Changes In Contrast Enhancement Research Articles

Principal component analysis of breast DCE‐MRI adjusted with a model‐based method

To investigate a fast, objective, and standardized method for analyzing breast dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) applying principal component analysis (PCA) adjusted with a model-based method. 3D gradient-echo DCE breast images of 31 malignant and 38 benign lesions, recorded on a 1.5T scanner, were retrospectively analyzed by PCA and by the model-based three-timepoints (3TP) method. Intensity-scaled (IS) and enhancement-scaled (ES) datasets were reduced by PCA yielding a first IS-eigenvector that captured the signal variation between fat and fibroglandular tissue; two IS-eigenvectors and the two first ES-eigenvectors captured contrast-enhanced changes, whereas the remaining eigenvectors captured predominantly noise changes. Rotation of the two contrast-related eigenvectors led to a high congruence between the projection coefficients and the 3TP parameters. The ES-eigenvectors and the rotation angle were highly reproducible across malignant lesions, enabling calculation of a general rotated eigenvector base. Receiver operating characteristic (ROC) curve analysis of the projection coefficients of the two eigenvectors indicated high sensitivity of the first rotated eigenvector to detect lesions (area under the curve [AUC] > 0.97) and of the second rotated eigenvector to differentiate malignancy from benignancy (AUC = 0.87). PCA adjusted with a model-based method provided a fast and objective computer-aided diagnostic tool for breast DCE-MRI.

Change in contrast enhancement of HCC on 1-month follow-up CT after local radiotherapy: An early predictor of final treatment response

Background The purpose of this study was to evaluate the change in contrast enhancement of HCC on 1-month follow-up CT after local radiotherapy (RT) as an early predictor of final treatment response. Materials Fifty patients who underwent local RT for HCCs had both pre-RT and post-RT CT scans including 1-month follow-up CT. We assessed the final treatment response by using the change in maximal tumor size on 6–12-month follow-up CT scan after RT. We also evaluated the change in tumor enhancement between pre-RT and 1-month follow-up CT scans. Results A final treatment response was achieved in 27 (54%) of 50 patients, who showed either a complete response ( n = 11) or a partial response ( n = 16). Compared with non-responsive patients ( n = 23), responsive patients showed a significant decrease in tumor enhancement on 1-month follow-up CT after RT in both objective and subjective analyses (each P < 0.001). Conclusion The change in contrast enhancement of HCC seen on the 1-month follow-up CT in patients after local RT may be used as an early predictor of final treatment response.

Cerebral ultrasound perfusion imaging in a migraine attack with prolonged aura

Sirs: There is a frequent observation of reduced regional cerebral blood flow during the aura phase of migraine. Several studies employing different cerebral imaging techniques [2] provided the same evidence of transient, spatially restricted changes in cerebral blood flow during the aura phase of migraine. These changes have not been consistently observed in migraine without aura [5]. Because of the unpredictable episodic onset of migraine attacks, a non-invasive bedside method like transcranial ultrasound is desirable in order to further understand the underlying hemodynamic changes. Transcranial Doppler (TCD) studies has not shown consistent results, probably because it measures cerebral blood flow velocity which is susceptible to changes in vessel diameter. Cerebral ultrasound perfusion imaging (CUPI) is a new technique that utilizes contrast-specific harmonic imaging to display cerebral perfusion through the analysis of bolus injection kinetics. We present a 31-year-old woman, with sudden onset of numbness and weakness of the right hand followed by aphasia, who was emergently admitted to our stroke unit for thrombolytic therapy. The initial TCD assessment showed normal flow velocities in extraand intracranial arteries. CUPI was then immediately performed, about 3 hours after symptom onset, using a GE Logiq 7 system, with harmonic Phase Inversion mode in bilateral approach from the contralateral side to the supposed pathology at the diencephalic plane. CUPI was performed by bolus-kinetics using 2.4 ml SonoVue (Bracco international BV, Germany) flushed by 5 ml saline. The pathologically perfused areas were detected according to the changes in contrast-enhancement on the gray-scale images in cine mode. The perfusion-parameters of these areas were drawn from the time-intensity curves (TIC) of manually selected region of interest (ROI). The reference perfusion-parameters were drawn from apparently normally perfused areas in both hemispheres. CUPI revealed an area of hypoperfusion in the left temporooccipital region with inhomogeneously prolonged time-to-peak (TTP) and diminished peak-intensity (PI) (Fig. 1a) corresponding to the topography of aura symptoms. Despite persisting symptoms, MRI (including diffusion weighted imaging) revealed normal findings. Within one hour, the patient developed left-sided throbbing headache with nausea and photophobia. The patient’s history revealed a similar episode with completely inconspicuous investigations. The episode was defined as migraine with prolonged aura. The neurological deficits gradually subsided with remaining minimal subjective numbness of the left hand and slowing of speech. The EEG depicted regional slowing of EEG activity temporooccipitally matching the hypoperfused area. The postictal ultrasound examination (about 24 hours after symptom onset) then showed a relative hyperperfusion of the previously hypoperfused area (Fig. 1b). These changes were accompanied by a relative flow velocity increase in the left posterior cerebral artery on TCD. A second MRI examination (including DWI and FLAIR) done 4 days after symptom onset and a lumbal puncture revealed normal findings. The clinical and MRI findings did not support ischemic origin [7, 8]. Understanding of migraine pathophysiology has always been impeded by its paroxysmal and unpredictable nature. However, it is widely considered – although not fully understood – that spreading cortical depression may explain the neurological deficits during aura. Spreading depression is either accompanied [10] or followed by [3] spreading oligemia which is not limited to neurovascular territories. However, the extent of CBF reduction is lower than that associated with ischemic injury [10]. Hyperemia following hypoperfusion was also reported in migraine with aura in a SPECT study [1]. Animal experiments have provided evidence of disturbance of the autoregulation of cerebral blood flow in response to hypotension during the initial phase of cortical spreading depression [6]. Data on cerebral autoregulation in migraneurs are scarce and are only available interictally with differing results mainly presenting normal dynamic autoregulation. Ictal autoregulation has not been assessed so far and has not been investigated in the presented patient. LETTER TO THE EDITORS

Potential Value of MR Spectroscopic Imaging for the Radiosurgical Management of Patients with Recurrent High-Grade Gliomas

Previous studies have shown that metabolic information provided by 3D Magnetic Resonance Spectroscopy Imaging (MRSI) could affect the definition of target volumes for radiation treatments (RT). This study aimed to (i) investigate the effect of incorporating spectroscopic volumes as determined by MRSI on target volume definition, patient selection eligibility, and dose prescription for stereotactic radiosurgery treatment planning; (ii) correlate the spatial extent of pre-SRS spectroscopic abnormality and treatment volumes with areas of focal recurrence as defined by changes in contrast enhancement; and (iii) examine the metabolic changes following SRS to assess treatment response. Twenty-six patients treated with Gamma Knife radiosurgery for recurrent glioblastoma multiforme (GBM) were retrospectively evaluated. All patients underwent both MRI and MRSI studies prior to SRS. Follow-up MRI exams were available for all 26 patients, with MRI/MRSI available in only 15/26 patients. We observed that the initial CNI 2 contours extended beyond the pre-SRS CE in 25/26 patients ranging in volume from 0.8 cc to 18.8 cc (median 5.6 cc). The inclusion of the volume of CNI 2 extending beyond the CE would have increased the SRS target volume by 5-165% (median 23.4%). This would have necessitated decreasing the SRS prescription dose in 19/26 patients to avoid increased toxicity; the resultant treatment volume would have exceeded 20cc in five patients, thus possibly excluding those from RS treatment per our institutional practice. MRSI follow-up studies showed a decrease in Choline, stable Creatine, and increased NAA indicative of response to SRS in the majority of patients. When combined with patient survival data, metabolic information obtained during follow-up MRSI studies seemed to indicate the potential to help to distinguish necrosis from new/recurrent tumor; however, this should be further verified by biopsy studies.

Use of 11C-methionine PET to monitor the effects of temozolomide chemotherapy in malignant gliomas

The purpose of this study was to monitor the metabolic effects of temozolomide (TMZ) chemotherapy in malignant gliomas by means of repeated positron emission tomography (PET) with [(11)C]methionine (MET). Fifteen patients with histologically proven malignant glioma were treated by TMZ chemotherapy. MET-PET studies were performed before and after the third cycle of TMZ chemotherapy in all patients, and in 12 patients also after the sixth cycle. Gadolinium-enhanced MRI studies were performed in 12 patients before the first and after the sixth cycle. Clinical status was assessed by the modified Rankin scale. Long-term outcome was assessed by calculating the time to progression (TTP) in months. Decline in MET uptake during therapy corresponded to a stable clinical status. The median TTP was significantly longer in patients with decline in MET uptake than in those with increasing MET uptake (23 vs 3.5 months; p=0.01, log rank test). There was no significant correlation between change in MET uptake and change in contrast enhancement during treatment for all patients. The present data demonstrate that clinical stability, which is often achieved under TMZ chemotherapy of malignant glioma, corresponds to a decline in or stability of tumour amino acid metabolism. Tumour responses can already be demonstrated with MET-PET after three cycles of chemotherapy, and absence of progression at that time indicates a high probability of further stability during the next three cycles. A reduction in MET uptake during TMZ treatment predicts a favourable clinical outcome. Molecular imaging of amino acid uptake by MET-PET offers a new method of measurement of the biological activity of recurrent glioma.

Characterization of focal hepatic lesions on diffusion-weighted MRI

目的 探讨MR扩散加权成像(DWI)对肝脏局灶性病变定性诊断的价值.方法对70例肝脏局灶性病变行DWI,计测表观扩散系数(ADC)值,同时作多期动态增强MRI,观察病灶各期强化模式.结果肝细胞癌、胆管细胞癌及转移癌的ADC值(单位:mm2*s-1*10-3)分别为1.33±0.17、1.23±0.17、1.29±0.13,三者之间差异无统计学意义(P>0.05);肝血管瘤、肝囊肿ADC值分别为2.33±0.22、4.04±0.51,恶性肿瘤ADC值均低于良性病变.恶性肿瘤平均ADC值1.29±0.16;与良性病变间差异有统计学意义(P<0.05).在动态增强扫描中,37.1%肝癌、78.9%胆管细胞癌与31.9%转移瘤病灶可见门静脉期与延迟期强化.结论 DWI可成为1种有用的定性诊断肝脏局灶性病变的方法。

Equivalent uniform dose predicts delayed hyperintensity on T1-weighted magnetic resonance imaging after combined proton and photon irradiation in paranasal sinus cancer

To determine the prognostic factors of delayed hyperintensity on T1-weighted Magnetic Resonance Imaging (MRI) after accelerated hyperfractionated radiotherapy with combined protons and photons in patients with locally advanced paranasal sinus cancer. Between July 1991 and December 2001, 105 patients with newly diagnosed non-metastatic paranasal sinus cancer received accelerated hyperfractionated radiotherapy using combined protons and photons. Fifty-three patients with minimum follow-up of 18 months and with local control were used for the study. There were 31 males and 22 female, with a median age of 49 years. All but two patients had locally advanced diseases; T3 in 13 and T4 in 37. Twelve patients had meningeal or brain extension. The primary site was maxillary and/or ethmoid sinus in 22, nasal cavity extended to the ethmoid in 19, sphenoid sinus in 9, and others in 3 patients. The median primary target volume was 79 cc (range 4.7-216). There were 13 squamous cell carcinoma, 19 carcinoma with neuroendocrine differentiation, 11 adenoid cystic carcinoma, 5 sarcoma, and 5 with other histologic types. Seventy-six percent of patients underwent surgical resection before radiation. Most patients with carcinoma with neuroendocrine differentiation received neoadjuvant cisplatin and etoposide chemotherapy. The median dose delivered to the primary target volume was 69.8 Cobalt-Gray-Equivalent (CGE) (range 60-80). Three accelerated hyperfractionated (BID) protocols were used: 1.6CGE BID in 29; 15–20 CGE with conventional daily fractionation (QD) then 1.8/1.4 CGE BID in 8; and 15-20 Gy QD then 1.8+1.5 CGE BID in 16 patients. Delayed brain changes were assessed clinically and radiographically with MRI. Two four- grade scales were developed to characterize MRI changes according to the extent and characteristics of Hyperintensity on T1-weighted and T2-weighted images. Dose Volume Histograms (DVHs) were generated for the frontal and temporal lobes. Equivalent Uniform Dose (EUD) value was calculated for each individual lobe. With a median clinical follow-up of 65 months (range 18-138), 8 patients developed seizures: uncal epilepsy in 4, petit mal in 2, and grand mal in 2 patients. Seven patients developed short-term memory difficulties. Two patients experienced personality changes. With a median 36 months follow-up after the development of first clinical symptoms, seizures were persistent in 4 patients but completely controlled in 4 others. Two patients experienced worsening of their short-term memory deficits. Fifty patients were available for delayed radiographic analysis. With a median radiographic follow-up of 54 months (range 10-132), 26 patients developed gadolinium-enhancement on T1-weighted images of the brain. Fifty-six percent of patients who developed contrast enhancement had a complete or partial clinical and radiographic response with steroids. EUD was calculated for 200 brain lobes, 62 of them with gadolinium-enhancement on T1-weighted images. The average EUD was 51.2 ± 5.0Gy versus 39.6 ± 10.0Gy for the lobes with and without any MRI change (p < 0.0001), respectively. On univariate analysis, primary target dose (p = 0.01), maximal dose (p < 0.0001), and EUD (p < 0.0001) (figure below) were predictive for contrast enhancement changes. Gender, surgery prior to irradiation, use of chemotherapy, age, hypertension, diabetes, anemia, and smoking were not predictive. On multivariate analysis, EUD was the most significant predictive of delayed contrast enhancement changes. EUD predicts delayed gadolinium-enhancement on T1-weighted magnetic resonance imaging after accelerated hyperfractionated radiotherapy with combined proton and photon irradiation in paranasal sinus cancer.

Functional CT imaging in oncology.

The two-compartment pharmacokinetics exhibited by iodinated contrast media makes these agents well suited to the study of tumour angiogenesis in which new vessels are not only produced in greater number but also are abnormally permeable to circulating molecules. The temporal changes in contrast enhancement of tumours on CT have been shown to correlate with histopathological assessments of angiogenesis with the intravascular and extravascular phases of contrast enhancement reflecting microvessel density and vascular permeability, respectively. By quantifying tumour contrast enhancement to capture physiological information about the vascular system, functional CT can provide a useful adjunct to the anatomical information afforded by MDCT in oncology, aiding with tumour diagnosis, risk stratification and therapy monitoring. By simultaneously assessing tumour vascularity and metabolic demand, the broader expansion of integrated MDCT/PET imaging will support highly sophisticated assessments of tumour biology within a single examination.

Computed tomography perfusion imaging in acute stroke.

The development of thrombolytic and neuroprotective agents for the treatment of acute stroke has created an imperative for improved imaging techniques in the assessment of acute stroke. Five cases are presented to illustrate the value of perfusion CT in the evaluation of suspected acute stroke. To obtain the perfusion data, a rapid series of images was acquired without table movement following a bolus of contrast medium. Cerebral blood flow, cerebral blood volume and mean transit time were determined by mathematically modelling the temporal changes in contrast enhancement in the brain and vascular system. Pixel-by-pixel analysis allowed generation of perfusion maps. In two cases, CT-perfusion imaging usefully excluded acute stroke, including one patient in whom a low-density area on conventional CT was subsequently proven to be tumour. Cerebral ischaemia was confirmed in three cases, one with an old and a new infarction, one with a large conventional CT abnormality but only a small perfusion defect, and one demonstrating infarct and penumbra. Perfusion CT offers the ability to positively identify patients with non-haemorrhagic stroke in the presence of a normal conventional CT, to select those cases where thrombolysis is appropriate, and to provide an indication for prognosis.

MR imaging of pituitary adenomas after gamma knife stereotactic radiosurgery.

The purpose of this study was to evaluate the response of pituitary adenomas to radiosurgery as manifested by changes in size and appearance on serial MR imaging. Over a mean follow-up period of 36 months, changes in 44 pituitary adenomas were assessed on 147 enhanced MR imaging studies. Prior surgery had been performed in 36 tumors (82%). At the time of radiosurgery, mean tumor volume was 5.9 +/- 0.8 cm(3) (mean diameter, 2.2 cm). The mean reduction in volume at last follow-up was 41% (+/- 5%, p < 0.001), and a decrease in tumor volume of 25-100% was observed in 34 tumors (77%). Mean reduction in tumor volume at 6 months after radiosurgery was 9% (p = 0.095); at 1 year, 24% (p < 0.001); at 2 years, 34% (p < 0.001); at 3 years, 41% (p < 0.001); and at 4 years, 50% (p = 0.008). Six months after radiosurgery a slight and transient increase in size was observed in 21% of tumors. During follow-up, neither decreased contrast enhancement nor cyst development was associated with changes in tumor volume. Tumor control was observed for most pituitary adenomas after radiosurgery and occurred gradually over a period of several years. A small increase in tumor size might be observed in the first 6 months after radiosurgery. In most cases, reductions in tumor size were not accompanied by a change in contrast enhancement or cyst formation.

Post-radiotherapy contrast enhancement changes in fast dynamic MRI of cervical carcinoma.

This pilot study determines fast dynamic gadolinium enhanced MRI contrast enhancement parameters (onset of enhancement and time to peak enhancement) before and after radiotherapy in 10 cervical carcinoma patients. Before radiotherapy, onset of enhancement and time to peak enhancement were early, with a median of 4.5 and 5.2 seconds, respectively. High-grade tumors showed early enhancement, compared with low-grade. After radiotherapy, contrast enhancement patterns differed. In survivors, onset of enhancement after radiotherapy was later than before radiotherapy. In non-survivors, onset of enhancement after radiotherapy was still early. The median difference in onset of enhancement before and after radiotherapy in survivors and non-survivors was an increase of 3.2 and a decrease of 1.1 seconds, respectively. Early onset of enhancement after radiotherapy was a better predictor for survival than a high-signal intensity zone on post radiotherapy unenhanced T1/T2-weighted MRI. It is concluded that enhancement parameters from fast dynamic Gd-enhanced MR images can provide additional functional information with regard to tumor vascularization, and may have prognostic significance. It complements clinical examination and unenhanced MRI in determining the effectiveness of radiotherapy treatment in cervical carcinoma. Future studies will focus on the clinical utility and improvements of the estimation of contrast-enhanced parameters with this new technique.

THE POTENTIAL INFLUENCE OF FINE-NEEDLE ASPIRATION ON MR IMAGING OF THE BREAST

The aim of this study was to determine whether fine-needle aspiration biopsy (FNAB) of breast lesions causes structural changes or changes in contrast enhancement, that could impair the evaluation of these lesions at MR investigation of the breast. Fifteen patients with 17 lesions were examined with MR imaging of the breast both before and after the FNAB with a mean interval of 7.1 days. At both examinations, signal intensities were measured pre- and post-contrast enhancement in the lesions as well as in surrounding breast parenchyma and muscle. Imaging with contrast enhancement was performed semidynamically with two images obtained in rapid sequence (acquisition time 6.23 min) immediately after bolus injection of gadopentetate dimeglumine, 0.1 mmol/kg b.w., and the contrast enhancement in both images was calculated. The diagnostic value of MR images was unimpaired by FNAB, and no statistical difference between contrast enhancement in corresponding images obtained before and after FNAB was found, either within the lesions or in the breast parenchyma or muscle. FNAB of the breast can be performed without impairing the diagnostic outcome of MR investigation.

The Potential Influence of Fine-Needle Aspiration on MR Imaging of the Breast

The aim of this study was to determine whether fine-needle aspiration biopsy (FNAB) of breast lesions causes structural changes or changes in contrast enhancement, that could impair the evaluation of these lesions at MR investigation of the breast. Fifteen patients with 17 lesions were examined with MR imaging of the breast both before and after the FNAB with a mean interval of 7.1 days. At both examinations, signal intensities were measured pre- and post-contrast enhancement in the lesions as well as in surrounding breast parenchyma and muscle. Imaging with contrast enhancement was performed semidynamically with two images obtained in rapid sequence (acquisition time 6.23 min) immediately after bolus injection of gadopentetate dimeglumine, 0.1 mmol/kg b.w., and the contrast enhancement in both images was calculated. The diagnostic value of MR images was unimpaired by FNAB, and no statistical difference between contrast enhancement in corresponding images obtained before and after FNAB was found, either within the lesions or in the breast parenchyma or muscle. FNAB of the breast can be performed without impairing the diagnostic outcome of MR investigation.

Changes in contrast enhancement of hepatocellular carcinoma and liver: effect of temporary occlusion of a hepatic vein evaluated with spiral CT.

To assess the hemodynamics of the liver and of hepatocellular carcinomas (HCCs) with hepatic vein occlusion. Selected hepatic veins were temporarily occluded with a balloon catheter in 21 patients with 28 nontreated nodular HCCs. Computed tomographic (CT) arteriography was performed without and with temporary occlusion of a hepatic vein that drained the blood from segmental liver parenchyma containing tumor by using a unified spiral CT and angiography system. The degree of enhancement and change in appearance of the HCC in each condition were compared. All HCCs were well-enhanced, almost round masses at CT arteriography. At CT arteriography with hepatic vein occlusion, however, HCCs were changed as follows: (a) the absolute attenuation of the HCC was decreased in 27 (96%) of 28 tumors compared with that at CT arteriography without hepatic vein occlusion, while attenuation of the surrounding liver parenchyma was increased; (b) the size of the highly enhanced area in HCC became smaller in 17 (61%) tumors (of these, two disappeared); and (c) the shape was changed in 12 (43%) tumors. Hepatic vein occlusion resulted in reciprocal hemodynamic changes in the liver parenchyma relative to HCCs: Enhancement of the liver increases and that of HCCs decreases.

Time-course changes of contrast enhancement in iron colloid enhanced MRI in patients with hepatocellular carcinoma.

Time-course changes in contrast enhancement of chondroitin sulphate iron colloid (CSIC), an MR contrast agent, were determined in 12 patients with 20 lesions of classical hepatocellular carcinoma (HCC). Spin echo T1 weighted (T1WI) and T2 weighted images (T2WI) were obtained before administration of CSIC and 1, 6 and 24 h after injection. The signal-to-noise ratio (SNR) in the tumour region and the liver and the tumour-to-liver contrast-to-noise ratio (CNR) were calculated, and time-course changes of these ratios were determined. SNRs for tumour before the administration of contrast medium did not differ significantly from SNRs after administration on T1WI or T2WI. SNRs for the liver on both T1WI and T2WI were significantly lower at each time point after administration than before administration. The tumour-to-liver CNRs for both T1WI and T2WI were significantly higher after administration than before administration. The maximum CNR was observed 6 h after administration on both T1WI and T2WI. The contrast enhancement was maintained for at least 24 h, with a peak at 6 h after administration. The prolonged enhancement obtained with CSIC has extended the time during which effective contrast is maintained.

Noise-free contrast improvement with a low frequency polarizing filter: a practical evaluation

Contrast improvement in a coherent image enhancement system by very low spatial frequency attenuation is shown, demonstrating possible errors incurred by incorrect attenuation. A novel way to achieve a continuous range of low frequency attenuation is introduced. The variable attenuation is produced by constructing the spatial filter from polarizing material and altering the relative polarization between the object transparency illumination and the spatial filter. This technique gives the observer control over a continuous change in contrast enhancement and greatly increases the versatility of low frequency spatial filtering. Coherent imaging systems are usually contaminated by noise, and a simple way to reduce the noise content in the image is shown.