Preclinical and clinical evaluation of the image quality of the Iso C 3D image intensifier in comparison to computer tomography for its use in the pelvic area

Abstract

Intraoperative three-dimensional visualisation using the Siremobil Iso C 3D (Siemens, Erlangen, Germany) has been approved for use in spine and long bone surgery since its recent clinical launch. Insufficient visualisation quality, seen in obese patients and in cases of low bone density, has somewhat limited its use, however. The first experiences with intraoperative 3D visualisation were attempted using intraoperative CT in the OR, a space consuming technique requiring structural hardware adaptations. Since then, CT scanning within the OR has only been realized in a low number of hospitals, due to the high costs involved and limited hardware mobility. The Siemens mobile C arm (Siremobil Iso C 3D), however, allows acquisition of two-dimensional X-ray images together with the creation of 3D reconstructions. In preparation for clinical use of the Siremobil Iso C 3D in pelvic surgery, the aim of this study was to grade the quality of visualisation in comparison to the gold standard computer tomography in four therapy relevant pelvic regions in 8 human cadavers, including SI screws to exemplify implants in the dorsal pelvic ring. Besides the influence of body mass index (variation from 20.2 to 42.9) and interference of metal artefacts, visualisation quality was evaluated in different pelvic regions. In the regions sacroiliac joint, acetabulum, femoral neck and anterior pelvic ring a score with five subgroups was used, rating the applicability of Siremobil Iso C 3D in pelvic surgery. Visualisation of muscle structures, bony structures and soft tissue was assessed. Grading of image quality in comparable standard projections was performed independently by three surgeons and three radiologists. Each of them rated 12 anatomic structures twice in above-mentioned regions of every cadaver, the subjective best and worst image. Those anatomic structures are sacral foramina, sacral nerve roots, SI joint, intervertebral space L5/S1, osteophyts, muscles, acetabular joint line, acetabular cartilage, subchondral cysts, acetabular fossa, femoral head and os pubis. Average value was calculated for each anatomic region from all assessments of structures. Dependences to region, anatomic structure, BMI and metal artefacts were analysed. Statistic analyses were done by use of Brunner non-parametric analysis of variance and chi-square test. Visualisation quality with metal implant artefacts in dorsal pelvic ring is significantly better in CT. Without metal artefacts statistical significance was only seen in acetabular joint and subchondral cysts, last in dependency to examiner. Visualisation quality of Siremobil Iso C 3D appeared sufficient for both intraoperative and postoperative control in cases with a known preoperative diagnosis. There was no influence of body mass index found in any of the 8 cadavers. Implants positioned in the dorsal pelvic ring reduced visualisation quality, but sufficient estimation of bony structures was still possible. For primary diagnostics, computer tomography remains a clearly superior option due to superior image quality. For intraoperative control of reduction and positioning of implants in pelvic surgery, however, the additional intraoperative use of Siremobil Iso C 3D is considered to offer clear advantages over current two-dimensional C-arm visualisation tools. This is confirmed by first experiences of intraoperative use of Iso C 3D in 11 patients since clinical approval of Siremobil Iso C 3D for pelvic surgery. C11 placement of SI screw by Iso C 3D navigation was done perfectly in two cases after reduction control.