The path to a filmless radiology department: the HUP experience.
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Computer Communication Networks↗
Biomedical subjects
R Mezrich
Publications and source records attributed to R Mezrich.
Proposed simulation of volumetric image navigation using a surgical microscope.
This paper describes a simulated surgical setup based on modern, frameless stereotactic techniques that enable surgeons to visualize the field of view of the surgical microscope, overlaid with the segmented volumetric medical images, of a localized area of the patient's head. Using this "true three-dimensional" navigation system, the surgeon visualizes the surgical site while exploring the inner layers of the patient's anatomy via the surgical microscope. It also allows the surgeon to "fly through," and around, the site of the surgery to visualize several alternatives and qualitatively choose what he or she believes is the best surgical approach. Moving surgical devices are tracked with stereo vision cameras, allowing determination of their spatial relationship to the target lesion.
Brain↗
Interventional MRI rides wave of new technology.
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Brain Diseases↗
Peri- and postoperative magnetic resonance imaging localization of pallidotomy.
Postoperative magnetic resonance imaging (MRI) of basal ganglia functional lesions illustrates the accuracy of preoperative target localization. The technique of perioperative MRI and CT localization for pallidotomy will be discussed and correlated with the center of the lesion on postoperative standard MRI as well as three-dimensional (3-D) volume acquisition of image. Using a 1.5-tesla Signa system, a conventional acquisition of 128-slice, 256 x 256 matrix spoiled grass (SPGR) images were used for 3-D reformation. This allowed approximately 1 x 1 x 2 mm resolution over a 24-cm field of view in a T-1-weighted image. The display affords a volumetric analysis of the anatomic location and relation of the post-ventral pallidotomy to adjacent structures. Accuracy lesion placement based on perioperative MR coordinates and revealed on postoperative images is confirmed. The volume of the lesion as well as its location are factors that affect clinical outcome.
Basal Ganglia↗
Magnetic resonance imaging applications in uterine cervical cancer.
We have discussed the importance of staging in making decisions about the type and extent of surgery and in determining prognosis, and at the same time have noted the remarkably poor accuracy of clinical staging. We have detailed the present and potential accuracy of MR imaging for assessing size and extent of tumor and its advantages compared to clinical and other (primarily CT) staging. The question that naturally arises is that if MR imaging is so good, why isn't it used more often? In a critical review of the use of CT for staging, Moore et al noted that "Ultimately, a diagnostic test can be considered useful only if it provides information leading to a change in therapy with patient benefit." In a retrospective review of 246 patients divided into those who did and those who did not undergo pretreatment CT, they found that only 8 patients had improved survival from treatment modifications based on CT, while in the same group 8 patients underwent additional surgical procedures because of CT findings that proved to be erroneous. They concluded that "Considering the high cost and limited benefit, CT for cervical cancer staging is not recommended." Although this sort of critical outcome analysis has not yet been done for MR imaging, it is evident from our discussion that MR imaging has much to offer that CT does not, and that MR imaging can indeed provide information leading to a change in therapy. Unlike CT, MR imaging can measure accurately the size of the tumor, determine whether or not it is confined within the cervix, and determine extension to the vagina, parametrium, or myometrium. MR imaging even has advantages in assessing lymph node involvement and is particularly recommended when clinical tumor diameter approaches 3 cm, in which case the incidence of lymph node metastasis approaches 50%. With rapid improvements in techniques and hardware, especially dedicated coils, fast acquisition pulse sequences, and dynamic enhancement methods, it can be expected that MR imaging will become even more accurate in identifying and staging disease. Given this, the question still remains as to why MR imaging is not used more in the work-up of patients with cervical cancer. In part this may be caused by na lack of awareness by clinicians of the advantages of MR imaging in this application. In part this may be caused by limited availability of MR imaging systems, although by now most midsized and probably all large hospitals have at least one MR imaging unit.(ABSTRACT TRUNCATED AT 400 WORDS)
Cost-Benefit Analysis↗
Unilateral leg edema caused by abdominoscrotal hydrocele: elegant diagnosis by MRI.
A 5-month-old boy presented with bilateral hydroceles since birth and right leg edema. An ultrasound of the pelvis showed a 4-cm cystic mass that was diagnosed as a teratoma or cystic hygroma. Magnetic resonance imaging was performed, which showed a dumbbell shaped contiguous, fluid filled mass extending intraabdominally through the inguinal canal from the scrotum. The cystic portion in the right iliac fossa was lying on the right iliac vessels, which were patent. A bilateral hydrocelectomy was performed, and the intraperitoneal sac was completely excised through the inguinal incision. The edema of the right leg disappeared a few days after surgery.
Humans↗
The comparative evaluation of three-dimensional magnetic resonance for carotid artery disease.
Conventional angiography is the current standard for the evaluation of carotid artery disease. The excellent resolution of this invasive study is offset by the potential for contrast-related, embolic, and puncture site complications. Three-dimensional magnetic resonance angiography may offer a noninvasive diagnostic alternative. We examined this possibility by performing both conventional angiography and three-dimensional magnetic resonance angiography in 13 patients. Cervical duplex scans were also obtained in these patients. Contiguous transverse cervical magnetic resonance images were acquired in a 1.5 tesla magnet, by use of a posterior neck coil and a gradient echo pulse sequence. These "raw" data were transferred to a real-time workstation where three-dimensional cervical arterial images were reformatted, magnified, and examined from multiple angles. Total study time from patient positioning to image generation was approximately 30 minutes. In all patients, on three-dimensional magnetic resonance angiography the common, external, and internal carotid arteries and distal vertebral arteries were easily discernable and correctly identified as patent, stenotic, or occluded. Three-dimensional magnetic resonance angiography was not accurate in detecting carotid ulcers. The degree of internal carotid artery stenosis measured from the three-dimensional magnetic resonance angiography studies correlated well with the internal carotid artery stenosis measured with conventional angiography (r = 0.866, r2 = 75.1%, p = less than or equal to 0.0001). This recent technologic advance represents significant progress toward achieving the goal of completely noninvasive vascular assessment in this patient population.
Aged↗
Interleaved magnetic resonance and ultrasound by electronic synchronization.
Increasing attention has been directed toward using magnetic resonance imaging (MRI) to assess blood flow velocity. Complete acceptance of this application requires validation of MRI-derived flow measurements against an accepted flow measurement technique such as Doppler ultrasound in an in vivo situation. To provide an accurate correlation in the presence of rapid changes in blood flow, the MR acquisition should be made nearly simultaneously with the ultrasonic measurements. Unfortunately, standard ultrasound equipment generates radio frequency signal which interferes with MRI. Near-simultaneous acquisition of MR data and ultrasonic blood flow data should be possible if the two measurements are properly synchronized. In the technique presented, ultrasound is made to peacefully coexist with MRI by gating the ultrasound so that it is disabled during the time of MR data acquisition. Phantom and animal experiments confirm the use of this procedure. Although we did not specifically test new fast-scan MR techniques, our technique is completely general and should work equally well with spin-echo as well as newer fast scanning MRI techniques.
Animals↗
The role of vascular tone in the control of upper airway collapsibility.
Upper airway collapsibility may be influenced by both muscular and nonmuscular factors. Because mucosal blood volume (and therefore vascular tone) is an important determinant of nasal airway patency, vascular tone may be an important nonmuscular determinant of pharyngeal collapsibility. This hypothesis was tested in two experimental models. First, upper airway closing (CP) and opening (OP) pressures and static compliance were measured in nine anesthetized, sinoaortic-denervated, paralyzed cats with isolated upper airways. Vascular tone was decreased with either papaverine or sodium nitroprusside (NTP), and increased with phenylephrine (PE), whereas blood pressure and end-tidal CO2 were maintained constant. Vasodilation increased CP (control = -10.4 +/- 1.3, NTP = -7.3 +/- 1.2 cm H2O; p less than 0.05) and OP (control = -7.9 +/- 1.5, NTP = -3.3 +/- 1.8 cm H2O; p less than 0.05). In contrast, vasoconstriction tended to decrease CP (control = -10.7 +/- 1.5, PE = -11.7 +/- 1.4 cm H2O; p less than 0.09) and OP (control = -8.1 +/- 1.2, PE = -9.9 +/- 1.9 cm H2O; p less than 0.1). Thus, vasodilation increased and vasoconstriction tended to decrease upper airway collapsibility. Upper airway static compliance was unchanged during either drug infusion. In order to assess changes in pharyngeal cross-sectional area (CSA) that occurred during vasodilation, magnetic resonance imaging was utilized in seven cats. During vasodilation with NTP, pharyngeal CSA was reduced from 0.44 +/- 0.10 to 0.30 +/- 0.09 cm2 (p less than 0.05), and pharyngeal volume was reduced from 15.3 +/- 2.4 to 13.9 +/- 2.7 cm3 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Airway Resistance↗
Magnetic resonance imaging of acute occlusive intestinal ischemia.
The mortality of acute superior mesenteric artery occlusion and mesenteric infarction remains high, in part because of the failure to identify the patients with the disorder. A reliable noninvasive diagnostic study may facilitate earlier definitive diagnosis and therapy. Proton magnetic resonance imaging may offer a noninvasive diagnostic alternative. We examined this possibility by using an experimental rabbit model of acute superior mesenteric artery occlusion in this study. Animals were scanned 1 hour after the ischemic insult. Relative intestinal wall signal intensity was increased in experimental (ischemic) animals when compared to sham operated controls on T2-weighted (4.35 +/- 0.5 vs 2.57 +/- 0.31, p less than 0.02) and proton spin density-weighted images (2.1 +/- 0.2 vs 1.4 +/- 0.21, p less than 0.05). Significant increases in image intensity were found on T2-weighted and proton spin density images when compared to control animals. Differences between groups could be further highlighted after the administration of a paramagnetic contrast agent gadolinium diethyltriamine pentacetic acid on T1-weighted images. The data from this preliminary study demonstrate that proton magnetic resonance imaging may be used to discriminate between ischemic and nonischemic small intestine. This noninvasive tool may someday become clinically useful to enhance our diagnostic capabilities when a diagnosis of acute superior mesenteric artery occlusion is being entertained.
Animals↗
Application of magnetic resonance imaging technique in determining canine muscle and human free-flap viability.
Magnetic resonance imaging technique is an exciting, new, safe clinical tool that provides a noninvasive way to monitor free-tissue transfers. Magnetic resonance imaging (MRI) produces a cross-sectional tomographic image at higher resolution than conventional CAT scans and provides a dynamic and physiologic assessment of transferred tissue. We first studied ischemic muscle in the beagle hindlimb gracilis muscles and found an incremental and definitive increase in signal strength both over time and in comparing complete devascularization to partial devascularization. In the right hindlimb (partially devascularized), there was an average increase in T2 (measured in milliseconds) of 2.5 percent at 1 hour, 16.72 percent at 3 hours, and 16.45 percent at 12 hours as compared to normal undisturbed muscle. Similarly, the left hindlimb (completely devascularized) measurements increased from 10.97 percent at 1 hour to 24.02 percent at 3 hours to 47.75 percent at 12 hours. Possible explanations for T2 increases include an increase in intercellular and intracellular water, a change in pH, and possible protein metabolism changes. Clinical studies in seven patients with free flaps have shown "normal" T2 values in healthy tissue comparable to undisturbed canine gracilis muscle and the change in contour and composition of tissue over time. The clinical usefulness of these data is apparent.
Adolescent↗
Magnetic resonance imaging of the adrenal glands.
Applications of nuclear magnetic resonance (NMR) to the adrenal gland have received considerable attention in recent years. Using high field strength magnets and surface coil technology, images of normal and abnormal adrenal glands have been obtained that compare favorably, and in some instances excel, computed tomography (CT) with respect to both image quality and, to a greater degree, differentiation of pathology. This article reviews the current state of magnetic resonance (MR) imaging of normal and abnormal adrenal glands, compares MR with CT imaging, and indicates where NMR spectroscopy has been of greatest value to date in the study of adrenal gland disease.
Adenoma↗
Differences in the attenuation of ultrasound by normal, benign, and malignant breast tissue.
In quantitative measurements of the attenuation of ultrasound in 18 samples of variously normal, benign, and malignant breast tissue, we found significantly different ranges of attenuation. As observed in previous in vivo studies, with the exception of medullary carcinoma, malignant tissue produces the most attentuation of ultrasound in the frequency range of 1.5 to 3.0 MHz we employed. The apparatus, measurement method, results, and the possible causes of the differences in attenuation are presented.
Breast Diseases↗
Variation of lateral ventricular volume during the cardiac cycle observed by MR imaging.
CSF pulsation suggests variation in the size of the cerebral ventricles during the cardiac cycle. The arterial blood flow and venous outflow are two major components that contribute to the variation. High-resolution MR imaging with cardiac gating provides sharp delineation of the cerebral ventricles with clear boundaries. Subtle changes in the size of the ventricles during the cardiac cycle are measurable with high precision and accuracy by using a sophisticated automated edge-detection algorithm. In 12 normal individuals, the cerebral ventricles were examined, and the size of the lateral ventricles showed a 10-20% change during the cardiac cycle. The pattern is complex but similar in appearance to the intracranial pressure pulse waveform. The variation suggests that the choroid plexus may play a greater role as a source of CSF pulsation that currently acknowledged. The ability to measure the variations in ventricular volume has clinical implication as a noninvasive method for the diagnosis of diseases with abnormal brain elasticity.
Adult↗