Assessment of bone marrow blood flow using positron emission tomography: no relationship with bone marrow cellularity

Bone marrow MR perfusion imaging and potential for tumor evaluation

The physiology of bone perfusion is reviewed outlining how it can be measured with dynamic contrast-enhanced MRI as well as intravoxel incoherent imaging. Evaluation of bone perfusion provides a potential means of assessing tumor activity and treatment response beyond that possible with standard MR imaging.

Characterizing the Bone Marrow Environment in Advanced-Stage Myelofibrosis during Ruxolitinib Treatment Using PET/CT and MRI: A Pilot Study

Current diagnostic criteria for myelofibrosis are largely based on bone marrow (BM) biopsy results. However, these have several limitations, including sampling errors. Explorative studies have indicated that imaging might form an alternative for the evaluation of disease activity, but the heterogeneity in BM abnormalities complicates the choice for the optimal technique. In our prospective diagnostic pilot study, we aimed to visualize all BM abnormalities in myelofibrosis before and during ruxolitinib treatment using both PET/CT and MRI. A random sample of patients was scheduled for examinations at baseline and after 6 and 18 months of treatment, including clinical and laboratory examinations, BM biopsies, MRI (T1-weighted, Dixon, dynamic contrast-enhanced (DCE)) and PET/CT ([¹⁵O]water, [¹⁸F]NaF)). At baseline, all patients showed low BM fat content (indicated by T1-weighted MRI and Dixon), increased BM blood flow (as measured by [¹⁵O]water PET/CT), and increased osteoblastic activity (reflected by increased skeletal [¹⁸F]NaF uptake). One patient died after the baseline evaluation. In the others, BM fat content increased to various degrees during treatment. Normalization of BM blood flow (as reflected by [¹⁵O]water PET/CT and DCE-MRI) occurred in one patient, who also showed the fastest clinical response. Vertebral [¹⁸F]NaF uptake remained stable in all patients. In evaluable cases, histopathological parameters were not accurately reflected by imaging results. A case of sampling error was suspected. We conclude that imaging results can provide information on functional processes and disease distribution throughout the BM. Differences in early treatment responses were especially reflected by T1-weighted MRI. Limitations in the gold standard hampered the evaluation of diagnostic accuracy.

The value of bone marrow, liver, and spleen imaging in diagnosis, prognostication, and follow-up monitoring of myeloproliferative neoplasms: a systematic review

Background

Diagnostic and treatment response criteria for the JAK2/CALR/MPL mutation-related myeloproliferative neoplasms (MPNs) are largely based on bone marrow (BM) biopsy results. However, these biopsies have several limitations, such as the risk of sampling error. Also, the prognostic impact of BM abnormalities is largely unclear. Although not currently used in clinical practice, imaging techniques might offer additional information. In this review, we investigated the value of BM, liver, and spleen imaging for diagnosis, prognostication, and response monitoring of the JAK2/CALR/MPL mutation-related MPNs (i.e. essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF)).

Methods

A systematic literature search was performed via PubMed, Embase and the Cochrane Library up to 2020 March 26th. Of 5505 identified records, 55 publications met the eligibility criteria (i.e. containing original data on the imaging appearance of BM, spleen, or liver in adult ET, PV, or MF patients, published in a peer-reviewed journal, written in English).

Results

Many explorative studies described imaging features, sometimes with comparisons to clinical characteristics. Studies reporting measures of diagnostic accuracy included 1) splenic transient elastography to predict BM fibrosis grade in MF, 2) dynamic contrast-enhanced MRI to discern MF patients from ET patients and healthy controls, and 3) 18-fluorodeoxyglucose PET to detect residual disease after stem cell transplantation in MF. The diagnostic accuracies of radiography and ^99mTc-colloid scintigraphy were derived from several other articles. Except for the study on 18-fluorodeoxyglucose PET, we established substantial concerns regarding risk of bias and applicability across these studies, using the QUADAS-2 tool. Three publications described a correlation between imaging results and prognosis, of which one quantified the effect.

Conclusions

Based on current data, MRI (T1-weighted/STIR, Dixon) seems especially promising for the evaluation of BM fat content - and indirectly cellularity/fibrosis - in MF, and possibly for estimating BM cellularity in ET/PV. 18-fluorodeoxyglucose and 18-fluorothymidine PET/CT might be useful for evaluating BM fibrosis, with good reported accuracy of the former for the diagnosis of residual disease. Further research on these and other techniques is warranted to determine their exact value. Future researchers should improve methodology and focus on evaluation of diagnostic accuracy and prognostic implications of results.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40644-021-00405-7.

Review: tissue engineering: reconstitution of human hematopoiesis ex vivo

The reconstruction of functioning human tissues ex vivo is becoming an important part of biotechnology. There are compelling scientific, clinical, and biotechnological reasons for fully or partially reconstituting human tissues such as skin, bone marrow, and liver ex vivo. In particular, bone marrow is a tissue of much importance, and there are significant societal and health benefits derived from a successfully constructed ex vivo hematopoietic system. In this article, we review the current status of this effort. The topics covered include the current understanding of the biology of human hematopoiesis, the motivation for reconstructing it ex vivo, the current state of ex vivo human hematopoietic cultures, the development of important metrics to judge culture performance, and an approach based on in vivo mimetics to accomplish this goal. We discuss some applications of functional ex vivo hematopoietic cultures and the biological and engineering challenges that face research in this area.

Bone marrow hypervascularity in patients with myelofibrosis identified by infra-red thermography

Infra-red thermography was used to assess bone marrow vascularity in six patients with myelofibrosis secondary to myeloproliferative disorders (four primary myelofibrosis and two primary proliferative polycythaemia). The technique was evaluated with conventional static and dynamic radio-isotopic imaging and with immunohistochemical staining of bone marrow biopsies. Infra-red thermography identified increased bone marrow blood flow in patients with established myelofibrosis and correlated with dynamic radio-isotopic studies of blood flow and hypervascularity identified by immunohistochemistry. Increased bone marrow blood flow and vascular proliferation was not confined to the central bone marrow but also extended into the peripheral marrow of the long bones. Endothelial cell proliferation may be an initiating event in the pathogenesis of myelofibrosis but evaluation of bone marrow vascularity and blood flow has hitherto relied on invasive and complicated techniques. This study has identified bone marrow hypervascularity in patients with myelofibrosis and shown infra-red thermography to be a simple non-invasive method of assessing vascularity. This non-invasive technique may be used to study disease progression and response to therapeutic regimens in patients with myelofibrosis and to study bone marrow blood flow in other bone marrow disorders.

Age-related changes in the hemodynamics of the femoral head as evaluated by early phase of bone scintigraphy

OBJECTIVE

The femoral head is reported to be in a markedly hypoemic state as compared with other tissues even under normal conditions, and it is therefore necessary to understand its hemodynamics to investigate the pathogenesis of hip disorders. It is known that aspects of intraosseous hemodynamics including blood flow and blood pool can be evaluated soon after radioisotope administration. In this study, hemodynamic changes in the femoral head according to gender and age were examined by investigating accumulation of radioisotope in the tissue during the early phase of bone scintigraphy.

METHODS

The subjects of this study consisted of 58 joints of 31 men and 75 joints of 41 women, whose ages ranged from 15 to 87 years (average age: 67.9 years). Images of bone scintigraphy were obtained for 15 to 20 minutes at 5 minutes and at 3 hours after radioisotope administration. The ratio of accumulation in the femoral head to that in the diaphysis (head-to-diaphysis ratio, HD ratio) was calculated.

RESULTS

HD ratios obtained 15-20 minutes later ranged from 0.01 to 7.35 (1.88 +/- 0.91, mean +/- SD). HD ratios decreased with age, and a significant inverse correlation was observed between age and HD ratio, demonstrating a correlation coefficient of -0.27 (p = 0.001). The HD ratio among men was 0.01-3.57 (1.66 +/- 0.71), while that among women was 0.53-7.35 (2.05 +/- 1.01), and a significant difference was observed in HD ratio between men and women (p = 0.02). There was a significant difference in HD ratios between men and women in their teens to forties (p = 0.03), while no significant differences was observed in the other age groups.. HD ratios obtained 3 hours later ranged from 0.44 to 6.32 (1.95 +/- 0.79, mean +/- SD), and no significant correlation was observed between age and HD ratio, demonstrating a correlation coefficient of -0.14.

CONCLUSION

The present study demonstrated that blood flow and blood pool of the femoral head decrease with aging particularly in women. This hemodynamic deterioration of the femoral head caused by aging may have an effect on the onset and progression of hip disorders by influencing bone metabolism.

Blood flow and blood volume in the femoral heads of healthy adults according to age: measurement with positron emission tomography (PET)

OBJECTIVE

To deepen understanding of hemodynamics in the femoral head, i.e., the essential factor in clarifying pathogenesis of hip disorders, this study examined blood flow and blood volume in the femoral heads of healthy adults, and their changes with age, by using positron emission tomography (PET).

METHODS

In 16 healthy adult males (age: 20-78 years old, mean age: 42 years), blood flow was measured by means of the H2(15)O dynamic study method, and blood volume was measured by means of the (15)O-labeled carbon monoxide bolus inhalation method.

RESULTS

Blood flow was 1.68-6.47 ml/min/100 g (mean +/- SD: 3.52 +/- 1.2), and blood volume was 1.67-6.03 ml/100 g (mean +/- SD: 3.00 +/- 1.27). Blood flow significantly decreased (p < 0.01) with age, and blood volume significantly increased (p < 0.05).

CONCLUSION

PET was useful in the measurement of blood flow and blood volume in the femoral heads. With age, physiological hemodynamic changes also increased in femoral heads.

Measurement of bone marrow blood volume in the knee by positron emission tomography

Positron emission tomography was used to measure bone marrow blood volume (BBV), an important hemodynamics parameter, in the knee. The subjects were 11 healthy male volunteers (mean age, 23.6 years; range, 21-27 years). The 15O-labelled carbon monooxide (C15O) single-breath inhalation method was used. In the distal femur, regional (r) BBV in the posterior area of the epiphysis (medial, 2. 25 ml/100 cm3 bone marrow; lateral, 2.03 ml/100 cm3) was significantly less than that in the anterior area of the epiphysis (medial, 3.48 ml/100 cm3; lateral, 3.01 ml/100 cm3) and that in the metaphysis-to-distal diaphysis (2.90-3.67 ml/100 cm3). In the proximal tibia, rBBVs in the metaphysis-to-proximal diaphysis (2. 32-2.76 ml/100 cm3) were significantly less than those in the area of the physis (medial, 3.30 ml/100 cm3; lateral, 3.53 ml/100 cm3). These regional differences in rBBV within the knee may be associated with the development of ischemic bone marrow disorders, such as steroid-induced osteonecrosis, in the knee.

Determination of specific oxygen uptake rates in human hematopoietic cultures and implications for bioreactor design

Oxygen plays an important role in the cultivation of primary cells ex vivo. In this study, we used hermetically sealed tissue culture well inserts equipped with oxygen electrodes to measure the oxygen utilization of cultured human bone marrow mononuclear cells (BM MNCs). The oxygen uptake rate (OUR) of BM MNCs was determined during a 14-day culture in which both adherent and nonadherent cells were present. Early in the culture, the cells exhibited very low OURs. The specific OURs (uptake rate per cell) were at approximately 0.005 mumol/10(6) cells/hr shortly after the initiation of culture. The OUR then increased as the cultures developed. After about 8 to 10 days of cultivation the specific OURs had increased to 0.038 +/- 0.006 and 0.025 +/- 0.005 mumol/10(6) cells/hr for adherent and nonadherent cells, respectively, after which no further increase was observed. Based on these oxygen uptake rate data, a mathematical model of oxygen diffusion was formulated and use to investigate issues associated with hematopoietic bioreactor design, including initial cell density, medium depth, reactor configuration, and oxygen partial pressure. In situ OUR measurements confirmed predicted oxygen limitations based on the mathematical model and the experimentally determined OURs. High-density hematopoietic cultures present design challenges in terms of sufficient and uniform delivery of oxygen to an active hematopoietic culture. These challenges can be met by using parallel-plate bioreactors with thin liquid layers.

The measurement of blood flow in humans using radioactive tracers

Since the first description of the movement of blood around the body by William Harvey, the accurate measurement of blood velocity has provided a major challenge for medical science. This review looks at the contribution made by techniques using radioactive tracers. Initially consideration is given to the fundamental problem of how to measure the amount of radiotracer in an organ with sufficient accuracy, using both single-photon and positron-emitting tracers. The various models used to link tracer behaviour with blood flow are then discussed and the article closes with a detailed review of the clinical applications of blood flow measurements.

Decreased blood flow to rat bone marrow, bone, spleen, and liver in acute leukemia

An acute promyelocytic leukemia in the rat (BNML) has been used in model studies on pathogenesis and therapy of human acute myeloid leukemia. The blood supply to bone marrow during BNML development has hitherto not been examined, even though in general, blood flow to hematopoietic tissues might affect drug treatment and marrow transplantation regimes. We measured the perfusion of various organs during the course of the disease in untreated rats and in rats given one injection of cyclophosphamide treatment. Organ perfusion was measured with radioactive microspheres. Blood flow per gram tissue to the bone marrow, bone, spleen, and liver declined gradually during the leukemic progression, thus paralleling the growth of leukemic deposits. Cyclophosphamide treatment retarded, but did not reverse, the decreasing perfusion of these tissues.

Rapid medium perfusion rate significantly increases the productivity and longevity of human bone marrow cultures

Long-term in vitro human hematopoietic (Dexter) cultures are limited both in their longevity (8-12 weeks) and in their cell production over time. Hematopoiesis in vivo continues unabated throughout life, suggesting that failure to obtain continuous hematopoiesis in vitro is probably due to the failure of culture conditions to accurately reproduce the in vivo state. Since bone marrow cells in vivo exist at high density and are rapidly perfused by plasma components, we examined the effects of the culture medium perfusion rate and inoculum density on longevity and productivity of human bone marrow cultures. Culture efficiency and longevity were relatively independent of the variation in inoculum density from 10(6) to 5 x 10(6) cells per ml but were significantly altered by the medium perfusion rate. Increased culture perfusion was superior to traditional Dexter schedules, with 0.5 medium volume exchange per day (3.5 volume per week) being optimal. The cultures under these conditions demonstrated an increasing rate of cell production from weeks 4 to 10, with the cell production rate doubling approximately every 2 weeks. Following weeks 10-12 in culture, the cell production rate of all cultures decayed. Production of nonadherent progenitor cells was also highest in cultures perfused at 3.5 medium volume exchanges per week, where progenitor cell production was stable from weeks 6 to 18. The nonadherent cells collected were predominantly macrophages by week 19, except for the cultures perfused at a rate of 3.5 volumes per week and seeded at 5 x 10(6) cells per ml, in which production of granulocytes remained high through week 19. Establishment of more optimal perfusion conditions supports the continuous stable generation of progenitor cells over 5 months in culture, suggesting that primitive stem cells are surviving and proliferating in these cultures.

Culture perfusion schedules influence the metabolic activity and granulocyte-macrophage colony-stimulating factor production rates of human bone marrow stromal cells

The metabolic function and GM-CSF production rates of adherent human bone marrow stromal cells were investigated as functions of medium and serum feeding rates. A range of medium exchange schedules was studied, ranging from a typical Dexter culture protocol of one weekly medium exchange to a full media exchange daily, which more closely approximates what bone marrow cells experience in situ. Glucose consumption was found to be significantly higher at full daily exchange rate than at any other exchange schedule examined. However, the lactate yield on glucose was a constant, at 1.8 mol/mol, under all conditions considered. Differential serum vs. medium exchange experiment showed that both serum supply and medium nutrients were responsible for the altered behavior at high exchange rates. Glutamine consumption was found to be insignificant under all culture conditions examined. A change in exchange schedule from 50% daily medium exchange to full daily medium exchange after 14 days of culture was found to result in a transient production of GM-CSF and a change in metabolic behavior to resemble that of cultures which had full daily exchange from day one. These results suggest that both stromal cell metabolism and GM-CSF production are sensitive to medium exchange schedules. Taken together, the data presented indicate that attempts to model the function of human bone marrow in vitro may be well served by beginning with medium exchange schedules that more closely mimic the in vivo physiologic state of bone marrow.

Recent advances in bone marrow scanning

Interest in bone marrow scanning has been renewed as the result of the development of radiopharmaceuticals for evaluating specific aspects of bone marrow anatomy, physiology and pathology. This article provides a brief review of bone marrow structure, blood flow and function essential to the understanding of basic principles of bone marrow radionuclide imaging. The prospects and limitations of imaging haematopoietic bone marrow in man using indium 111 chloride, technetium-99m (99mTc)-labelled microcolloid or 99mTc-labelled monoclonal antigranulocytic and antimyelocytic antibodies are discussed in more detail. The technical aspects of bone marrow scintigraphy are presented. Results of more recent studies evaluating bone marrow scanning in circulatory, inflammatory and in systemic haematological disorders are summarized. Special attention is paid to the concept of bone marrow micrometastases and its implications for the follow-up of patients with malignant tumours. Recent results suggest that immunoscintigraphy of bone marrow may provide a novel and sensitive approach for establishing the presence and extent of bone marrow infiltration.