Dynamic Enhancement Magnetic Resonance Imaging Research Articles

Optimal hyperthermia (HT) treatment of advanced extremity sarcomas using combined Dynamic-Enhanced Magnetic Resonance Imaging (DE-MRI) and Magnetic Resonance Thermal Imaging (MRTI)

Optimal hyperthermia (HT) treatment of advanced extremity sarcomas using combined Dynamic-Enhanced Magnetic Resonance Imaging (DE-MRI) and Magnetic Resonance Thermal Imaging (MRTI)

Contrast‐enhanced MRI of ductal carcinoma in situ: Characteristics of a new intensity‐modulated parametric mapping technique correlated with histopathologic findings

To identify morphologic and dynamic enhancement magnetic resonance imaging (MRI) features of pure ductal carcinoma in situ (DCIS) by using a new intensity-modulated parametric mapping technique, and to correlate the MRI features with histopathologic findings. Fourteen patients with pure DCIS on pathology underwent conventional mammography and contrast-enhanced (CE) MRI using the intensity-modulated parametric mapping technique. The MR images were reviewed and the lesions were categorized according to morphologic and kinetic criteria from the ACR BI-RADS-MRI Lexicon, with BI-RADS 4 and 5 lesions classified as suspicious. With the use of a kinetic curve shape analysis, MRI classified seven of 14 lesions (50%) as suspicious, including four with initial-rapid/late-washout and three with initial-rapid/late-plateau. Using morphologic criteria, MRI classified 10/14 (71%) as suspicious, with the most prominent morphologic feature being a regional enhancement pattern. Using the intensity modulated parametric mapping technique, MRI classified 12/14 cases (86%) as suspicious. Parametric mapping identified all intermediate- and high-grade DCIS lesions. The intensity-modulated parametric mapping technique for breast MRI resulted in the highest detection rate for the DCIS cases. Furthermore, the parametric mapping technique identified all intermediate- and high-grade DCIS lesions, suggesting that a negative MRI using the parametric mapping technique may exclude intermediate- and high-grade DCIS. This finding has potential clinical implications.

Discretizing large traceable vessels and using DE-MRI perfusion maps yields numerical temperature contours that match the MR noninvasive measurements.

The success of hyperthermia treatments is dependent on thermal dose distribution. However, the three-dimensional temperature distribution remains largely unknown. Without this knowledge, the relationship between thermal dose and outcome is noisy, and therapy cannot be optimized. Accurate computations of thermal distribution can contribute to an optimized therapy. The hyperthermia modeling group in the Department of Radiotherapy, University Medical Center Utrecht devised a Discrete Vasculature [Kotte et al., Phys. Med. Biol. 41, 865-884 (1996)] model that accounts for the presence of vessel trees in the computational domain. The vessel tree geometry is tracked using magnetic resonance (MR) angiograms to a minimum diameter between 0.6 and 1 mm. However, smaller vessels (0.2-0.6 mm) are known to account for significant heat transfer. The hyperthermia group at Duke University Medical Center has proposed using perfusion maps derived from dynamic-enhanced magnetic resonance imaging to account for the tissue perfusion heterogeneity [Craciunescu et al., Int. J. Hyperthermia 17, 221-239 (2001)]. In addition, techniques for noninvasive temperature measurements have been devised to measure temperatures in vivo [Samulski et al., Int. J. Hypertherminal, 819-829 (1992)]. In this work, a patient with high-grade sarcoma has been retrospectively modeled to determine the temperature distribution achieved during a hyperthermia treatment. Available for this model were MR depicted geometry, angiograms, perfusion maps, as necessary for accurate thermal modeling, as well as MR thermometry data for validation purposes. The vasculature assembly through modifiable potential program [Van Leeuwen et al., IEEE Trans. Biomed. Eng. 45, 596-604 (1998)] was used in order to incorporate the traceable large vessels. Temperature simulations were made using different approaches to describe perfusion. The simulated cases were the bioheat equation with constant perfusion rates per tissue type, perfusion maps alone, tracked vessel tree and perfusion maps, and generated vessel tree. The results were compared with MR thermometry data for a single patient data set, concluding that a combination between large traceable vessels and perfusion map yields the best results for this particular patient. The technique has to be repeated on several patients, first with the same type of malignancy, and after that, on patients having malignancies at other different sites.

Dynamic gadolinium-enhanced MR imaging of pituitary adenomas: usefulness of sequential sagittal and coronal plane images

Dynamic magnetic resonance (MR) imaging for pituitary adenomas is usually performed in a coronal direction; however, small lesions between slices, or lesions located at the anterior or posterior aspect of the pituitary gland might be overlooked on MR images in only the coronal direction. The purpose of our study was to evaluate whether consecutive dynamic MR images in the coronal and sagittal planes improve detection of pituitary adenomas. Eighteen patients with pituitary microadenomas and nine with healthy pituitary glands were included in this study. MR images were performed with 1.5 T superconductive units and commercially-available head coils. After a 5 ml gadolinium contrast injection, eight serial dynamic sagittal images were obtained. Within 3 or 6 min, this was followed by a 10–15 ml gadolinium injection and acquisition of eight serial dynamic coronal images. Dynamic MR images and conventional noncontrast- and contrast-enhanced sagittal and coronal T1-weighted images were evaluated independently in a blind fashion by two neuroradiologists regarding the depiction of pituitary microadenomas. The sensitivities of dynamic enhanced MR imaging in the detection of microadenomas were 61.1% in sagittal direction, 72.2% in coronal direction respectively, and were superior to those of conventional noncontrast- and contrast-enhanced T1-weighted imaging (22.2–50%). The sensitivity of a combination of sagittal and coronal dynamic enhanced MR imaging for the detection of microadenomas was 88.9% and was superior to those of conventional noncontrast- and contrast-enhanced T1-weighted imaging combining sagittal and coronal directions (61.1%, 61.1%) ( P<0.05, P<0.05, respectively). The specificity and accuracy of dynamic enhanced MR imaging with combination of sagittal and coronal images was 88.9% respectively. Dynamic gadolinium-enhanced MR imaging, especially using both sagittal and coronal planes, was concluded to be useful for the detection of pituitary microadenomas.

3D numerical reconstruction of the hyperthermia induced temperature distribution in human sarcomas using DE-MRI measured tissue perfusion: validation against non-invasive MR temperature measurements.

Essential to the success of optimized thermal treatment during hyperthermia is accurate modelling. Advection of energy due to blood perfusion significantly affects the temperature. Without accurate estimates of the magnitude of the local tissue blood perfusion, accurate estimates of the temperature distribution can not be made. It is shown here that the blood mass flow rate per unit volume of tissue in the Pennes' bio-heat equation can be modelled using a relative perfusion index (RPI) determined with dynamic-enhanced magnetic resonance imaging (DE-MRI). Temperature distributions in two patients treated with hyperthermia at Duke University Medical Center for high-grade leg tissue sarcomas are modelled, and the resultant temperatures are compared to measured temperatures using a non-invasive MR thermometry technique. Significant correlations are found between the DE-MRI perfusion images, the MR temperature images, and the numerical simulation of the temperature field. The correlation between DE-MRI measured values and advective heat loss in tissue is used to scale the perfusion distribution, thereby allowing the continuum model to account for the local thermal impact of vasculature in the tumour. Large vessels in tumour and neighbouring healthy tissue need to be taken into account in order to accurately describe the complete temperature distribution.

Experimental Cryosurgery of the Liver Under Magnetic Resonance Guidance

The feasibility and the advantages of magnetic resonance (MR)-guided interstitial cryosurgery of the liver in an 0.5 Tesla open MR system have been evaluated. Cryosurgery was performed using an Erbocryo PS system with a nonmagnetic cryoprobe of 6 mm diameter. The probe was inserted into the liver parenchyma under real-time MR control. Using continuous MR imaging two freezing cycles of 12 min each were applied. After conventional and dynamic gadolinium-enhanced MR imaging, the animals were sacrificed after 30 min, 3 hr, 24 hr, 7 days, and 21 days. Each lesion was analyzed using light microscopy.A total of seven cryolesions were made in five animals without any complications from cryosurgery. During real-time imaging, cryolesions appeared as a hemispherical growing signal loss with a mean volume of 16.4 cm3. Macroscopic volumes of the lesions showed a good correlation with dynamic enhanced MR images during follow-up, whereas real-time images usually showed an underestimation of the lesion volumes. Cryosurgery of the liver in an open-configuration MR system is a feasible and safe method. MR imaging allows the guidance and the follow-up of cryolesions of the liver with good.

Experimental cryosurgery of the liver under magnetic resonance guidance

The feasibility and the advantages of magnetic resonance (MR)-guided interstitial cryosurgery of the liver in an 0.5 Tesla open MR system have been evaluated. Cryosurgery was performed using an Erbocryo PS system with a nonmagnetic cryoprobe of 6 mm diameter. The probe was inserted into the liver parenchyma under real-time MR control. Using continuous MR imaging two freezing cycles of 12 min each were applied. After conventional and dynamic gadolinium-enhanced MR imaging, the animals were sacrificed after 30 min, 3 hr, 24 hr, 7 days, and 21 days. Each lesion was analyzed using light microscopy. A total of seven cryolesions were made in five animals without any complications from cryosurgery. During real-time imaging, cryolesions appeared as a hemispherical growing signal loss with a mean volume of 16.4 cm3. Macroscopic volumes of the lesions showed a good correlation with dynamic enhanced MR images during follow-up, whereas real-time images usually showed an underestimation of the lesion volumes. Cryosurgery of the liver in an open-configuration MR system is a feasible and safe method. MR imaging allows the guidance and the follow-up of cryolesions of the liver with good accuracy.

Experimental cryosurgery of the liver under magnetic resonance guidance.

The feasibility and the advantages of magnetic resonance (MR)-guided interstitial cryosurgery of the liver in an 0.5 Tesla open MR system have been evaluated. Cryosurgery was performed using an Erbocryo PS system with a nonmagnetic cryoprobe of 6 mm diameter. The probe was inserted into the liver parenchyma under real-time MR control. Using continuous MR imaging two freezing cycles of 12 min each were applied. After conventional and dynamic gadolinium-enhanced MR imaging, the animals were sacrificed after 30 min, 3 hr, 24 hr, 7 days, and 21 days. Each lesion was analyzed using light microscopy. A total of seven cryolesions were made in five animals without any complications from cryosurgery. During real-time imaging, cryolesions appeared as a hemispherical growing signal loss with a mean volume of 16.4 cm3. Macroscopic volumes of the lesions showed a good correlation with dynamic enhanced MR images during follow-up, whereas real-time images usually showed an underestimation of the lesion volumes. Cryosurgery of the liver in an open-configuration MR system is a feasible and safe method. MR imaging allows the guidance and the follow-up of cryolesions of the liver with good accuracy.

健常顎口腔領域組織（６例）における経時的造影 ＭＲＩの分析

Six healthy volunteers underwent dynamic enhanced magnetic resonance (MR) imaging to evaluate the enhancement pattern of normal structures of the oral and maxillofacial region. Dynamic enhanced MR imaging was performed with a 1.5-T superconducting MR Imager and a T 1 weighted spin echo sequence in the coronal plane (five volunteers were evaluated at the mandibular molar plane, and one at the submandibular gland). The results of these study were as follows:1. The mucosal surface of the inferior and middle conchae, nasal wall, hard palate, and tongue showed a short time to peak and a gradual wash-out pattern.2. The submandibular gland and the sublingual space, which contained the sublingual gland, showed a short time to peak and a rapid wash-out pattern.3. The intrinsic muscles of the tongue appeared as structures with higher signal intensity than extrinsic muscles on precontrast scans, and showed a long time to peak and a gradual wash-out pattern.4. The bone marrow of the mandible, subcutaneous fat, and genioglossus muscle showed a pattern of no change.

Dynamic enhancement MRI of anterior lobe in pituitary dwarfism

Dynamic enhancement MRI of anterior lobe in pituitary dwarfism

Dynamic enhancement MRI of anterior lobe in pituitary dwarfism.

We examined 23 patients with pituitary dwarfism by dynamic MRI; with a repetition time of 150 or 50 ms. The time-enhancement difference curves of selected regions in the anterior lobes were plotted. Another 48 patients with no definite clinical pituitary disfunction were examined with the same technique. We found that the intensity of maximum enhancement in both groups was similar, but the time to achieve maximum enhancement was delayed in pituitary dwarfism with or without stalk transection; the time seemed longest with stalk transection. There was little difference in enhancement between patients with multiple hormone deficiency or isolated growth hormone deficiency. Dynamic MRI of the anterior lobes may be an important functional imaging study, and our results imply that poor perfusion is a useful finding in pituitary dwarfism, especially in patients without stalk transection and normal pituitary height.

Comparison of the effects of hydralazine on tumor and normal tissue blood perfusion by MRI

Purpose : The differential effects on blood perfusion of the vasodilator hydralazine (HYD) between tumor and normal muscle have been measured using the dynamic enhanced-magnetic resonance imaging (DE-MRI) technique. Methods and Materials : DE-MRI is a noninvasive method of determining blood perfusion in tumors and normal tissues using the MR contrast agent Gd-DTPA. Hydralazine is currently being used in an attempt to increase tumor response to bioreductive agents and to hyperthermia. Results : We show that a dose of 1.2 mg/kg HYD causes an increase in tumor perfusion while doses ≥ 2.5 mg/kg cause a decrease in tumor perfusion. The latter was accompanied by a dose-dependent increase in normal muscle perfusion consistent with the “steal effect.” Conclusion : This study demonstrates the sensitivity of the DE-MRI technique and its capability of providing estimates of blood perfusion in normal and tumor tissue as well as in smaller regions of a solid tumor. Such features would make it clinically useful in the study of tumor response to radiation therapy and chemotherapy in patients.

Functional evaluation of normal and ischemic kidney by means of gadolinium-DOTA enhanced TurboFLASH MR imaging: A preliminary comparison with 99mTc-MAG3 dynamic scintigraphy

The functional value of TurboFLASH MR imaging in the assessment of dynamic contrast enhancement and renal perfusion anomalies was evaluated in seven patients, who also underwent renal scintigraphy in baseline conditions. The basal renograms obtained from MAG-3 scintigraphy (mercapto acetyl triglycine, MAG3-S) and from Gd-DOTA-enhanced turboFLASH MRI were compared. After hydration, the protocol used consisted in breath-hold coronal turboFLASH acquisitions after IV bolus of Gd-DOTA (4 s every 20 s during 10 min) for MRI, and IV bolus of 370 MBq of 99mTc-MAG3 followed by 60 frames of 1 s and then 120 frames of 10 s for MAG3-S. Relative renal functions were computed for both methods by calculation of the integral of the uptake phase between the first and the second minute. Renograms exhibited 10 normal and 4 ischemic kidneys. There was a close correlation between the contrast enhancement of MRI and isotopic uptake in normal and ischemic kidneys. Global renograms of MRI correlated with MAG3-S (r = .82, p < .001) with similar curve shape and time to peak. Relative renal function of the right and left kidney were closely correlated in all patients (r = .98, p < .001), although there was a tendency for MR to overestimate MAG3-S evaluation in kidneys with severe basal dysfunction. Enhanced turboFLASH provides noninvasive assessment of renal perfusion in patients with renovascular disease. Accurate renograms are obtained with dynamic-enhanced MRI, but the relative renal function seems to be overestimated in low values of ischemic kidneys, and needs further comparative evaluation.