Effect of gadopentetate dimeglumine on proton magnetization transfer in protein solutions and tissues at 0.1 Tesla.
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Animals↗
Biomedical subjects
M Komu
Publications and source records attributed to M Komu.
Magnetization transfer contrast in gadopentetate-dimeglumine-enhanced breast magnetic resonance imaging at 0.1 Tesla.
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Adult↗
Relaxation times of normal breast tissues. Changes with age and variations during the menstrual cycle.
The influence of age on the relaxation times of normal breast parenchyma and its surrounding fatty tissue were evaluated, and the variations during a normal menstrual cycle were analyzed using an ultra low field 0.02 T imager. Thirty-nine healthy volunteers aged 21 to 59 years were examined to determine T1 and T2 relaxation times, and 8 of these volunteers were studied once weekly during one menstrual cycle. The only significant trend was an increase in the T2 of breast parenchyma with increasing age. During the menstrual cycle there was a slight but insignificant (p = 0.10) increase in T1 of the breast parenchyma values during the latter half of the menstrual cycle, and a corresponding increase in T2 values between the 2nd and 3rd weeks of the menstrual cycle, which was significant (p = 0.003).
Adult↗
Magnetic resonance imaging of patellofemoral relationships.
Patellofemoral relationships were analyzed in 11 patients (13 knees) with patellar dislocation and 15 asymptomatic subjects (15 knees) at 0 degree and 20 degrees of flexion. The measurements were made from five consecutive axial images through the patellofemoral joint. The six indices measured were lateral patellar tilt (LPT), lateral patellofemoral angle (LPA), lateral patellar displacement (LPD), patella-lateral condyle index (L/PW), congruence angle (CA), and sulcus angle (SA). The reproducibility of the method was evaluated. The difference between the two study groups was more evident at 0 degree than at 20 degrees of knee flexion. Significant differences were noted between measurements made at different levels of the joint, particularly in the controls. Isometric contraction of the quadriceps muscle lateralized and tilted the patella slightly in both groups. L/PW with and without quadriceps muscle contraction, and LPA with reference to the anterior condyles differentiated between the two study groups most clearly. LPT and LPA with reference to the anterior condyles differentiated the study groups better than LPT and LPA with reference to the posterior condyles. The reproducibility was good except for inter-observer comparison of CA and SA. The use of an imaging plane selected at the midpoint of the patellar articular cartilage increases the sensitivity of the measurements, since it takes into account both the height of the patella and the tendency towards lateralization. These results indicate that patellar tilt is best measured with the LPA index and patellar lateralization with the L/PW index at 0 degree knee flexion. This study should always include isometric contraction of the quadriceps muscle.
Adolescent↗
Relaxation time changes of the uterus during the menstrual cycle: correlation with hormonal status.
Six women volunteers underwent pelvic MR imaging at 0.02 T four times during their menstrual cycle. The T1 and T2 relaxation times of the myometrium and endometrium were measured and correlated with the serum estradiol and progesterone levels. The magnitude of the relaxation times were highly individual but the pattern of their variation during the menstrual cycle was similar. The relaxation times were shortest at the beginning and end of the cycle. The most rapid increase occurred during the proliferative phase, followed by little or no increase through to the middle of the secretory phase. The T1 and T2 times of the endometrium correlated directly with the serum estradiol levels during the entire menstrual cycle (r = 0.5, P = 0.02) and the T2 times of the endometrium with the serum progesterone levels during the secretory phase (r = 0.6, P = 0.05). The correlation between the relaxation times of the myometrium and the serum hormonal levels was poor. The results indicate that the relaxation times of the myometrium and endometrium vary during the menstrual cycle reflecting the serum hormonal status. MR imaging of the uterus with relaxation time measurements may be clinically useful to examine the menstrual cycle and its pathology.
Adult↗
MR relaxation times and fiber type predominance of the psoas and multifidus muscle. An autopsy study.
MR relaxation times, fiber composition, nonmyofiber space, water content, and fat content of human psoas and multifidus muscle samples of 10 male cadavers were studied in vitro. The T1 and T2 relaxation times of multifidus muscle were significantly longer than those of the psoas muscle. On average, type 1 fibers (slow fibers with a small cross-sectional diameter) predominated in both muscles. There was no correlation between the relative mass of type 1 or 2 fibers (fast fibers with a large cross-sectional diameter) or nonmyofiber space and the relaxation times. The quantity of fat in the muscle did not correlate with the relaxation times either.
Adolescent↗
Breast coil design for low-field MRI.
Four double-breast coils were designed for the low-field resistive magnet MR imaging of female breasts at 0.02, 0.04, and 0.1 T. The signal-to-noise ratio is optimized by shaping the coils, by constructing two different size coils at 0.02 T, and by using special wire for the turns of the solenoidal coils. The approximate linear dependence of the SNR on the Larmor frequency is estimated.
Breast↗
Analysis of longitudinal relaxation rate constants from magnetization transfer MR images of human tissues at 0.1 T.
The human calf muscle was examined by using the magnetization transfer MR imaging technique. The time-dependent saturation transfer (TDST) method was applied at low magnetic field 0.1 T in order to measure the mobile water relaxation time T1w, the magnetization transfer rate Rwm from water to solid macromolecules, and the magnetization transfer contrast (MTC) of the human tissue. The magnetization transfer contrast of 0.67 was attained. The transfer rate Rwm was 4.5 sec-1 (+/- 0.3 sec-1) for the anterior tibial muscle and 5.0 sec-1 (+/- 0.4 sec-1) for the gastrocnemius muscles. The values of Rwm are considerably larger than the values of corresponding relaxation rates measured at high fields. The relaxation rate measurements of human tissues in vivo was shown to be possible at 0.1 T even within the framework of normal routine MR imaging. Magnetization transfer MR imaging is a very promising and practical method in order to assess the relaxation processes in heterogeneous human tissues in vivo, and it can improve the tissue characterization possibilities of MR imaging techniques.
Humans↗
Preoperative tissue characterization with chemical shift imaging: a case report of an epidermal cyst.
We introduce here a case of an epidermal cyst, which was preoperatively examined with chemical shift MR imaging at 0.1-T magnetic field. The case shows that fat/water separation method can be successfully used in tissue characterization.
Epidermal Cyst↗
Tissue characterization by image processing subtraction: windowing of specific T1 values.
A method for windowing specific T1 values is presented. A 1.0 T imager with two routine pulse sequences was employed: A T1-weighted spin echo (SE) sequence and a short tau inversion recovery STIR sequence (fat-suppressed IR). A T1 window for fat was obtained by subtracting the STIR image from the SE image. Negative values were coded black. The method was tested on a normal human thigh, on a human liver with confirmed fatty infiltration, and on the livers of four live burbots. The fat-containing tissues of the two human volunteers were well depicted. The differences in fat concentration among the burbot livers were also clearly shown. The fat intensity seen in the images correlated well with the chemically measured fat concentration. This subtraction method for windowing T1 values proved feasible for fat. The method could be used for tissues with other short T1 values as well.
Adipose Tissue↗
Magnetic resonance imaging of the uterus at an ultra low (0.02 T) magnetic field.
In vivo pelvic imaging of 39 women and in vitro relaxation time measurements of four uterine specimens were performed using an ultra low field (0.02 T) MRI unit. Average T1 times measured in vitro at 37 degrees C for the myometrium and endometrium were 206 ms (SD 47 ms) and 389 ms (SD 21 ms), respectively. Corresponding T2 times were 95 ms (SD 20 ms) and 167 ms (SD 13 ms). The proton relaxation of almost all myometrial specimens proved to be biexponential, but of all endometrial specimens was monoexponential. Contrast measurements between endometrium versus myometrium and myometrium versus the junctional zone were performed after imaging 18 volunteer women using different pulse sequence parameters. Normal uterine structures were optimally demonstrated by SE 700/70. Relatively short repetition times could be used, because spin-lattice relaxation times were short at the low magnetic field. Consequently, the short repetition times allowed averaging of four excitations to create adequate images within an acceptable scanning time. In addition to T2-weighted images a T1-weighted inversion recovery sequence with a short inversion time of 50 ms (IR 1000/50/40) adequately differentiated the three uterine zones. Although pathologic lesions of the uterus including leiomyomas, anomalies and carcinomas were well demonstrated, especially with the T2-weighted spin echo pulse sequence, further investigations are needed to evaluate the optimal technique for ultra low field MR imaging of uterine tumors.
Adenocarcinoma↗
T1 in subacute and chronic brain infarctions. Time-dependent development.
RATIONALE AND OBJECTIVES: Time-dependent behavior of T1 in brain infarcts and in brain tissue of the contralateral hemisphere was studied in the subacute and early chronic stages of stroke. METHODS: T1 was measured from magnetic resonance images (MRIs) of 29 patients as a function of infarct location and age. Another group of 11 patients was studied with consecutive MRI studies during the first 5 weeks after the onset of infarct, and the distribution of T1 in the infarctions was analyzed from T1 maps using a histographic method. RESULTS: During the first 2 months after a stroke, T1 was longer in the infarcted gray matter than in the infarcted white matter (P = .002), and prolonged linearly in both. The histographic analysis showed a component arising from tissue breakdown products that could be identified for up to 5 weeks. A transient lengthening in T1 of the contralateral hemisphere, reaching a maximum at 3 weeks, also was observed. CONCLUSIONS: These characteristics of recent infarctions differentiate them from older, gliotic lesions. The lengthening of T1 in the contralateral hemisphere may reflect remote flow and metabolic effects of brain infarctions.
Acute Disease↗
Determination of fat content of burbot (Lota lota) liver with low field MR imaging (0.04 T).
A reconstructed separate fat image was used for studying the fat content of the liver of 12 dead and six living fasting burbots (Lota lota) in a 0.04 T magnetic field with olive oil as a reference. The correlation between the MR intensities and the results of the cytological, histological and chemical fat measurements, as well as chemically measured water, collagen and total protein contents were examined. The MR signal intensity in reconstructed fat images correlated well with the changes in fat content of the liver in living fish (r = 0.69, P = 0.0014). Also the contents of water (r = -0.66, P = 0.003) and total protein (r = -0.91, P = 0.013) correlated significantly with the MR signal intensity. The reconstructed fat image is thus a reliable method for following the changes in tissue fat content. The living burbot is an applicable test animal for studying the hepatic fat content with MR.
Animals↗
Disc degeneration in magnetic resonance imaging. A comparative biochemical, histologic, and radiologic study in cadaver spines.
Magnetic resonance imaging (MRI) findings of 89 autopsied intervertebral discs from 22 cadaveric lumbar spines were correlated with biochemical composition, conventional radiography, and histologic structure to study the nature of disc intensity changes seen in MRI. Discs with a low signal intensity on T2-weighted MRI were characterized by shortening of relaxation times, dehydration, and decreases in total proteoglycan content and chondroitin-keratan sulfate ratios in the nucleus pulposus. This corresponded well with previously published studies. In histologic structure, no obvious differences between MRI findings were found. In conclusion, a low signal intensity in a lumbar disc on T2-weighted MRI probably reflects a true biochemical disc degeneration, but its relation to structural degenerative changes is uncertain. Therefore, MRI seems to be a sensitive and a specific imaging modality for detecting pathologic biochemical disc changes in the spine of a young adult.
Adult↗
MR imaging of patellar cartilage degeneration at 0.02 T. Study of 23 cadaveric patellae.
MR imaging with a 0.02 T resistive magnet was used to establish the correlation between the histologic grading of patellar cartilage degeneration and fat water separation images or T1- and T2-relaxation times. We examined 23 cadaveric patellae. There was a positive correlation between histologically graded cartilage degeneration and T1-relaxation time. Patellar cartilage was well differentiated from surrounding structures on chemical shift water proton images, and an evaluation of cartilage degeneration was possible. No correlation was found between cartilage damage and T2-relaxation time. Chemical shift imaging at 0.02 T is easy to perform and gives further information of cartilage disorders.
Adult↗
Proton relaxation enhancement of albumin, immunoglobulin G, and fibrinogen labeled with Gd-DTPA.
Bovine serum albumin, immunoglobulin G, and fibrinogen were labeled with Gd-DTPA using a bifunctional chelating agent DTPA anhydride. The protein-(Gd-DTPA) conjugates had 1.4- to 2.0-fold greater longitudinal relaxivities at 0.02 and 0.44 T than the relaxivity of plain Gd-DTPA. The increase of longitudinal relaxivity was not directly related to the size of carrier protein. Up to 50 Gd-DTPA chelates per protein, longitudinal relaxivity of the conjugates was proportional to the concentration of Gd and independent of the Gd/protein ratio.
Animals↗
Patellar motion analyzed by magnetic resonance imaging.
We have analyzed the normal patellar motion during the first 30 degrees of knee flexion by magnetic resonance imaging (MRI). Ten males and 10 females without knee symptoms were examined. The patellar articulation was imaged both sagittaly and axially with the knee flexed 0, 10, 20, and 30 degrees. The axial images were produced through the middle of the patellar articular cartilage. When the knee was in extension compared to 30 degrees flexion, the sulcus angle was greater, the lateral patellofemoral angle was smaller, there was more lateral patellar displacement, the patella tilted more laterally, and the congruence angle was directed more laterally. Differences between males and females were found.
Adult↗
Paramagnetic contrast enhancement at 0.02 T: an experimental study using Gd-DOTA in normal and hydronephrotic kidneys.
Both normal and experimentally hydronephrotic rabbits were imaged at 0.02 T using partial saturation (PS 160/30) and inversion recovery (IR 1000/200/40) sequences. The signal intensity of normal renal medulla and cortex markedly increased after the injection of 0.1 mmol/kg of Gd-DOTA. In the unilateral total hydronephrosis the dilated renal pelvis did not contrast enhance after 15 and 35 min of Gd-DOTA injection. The enhancement pattern was similar in 1- and 3-week-old hydronephrosis. The effect of Gd-DOTA on renal T1 times at 0.02 T was studied using rats. Fifteen minutes after the Gd-DOTA injection (0.1 mmol/kg) the T1 times of excised rat kidneys decreased from 311 to 90 ms. The authors conclude that the enhancement of the MR signal of the kidney by Gd-DOTA at an ultralow magnetic field (0.02 T) is similar to its enhancement at higher fields (greater than 0.15 T).
Animals↗