Dual-frequency proton spin relaxation measurements on tissues form normal and tumor-bearing mice

Detection of a systemic effect of malignancy in vivo by magnetic resonance imaging

In animals bearing tumors prolongation of spin lattice relaxation time (T1) has been detected in vitro in organs not directly affected by the malignancy. This has been termed the "Systemic Effect." In this study the possible existence of such an effect in the liver, muscle and fat of humans with lymphoma has been investigated. In vivo T1 measurements were made using a low field strength (0.08 Tesla) magnetic resonance imager. The mean liver T1 for 19 lymphoma patients with normal liver histology was 206 ms, compared with a mean of 191 ms for 61 volunteers (p less than 0.0001). Among these patients prolongation of liver T1 was related to the extent of disease elsewhere in the body. For 23 patients with Hodgkin's disease (HD) examined at the time of diagnosis, liver T1 was significantly correlated with other known markers of disease extent or activity (alkaline phosphatase level, erythrocyte sedimentation rate and the presence of systemic symptoms). No such correlations were observed among 25 patients with non-Hodgkin's lymphoma (NHL). Muscle and fat T1 was measured in 26 patients with lymphoma, 14 patients with acute leukemia and 88 volunteers. Seven of the patients with lymphoma and 2 of those with leukemia had muscle T1 values above the range observed for volunteers. Similarly, 3 patients with lymphoma and 1 with leukemia had prolonged fat T1. These findings indicate that a systemic effect of malignancy on T1 is detectable in a proportion of humans with lymphoma or leukemia.

New polyvinyl alcohol gel material for MRI phantoms

Nambu PVA gel which is produced by repeated freezing and thawing of PVA solution has overcome almost all of the problems which present substances have: It is close to human soft tissue in MRI parameters. MRI parameters (1H density, T1, T2) are adjustable to some extent. It has appropriate physical characteristics. The important problem with PVA gel is long-term stability. It is assumed that this problem can be solved by its periodic calibration and replacement.

In vivo measurements of NMR relaxation times

A series of solenoidal NMR probes were built to measure T1 and T2 relaxation times in vivo in the mouse, over the frequency range of 5 to 60 MHz, using inversion-recovery and spin-echo pulse sequences. KHT tumors growing in the legs of C3H mice were studied and compared with normal mouse legs. The tumor relaxation times were studied at 10 MHz during the course of tumor growth and as a function of frequency when the tumor had a mass of approximately 0.9 g. Mouse legs with tumors have higher T1 and T2 values than those without tumors over the frequency range of 5 to 60 MHz. Significant changes in both relaxation times were detected before a palpable mass could be detected. T1 contrast between normal and tumor-bearing legs decreased with increasing frequency, while T2 contrast remained nearly constant. A comparison between in vivo and in vitro measurements was done using four different types of sample preparation: live mouse, dead mouse, excised whole mouse leg, and tissue sample. These studies showed small but significant differences between the relaxation times measured in vivo and those measured in vitro.

Enhanced T1 differentiation between normal and dystrophic muscles

Proton spin-lattice relaxation times (T1) of pectoralis major muscles from normal (Line 412) and homozygous dystrophic (Line 413) chicks was measured by FONAR QED 80 at 1.69 MHz. The T1 values of dystrophic muscles (216.8 +/- 17.3 ms) was two-fold higher than those of normal muscles (110.2 +/- 8.1 msec). When these values were compared with the T1 values obtained at high frequencies (20 MHz and 32 MHz), the T1 differentiation between normal and dystrophic muscles was considerably enhanced at 1.69 MHz. Based on these results, we suggest that the high resolution of T1 obtained at low frequency (1.69 MHz) could be effectively used to detect the degenerative processes in muscles by the NMR techniques.

Characterization of proton NMR relaxation times in normal and pathological tissues by correlation with other tissue parameters

To help understand which tissue parameters best account for the water proton NMR relaxation times, the longitudinal relaxation time (T1), the transverse relaxation time (T2), and the water content of 16 tissues from normal adult rats were measured at 10.7 MHz and 29 degrees C. Regression analyses between the above and other tissue parameters were performed. These other tissue parameters included: the amounts of various organic and inorganic components, protein synthetic rate, oxygen consumption rate, and morphological composition. In addition, the differences in T1, T2, and water content values between normal liver and malignant tumor (Morris #7777 a transplantable hepatoma) were studied to help understand how a disease state can be detected and characterized by NMR spectroscopy. The results of this study and information from the literature allow the following generalizations to be made about tissue T1 and T2 values: (1) Each normal tissue has rather consistent and characteristic T1 and T2 relaxation times which are always shorter than the T1 and T2 of bulk water; (2) tissues with higher water content tend to have longer T1 relaxation times; (3) tissue T2 values are not, however, as well correlated with water content as T1 values; (4) tissues with shorter T1 values have higher calculated hydration fractions, greater amounts of rough endoplasmic reticulum, and a greater rate of protein synthetic activity; (5) tissues with higher lipid content, associated with intracellular non-membrane bounded lipid droplets, tend to have longer T2 values; (6) tissues with greater overall surface area, whether in the form of cellular membranes or intracellular or extracellular fibrillar macromolecules, tend to have shorter T2 values; (7) the differences between T1 and T2 values between tumor and normal tissues correlated with differences in the volume fraction (amounts) of extracellular fluid volumes and in the amounts of membrane and fibrillar surface area in the cells. The above generalizations should be useful in predicting T1 and T2 changes associated with specific tissue pathologies.

The systemic effect of cancers on human sera proton NMR relaxation times

In animal models of cancer, an elevation of T1 and T2 in uninvolved tissues and in the blood of tumor bearing animals has been termed "the systemic effect." This study reports T1 values in sera of human patients from Genoa, Italy, with several types of cancer and non-cancerous diseases. T1 values were significantly elevated over normal controls (1628 +/- 113 ms) in colorectal cancers (1725 +/- 149 ms) and stomach cancers (1817 +/- 219 ms). However a systemic effect was not demonstrated in acute myeloid leukemia, chronic lymphatic leukemia, chronic myeloid leukemia, or plasma cell myeloma, or in pancreatic and lung cancers. Noncancerous states of cirrhosis, chronic hepatitis, and monoclonal gammapathies did not show a T1 elevation. In general, T1 values of sera correlated with protein content of the sera; however, a disproportionate contribution of gamma-globulin protein on water proton relaxation times was observed in several cases.

Distinction between normal and leukemic bone marrow by water protons nuclear magnetic resonance relaxation times

Pulsed nuclear magnetic resonance studies have been carried out on bone marrow of normal human subjects and patients with leukemia: chronic myeloid leukemia (CML) and acute myeloid leukemia (AML). It was observed that the proton spin-lattice relaxation time (T1) value was discriminatory in the normal and leukemic cases with a statistical significance of (p less than 0.01). Ouabain treatment of cells did not show any perceptible change of T1 value when compared with the nontreated cells, indicating that the concomitant cation effluxes do not affect spin-lattice relaxation time. The water contents of normal, leukemic, and ouabain treated cells were in the range 60%-80%. Higher Fe levels were encountered in the normal than the leukemic samples, while levels of Zn, Cu, Mn, Co, and Ni were elevated in the leukemic samples compared with the normals. Despite the T1 differences observed, the multiparameter studies do not uniquely pinpoint factors responsible for the elevation of T1 in the malignant state.

In vivo NMR imaging and T1 measurements of water protons in the human brain

Nuclear magnetic resonance (NMR) proton density images of the human brain have been made by the FONAR method. Spin-lattice relaxation times, T1, of water hydrogen protons have been determined at random positions within frontal and temporal regions of the human brain. The primary purpose of this ongoing research is to accumulate a large data base of normal T1 values for water protons in normal human brain tissue. Our experience to date includes 31 measurements on 18 volunteer subjects, and the mean value +/- standard deviation is 215 +/- 42 msec. In addition, two metastatic lesions of the brain were studied and found to have T1 values longer than those for normal brain tissue.

A review of the magnetic resonance response of biological tissue and its applicability to the diagnosis of cancer by NMR radiology

It is now possible to produce cross-sectional NMR images of humans on a routine basis (52-54). Furthermore, there is a growing body of evidence from studies in vitro indicating that cancerous tissue has a significantly different NMR response from healthy tissue. Provided sufficient knowledge of the density, relaxation times, and their interrelation is available, then the technique of NMR radiology may with care be optimized to give considerable improvement over existing techniques in soft tissue discrimination and tumor detection. However, the first-order correlation of relaxation times with water density does raise the question of the uniqueness of diagnosis. Furthermore, the extrapolation of in vitro measurements to the situation in vivo is seen to be complicated by such factors as blood content, muscle and fluid motion, contributions from fat, and fluid in tissue spaces. Considerable study is required in vivo to resolve these uncertainties.