Image guidance can be accomplished with several different modalities. These include fluoroscopy, computed tomography, computed tomography combined with a multidirectional fluoroscope, computed tomographic fluoroscopy, and magnetic resonance imaging.8 The choice of equipment is determined by its availability, operator preference, and by the location and size of the suspected lesion. A CT-guided spine biopsy can be performed without or with the use of a stereotactic apparatus to guide the insertion of the biopsy needle.9-11 The use of MRI requires the simultaneous use of MR-compatible equipment, both for patient monitoring and for performing the biopsy procedure.
The modality selected depends upon its availability and the training and experience of the operator. The cross-sectional modalities afford the advantage not only of precise lesion localization but also of "critical" structure (e.g., lung, aorta, carotid artery) identification. In experienced hands, however, fluoroscopy-guided biopsies tend to be performed more quickly and with good patient safety. For cervical spine biopsy, CT, fluoroscopy, or CT with fluoroscopy facilitates the selection of an optimal biopsy trajectory that yields access to the lesion but avoids critical neck structures. Numerous factors influence the total procedure time, but the average time using local anesthesia is approximately 30 minutes. This assumes that the patient is cooperative and that the radiologist and the radiology technologist are experienced in biopsy procedures.12
Several biopsy needle systems are commercially available (Table 5.3). The system that is utilized depends upon the lesion type (soft tissue or osseous), the lesion location (vertebra, disc space, paraspinal soft tissues), and the method of specimen acquisition (aspiration biopsy vs core biopsy). Aspiration biopsy can be performed with a 22- or 20-gauge stylet-bearing needle. Core biopsy can be performed with a trephine or beveled tip (usually 11-, 12-, or 14-gauge) bone biopsy needle or a soft tissue-cutting needle (usually 18 gauge) (Figure 5.3). These core biopsy needles can be used as part of either a tandem needle system or a coaxial system. In the tandem tachnique, the needle that is used in the initial application of local anesthesia both localizes the lesion and serves as a visual guide. In a simultaneous tandem system, the biopsy needle is placed alongside a thin needle that was previously placed to anesthetize the biopsy tract. In a sequential tandem system,
Table 5.3. Some commercially available biopsy systems
System Manufacturer or city
Aspiration 3.5-6 in. 18- to 22-gauge spinal needles
10-20 cm 22-gauge Chiba needles
Ackermann Elson Franseen Geremia Jamshidi Parallax the biopsy needle is advanced along a tract previously created by the smaller anesthetizing needle.
Coaxial needle systems have increased in popularity.13 The biopsy needle is advanced over the anesthetizing and localizing needle (22 gauge). The localizing needle has a removable hub and serves as a mechanical guide for the biopsy needle. A guiding cannula, through which multiple biopsy needle passes can be made, is left in place. Coaxial biopsy needle systems are particularly helpful for cervical spine biop-
Becton-Dickinson, Rutherford, NJ Cook Co., Bloomington, IN
sies. The major advantages of the coaxial system, therefore, are a decreased procedure time, resulting from better accuracy, and decreased procedure complications. Only a single biopsy tract is used with the coaxial system, thus avoiding the risk of additional soft tissue structure injury associated with a second pass. Additionally, the guiding cannula can serve as a guide for fine-needle aspiration prior to core biopsy, or for obtaining multiple core biopsy samples with a soft tissue-cutting needle. An 18-gauge spring-loaded biopsy needle is used to obtain soft tissue cores. Accessory guidance systems have been developed to facilitate needle localization. These vary in complexity and are infrequently used in routine practice.
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