Hematopoietic reconstitution after bone marrow transplantation: assessment with MR imaging and H-1 localized spectroscopy

The evolving role of MRI in oncohaematological disorders

Magnetic resonance imaging (MRI) has opened new possibilities to current diagnostic radiology in the evaluation of bone marrow. Compared with other imaging modalities, MRI is the only technique able to directly visualise bone marrow with its different components of red and yellow marrow. Other advantages of MRI are high-contrast resolution and multiplanar view, as well as extensive coverage of the skeleton with whole-body MRI (WBMRI). However, specificity of signal alterations of bone marrow is low. Therefore, MRI findings need to be integrated with clinical and laboratory findings as well as with haematological and oncological evaluation. MRI provides information that effectively aids diagnosis, staging and follow-up of various bone marrow disorders. There is increasing interest in the capabilities of MRI in the evaluation of bone marrow, in particular of haematological malignancies. According to some authors much work remains to be done to improve sensitivity and specificity of MRI in order to define the real clinical value of this imaging modality in the multidisciplinary management of patients with a haematological malignancy. This article presents recent developments and perspectives in the use of MRI in oncohaematological diseases.

Magnetic resonance investigation of bone marrow following priming and stem cell mobilization

PURPOSE

To evaluate application of MRI and magnetic resonance spectroscopy (MRS) to monitor bone marrow cellularity during pretransplant priming with chemotherapy and hematopoietic growth factor (HGF) administration.

MATERIALS AND METHODS

A total of 10 lymphoma and myeloma patients, in remission following induction therapy and considered eligible for high-dose therapy and autologous stem cell transplantation, were included in the study. MR investigation was scheduled four times: at study entry, and one, two, and four weeks following priming. Priming with cyclophosphamide and recombinant human granulocyte colony-stimulating factor (rhG-CSF) started the day after study entry. MR parameters studied in a region of interest were as follows: bone marrow intensity on short-time inversion-recovery (STIR) turbo spin-echo (TSE; thus STIRTSE) and on T1-weighted TSE (T1TSE) images, T2 value for fat component, T2 value for water component, water/fat ratio (W/F), T1 value for fat component, and T1 value for water component.

RESULTS

The results did not support the hypothesis that hematopoietic expansion quantitated and monitored by MR correlates to the level of mobilized progenitor cells.

CONCLUSION

The results indicate that release of stem cells is a more complex phenomenon than hematopoietic expansion and reduction of fat tissue in bone marrow.

Proton MR spectroscopy of the femoral head—Evaluation of patients at risk for avascular necrosis

PURPOSE

To detect alteration of the fatty component by measuring the in vivo lipid and water content of normal-looking femoral heads of patients with and without risk for avascular necrosis (AVN) by using proton MR spectroscopy (MRS).

MATERIALS AND METHODS

Marrow composition was measured by proton MRS (TR/TE = 5000/20 msec) in a sample volume placed in the epiphysis of the intact femoral heads of patients with unilateral osteonecrosis of the hip (group 1, N = 61, then excluding the post-traumatic or steroid user, final N = 45) and age-matched controls (group 2, N = 49). Three response variables were derived from MRS: the lipid linewidth (LW), water LW, and lipid/water ratio.

RESULTS

Of the three variables, the lipid and water LWs differed significantly between groups (P < 0.001 and P = 0.05, respectively; t-test). The lipid/water ratio had borderline significance (P = 0.06). The three variables differed significantly between groups when multivariate regression (P < 0.0001) was analyzed; and age and sex had no significant effect on the three dependent variables.

CONCLUSION

Proton MRS can depict alteration in the lipid and water composition of normal-looking femoral heads with and without AVN on the contralateral hip. Proton MRS may be a potential tool for investigating of the femoral head component in vivo and predicting the risk for development of AVN.

Fat fractions and spectral T2 values in vertebral bone marrow in HIV- and non-HIV-infected men: a 1H spectroscopic imaging study

Fat fractions and spectral T2 values of fat and water within the vertebral marrow of non-HIV- and HIV-infected men were measured with the use of a Carr-Purcell-Meiboom-Gill (CPMG) line scan spectroscopic imaging sequence. The fat fraction for the HIV-infected men (0.29 +/- 0.08) was significantly lower (P < 0.05, Student's unpaired t-test) than the fat fraction found in non-HIV-infected men (0.40 +/- 0.12). The mean water and fat T2 values did not differ between the two groups, and did not show any systematic dependence on fat fraction over the wide range of fat fractions encountered in this study. The marrow water and fat T2 values measured with the CPMG approach were markedly longer than the spectral T2 values reported by other groups using the more common point-resolved spectroscopy (PRESS) and stimulated-echo acquisition mode (STEAM) acquisitions. Proton spectroscopic studies of vertebral marrow revealed differences between non-HIV- and HIV-infected men that may prove useful for studying the effects of this disease and/or antiretroviral agents on body composition.

Vertebra disc ratio as a parameter for bone marrow involvement and its application in Gaucher disease

OBJECTIVE

To establish the vertebra disc ratio (VDR), the ratio of the average T1-weighted gray value of disc L3 and intervertebral disc L3/L4, as a parameter for bone marrow involvement. To explore its value as alternative for bone marrow fat fraction measured with Dixon Quantitative Chemical Shift Imaging (Ff) in Gaucher disease (GD).

METHODS

Age dependency and normal value for the VDR were determined in 46 controls. The VDR in untreated GD (n = 22) and long-treated GD (7.5 years; n = 19) were compared with it. The changes in VDR in treated (n = 33) and untreated (n = 8) GD were calculated. The correlation between VDR and Ff was determined.

RESULTS

Age dependency was small. The normal VDR was 1.90 +/- 0.30, both untreated GD (1.29 +/- 0.31) and long-treated GD (1.70 +/- 0.33) differed significantly from normal. Changes in treated GD were significant in the first four treatment years, in untreated GD they were not. The correlation with Ff was 0.86.

CONCLUSIONS

The VDR is a useful parameter for evaluation of bone marrow of patients with GD. The VDR correlates very well with Ff, so applicability is expected in diseases in which Ff has proven to be useful.

Proton MR spectroscopy of the lumbar spine in patients with glycogen storage disease type Ib

Glycogen storage disease type Ib is an autosomal recessive inherited metabolic disorder resulting from deficiency of the microsomal glucose-6-phosphatase enzyme system. Six patients (three of which were treated with granulocyte colony stimulating factor) suffering from this disease were examined using image guided localized proton magnetic resonance (MR) spectroscopy. The relative signal intensities of water and lipid protons of the lumbar spine were determined. Comparison was made with iliac crest biopsies in the glycogen storage disease type Ib patients and localized proton MR spectroscopic values of the lumbar spine obtained by thirteen healthy volunteers. The data demonstrate for the first time that hypercellularity and myeloid hyperplasia in subjects with glycogen storage disease type Ib due to functionally impaired leucocytes results in a strongly increased water proton signal with a very low or absent lipid signal in localized proton MR spectroscopy. Upon granulocyte colony stimulating factor treatment, the water proton signal in the lumbar spine is not further augmented.

Age- and sex-specific differences in the 1H-spectrum of vertebral bone marrow

Correct interpretation of 1H magnetic resonance (MR) studies of the red vertebral bone marrow in patients with disorders of the hematopoietic system requires knowledge of the dependence of the proton spectrum on age and sex. Infiltration of malignant cells causes a decreased red bone marrow fat signal, which is reversed upon successful treatment. The aim of this study was to establish a database of normal water/fat relations from a large group of volunteers. In all, 154 healthy volunteers from 11 to 95 years of age were examined using a 1.5-T MR system (ACS-NT, Philips). A volume of 2-8 ml in the center of a normal vertebral body was selected for spectroscopy using the PRESS sequence without water suppression (TR/TE 2 sec/40 msec). Signal intensities and T2 times of lipid and water resonances were determined. The relative fat signal intensity was calculated corrected for T2 relaxation. The relative proportion of protons in the fat signal increases with age from 24% in the age group 11-20 years to 54% in the group > or = 61 years. The proportion of fat in the vertebral bone marrow in female subjects is less than that in male subjects in the same age group (statistically significant at P < or = 0.01). In the central age group between 31 and 50 years, the difference is largest, at 12%; in the youngest and oldest age group this difference is small. T2 times are neither age nor sex dependent.

Prospective evaluation of bone marrow signal changes on magnetic resonance tomography during high-dose chemotherapy and peripheral blood stem cell transplantation in patients with breast cancer

RATIONALE AND OBJECTIVES

The authors evaluate bone marrow signal changes on magnetic resonance (MR) imaging during high-dose chemotherapy and peripheral blood stem cell transplantation (PBSCT).

METHODS

Fourteen patients with breast cancer without bone metastases underwent four sagittal MR imaging studies with T1-weighted, T2-weighted turbo spin-echo and inversion recovery sequences with short inversion time (STIR) of the lumbar spine: (1) during initial staging, (2) prior to high-dose chemotherapy after two cycles of induction chemotherapy, (3) early after PBSCT with a leukocyte exceeding 2000/microL, and (4) 6 to 8 weeks after PBSCT. Signal intensity ratios of averaged lumbar bone marrow to nucleus pulposus were measured and homogeneity was evaluated visually using a semiquantitative score.

RESULTS

Compared with the initial finding (1): Signal intensity ratios were altered significantly at (2): T1-weighted: -22% +/- 14, P < 0.001; T2-weighted: -11% +/- 11, P < 0.01; STIR: +33% +/- 31, P < 0.01; Signal intensity ratios were altered significantly at (3): T2-weighted: -23% +/- 12, P < 0.001, STIR: -22% +/- 23, P < 0.01; and Signal intensity ratios were altered significantly at (4): only STIR: -16% +/- 19, P < 0.01. Homogeneity scores decreased at (3) for T1-weighted and STIR sequences (-1.6 +/- 0.5 to -2.0 +/- 0.7, P < 0.01 and -1.0 +/- 0.5 to -1.4 +/- 0.5, P < 0.01, respectively) and at (4) for the latter sequence (-1.0 +/- 0.5 versus -1.4 +/- 0.5, P < 0.01). At (4), T1-weighted images were less homogenous than initially in 3 of 14 (21%) patients.

CONCLUSIONS

Magnetic resonance imaging demonstrates significant alterations of bone marrow composition during PBSCT but allows differentiation of benign therapy-related changes from those known in metastatic disease after completion of PBSCT.

Human in vivo comparative study of zinc and copper transmetallation after administration of magnetic resonance imaging contrast agents

RATIONALE AND OBJECTIVES

The authors compare in vivo transmetallation of three magnetic resonance contrast agents in humans in terms of their kinetic stability.

METHODS

Blood and urine samples were taken before and after the intravenous injection of gadolinium (Gd)-HP-DO3A, Gd-DTPA, or Gd-DTPA-BMA at 0.1 mmol/kg to healthy volunteers. Serum and urine were assayed for zinc, copper, and Gd, using inductively coupled plasma atomic emission spectrometer.

RESULTS

Gadolinium-DTPA-BMA caused the highest increase in zinc excretion among the three agents. Gadolinium-HP-DO3A did not cause a significant increase in zinc excretion. In serum, although Gd-DTPA-BMA exhibited a decrease in zinc concentration, the difference between the drugs was not statistically significant.

CONCLUSIONS

The difference in observed zinc excretion among the chelates studied reflects in vivo transmetallation of the magnetic resonance contrast media and correlates with the respective kinetic inertia for transmetallation, rather than thermodynamic stability constants. Gadolinium-HP-DO3A was found to be the most kinetically inert among the three drugs tested.

Proton MRS in Pott's spine--a case report

Proton Magnetic Resonance Spectroscopy was carried out at 1.5 T on a patient with histologically proven Pott's spine affecting D11 vertebral body. In addition to the significantly reduced signals from the lipids in the region between 1 and 2 ppm, a prominent resonance at 5.1 ppm is seen. The spectrum is very different from that recorded on the one hand for a normal spine and, on the other, for a tumor arising from the vertebral body of a patient.

Magnetization transfer in hemopoietic bone marrow examined by localized proton spectroscopy

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.

Characterization of bone marrow after transplantation by means of magnetic resonance

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.