement of the lesions in contrast-enhanced spectral mammography (CESM) and the final histopathological diagnosis in patients with BI-RADS 4 and 5 lesions. Material and Methods CESM was performed in 128 patients who had BI-RADS 4 and 5 lesions on mammography and underwent histopathological examination. A total of 128 index lesions were scored using a 4-point scale regarding the degree of contrast enhancement (0 = no contrast enhancement, 1 = minimal, 2 = moderate, 3 = marked), a score of 2 and 3 was accepted as suggestive of malignancy. The study was approved in our institutional scientific committee. Results In total, 76 (59.4%) of the lesions had benign histopathological results, whereas 52 of them had malignant results. Contrast enhancement was not observed in 22.7% of the lesions while 24.2% had minimal enhancement, 18.8% had moderate enhancement, and 34.4% had marked enhancement in CESM. The sensitivity of the degree of contrast enhancement in CESM was 98.1%, when the specificity was 77.6%, positive predictive value was 75%, negative predictive value was 98.3%, and accuracy was 85.9%. Conclusion This study demonstrated that the degree of contrast enhancement of the lesions in CESM may be used in daily practice with easily performing a visual scale in predicting the malignancy potential of the lesions.

Background The effect of gadolinium-based contrast agents on diffusion-weighted imaging (DWI) measurements of breast lesions is still not clear. Purpose To investigate gadolinium effects on DWI and apparent diffusion coefficient (ADC) in breast lesions and normal parenchyma with 3 Tesla contrast-enhanced MRI. Material and Methods Pre- and post-contrast DWI (b = 0 and b = 1000 s/mm2) were acquired in 47 patients. Measured ADC values, pre- and post-contrast T2 signal intensity (T2 SI) and contrast-to-noise ratio (CNR) were compared with Wilcoxon signed-rank and rank-sum test ( P Results Post-contrast ADC was reduced only in malignant lesions (−34%), T2 SI was reduced both in malignant (−50%) and benign (−36%) lesions. Post-contrast CNR was reduced in all groups except for benign lesions. Conclusion Gadolinium-based contrast agent causes a significant reduction in ADC values of malignant breast lesions.

Background Biphasic injection protocols are frequently used because they yield homogenous contrast enhancement. We hypothesize that with faster scanners and shorter scan times, biphasic injection protocols are no longer necessary. Purpose To evaluate whether a monophasic injection protocol is equivalent to a biphasic protocol in terms of contrast enhancement and homogeneity. Material and Methods Repeated high-pitch CTA (pitch 3) and conventional standard-pitch computed tomography angiography (CTA) (pitch 1.2) from the cervical region to the symphysis was performed in seven beagles (11.2 ± 2.5 kg) in a cross-over study design. Arterial contrast enhancement was measured along the z-axis in the ascending, descending, and abdominal aorta and the iliac arteries. The z-axis is the longitudinal axis of the human body and at the same time the direction in which the CT table is moving. The data were analyzed using repeated measures ANOVA with a post-hoc t-test and visual assessment of the scans. Results In high-pitch CTA, monophasic injection protocols were superior to biphasic injection protocols in enhancement levels ( P Conclusion High-pitch CTA monophasic injection protocols are superior to biphasic injection protocols, due to a higher and more homogeneous contrast enhancement with the same amount of contrast medium used.

Background Intracranial lesions exhibit clear contrast enhancement in T1-weighted imaging, but the mechanism whereby contrast-enhanced susceptibility-weighted imaging (CE-SWI) generates signals remains unclear. Contrast enhancement patterns cannot be reliably predicted. Purpose To explore the mechanism of CE-SWI contrast enhancement. Material and Methods Fifty-five patients were retrospectively enrolled. All of the imaging employed a clinical 3T magnetic resonance imaging (MRI) system fitted with a 32-channel head coil. Minimum-intensity projection reformatted images were evaluated. Intracranial lesions and brain parenchymal intensities were explored using SWI and CE-SWI. signal intensity rates were calculated by dividing the lesional intensity by the white matter intensity, after which the SWI and CE-SWI signal intensity rate were compared. Two observers independently performed intralesional susceptibility signal analysis. Results After contrast medium administration, malignant and extra-axial tumors exhibited obvious contrast enhancement on CE-SWI ( P Conclusion Contrast media can either reduce or increase SWI signal intensities. The dual contrast feature of CE-SWI can be useful when exploring intracranial disorders.

Background The contrast enhancement of pulmonary nodules is a differential diagnostic criterion which can be helpful in staging investigations. Purpose To investigate the impact of dual-energy computed tomography (DECT) with regards to the evaluation of pulmonary nodules with emphasis on metastatic lesions. Material and Methods DECT scans of the thorax were performed in 70 consecutive patients. Data of the lung were acquired in the arterial and in delayed venous phase. The virtual native and overlay image data based on arterial and delayed venous phase of these lesions were compared using CT density values (HU) within the nodule tested for statistical significance. Results A total of 156 pulmonary lesions ≥5 mm were identified on 70 DECT scans. There were no significant differences between the CT-value measurements in the virtual native images based on the arterial and delayed venous phase (27.9+/–3.9 HU vs.28.1+/–4.2 HU, P = 0.89) and between the CT-value measurements in the overlay images based on the arterial und delayed venous phase (35.5+/–6.8 HU vs. 36.6+/–5.0 HU, P = 0.75). Metastases of colorectal carcinoma (51.4+/–9.4 HU vs. 32.5+/–8.9 HU, P = 0.0001), malignant melanoma (56.1+/–6.4 HU vs. 34.2+/–1.6 HU, P = 0.0045), and thyroid cancer (53.5+/–15.5 HU vs. 15.7+/–4.2 HU, P = 0.001) showed a distinct wash-out, whereas metastases of lung cancer (23.1+/–6.3 HU vs. 58.6+/–4.8 HU, P = 0.001), salivary gland cancer (41.4+/–20.3 HU vs. 65.7+/–15.7 HU, P = 0.023), and sarcoma (56.2+/–7.4 HU vs. 90.2+/–3.4 HU, P = 0.001) had an increased enhancement in the delayed venous phase. Conclusion The contrast enhancement behavior of pulmonary metastases can be evaluated with DECT and depends on the type of the primary malignant tumor.

Purpose: To assess the magnetic resonance imaging (MRI) signal and contrast-enhancement features of uterine fibroids before and after embolization, and to determine whether or not there are pre-embolization MRI characteristics that predict the volume reduction of fibroids. Material and Methods: Uterine fibroid embolization (UFE) was carried out in 28 fibroids of 20 patients, all of whom were symptomatic. The patients were prospectively evaluated with T1-weighted, T2-weighted, and gadolinium-enhanced T1 MRI sequences before and 6 months after embolization. The relationship between the characteristics of MRI signal and contrast-enhancement features of fibroids before the procedure and the change in size of the lesions after treatment was investigated. Results: Before embolization, the mean volume of fibroids was 123 cm3 (8–560 cm3). The decrease rate in fibroid volumes was 44.6% (range 7–70%) 6 months after embolization. Volume reduction was more prominent in fibroids that had a high signal intensity on T2-weighted images and a marked contrast enhancement on T1-weighted images ( P Conclusion: MRI is an effective method for revealing size and signal changes of fibroids after embolization. MRI signal characteristics and the contrast-enhancement pattern of fibroids before embolization can predict tumor volume reduction after embolization.

Purpose: To evaluate the potential of dynamic contrast enhanced (DCE) 3D EPI in the location of prostate cancer. Material and Methods: A DCE 3D EPI scan was included in the magnetic resonance imaging protocol for prostate examination. Twenty‐eight patients who subsequently underwent radical prostatectomy were included in the study. T2‐weighted (T2W) Turbo Spin Echo (TSE) images were initially evaluated by two radiologists. Parametric images reflecting contrast enhancement were added and new evaluations performed. The results were compared with histology from resected specimens. Accuracies and interobserver agreements were calculated. Results: Interobserver agreement was κw=49±3% for the T2W technique and κw=30±3% for the combined techniques. No statistically significant advantages were found for location of tumor in the prostate or in the seminal vesicles by adding the DCE information. Conclusion: DCE 3D EPI did not improve tumor location compared with that of T2W TSE images. Further investigation is needed on how best to exploit the DCE technique.

To evaluate the value of serially obtained spinal MR images in the diagnosis and clinical follow-up of childhood Guillain-Barré syndrome (GBS), and the time period for resolution of contrast enhancement during the course of illness.Contrast-enhanced spinal MR images of 11 pediatric patients with GBS were reviewed prospectively. In the first group of 6 patients, follow-up MR was performed three times after the 1st, 3rd and 6th months after onset of the disease. In the second group (the other 5 patients) who had not accepted serial MR examinations, control MR was repeated once after 1 year. Patients were graded clinically into five categories according to their initial clinical signs and symptoms and three grades (mild, moderate and severe) according to level of contrast enhancement on T1-weighted images to correlate the severity of enhancement with clinical findings and recovery.Ten of the 11 patients revealed contrast enhancement in varying degrees in the spinal nerve roots surrounding the conus medullaris and extending the length of the cauda equina. One patient showed no contrast enhancement. Anterior nerve roots enhanced more intensely than the posterior roots in 3 patients. Follow-up MR images in all patients revealed diminishing or resolving contrast enhancement in the nerve roots as the clinical symptoms improved.We suggest contrast-enhanced spinal MR imaging as a supplementary diagnostic modality in diagnosing GBS, especially when the clinical and electrophysiological findings are equivocal. Follow-up images may play a role in predicting the clinical course of the disease.

Purpose: To study the pattern of contrast enhancement in MR and CT of oligodendrogliomas and to compare this with other imaging findings and with histopathological grading criteria. Material and Methods: 20 patients with oligodendrogliomas (12 low-grade WHO II and 8 anaplastic WHO III) were reviewed. 20 complete MR investigations, 20 non-enhanced CT studies and 16 CTs after contrast enhancement were estimated blindly without knowledge of the tumour histological grades. Results: All anaplastic oligodendrogliomas showed tumour contrast enhancement on MR and CT images. Also in 6/12 low-grade oligodendrogliomas the contrast was enhanced on MR imaging. In 5 of these, tumour calcifications were detected by CT. The remaining 6/12 WHO grade II cases showed no significant MR contrast enhancement. Of the oligodendrogliomas grade II, CT showed contrast uptake in 3 cases and no enhancement in 6, while in 3 cases postcontrast CT was not available. A comparison of contrast enhancement with tumour grade resulted in a p-value of 0.042 for MR and of 0.011 for CT. A combined statistical test of tumour grade and calcifications detected by CT compared with MR contrast enhancement showed a significant correlation ( p=0.014). Conclusion: These data demonstrated that a clear grading of oligodendrogliomas based on the image criterion MR contrast enhancement was not possible. We suppose that, besides tumour neovascularisation, additional factors such as calcifications may disturb the blood-brain barrier.

Purpose: To find out if round atelectases (RAs) of a lung enhance more than pulmonary malignant tumors. Material and Methods: Twelve patients with RA and 16 patients with malignant lung tumor (MLT) evidenced on CT examination were selected (14 RAs and 16 MLTs). Two patients had 2 RAs. The examination data were reviewed on a work station and the attenuation values of RAs and tumors were measured. Results: At enhanced CT the density of RAs varied from 88 to 190 HU whereas for MLTs the density varied from 30 to 71 HU. The difference between attenuation values of RAs and MLTs was statistically significant. Conclusion: The attenuation values of RAs after contrast enhancement seem to differ from those of MLTs, at least during the first minute after contrast injection, and thus serve as a useful aid in the differential diagnosis of these masses.

Purpose: To evaluate if static post-contrast MR imaging was adequate to assess tumor viability after pre-operative radiotherapy in soft tissue sarcoma. Material and Methods: Post-contrast MR imaging of 36 soft tissue sarcomas performed 0-54 days (median 13 days) after pre-operative radiotherapy, were retrospectively reviewed and compared to post-operative histopathology reports. The contrast enhancement of the tumor was visually graded as minor, moderate or extensive. From the post-operative histopathology reports, three types of tumor response to radiotherapy were defined: Poor, intermediate or good. The size of the tumors before and after radiation was compared. Results: Even if most viable tumors enhanced more than non-viable tumors, there was major overlapping and significant contrast enhancement could be seen in tumors where histopathological examination revealed no viable tumor tissue. Based on histopathology, there were 12 good responders; 8 of these showed minor, 3 moderate and 1 extensive contrast enhancement on MR imaging. Sixteen tumors had an intermediate response; 3 showed minor, 8 moderate and 5 extensive enhancement. Eight tumors had poor response; none showed minor enhancement, 3 moderate and 5 extensive enhancement. Both increase and decrease in tumor size was seen in lesions with a good therapy response. Conclusion: Static post-contrast MR imaging cannot reliably assess tumor viability after pre-operative radiotherapy in soft tissue sarcoma. In tumors with no viable tumor tissue, moderate and extensive contrast enhancement can be seen.

Purpose: To evaluate the use of MR imaging using standard sequences in the differentiation of common vascular birthmarks of soft tissues in childhood. Material and Methods: Forty-three lesions in 37 children (median age 33 months) with hemangiomas (n=25), venous (n=8) and lymphatic (n=10) malformations were retrospectively studied. Images were obtained with a 0.2 T and a 1.5 T MR unit, using T1-weighted spin-echo, T2-weighted turbo spin-echo and turbo STIR sequences. In addition, 19 contrast studies were evaluated. Signal intensities and morphological characteristics were analyzed. Results: All hemangiomas were hyperintense in T2-weighted, and mostly (22/25) isointense compared to the surrounding skeletal muscle in T1-weighted images. The lesions were homogeneous or mildly inhomogeneous and well defined. Venous and lymphatic malformations showed similar patterns. Contrary to other lesions, no vessels or lobular architecture were detectable and contrast enhancement was absent in lymphatic malformations. Conclusion: A reliable differentiation between hemangiomas, venous and lymphatic malformations in childhood is not possible by standard MR sequences alone. Contrast media may be helpful as lymphatic malformations show no contrast enhancement. The main role of MR imaging is to determine the local extent or infiltration of deeper tissue layers and narrow the differential diagnosis of other soft tissue tumors.

Purpose: Can a complementary 3-D T1-weighted sequence (MPRAGE) facilitate the evaluation of contrast enhancement in patients with widespread and early contrast enhancement in our standard 3-D T1-weighted FLASH sequence? Material and Methods: Twenty patients with 21 breast lesions were examined with both FLASH and MPRAGE sequences. the MR examinations were reviewed independently by three radiologists. Results: In both the FLASH and MPRAGE sequences, 11 lesions were true-positive. In the FLASH sequence alone, 3 lesions were true-negative and 13 false-positive in comparison to the MPRAGE sequence alone in which 10 lesions were true-negative and 6 false-positive. Seven lesions that were false-positive in the FLASH sequence were true-negative in the MPRAGE sequence: this shows that MPRAGE has the potential to downgrade the false-positive findings found in the FLASH sequence. Conclusion: Due to its higher sensitivity, FLASH is the sequence of first choice at routine examination. However, when atypical increased enhancement was found, the addition of the MPRAGE sequence improved the specificity of the MR investigation.

Purpose: the aim of the study was to explain why breast lesions are enhanced by contrast medium at MR imaging and to elucidate the histopathological basis for the overlap in the enhancement patterns of benign and malignant breast lesions Material and Methods: Ten invasive breast carcinomas and 10 benign breast lesions were selected for the study. of the 10 carcinomas, 5 showed a strong and early contrast enhancement, and 5 did not. of the 10 benign lesions, 5 showed a strong and early contrast enhancement, and 5 showed no enhancement. the following morphometric variables were evaluated: proliferation cell index of neoplastic parenchymal cells, S-phase fraction, nuclear ploidy analysed by image DNA-cytometry, microvessel density, and the percentage proportion of the interstitial area Results: Contrast enhancement was related to the proliferating activity of the hyperplastic or neoplastic parenchymal cells and was inversely correlated with the interstitial area in carcinomas as well as in benign tumours and non-neo-plastic lesions of the breast Conclusion: Morphometric variables play an important role in the general mechanism of MR contrast enhancement in examinations of the breast and explain the histopathological basis for the overlap in the enhancement patterns of benign and malignant breast lesions

Forty-five patients with known or suspected musculoskeletal tumors were examined with static and dynamic MR imaging to evaluate the safety, tolerability and diagnostic utility of gadodiamide injection and to assess the diagnostic value of dynamic MR imaging and parametric “first-pass” (FP) images. The proportion of patients presenting more diagnostic information on the contrast-enhanced compared to the precontrast spin-echo examinations was determined. The dynamic enhancement characteristics were evaluated with time-intensity curves and parametric images of the FP enhancement rate. The tolerance of gadodiamide injection was good. Contrast enhancement was useful for delineating tumor from muscle, and differentiating viable from necrotic tissue and cystic from solid lesions. Malignant tumors showed a significantly higher slope value, earlier onset of enhancement, and higher maximum enhancement than benign lesions. However, slope values could not be used to predict the malignant potential of a lesion, due to overlap between highly vascular benign and low vascular malignant lesions. By displaying highly vascular areas, parametric FP images provided useful information on the most active part in a tumor before biopsy and for assessing the incorporation of bone-chip allografts. Static, dynamic and FP MR imaging using gadodiamide injection appears safe and provides useful information for diagnosis, biopsy and follow-up of musculoskeletal lesions.

Gd-DTPA-enhanced MR imaging of 15 patients with primary mediastinal Hodgkin's disease was done before, during and after treatment. A total of 43 MR examinations were performed. After successful treatment, 13 patients had residual masses with reduced signal intensity (SI) ratio in the T2-weighted images. The majority of these also had decreased contrast enhancement as compared with the corresponding primary tumour. There was a significant positive correlation between the contrast enhancement and the SI ratios in the T2-weighted images of the primary tumours and/or the residual masses. Necrosis was seen in 3 of the primary tumours and one patient had a cystic residual mass. These necrotic/cystic lesions were easier to detect with the use of Gd-DTPA. Low SI ratio in the T2-weighted image and low contrast enhancement of the residual mass seem to indicate residual inactivity. Gd-DTPA facilitates the differentiation between cystic/necrotic and solid lesions.

Gadodiamide injection was administered intravenously to 49 patients with known or suspected CNS lesions undergoing MR imaging. Two parallel groups were used to evaluate the efficacy and safety of single doses of 0.1 (25 patients) and 0.3 (24 patients) mmol/kg b.w. The principal measures of efficacy were diagnostic yield of MR and the overall contrast enhancement. Adverse events and serum bilirubin were the main safety parameters. Contrast enhancement of the lesion was observed for 16 patients in each dose group. Thirteen patients in the 0.1 and 17 in the 0.3 mmol/kg group had their diagnosis amended following the postcontrast image, but only one patient in each dose group had their management affected by new information from the postcontrast image. The overall diagnostic utility of gadodiamide injection was good, but there were no differences between the 2 doses studied in this respect. No injection-associated discomfort or other adverse events were reported. No clinically important changes in serum bilir...

A retrospective analysis of the CT examinations of 45 patients with squamous cell carcinomas of the tongue, floor of the mouth and tongue base with long-term follow-up is presented. The aim of the study was to determine whether differences in tumor contrast enhancement and tumor demarcation at contrast-enhanced CT were correlated to prognosis in terms of posttreatment residual tumor or local recurrence. Ill-defined tumor margins were by means of multiple regression analysis significantly correlated to local failures (p = 0.043). This feature was, however, not associated with a significant decreased survival. The degree of tumor contrast enhancement did not parallel variations in the histopathologic composition of the tumors.

A bowel labeling agent is important for improving abdominal MR. Besides providing contrast between the bowel and other organs, the contrast agent itself is a potential source of artifacts. The artifacts created by superparamagnetic particles (SPP) subjected to motion have been studied in vitro at 0.5 T, and compared to artifacts created by a paramagnetic compound. Apart from the expected static effects of the SPP, movement induced additional artifacts were seen as signal displacements in the phase-encoding direction. The artifacts were obvious at an iron concentration of 1 mg Fe/ml, barely visible at 0.2 mg Fe/ml, and completely absent at 0.1 mg Fe/ml. Artifacts were also evident with the SPP outside the imaging slice. This further emphasizes the importance of choosing the lowest effective dose when using SPP contrast agents. For the paramagnetic agent, motion propagated artifacts consisted of high and low signal regions in a mosaic pattern.

A double-blind, randomized parallel phase III study in MR imaging of the central nervous system was conducted to compare the safety and diagnostic utility of gadodiamide injection and gadopentetate dimeglumine at a dose of 0.1 mmol/kg b.w. in 60 adult patients. Seven patients in the gadodiamide injection group experienced 10 adverse events, 5 of the events possibly related to the contrast agent. in the gadopentetate dimeglumine group 5 patients reported 3 contrast agent-related adverse events out of 8 events. All events were transient and required no treatment. Seven incidents of patient discomfort, and some minor changes in vital signs and laboratory parameters were of no clinical concern. Contrast enhancement was observed in 60% and 44% of the patients with structural abnormalities in the gadodiamide injection group and gadopentetate dimeglumine group, respectively. No difference in overall efficacy was observed. Gadodiamide injection was found to be a safe and effective contrast agent

A 53-year-old Japanese woman presented with a mass of the hard palate that was histologically diagnosed as myoepithelioma. By CT, the well-demarcated ovoid isodense mass showed faint contrast enhancement. By MR imaging, the mass was homogeneous and isointense on T1-weighted images with homogeneous enhancement after administration of contrast material and markedly hyperintense on T2-weighted images. Myoepithelioma should be kept in mind as differential diagnosis of hard palatine tumors.

Abdominal CT scans from 160 examinations performed on pediatric patients using iohexol 2 percent as contrast medium for bowel enhancement were evaluated retrospectively. When diluted with a beverage of the child's choice, iohexol has a neutral taste and cannot be detected, and 139 out of 142 patients drank the full amount of dilute contrast offered to them. The enhancement of bowel in the area of interest was graded as good (58%), reasonable (23%), or poor (19%). The contrast medium was prepared from leftovers from our angiocardiography studies. We conclude that the use of water-soluble contrast medium in a low concentration is a safe and cost-effective way of facilitating ingestion of sufficient amounts of the medium in oncologic pediatric patients undergoing cytotoxic and/or radiation treatment.

Purpose: to report the occurrence, degree, frequency, and duration of contrast enhancement in the craniopharyngioma cyst wall as caused by irradiation Material and Methods: Eight patients with cystic craniopharyngiomas had comparable CT or MR studies before and after either external irradiation of the cyst (n=5) or 32P instillation into the cyst (n=3) Results: A minimal to marked increase in cyst-wall enhancement was seen at 66–157 days after 32P instillation in 3/3 cases and at 112–495 days after external irradiation in 3/5 cases. the increased enhancement was always associated with a variable interim increase in the thickness of the enhanced cyst wall Conclusion: CT or MR imaging after the irradiation of cystic craniopharyngiomas usually demonstrated an increase in thickness and enhancement in the cyst wall. Such changes may be due to the irradiation alone and do not necessarily represent infection or increased neoplastic activity. the timing is uncertain as to the earliest possible development of such changes and their maximum duration, but they were seen as early as 66 days post-irradiation and as late as 495 days post-irradiation

Purpose: Cavernous hemangiomas of the adrenal gland are rare, and we here describe CT and MR features of an additional case including delayed contrast CT. Results: On CT, the tumor appeared as a well-delineated mass. Fatty areas and calcifications were seen. On delayed contrast CT, a progressive enhancement from the periphery to the center of the tumor was noticed, similar to the contrast enhancement of liver hemangiomas. In T1-weighted MR images, a hypointense tumor with a central stellate area of hypointensity was found. The tumor had a predominantly peripheral contrast enhancement. Conclusion: CT and MR findings of adrenal hemangiomas are in some cases similar to those of liver hemangiomas. A tumor resection must be considered if the tumor changes in appearance or size.

The non-ionic monomeric contrast media iopamidol and iohexol were compared concerning enhancement in the organs of the upper abdomen in CT. The average peak enhancement above the base line for the 2 contrast media in the liver, vena cava, aorta and spleen was calculated. No difference between the contrast media was found with regard to increase in contrast enhancement. No correlation between the peak enhancement and body weight and body surface was found with either of the 2 contrast media.

Computed tomography (CT) was performed in 3 patients with benign tumors of the median nerve, histologically confirmed as neurilemmoma, fibrolipoma and hemangioma. The neurilemmoma showed a ring-shaped contrast enhancement. The fibrolipoma presented with areas of solid soft tissue and areas of fat. The hemangioma was a solid tumor with a lacunar, vascular contrast enhancement. According to our experience and to the previous literature CT gives useful information regarding the anatomic location, size, and relationship of peripheral nerve sheath tumors to surrounding structures, and may help to differentiate between various tumor types.

Computed tomography (CT) scans of the urinary bladder were taken before and in combination with intravenous contrast medium injection in 30 patients with invasive bladder carcinoma. Three different ways of injecting the same amount of intravenous contrast material were used in three groups, each consisting of ten patients. In the first group the contrast medium was given during 90 seconds, in the second group during 40 seconds and in the third one, the first half during 20 seconds and the second half during 90 seconds. The attenuation in the tumors and in the bladder wall was measured in Hounsfield units. Independent of injection method, all tumors showed significantly higher contrast enhancement than the bladder wall when the injection was terminated. The difference in contrast enhancement was greatest in the group where the shortest injection time was used and greatest immediately after the conclusion of the injection. The difference in contrast enhancement between tumor and bladder wall was visible on the monitor in all cases.

This prospective and consecutive study of 74 patients with completed stroke elucidates occurrence, localization and evolution of lacunar infarcts on repeated CT examinations. Twenty patients had large infarcts (diameter greater than 3 cm), 25 medium-sized infarcts (diameter greater than or equal to 1.5 cm - less than or equal to 3 cm), and 16 had lacunar infarcts (diameter less than 1.5 cm). In 13 patients no infarct was seen. The lacunar infarcts were characterized by delayed appearance on CT, low incidence of fog effect, and infrequent presence of contrast enhancement. In 9 of the 16 patients (56%) the lacunar infarct could be identified on the first CT, performed approximately 3 days after the stroke. In 2 patients the infarct was first revealed on the second (2 weeks post stroke) and in 5 on the third CT (6 months post stroke). The delayed appearance might be due to a partial volume effect. Early development of fog effect may also be considered. As contrast enhancement was observed in only 8 per cent of the patients with lacunar infarcts on CT, and in 70 per cent of the entire group of patients in our series with ischemic infarcts, contrast enhancement seemed to be a function of lesion size.

The usefulness of computed tomography (CT) for the diagnosis of pulmonary embolism (PE) was demonstrated in two cases. Employing dynamic, contrast-enhanced CT, both direct and indirect signs of PE may be rapidly and conveniently demonstrated. Possible contraindications for therapy may be diagnosed simultaneously and follow-up examinations after therapy may be readily performed. The method serves as a good complement when PE must be verified before treatment with potent agents.