For Clinicians

Bone Case 1 Answers

1) Name the radiopharmaceutical

Imaging is achieved using 99Tcm-labelled diphosphonates (e.g. MDP) which become incorporated into the hydroxyapatite crystal matrix as new bone is formed. Uptake in bone is dependent on local blood flow and the degree of osteoblastic activity.

600MBq is the usual amount for adult with a scaled dose for children dependent on body weight. Up to 800MBq may be given for SPECT studies

2) Describe how imaging is performed

The patient should be well hydrated by drinking at least one litre of fluid between injection and imaging. The patient should be void their bladder immediately prior to imaging; and if a catheter is present, the bag should be emptied before imaging.

Images should be obtained no earlier than 2-3 hours after injection. Either whole body imaging or multiple overlapping spot images may be obtained. If spot views are chosen, the anterior and posterior pelvic images should be acquired first, in order to minimize bladder activity. Minimum technique should include anterior and posterior views of the axial skeleton and proximal limbs. Distal limbs should be included if clinically indicated.

Where bladder activity obscures pelvic structures, lateral or squat views may be obtained or a further post-void image undertaken. If the patient is unable to empty the bladder, masking the retained urinary activity with lead shielding will allow improved detail in the rest of the pelvis.

3) Are there any abnormal areas of uptake?
4) If so, where?

This is a normal scan. Note normally raised uptake within the breast tissue. Compare the clarity of the visualization of the ribs in this slender female with the appearances of this larger male simply due to overlying soft tissue.

5) When is it appropriate to perform bone scintigraphy when staging patients with breast cancer?

There is little point in performing bone scintigraphy on asymptomatic patients with early stage (i.e. small) breast tumours with no obvious metastases, as incidence of metastases is very low. Certainly those with higher-grade tumours, higher stage tumours ± nodal spread have a much higher incidence of bony metastatic disease. Any patient with symptoms should have bone scintigraphy irrespective of stage or grade as it is more sensitive than plain films. The role of staging with PET and MRI is not entirely clear and currently reserved for problematic cases, particularly for defining disease in the vertebral column or when there are single, equivocal bony lesions.

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The text is entirely the opinion of the author and does not necessarily reflect that of RUH NHS Trust or the Bristol Radiology Training Scheme. Website content devised by Paul McCoubrie.