New needle for MR-guided aspiration cytology of the head and neck.
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Biopsy, Needle↗
Biomedical subjects
R Lufkin
Publications and source records attributed to R Lufkin.
Simplified endoscopic photography for anatomic correlation with CT and MR of the larynx and pharynx.
Improvements in photographic film and the availability of fluid light transmitters rather than fibro-optics permit endolaryngeal and nasopharyngeal photography to be conducted using the same light levels as simple diagnostic examinations of these areas. The added perspective of endoscopic examination can often clarify many confusing bulky lesions that distort CT and MR anatomy. Thus endoscopic photography is a tremendous teaching tool.
Adolescent↗
Magnetic resonance imaging of the brainstem and cranial nerves.
Ten normal human volunteers and 44 patients with pathology of the brainstem or cranial nerves were scanned using a. 3 Tesla permanent MR imaging system. MR images were obtained of the cranial nerves and brainstem using various spin-echo pulse sequences and scanning planes. 4 mm thick sections with .75 mm pixels on a 256 display matrix were used whenever possible. The normal MR images were correlated with thin section cryodissection specimens of fresh human cadavers. Brainstem structures including major nuclei and tracts were then identified. The cranial nerves were followed through the subarachnoid cisterns and the base of the skull. Pathological involvement of the brainstem by tumors, infarcts, and demyelinating disease was well shown and correlated with clinical findings. Examples of optic glioma, fifth, eighth, and twelfth nerve schwannomas as well as other cranial nerve pathology were also demonstrated. Magnetic resonance produces excellent images of cranial nerves and brainstem with high contrast resolution. Unlike CT, there is no beam hardening artifact from bone. T1 weighted images maximize brainstem-CSF contrast and are useful for demonstrating the external anatomy of the brainstem and cranial nerves. The T2 weighted images show internal brainstem anatomy, CSF within neural foramina, and highlight many pathological conditions.
Adult↗
Magnetic resonance imaging of the facial nerve. Normal anatomy and pathology.
Magnetic resonance imaging with surface coils permits visualization of the facial nerve from within the brainstem and continuing through a major portion of the parotid gland. Diagnostic capabilities have been expanded to include white matter disease that affects the tracts of the facial nerve within the brainstem and tumors of the parotid gland that involve the facial nerve trunks after the nerve exists from the stylomastoid foramen.
Facial Nerve↗
Magnetic resonance imaging of the nasopharynx and skull base.
Ten patients with a normal nasopharynx and 36 patients with pathology of the nasopharynx or skull base were studied with magnetic resonance imaging (MRI). Four millimeter thick axial, coronal, and often sagittal scans were obtained using SE 500/28 and SE 2000/56 pulse sequences. The normal scans were compared with cadaver cryosections. Correlation was made with computed tomography (CT) scans as well as with clinical history and physical examination whenever possible. MRI clearly provided superior information compared with CT and other imaging studies. Advantages of MRI over CT include 1) the delineation of tumor infiltrations of the longus colli muscles, rectus capitus muscles, and muscles of mastication, 2) demonstration of tumor extensions into the skull base or parapharyngeal spaces, and 3) demonstration of both normal and pathologic cranial nerves. For all these reasons, MRI is currently the imaging study of choice for pathology of the nasopharynx and skull base.
Adult↗
Comparison of computed tomography and pluridirectional tomography of the temporal bone.
During pluridirectional tomography dense bone creates ghost shadows that simulate chronic disease and soft-tissue masses within the middle ear cavity. This effect was demonstrated in three dried skulls. Cholesteatomas were simulated in three more temporal bones with a mixture of 2% iodine in paraffin. Three different high-resolution computed tomographic scanners clearly demonstrated middle ear anatomy and the simulated soft-tissue masses in the skulls.
Cholesteatoma↗
MR-guided percutaneous ethanol ablation of liver tissue in a .2-T open MR system: preliminary study in porcine model.
The purpose of this study was to test the feasibility of MR-guided percutaneous ethanol ablation of liver tissue on a .2-T open MR scanner. Needles were placed by MR guidance first into an ex vivo sheep liver and then into livers of three anesthetized pigs, and injection of 10 ml of 96% alcohol was performed. T1 fast low-angle shot (FLASH), T2 turbo spin echo (TSE), and T1 spin echo (SE) images were obtained after incremental volumes of injection. In one pig, simultaneous injection of saline into normal liver was also performed with subsequent pathological correlation. Ethanol-infiltrated liver was hypointense to liver on all sequences, whereas saline caused no tissue signal changes on T1 SE and either isointense or hyperintense changes on T2 TSE images. Pathological examination confirmed ethanol-induced acute liver changes as compared with the control. MR guidance of needle placement and monitoring of ethanol effects on liver tissue is feasible. This may have implications for potential MR-guided hepatic tumor ablation.
Animals↗
Phase imaging on a .2-T MR scanner: application to temperature monitoring during ablation procedures.
Proton phase shift imaging methods with keyholing were developed to rapidly monitor temperature during MR-guided radiofrequency (RF) interventional procedures on a .2-T open configuration scanner. Temperature calibration was performed on thermally controlled gel phantom and ex vivo bovine liver samples. Keyholing methods were implemented for rapid imaging and tested both in simulation experiments and in the gel phantom. Phase drifts from extraneous sources were monitored and compensated for using reference phantoms. Sequence parameters TE, TR, and flip angle (FA) were optimized for maximum temperature sensitivity and minimum noise. Reduction of phase noise from coupling of the magnetic field to external perturbations using navigator-echo-based correction schemes were also investigated. The extraneous phase drifts from the magnet could be minimized by keeping the electromagnet on continuously. Navigator echo corrected keyholed FLASH sequences (TE = 30 msec, TR = 60 msec, FA = 40 degrees, 64 x 128 matrix) were used to monitor the RF lesioning process in gel phantoms yielding images every 4 seconds with a temperature sensitivity of .015 ppm/degree C. RF ablation in the bovine tissue was monitored using navigator-echo-corrected keyholed fast low angle shot (FLASH) sequences (TE = 30 msec, TR = 100 msec, FA = 40 degrees, 128 x 256 matrix) with a temporal resolution of 13 seconds and a temperature sensitivity of .007 ppm/degree C. The results indicate that monitoring of an RF ablation procedure by mapping temperature with sufficient temporal resolution is possible using phase images of FLASH sequences on a .2-T open scanner.
Animals↗
Paranasal sinuses in pediatric patients by MRI: normal development and preliminary findings in disease.
A two-part study using medium field strength magnetic resonance imaging (MRI) was designed to describe the normal paranasal sinus development and to provide preliminary criteria for clinical sinus disease. In part I of the study the paranasal sinuses were retrospectively evaluated in 80 infants and children aged 0-17 years undergoing brain MRI for indications both unrelated and related to sinus disease. We developed MRI criteria for independent grading of paranasal sinus development and 'anatomical' sinus disease, i.e., disease as seen by the radiologist. We quantified the variability in extent of sinus pneumatization (a measure of sinus development) in infants and young children. Part II of the study was a double-blind prospective study in 21 patients to correlate 'anatomical' disease with 'clinical' sinus disease. In this limited preliminary study, clinical sinus disease was only seen in the patients with moderate or severe anatomical disease (sensitivity 100%; specificity 100%).
Adolescent↗
Pulse sequence optimization for use with a biopsy needle in MRI.
The purpose of this study was to assess the degree of conspicuity and amount of field distortion caused by a biopsy needle designed specifically for use in MRI studies. Toward this, a number of pulse sequences including spin and field echo were used. Parameters such as field of view, strength of read gradient, direction of read gradient, echo time and slice thickness were varied. The effect of these manipulations on needle visualization was studied. Partial voluming errors with thicker slices decreased needle conspicuity. Smaller field of view improved needle visualization as a result of magnification effect. Shallow read gradient strengths also increased needle conspicuity. Increased image artifacts were noted on field-echo sequences compared to spin echo. This effect increased with longer echo times. This reflects T2* effects on field-echo images.
Biopsy, Needle↗
Automated MR imaging protocols for improved patient throughput.
The total time spent on each patient during an MR study determines patient throughput and ultimately influences MR scan charges. Actual data acquisition often represents only a small portion of this examination time. Other functions such as patient loading and unloading, positioning, coil placement, scan setup, and image reconstruction time also contribute to the total examination time. We describe a technique for creating automated imaging protocols for standard MR examinations which optimize these functions, thereby decreasing operator interventions and shortening the overall examination time. A prototype sequence for examining the larynx and neck was developed which allowed three sequential multiple slice acquisitions to be obtained in three orthogonal planes with a single operator setup step. All tuning and scan placement after this first step was done under computer control. The new sequence allowed larynx and neck studies to be performed in less than 30 min for spin echo and under 16 min for field echo instead of the 50-60 min required by previous methods. The new technique should be useful for improving patient throughput for a cariety of standardized examinations including the temporal bone, head and neck, joints, and other regions.
Computers↗
Magnetic field strength dependence of chemical shift artifacts.
The dependence of proton MRI chemical shift artifacts on main magnetic field strength was investigated using three MR whole body systems from 0.3 to 1.5 T with both permanent and superconducting magnet designs. The magnetic field gradients varied from 0.09 to 1.0 gauss/cm. The image bandwidth varied from 8.54 to 32 kHz. Both phantoms and normal volunteers were studied. The chemical shift misregistration error in hertz was determined by the main magnetic field strength of the system which was proportional to the Larmor frequency. The actual image error in millimeters was determined by a combination of the shift in hertz as well as by the amplitude of the magnetic field gradients applied to form the image. Steeper gradients mapped a given shift in hertz onto a smaller millimeter displacement. The higher field strength systems tended to use steeper magnetic field gradients, but this increase was not enough to offset the higher absolute shift in hertz due to the higher Larmor frequencies. In general, the chemical shift in millimeters tended to increase with the increasing field strength despite the steeper imaging gradients. Based on these findings, strategies for minimizing the chemical shift artifact may be developed.
Adipose Tissue↗
Low cost MRI of the paranasal sinuses.
The use of automated tuning, automated MR protocol sequences, surface coils, and grouping of patients with similar examinations, patient throughput can be greatly accelerated for MRI scanning. These measures coupled with high volume scanning permit significant reductions in cost so that MRI can be performed at a price range equal to or less than plain films for some examinations. The ability of MRI to perform axial, sagittal and coronal scans with excellent tissue contrast raises the possibility of substituting MRI for sinus x-rays. Based on our preliminary experience we have the opinion that MR is equal to/or better than CT in this region. This preference is currently being investigated. Only the cost issue will be addressed in this report.
Costs and Cost Analysis↗
Comparison of T1 and T2 weighted images of the lumbar spine.
In order to develop an optimal routine magnetic resonance (MR) spine scanning protocol, we have compared the relative efficacy of performing T1- and T2-weighted images in patients with various disorders of the lumbar region. Forty cases were randomly selected from studies performed from 1984 to 1987 and the T1- and T2-weighted images of each case were separated and interpreted blindly and independently by two neuroradiologists. Our results indicate no significant difference between T1- and T2-weighted images in the depiction of disc protrusion. The T2-weighted images were superior in depicting disc dessication, but the clinical significance of identifying a dessication disc remains uncertain. No significant difference in the depiction of osteophytes was seen between T1- and T2-weighted images. Cases of tethered cord, metastatic disease, and arachnoiditis were better delineated with T1-weighted images. The increase in signal of cerebrospinal fluid (CSF) with T2-weighting often obscured lesions within the spinal canal. In a signal case of postoperative discitis, the T2-weighted images disclosed disc space abnormalities and epidural fluid collections not appreciated on T1-weighted images. The T1-weighted images, however, did show thecal sac and adjacent epidural extension more clearly. In cases of metastatic disease, increase in the signal of metastases with T2 weighting often rendered them isointense to surrounding medullary bone. Given the lack of superiority of T2-weighted images over T1-weighted images in evaluating intervertebral disc protrusions and the superiority of T1-weighted images in depicting nearly all other abnormalities observed in this series, we no longer acquire T2-weighted images of the lumbar spine on a routine basis.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Magnetic resonance imaging of the craniocervical junction.
Magnetic resonance imaging has become the study of choice for the majority of abnormalities of the craniocervical junction as well as for demonstration of primary pathology of the spinal cord, and brain stem. Although the applications of MR are currently limited by its high cost, relatively long scan time, and low sensitivity to calcification, new pulse sequences, faster scan strategies, and lower cost MR scanner are changing this situation. MR contrast agents and the use of 3-D imaging techniques combined with gradient echoes promise to play a role in MR of the craniocervical junction in the near future.
Arnold-Chiari Malformation↗
Approaches to fast MR imaging.
Fast MR scanning may be accomplished through a number of strategies as discussed below. Each technique accomplishes improvements in scan time at the expense of signal and noise, spatial resolution, contrast resolution or other imaging artifacts. The scanning strategies discussed are in a variety of stages of clinical implementation, although several are already in wide spread use. All the existing techniques offer improvements in scan time, but they are still far from the theoretical limits imposed by the physics of MR scanning and further reduction in MR scanning time maybe expected in the future.
Image Enhancement↗
MR imaging of acute subarachnoid hemorrhage.
The MR appearance of acute subarachnoid hemorrhage experimentally produced in Macaca monkeys and observed in patients with clinically documented acute subarachnoid hemorrhage is presented. Subarachnoid hemorrhages were produced in two Macaca Nemestrema monkeys using the technique of Frazee. CT and MR imaging were performed immediately after the procedure and at frequent intervals up to two week post hemorrhage. MR including T1 and T2 weighted multiplanar spin echo images were obtained. The imaging studies were compared with clinical evaluations and pathological specimens of all animals. Findings in the experimental animals are correlated with those observed in patients with clinically documented subarachnoid hemorrhage. The results show that acute subarachnoid hemorrhage (SAH) can be detected with MRI as isointense signal replacing normally black CSF spaces on T1 weighted images. Signal changes most likely relate to protein water binding associated with the clotting mechanism rather than oxidative denaturation of hemoglobin. Imaging performed experimentally and clinically beyond four days, however, showed a marked increase in signal intensity on T1 weighted images which probably does result from methemoglobin formation within the clot matrix. Although CT remains the gold standard in detecting acute SAH, MR does provide some sensitivity to its presence.
Acute Disease↗