CT-Guided Bone Aspiration Target
In CT-guided bone aspiration, the target is the deep bone marrow cavity, not the superficial cortical bone—the needle must penetrate through the cortical bone to reach the marrow space where diagnostic cellular material resides. 1, 2
Technical Approach and Anatomic Target
The procedure requires advancing the needle through the outer cortical bone into the medullary cavity to obtain adequate marrow specimens. 2 The cortical bone is merely the barrier that must be traversed, not the diagnostic target itself.
Key Technical Considerations
CT guidance significantly improves specimen adequacy compared to blind procedures, with 95% of CT-guided biopsies yielding adequate samples versus 79% for blind procedures (p = 0.0006). 2
The needle must penetrate the cortex completely to access the marrow space—specimens that remain subcortical are a common cause of inadequate biopsies. 3
Optimal needle depth extends 20-25 mm beyond the cortical penetration point to ensure adequate marrow sampling, as aspirating immediately after cortical penetration often results in specimens denuded of bone marrow cells. 4
Common Technical Pitfalls
Subcortical sampling is the most frequent cause of inadequate specimens in manual procedures (4/6 inadequate cases), occurring when the needle fails to fully penetrate the cortex into the marrow cavity. 3
Aspiration artifact increases when the needle is not properly positioned in the marrow space, with powered devices showing >10% aspiration artifact in 25/31 cases when technique is suboptimal. 3
Thick cortical bone (>13% of cases) can impede adequate penetration, making CT guidance particularly valuable for procedure planning and confirming proper needle placement in the marrow cavity. 2
Anatomic Variations Requiring CT Guidance
CT imaging identifies anatomic features that complicate blind procedures and necessitate image guidance for successful marrow access:
- Slanted posterior ilium (angle >30°) occurs in 30% of patients 2
- Rounded posterior ilium in 20% of cases 2
- Thick posterior ilium cortex in 13% of patients 2
- Posterior soft tissue thickness >3 cm in 40% of cases 2
These variations make CT guidance essential for confirming that the needle has successfully traversed the cortex and reached the marrow cavity, particularly in patients with higher BMI or increased soft tissue thickness. 2