Hepatic cavernous hemangioma: magnetic resonance imaging. Work in progress

Using a 0.35-T superconducting magnet and spin echo imaging, we prospectively evaluated 11 patients who had proved hepatic cavernous hemangioma. Magnetic resonance (MR) identified more lesions than either contrast-enhanced CT, or ultrasonography. The MR appearance was consistent; hemangiomas were homogeneous and generally isointense at short TR and TE intervals but were hyperintense at long TR intervals and greatly hyperintense at long TR and long TE intervals. However, the MR appearance of hemangioma was not specific; 2/14 other focal hepatic masses had similar features. The calculated relaxation times (T1, T2) were not useful in lesion characterization, although the intensity ratio of hemangioma to normal liver at the TR = 2.0 sec TE = 56 msec pulse sequence was useful in diagnosis since hemangiomas always had a ratio greater than 1.4.     

The intranuclear cleft of the intervertebral disk: magnetic resonance imaging

Three cadaver spines, 40 patients who were symptomatic for lumbar disk disease, and ten healthy subjects were examined by MR. T2 weighted spin echo images were used to evaluate the character of an intranuclear cleft. This cleft appears identical to annular tissue both on T2 weighted images and histologically. A 120 msec TE, 3 sec TR image was used to delimit the normal nucleus pulposus from the annulus. The incidence and age distribution of the cleft were calculated. An intranuclear cleft was present in all normal disks in both control and symptomatic subjects who were 30 years of age and older. If present in one disk, it was also present in 94% of the other disks in the same subject. This cleft represents a normal anatomic structure and appears to be a constant feature in subjects 30 years of age or older. Its absence, in the presence of an increased signal intensity within the disk, suggests a pathological process with a long T2 value, such as inflammation.     

MR imaging of the dilated biliary tract

The magnetic resonance (MR) examinations of 18 patients with dilated bile ducts were reviewed retrospectively to determine the capability of MR to demonstrate biliary dilatation, assess MR appearance of the dilated biliary tract using spin-echo techniques, and define the optimal MR imaging parameters (repetition time [TR] and echo time [TE]) for its demonstration. On images with short TR (0.5 sec) and TE (28 msec), the dilated intrahepatic and intrapancreatic bile ducts usually had lower signal intensity compared with the surrounding liver or pancreas; on images with long TR (2.0 sec) and TE (56 msec), they had higher signal intensity. Because of the observed variation in percentage of contrast between dilated bile ducts and surrounding liver and pancreas, two imaging sequences are recommended to obtain reliable demonstration of dilated intrahepatic and intrapancreatic bile ducts. The dilated common bile duct at the level of the hepatic hilus is best seen with a short TR and TE.     

Brucellar and tuberculous spondylitis: comparative imaging features

Radiographs, scintigrams, computed tomographic scans, and magnetic resonance (MR) images of 17 patients with brucellar spondylitis and 15 with tuberculous spondylitis were analyzed to identify distinguishing features. Characteristic findings of brucellar spondylitis included predilection for the lower lumbar spine (68% of lesions), bone destruction limited to the end plates, disk collapse (16 of 19 disks), and granulation tissue or localized soft-tissue edema (17 of 19 sites). MR imaging showed diffuse increased signal in vertebrae and disks on long repetition time (TR)/echo time (TE) images in four patients and focal increased signal with normal disks in one. Epidural extension was best seen on short TR/TE images in four. Tuberculous spondylitis was characterized by predilection for the midthoracic spine (73%), vertebral destruction with gibbus deformity (60%), disk collapse, and paraspinal abscesses (14 of 15). On MR images signal intensity of affected vertebrae was similar to but more severe than findings in patients with brucellar spondylitis. Scintigraphy was the least helpful in differentiating the two infections. Lesions of tuberculous spondylitis affecting the lower lumbar spine were difficult to differentiate from those of brucellar spondylitis.     

Cholecystitis: detection with MR imaging

The role of magnetic resonance (MR) imaging in the detection of gallbladder disease was evaluated in 39 individuals (16 healthy, five with asymptomatic gallstones, and 18 with clinical symptoms of gallbladder disease). MR imaging was performed after they fasted for 12 hours. Imaging sequences included a combination of repetition times (TR) of 0.5 and 1.5 sec and echo times (TE) of 28 and 56 msec. On the images obtained at TR = 0.5 sec and TE = 56 msec, gallbladder bile was hyperintense compared with the liver in all healthy and asymptomatic subjects and was hypointense (n = 9), isointense (n = 4), or hyperintense (n = 5) in symptomatic patients, eight of whom had surgical confirmation of cholecystitis. Comparison of normal versus pathologically proved cases for the presence of gallbladder disease yielded a specificity of 100%, sensitivity of 75%, and a significant difference of P less than .01. Thus, with a pulse sequence of TR = 0.5 sec and TE = 56 msec, MR was sensitive in detecting gallbladder disease. However, the role of MR in the radiologic workup of gallbladder disease will be determined by more experience with this modality.     

Intervertebral disk: normal age-related changes in MR signal intensity

The effect of age on the signal intensity of normal lumbar intervertebral disks was studied. Twenty-seven cadavers ranging in age from newborn to 79 years were studied with use of a 1.5-T magnetic resonance (MR) imager within 48 hours of death. The signal intensity in the central area of the disk was measured on a sagittal image obtained with a long repetition time (TR) and a long echo time (TE) and correlated to the age. A significant correlation between the decrease in signal intensity and age was found, although signal intensity changed less than 6% in 80 years. The decrease in signal intensity is concomitant with decreases in water and glycosaminoglycans and increases in collagen in the disk.     

Urinary bladder MR imaging. Part I. Normal and benign conditions

The normal urinary bladder and several benign entities of the bladder were examined in 50 patients by magnetic resonance (MR) imaging. Specific features assessed included appearance of the bladder wall, optimal repetition (TR) and echo delay (TE) parameters for bladder-wall demonstration, and differentiation among various benign abnormalities, including bladder-wall hypertrophy, inflammation, and mucosal congestion, on MR images. The bladder wall in the 30 healthy subjects was best displayed using a TR = 2 sec, TE = 56 msec image, which gave 60% contrast between the bladder wall and urine and 48% contrast between the bladder wall and fat. Demonstration of bladder-wall hypertrophy required similar imaging; bladder distention was necessary to demonstrate the thickness of the bladder wall. Congestion and inflammation were best demonstrated on TR = 2 sec, TE = 56 msec images, which gave 45% contrast. Normal and/or hypertrophic bladder wall were distinguished from inflammation and congestion on the basis of signal intensity variations and/or T1 and T2 relaxation parameters.     

Urinary bladder MR imaging. Part II. Neoplasm

The potential of magnetic resonance (MR) imaging for the evaluation and staging of bladder tumors was analyzed in 15 patients (11 cases of transitional cell carcinoma, two adenocarcinomas, one leiomyosarcoma, and one leiomyoma). Neoplasms were characterized by size, site, and growth pattern, and the accuracy of the staging was compared with the results of computed tomography and pathologic study. Malignancies were accurately detected and staged by MR imaging in 12 of 14 patients (85%). Tumor site and degree of bladder distention did not adversely affect detection; tumors greater than 1.5 cm were detected easily. In situ carcinoma (stage Tis) was not detected on MR images. Imaging in both sagittal and transverse planes was needed for optimal bladder evaluation. Bladder carcinoma was best displayed with a short echo delay time (TE) of 28 msec and repetition (TR) times of 1.0-2.0 sec: TR = 1.0 gave 34% contrast and TR = 2.0 gave 36% contrast between tumor and surrounding urine. Bladder-wall invasion by tumor was best evaluated with long TR (2.0 sec) and long TE (56 msec) (82% contrast). For assessing tumor extension into perivesical fat, short TR (0.5 sec) and TE (28 msec) were optimal (58% contrast). MR imaging offers an increased sensitivity for tumor detection and promises to greatly improve the staging of bladder neoplasms.     

A new diagnostic method of spondylodiscitis. Magnetic resonance imaging

Twenty four patients who were hospitalized for a suspicion of spondylodiscitis were prospectively evaluated with magnetic resonance imaging (MRI), radiology and radionuclide studies. Fifteen patients had an infectious spondylodiscitis, four had a vertebral degenerative disease, four had a rheumaticus spondylodiscitis, one had a chemical spondylodiscitis. The microbiological examinations and the clinical development bore the diagnosis out. Seven patients underwent Indium 111 scanning. The results of this scanning were correlated with MRI results. The MRI was performed with a 0.35 T whole body superconducting unit using spin echo technique. All patients were studied in the sagittal plane with two pulse sequences and more often with a surface-coil: TR 500 msec./TE 28 msec. and TR 2,000 msec./TE 60 msec. In all cases of true infectious spondylodiscitis the MRI results finding were characteristics. On the image obtained with the TR 500 msec./TE 28 msec., there was a confluent decreased signal intensity from the vertebral bodies and the intervertebral disk space. On the image obtained with TR 2,000 msec./TE 60 msec. there was an increased signal intensity from the vertebral bodies and the intervertebral disk space. The other spondylodiscitis have given a different MRI imaging, it was a confluent decreased signal intensity from the vertebral bodies and the intervertebral disk space on the twice pulse sequences. different images were obtained during the evolution of the infectious: first we observed a modification of the vertebral signal then the typical image that we described then a normal signal of the vertebral bodies with a pathological signal from the intervertebral disk space at last a degenerative intervertebral disk.(ABSTRACT TRUNCATED AT 250 WORDS)     

MR imaging of marrow changes adjacent to end plates in degenerative lumbar disk disease

MR studies of the lumbar spine in 41 patients were analyzed at 203 disk interspaces to assess the appearance and frequency of bone marrow signal changes in the vertebral bodies adjacent to normal and degenerated disks. Degenerative changes were found at 58 interspaces; an abnormal bone marrow signal was identified in 29 (50%) of these. On spin-echo pulse sequences with short and long repetition times (TRs) and echo times (TEs), an area of relative increased signal intensity was seen in the vertebral body adjacent to the disk in 24 cases (17 were bandlike on both sides of the disk, four were focal on one side of the disk, and three were bandlike and focal on one or both sides of the disk). In one patient decreased signal was noted on both short and long TR/TE imaging. In the other four patients decreased signal was noted on short TR/TE pulse sequences and increased signal was evident on long TR/TE. These marrow changes were not present adjacent to normal disks. The relatively high signal intensity on both short and long TR/TE pulse sequences suggests that the increased signal resulted from the conversion of normal hemopoietic bone marrow to fatty marrow. We conclude that bandlike or focal areas of high signal intensity in the bone marrow adjacent to degenerated intervertebral disks occur commonly on MR images of the spine and must not be confused with signal changes from tumors or infections involving the disk space and adjacent vertebral end plates.     

Optimizing MR imaging for detecting small tumors in the cerebellopontine angle and internal auditory canal

Relative resolving power was used to determine the optimal MR imaging pulse sequence for detecting small tumors of the internal auditory canal and the cerebellopontine angle. Resolving power takes into consideration these important image characteristics: signal-to-noise ratio, contrast, and spatial resolution. The study was performed on a 1.5-T magnet using a 256 X 256 matrix and a 3-mm slice thickness. The TR ranged from 400-2000 msec; the number of excitations was either two or six; and the pixel size was 0.94, 0.78, or 0.63 mm. Theoretical calculations of relative resolving power were compared with the relative resolving power of 45 control patients and 15 patients with small tumors of the cerebellopontine angle or internal auditory canal. A TR of 800 msec was optimal from theoretical calculations and proved optimal in control and tumor patients. Scans obtained with TR = 2000 msec, TE = 80 msec were inferior to short TR scans; such scans could fail to detect intracanalicular tumors. The relative resolving power in patients exceeded theoretical calculations because of greater than expected image contrast caused by low CSF signal intensity secondary to CSF pulsation.     

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°, 64 × 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/°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°, 128 × 256 matrix) with a temporal resolution of 13 seconds and a temperature sensitivity of .007 ppm/°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.     

Improvement of T2-weighted images of central nervous system by motion artifact suppression technique (MAST)

Standard spin echo sequences of MRI with and without motion artifact suppression technique (MAST) were compared in 45 paired images of brain and 21 paired images of spine. The images were obtained on a Picker 1.5 T system with TR = 2 sec and TE = 100 or 120 msec. MAST is a method of refocusing transverse magnetization at echo time by modification of the gradient waveforms. Transverse, coronal, and sagittal planes of brain were compared in 10 paired images obtained from adults and five paired images from children. The spine was studied in sagittal images, 11 cervical images of adults, five lumbar images of adults, and five lumbar images of children. MAST was proven to be valuable not only for the detection of lesions but also for picturing anatomical details as in MR-cisternography and MR-myelography and the effects of iron ions. MAST improves significantly the quality of T2-weighted images, especially in children.     

MR imaging of the lungs: value of short TE spin-echo pulse sequences.

OBJECTIVE. An experimental short echo delay (TE = 7 msec) T1-weighted spin-echo sequence was compared with a conventional (TE = 20 msec) T1-weighted spin-echo sequence in the assessment of normal and abnormal lung parenchyma. Comparison was also made with high-resolution CT of abnormal lung parenchyma. SUBJECTS AND METHOD. At 1.5 T, an experimental short echo delay T1-weighted multislice spin-echo sequence (TR = RR interval, TE = 7 msec) was compared with an optimal conventional T1-weighted spin-echo sequence (TR = RR interval, TE = 20 msec, spatial presaturation). Ten healthy volunteers were examined with both sequences. The mean signal intensity and signal-to-noise ratios were calculated in lung parenchyma for both sequences. Two radiologists compared the visualization of normal lung parenchymal structures with the two techniques. In 24 patients with diffuse lung disease, results with both MR sequences and with high-resolution CT were compared. RESULTS. The signal intensity was significantly greater (p < .001) with the TE of 7 msec than with the TE of 20 msec, resulting in a 3.5-fold improvement in the signal-to-noise ratio. The 7-msec TE improved visualization of lung parenchymal structures, including peripheral vessels, interlobular septa or veins, and centrilobular arteries. In the patients with diffuse lung disease, pulmonary parenchymal abnormalities were better visualized on the images with TEs of 7 msec than on images with TEs of 20 msec. When compared with high-resolution CT, the sequence with a TE of 7 msec provided comparable assessment of air-space opacification and dense consolidation, but it was inferior to high-resolution CT in the anatomic assessment of lung parenchyma. CONCLUSION. This experimental spin-echo sequence with a TE of 7 msec significantly improves the signal-to-noise ratio, allowing improved visualization of normal and abnormal pulmonary parenchyma when compared with conventional spin-echo images with a TE of 20 msec. Although anatomic detail remains inferior to that seen with high-resolution CT, the improved image quality with a TE of 7 msec suggests that assessment and follow-up of parenchymal lung disease might be possible with MR, thereby avoiding ionizing radiation.     

White matter lesion contrast in fast spin-echo fluid-attenuated inversion recovery imaging: effect of varying effective echo time and echo train length.

OBJECTIVE: Our aim was to determine whether the contrast between white matter lesions and normal-appearing white matter in fast spin-echo fluid-attenuated inversion recovery (FLAIR) images can be improved by lengthening the effective TE and the echo train length. SUBJECTS AND METHODS: Thirty patients with various white matter lesions were imaged using fast spin-echo FLAIR sequences (TR = 10,002 msec; inversion time = 2200) on a 1.5-T MR imaging system. For 14 patients, fast spin-echo FLAIR sequences with a TE of 165 msec and echo train length of 32 (fast spin-echo FLAIR 165/32) were compared with fast spin-echo FLAIR sequences with a TE of 125 msec and echo train length of 24 (fast spin-echo FLAIR 125/24). For 16 other patients, fast spin-echo FLAIR 165/32 sequences were compared with fast spin-echo FLAIR sequences with a TE of 145 msec and echo train length of 28 (fast spin-echo FLAIR 145/28). Signal difference-to-noise ratios were calculated between the lesions and normal-appearing white matter for a typical lesion in each patient. RESULTS: In both groups, a small but statistically significant increase in the signal difference-to-noise ratio was found on the fast spin-echo FLAIR sequences using the longer TE and echo train length. In the first group, signal difference-to-noise ratio increased from 18.7 +/- 4.7 (mean +/- SD) for fast spin-echo FLAIR 125/24 to 20.1 +/- 4.5 for fast spin-echo FLAIR 165/32 (p < .05). In the second group, the signal difference-to-noise ratio increased from 15.4 +/- 4.0 for fast spin-echo FLAIR 145/28 to 16.8 +/- 4.6 for fast spin-echo FLAIR 165/32 (p <.01). In addition, fast spin-echo FLAIR sequences with a longer TE and echo train length were obtained more rapidly (6 min for fast spin-echo FLAIR 125/24, 5 min 20 sec for fast spin-echo FLAIR 145/28, and 4 min 41 sec for fast spin-echo FLAIR 165/32). CONCLUSION: Lengthening the TE to 165 msec and echo train length to 32 in fast spin-echo FLAIR imaging allows both a mild improvement in the contrast between white matter lesions and normal-appearing white matter and shorter imaging times.     

Magnetic resonance imaging and spectroscopy of the periarticular inflammatory soft-tissue changes in experimental arthritis of the rat

Arthritis was induced in rats by intradermal injection of Freund's complete adjuvant. MRI was performed with a resistive imager operating at 0.35 T. A spin echo (SE) technique with TR = 0.5 and 2.0 seconds, TE = 28 and 56 msec was used. Transaxial images of hindpaws and knees were obtained at different times after injection of adjuvant. In vitro proton spectroscopy of normal and arthritic hindpaws was also performed. Histologic confirmation was obtained in each case. Inflammatory soft-tissue lesions were seen as focal areas of high intensity on spin echo images obtained with TR = 2.0 seconds and TE = 56 msec and were characterized by long T1 and T2 relaxation times and high spin density. In comparison with both conventional radiography and physical examination, early soft-tissue changes were detected more frequently by MRI. This study suggests that MRI is likely to be of value for the early diagnosis of arthritis.     

Dynamic MRI of hepatic tumors using gadolinium-DTPA--preliminary results

Dynamic magnetic resonance imaging (MRI) was performed in two patients with hepatic tumors (one cavernous hemangioma and one hepatoma). A sequential timed scanning technique with spin echo images (TR: 100 msec; TE: 20 msec; data acquisition time: 26 sec) was used with a bolus injection of 0.05 mmol/kg gadolinium DTPA. Dynamic MRI findings in the two cases were similar to those obtained with dynamic CT and angiography using iodinated contrast medium. Our early experience suggested that the less invasive technique of dynamic MRI could replace conventional dynamic CT in assessing the hemodynamics of hepatic tumors.     

3D MR sialography protocol for postradiotherapy follow-up of the salivary duct system

PURPOSE: To develop and evaluate an MR sialography protocol that reproducibly images the parotid and submandibular ducts over time, in 3D. Such a protocol is needed in order to investigate the possible radiation-induced changes to the salivary ducts in patients receiving radiotherapy to the head-and-neck. MATERIALS AND METHODS: MR sialography was performed on a 1.5-T MR scanner. Sequence parameters were optimized on 11 healthy volunteers. A 3D water-selective turbo spin echo (TSE) pulse sequence (TR/TE = 6000 msec/190 msec), using a two-element circular surface coil was applied twice in one MR session. In order to assess the reproducibility, the same procedure was repeated four to six months later. The quality of the MR sialograms was measured subjectively by developing a visibility scoring system and objectively by the means of contrast-to-noise ratio (CNR) of the ducts vs. fat (CNR(duct-fat)). RESULTS: High-quality, 3D MR sialographic images were obtained. The quality of the MR sialograms and the subjective visibility score of the salivary ducts were constant over time. The CNR(duct-fat) varied between volunteers (standard deviation, SD 26%) but it was relatively constant per volunteer (SD 5%). CONCLUSION: The MR sialography protocol presented in this study provides good quality 3D imaging of the major salivary ducts, submandibular duct, and the parotid duct and it can be used for the comparison of the salivary duct system of an individual over time.     

Obstetrical magnetic resonance imaging: fetal anatomy

Nine patients who were 34-36 weeks pregnant underwent magnetic resonance (MR) imaging. Sagittal images using spin echo technique (TR 2.0 sec, TE 28 msec) were optimal for delineating fetal anatomy. The fetal cardiovascular, pulmonary, and central nervous systems were depicted in all cases. The heart and major vessels were readily seen due to the natural contrast of flowing blood. The intensity of the fluid-filled lungs greatly increased with a longer TR or TE, delimiting thorax from liver. The brain was relatively featureless due to the lack of gray-white matter differentiation. The umbilical cord within the amniotic fluid and its insertion into the placenta and fetus was identified in all cases. MR is a new modality for fetal imaging that offers tissue-characterization information that complements the superior anatomic detail of ultrasound scanning.     

Magnetic resonance imaging of the lumbar spine--comparison of multiple spin echo and low flip angle gradient echo imaging

Sixteen patients including 13 cases with disk herniation and 3 cases with spondylosis of lumbar spine were examined on a resistive MRI system operating at 0.1 T. All lesions were studied with both multiple spin echo (MSE) and low flip angle gradient echo (LF) techniques to evaluate which technique is more effective in detecting the disk degeneration and the indentation on subarachnoid space. MSE images were obtained with repetition time (TR) of 1100-1500 ms or cardiac gating, an echo time (TE) of 30, 60, 90, 120, 150, and 180 ms symmetrical 6 echoes, and total acquisition time of more than 281 sec. LF images were obtained with TR of 500, 250, and 100 ms, TE of 18 ms, a flip angle of 30 degree, and total acquisition time of 128 sec. Eleven lesions of spinal disk degeneration and 12 of indentation on subarachnoid space were detected with LF. On the other hand, 26 lesions of spinal disk degeneration and 38 of indentation on subarachnoid space were detected with MSE. Although the parameters of LF employed in this study were relatively effective to emphasize T2*-based contrast, the ability of LF in detection of spinal disk degeneration and indentation on subarachnoid space is less than that of MSE. Signal contrast to noise ratios for normal disk and degenerative disk, epidural-fat and disk herniated material, CSF and disk herniated material, and epidural-fat and CSF were less than 4 with LF, but more than 4 with MSE.(ABSTRACT TRUNCATED AT 250 WORDS)