CT-DSA Evaluation of Embolization in Debulking Spinal Surgery

Vertebral osseus metastasis, can cause neoplastic spinal cord compression and neurological deficit. The treatment strategy depend on the pathological type, performance status, and life expectancy. The goal of treatment is to avoid neurological deterioration, to keep functional life, and to control bone pain. Treatment strategy involve multidisciplinary approaches between spinal surgeon, medical and radiation oncologist, and radiologist. When presence of acute neurological deterioration or intractable pain due to neoplastic compression or vertebral instability, surgical approach is often warranted. In term of surgical approach, simple decompression and fixation is often applied, but the long-term control rate is suboptimal. Aggressive spinal surgery, including extensive debulking surgery or spondylectomy, has relative longstanding effect to maintain neurological and oncological outcome.

Despite relative good outcome of aggressive spinal surgery, it is a relative massive procedure in which life-threatening blood loss commonly occur. To achieve better surgical outcome and decrease complication, preoperative embolization is suggested to control blood loss . The procedure is performed by an interventional radiologist to deliver embolic agent into vascular pedicles of target vertebra, in hope to achieve optimal devascularization of the tumour. The concept is simple and the similar procedure has been performed thousands of times in the world. However, its efficacy and utilization are not yet proven by clinical trials. When and how to perform this procedure largely depends on experience of operating interventional radiologist.

CT is an important imaging tool for spinal disease. Because of its rapid acquisition, adequate resolution, and easy reformatting, it is optimal for intolerable patients. Nevertheless, osseous structure is extremely radiopaque, evaluation of tumoral enhancement in vertebrae is not easy. Nevertheless, the enhancement of osseous tumour can be evaluated with advanced subtraction reformatting technique. The technique is similar to digital subtraction angiography (DSA) of catheter angiography, and we call it CT-DSA image. As compared with traditional catheter-based DSA, CT-DSA has following additional advantages: 1) non-invasiveness; 2) non-selective enhancement of the target; 3) allowing multiplanar reformatting and additional post-processing and quantification. The tool is very versatile to investigate the vascularity of the vertebral neoplasm. In our earlier result, we found the CT-DSA has good correlation with DSA in vascularity assessment, suggestive of its utilization in pre-operative and pre-embolization evaluation of spinal tumour. It can be used in semi-quntitative and quantitative fashion.

Traditionally, the efficacy of embolization is determined by surgical outcome, usually with gold standard of blood loss. However, blood loss is determined by many different factors, including tumor volume, surgical technique, and other anatomical factors. Using CT-DSA, evaluation of the embolization effect directly is possible. As the study can be repeated after embolization, the interval change can be observed with objective measurement.

In summary, using CT-DSA, it is possible to evaluate the vascularity of the osseous tumour and efficacy of devascularization after embolization before surgery. We can therefore design study to test efficacy of different intervention strategy, and find out the more beneficial indication, which can incorporate into clinical workflow and help patients.

Purpose

1. The establish subjective risk classification of debulking surgery in term of tumour vascularity
2. To subjectively evaluate efficacy of preoperative embolization
3. To design appropriate clinical workflow in management of patient with vertebral malignancy

Importance Vertebrae is 3rd most common site of metastatic malignancy, and is usually warrant aggressive spinal surgery. Since preoperative embolization is commonly done in this patient, it needs subjective tool to assess its efficacy and clear indication. By using CT-DSA, there is potential to provide tailored strategy of patient management before surgery.