Marrow uptake index (MUI): a quantitative scintigraphic study of bone marrow in aplastic anaemia

Aplastic anaemia affects the entire bone marrow. Current methods of assessment of bone marrow function, like bone marrow biopsy or peripheral blood examination are either invasive or inadequate and cannot be expected to represent fully the changes in the entire bone marrow tissue. This prospective study was undertaken to develop and standardise a new Nuclear Medicine technique called 'Dynamic Bone marrow Imaging'. Eleven patients and ten controls were studied. Serial images of the pelvis were obtained in frame mode following intravenous injection of 185-370 mBq of 99mTc S. Colloid, and an index, called the Bone Marrow Uptake Index (P) was calculated by taking into consideration the time activity curve obtained over the iliac crest. This was followed by static imaging of the entire bone marrow in all cases. It was possible to obtain excellent information regarding topographic distribution of bone marrow as well as detect early changes in bone marrow function following treatment. An attempt was also made to correlate bone marrow cellularity as obtained by bone marrow biopsy with the results of dynamic bone marrow scintigraphy. On the basis of the encouraging results obtained in the present study, the authors feel that dynamic bone marrow imaging is an excellent technique for the objective evaluation of bone marrow in aplastic anaemia. Aplastic anaemia affects the entire bone marrow tissue. Although much progress has been made in the management of this disease, many aspects of it await better understanding. There is almost total lack of knowledge regarding the distribution of functioning marrow in various phases of aplastic anaemia, such as in relapse and remission. Current methods of assessment of marrow function rely mainly on bone marrow biopsy and peripheral blood examination. Bone marrow biopsy is invasive and cannot be expected to represent fully the changes in the entire tissue. Changes in peripheral blood picture lag behind the changes in the bone marrow. Thus, there is a need for an investigation which is safe, simple, sensitive, non invasive and capable of assessing the global function of bone marrow. Radio-nuclide imaging of bone marrow requires labelling of one or more components of this widely dispersed tissue. The reticuloendothelial and erythropoietic components can be labelled with radio-colloids and radio-iron respectively. Experimental studies have shown that the reticuloendothelial and erythropoietic elements are invariably found together in the marrow and have similar distribution. This report is based on a prospective study of bone marrow function in patients with aplastic anaemia, using 99mTc. Sulphur colloid.