Magnetic Resonance Imaging

Many investigators consider magnetic resonance imaging (MR; Table 10.3) the imaging modality of choice in the initial evaluation of NB (Siegel et al. 2002; Sofka et al. 1999). Magnetic resonance has distinct advantages over CT including (a) the absence of ionizing radiation, (b) the ability to evaluate neural foraminal and epidural involvement, and (c) the ability to detect bone marrow disease. In addition, MR is ideal for defining the precise extent of skeletal in volvement, separating cortical bone from marrow involvement. Furthermore,invasion of the liver,kidney, and abdominal organs can readily be detected by MR imaging. This is particularly important in large, right-sided masses where separation of the mass from liver or kidney may be difficult by CT. By imaging in multiple planes, MR can usually demonstrate the relationship of the mass to adjacent organs. Gadolinium-enhanced scans can provide additional information in these cases (Kornreich et al. 1991). On MR neuroblastoma characteristically has prolonged

Table 10.4. Technetium-99m bone scintigraphy

Bone scanning principles

Image entire body with particular attention to patient position: knees and elbows should be as flat as obtainable to assess peri-articular uptake

Bladder should be empty for adequate visualization of the pelvis. In small children this may require bladder catheterization (if it can be safely done) or delayed images after voiding.

Scan technique

Intravenous injection of 25 mCi Tc-99m-MDP/1.73 m2, imaging begun 2-3 h after injection

Multi-headed gamma camera with low-energy collimator preferred

Computer acquisition

Single photon emission CT as needed

T1 and T2 relaxation times, demonstrating heterogeneous low signal on T1 and high signal on T2. Bright signal in the mass on T1-weighted imaging sequences represents hemorrhage. Although calcifications are not as readily identified on MR as on CT, they are visualized as areas of signal void. Nevertheless, non-visualization of calcifications should not be a significant deterrent to using MR for the initial evaluation of NB.

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