Twenty-one consecutive patients with MM (15 females, 6 males; median age 68 years, range: 39 – 88 years) participated in the study. The diagnosis of MM and the staging of disease were based on standard criteria [7
]. Four patients had disease stage I, 5 disease stage II and 12 disease stage III. Seventeen patients were entered into the study at first diagnosis of MM (prior to the first administration of chemotherapy or radiotherapy), 4 patients at disease progression. None of the patients had been irradiated in areas of the spine evaluated for myelomatous bone marrow infiltration by MRI or Tc-99m-MIBI scanning.
All patients underwent MRI of vertebrae TH12, L1, L2, L3, L4, L5 and S1. MRI was performed using a 1.0 Tesla Magneton Expert (Siemens) with a spinal coil. Sagittal images included a T1-weighted spin echo sequence and a fat-suppressed T2-weighted fast spin echo sequence. If a finding was ambiguous, the T1-weighted images were repeated after the intravenous injection of gadolinium chelate. All images were classified into two categories: normal findings and myelomatous involvement (focal, diffuse or heterogenous pattern) [1
Anterior and posterior whole body scans (8 min for each projection) were obtained ten minutes, 1 hour, 4 hours and (in four randomly selected patients) 24 hours after the intravenous injection of 555 MBq of Tc-99m-MIBI. A large field of view (LFOV) double head gamma camera (Elscint Helix; Haifa) equipped with a low-energy general purpose collimator was used. Additionally, one hour after tracer application, a posterior spot view of the lumbar vertebral column and pelvic area was performed using a low-energy high resolution collimator. The scans were classified as showing [3
- a normal pattern with only physiological uptake (i.e., heart, liver and spleen),
- a pathologic pattern, with areas of focal tracer uptake and/or diffuse bone marrow uptake.
The two investigators (evaluating either the magnetic resonance images or the images obtained by Tc-99m-MIBI scanning) were blinded with regard to tumor stage and to the findings by the opposite imaging method.
If MRI or Tc-99m-MIBI scanning revealed several pathologic areas in one and the same vertebra of an individual patient, these were counted as one positive finding for the respective examination method.
Mononuclear cells isolated from bone marrow aspirates were available in 16 patients. These cells were stained with two different monoclonal antibodies that recognize different epitopes of the P-glycoprotein in order to evaluate the multi drug resistance as a possible reason for missing Tc-99m-MIBI uptake [8
The study was performed in accordance with the Declaration of Helsinki, amended by the 29th (Tokyo) and 35th (Venice) World Medical Assembly, and in accordance with the pertinent national laws. The protocol was approved by the local ethical committees. Patients gave their informed consent prior to enrollment in the study.