No abstract

Magnetic resonance (MR) has become a new tool for noninvasive characterization of bone marrow in patients with hematological disorders in the past few years. Experiences gained from 1H MR imaging and spectroscopic investigations in 48 healthy volunteers and more than 130 patients with hematological disorders are reported and interpreted. Twenty-four of the patients underwent bone marrow transplantation (BMT) before the MR examinations. The findings in these studies provided noninvasive characterization and monitoring of vertebral marrow after BMT. Specifically, MR techniques were found to be suitable for studies of different aspects in physiological and pathological alterations of bone marrow: The water content within the marrow can be analyzed by chemical-shift selective-imaging techniques with good spatial resolution. Spectroscopic methods also allow more sensitive quantification of the signal fractions, as well as separate evaluation of the relaxation times of water and lipids. Relaxometry might be useful to characterize the cellular and extracellular portions of water molecules. Furthermore, the distribution of the magnetic field within small-volume elements of vertebral marrow can be measured. The field distribution is influenced by the trabecular density and the composition of the marrow. High amounts of hemosiderin in the marrow result in clearly broadened field distributions, demonstrated by increasing line widths in MR proton spectra. Magnetic resonance techniques can be used to assess not only the cellularity of the bone marrow, but also metabolic alterations in this compartment which result from cytotoxic treatment or immunological processes.

Lumbar bone marrow was assessed by means of magnetic resonance (MR) in 23 examinations of eight patients who underwent autologous bone marrow transplantation (ABMT) or peripheral blood stem cell transplantation (PBSCT). Various imaging and spectroscopic techniques were applied for measurements carried out prior to conditioning for ABMT/PBSCT and in the course of reconstitution and correlated with clinical and blood chemistry data in these patients. The signal intensity from lumbar bone marrow was determined in T1-weighted and water- and fat-selective MR images. The distribution of the magnetic field was demonstrated by a field-mapping method. Localized proton spectroscopy was performed from volume elements of 2 ml located in the central region of vertebral bodies in order to evaluate the fraction of the water signals, the transverse relaxation times T2 of the signals from water and lipids, and the line widths of the spectral signals. Regions of bone marrow after inflammatory conditions or intensive irradiation are shown to be not involved in marrow reconstitution. Additional information about marrow composition was obtained by the magnetic field mapping and by the line widths in the spectra. Considerable alterations of the amount of paramagnetic hemosiderin were revealed following transplantation. Patients with low water signal and strong local inhomogeneities of the magnetic field in the marrow prior to transplantation had a delayed hematopoietic reconstitution compared with the patients lacking these MR features.

The sensitivity of hemopoietic bone marrow to magnetization transfer is analyzed in 15 healthy volunteers and seven patients with different hematological disorders (inflammation, plasmacytoma, hemopoietic reconstitution after bone marrow transplantation). To obtain sufficient signal-to-noise ratio, a 90 degrees - 180 degrees - 180 degrees double spin echo (PRESS) single voxel spectroscopic method was combined with pulsed magnetization transfer. Several spectra were recorded from each volume element inside the vertebral marrow, alternately with and without prepulses for magnetization transfer. Water signals from marrow with increased content of extracellular water due to inflammation or edema revealed less magnetization transfer effects than marrow with increased intracellular water content due to high cellularity. The preliminary results show magnetization transfer to be a promising tool for the clinically important characterization of the water composition in red bone marrow.

Blood products should be irradiated during allogeneic stem cell transplantation and before performing autologous stem cell harvest for prevention of acute transfusion-associated graft-versus-host disease (TA-GVHD). Usually, irradiation of all blood products is continued lifelong in the allogeneic setting. Up to now, no broadly accepted rules exist concerning autologous stem cell transplantation. We present here the results of an inquiry sent to 47 German transplantation centers regarding the transfusion policy following autologous stem cell transplantation. The results of 35 answering centers are included. Ten out of 35 centers offer irradiated blood products lifelong to their patients, mainly for the prevention of mistransfusion of non-irradiated blood components to allogeneic recipients. Twenty-two out of 35 centers administer irradiated blood products for a special time span after autologous stem cell transplantation. In most centers, this time span is from 3 to 6 months. Only few centers (4/35) expand this time span to 1-2 years after transplantation. A minority of centers (3/35) gave non-irradiated blood products to all of their patients or to patients not suffering from acute leukemia or after total body irradiation (TBI) containing preparative regimens. Most centers (19/35) deliver irradiated blood products irrespective of the conditioning regimen. Fifty-three percent of the centers decide to donate irradiated blood products not depending on immunological reconstitution. But in most centers some kind of hematological reconstitution is a major criterion for termination of irradiated blood products. Sixty-four percent of the centers made no difference in transfusion policy in regard to the underlying disease. No center experienced cases of proofed TA-GVHD. Guidelines should be worked out concerning transfusion policy after autologous stem cell transplantation.