The recommended entry angle for superior hypogastric plexus block is different among references, and there is a need for suggesting a more accurate entry angle for this procedure. The investigators are trying to evaluate the entry angle for superior hypogastric plexus block by measuring these angle on the computed tomography image and apply these angle to the real patients.

Superior hypogastric plexus block is a kind of sympathetic plexus block which are used to control the pelvic pain caused by malignancy or other chronic condition. Classic posterior approach for this procedure is inserting the block needle at L4 -5 level and proceed the needle 45 degrees medially and 30 degrees caudally to reach the target of anterolateral space of L5 - S1 intervertebral space. Waldman et al. introduced a different angle of 30 degrees medial and caudal with the same approach, while Stevens et al. recommended 15 degrees medial and 20 degrees caudal. As such, the recommended angle for this procedure is different among references, and there is a need for suggesting a more accurate entry angle for this procedure. Therefore, we are trying to evaluate the entry angle for superior hypogastric plexus block by measuring these angle on the computed tomography image and apply these angle to the real patients.

Inclusion Criteria:

• Those undergoing abdominopelvic CT scan with pelvic malignancy or chronic pelvic pain with constitutional disease

Exclusion Criteria:

• Poor CT image with non-measurable axial or oblique entry angle

Those undergoing abdominopelvic CT scan with pelvic malignancy or chronic pelvic pain with constitutional disease