A mobile isocentric C-arm (Siemens PowerMobil) has been modified in our laboratory to include a large area flat-panel detector (in place of the x-ray image intensifier), providing multi-mode fluoroscopy and cone-beam computed tomography (CT) imaging capability. This platform represents a promising technology for minimally invasive, image-guided surgical procedures where precision in the placement of interventional tools with respect to bony and soft-tissue structures is critical. The image quality and performance in surgical guidance was investigated in pre-clinical evaluation in image-guided spinal surgery. The control, acquisition, and reconstruction system are described. The reproducibility of geometric calibration, essential to achieving high three-dimensional (3D) image quality, is tested over extended time scales (7 months) and across a broad range in C-arm angulation (up to 45 degrees), quantifying the effect of improper calibration on spatial resolution, soft-tissue visibility, and image artifacts. Phantom studies were performed to investigate the precision of 3D localization (viz., fiber optic probes within a vertebral body) and effect of lateral projection truncation (limited field of view) on soft-tissue detectability in image reconstructions. Pre-clinical investigation was undertaken in a specific spinal procedure (photodynamic therapy of spinal metastases) in five animal subjects (pigs). In each procedure, placement of fiber optic catheters in two vertebrae (L1 and L2) was guided by fluoroscopy and cone-beam CT. Experience across five procedures is reported, focusing on 3D image quality, the effects of respiratory motion, limited field of view, reconstruction filter, and imaging dose. Overall, the intraoperative cone-beam CT images were sufficient for guidance of needles and catheters with respect to bony anatomy and improved surgical performance and confidence through 3D visualization and verification of transpedicular trajectories and tool placement. Future investigation includes improvement in image quality, particularly regarding x-ray scatter, motion artifacts and field of view, and integration with optical tracking and navigation systems.
OBJECTIVE To report on the efficacy of TOOKAD® (WST 09; NegmaLerads, Magny‐Les‐Hameaux, France) vascular‐targeted photodynamic therapy (VTP) as a method of whole‐prostate ablation in patients with recurrent localized prostate cancer after the failure of external beam radiotherapy (EBRT). PATIENTS AND METHODS Patients received a fixed photosensitizer dose of 2 mg/kg and patient‐specific light doses as determined by computer‐aided treatment planning. Up to six cylindrical light‐diffusing delivery fibres were placed transperineally in the prostate under ultrasonographic guidance. The treatment response was assessed by measuring serum prostate‐specific antigen (PSA) levels, lesion formation (avascular areas of tissue) measured on 7‐day gadolinium‐enhanced T1‐weighted magnetic resonance imaging (MRI) and a 6‐month biopsy. RESULTS Treatment of the whole prostate was possible with minimal effects on surrounding organs. An increased light dose improved the tissue response, with MRI‐detectable avascular lesions, encompassing up to 80% of the prostate in some patients. A complete response, as determined by the 6‐month biopsy, required that patients received light doses of at least 23 J/cm2 in 90% of the prostate volume (D90 > 23 J/cm2). Of the 13 patients who received at least this light dose, eight were biopsy‐negative at 6 months. In this group of eight patients, PSA levels decreased and did so to negligible levels for those patients with a baseline PSA level of <5 ng/mL. Side‐effects were modest and self‐limited in most patients; there were recto‐urethral fistulae in two patients, one of which closed spontaneously. CONCLUSIONS TOOKAD‐VTP can produce large avascular regions in the irradiated prostate, and result in a complete negative‐biopsy response at high light doses. A response rate of more than half for those patients receiving the highest light doses shows the clinical potential of TOOKAD‐VTP to manage recurrence of prostatic carcinoma after EBRT.
Tookad vascular targeted photodynamic therapy salvage therapy is safe and well tolerated. Lesion formation is strongly drug and light dose dependent. Early histological and magnetic resonance imaging responses highlight the clinical potential of Tookad vascular targeted photodynamic therapy to manage post-external beam radiation therapy recurrence.
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