Safety and Feasibility of Intravascular Ultrasound-Guided Robotic

PurposePrevious studies have demonstrated the benefit of intravascular ultrasound (IVUS)-guided percutaneous coronary intervention (PCI) for preventing longitudinal geographic miss (LGM). However, it is yet unclear whether IVUS guidance is useful for robotic PCI (R-PCI). This retrospective observational study sought to compare expected stent landing positions between IVUS and angiography.MethodsA total of 58 consecutive patients with stable angina who underwent IVUS-guided R-PCI was enrolled. The stent landing position was angiographically marked using a balloon marker before stenting followed by measurements of the expected stent length using balloon pullback. Subsequently, pre-stenting IVUS was performed to determine stent landing. All pre-PCI IVUS images were assessed for lesion length and percent plaque volume (%PV) using both IVUS and angiographic marking. LGM was defined as a residual %PV > 50% at either the distal or proximal stent edge, any stent edge dissection, and/or additional stent deployment immediately after stenting. Major adverse cardiac events were assessed at the 6-month follow-up.ResultsThe included patients, 41 of whom were male, had an average age of 67.1 ± 10.1 years. IVUS guidance had significantly longer lesion lengths compared to angiographic marking. Based on IVUS-guided stent deployment, 9 cases exhibited LGM immediately after stenting. IVUS-marked landing points had a significantly smaller %PV and significantly larger LA compared to those for angiography. No adverse cardiac events were noted during the 6-month follow-up.ConclusionIVUS-guided R-PCI was safe and may be better at preventing LGM compared to angiography-guided R-PCI.

TO ASSESS THE DOSIMETRIC IMPACT ON PROSTATE, BLADDER AND RECTUM IN CARCINOMA PROSTATE DUE TO INTERFRACTIONALANATOMICAL VARIATION IN IMAGE GUIDED RADIATION THERAPY.

ABTRACT- Prostate cancer is second most frequent cancer in men and fifth leading cause of death worldwide. Most radiotherapy patients with prostate cancer are treated with intensity modulated radiotherapy. IMRT requires high spatial accuracy in localizing the target volume and high precision in treatment delivery, because even a small geographic miss can have a large dosimetric effect. However, the patient setup position and anatomy changes daily, particularly in the prostate region, due to rectum and bladder filling. Materials Methods: We analyzed 30 patients with prostate cancer patient treated with IMRT kV CBCT was performed for each patient twice per week during the entire course of treatment. The bladder, rectum, prostate and PTV were contoured on each CBCT scan. Results: Delivered dose of prostate D95% and prostate D100% was 99.15% and 93.66% respectively and mean value of V70 for bladder was 16% and delivered value was 16.45%. Whereas the mean value of V70 of plan for rectum was 18.12% and delivered value was 27.58%. Conclusion: Interfractional variation during prostate radiotherapy can results in substantial difference between planned and delivered doses, particularly in critical structure. IG-IMRT is useful tool in assessing dosimetric changes in critical structure due to interfractional anatomical interfractional anatomical variation in prostate radiotherapy.

MRI validation of Post-Prostatectomy Radiotherapy Contouring

Introduction: Level One Evidence has established the indications for, and importance of, adjuvant radiotherapy following radical prostatectomy. Several guidelines have addressed delineation of the prostate bed but with variable specification of the inferior border relative to the penile bulb or to the first CT slice distal to visible urine in the bladder neck. This work determines the correlation between the caudal aspect of the anastomosis shown by the tip of the urethrogram cone and MRI anatomy. Materials and Methods : Sixteen patients receiving adjuvant radiotherapy following prostatectomy underwent diagnostic MRI in addition to planning CT with Urethrogram. The CT Reference Slice, tip of urethrogram cone and superior aspect of penile bulb were delineated. Results: MRI clearly demonstrates the penile bulb but not the anastomosis. In these 16 patients, the tip of the urethrogram cone was a median 3.9 mm cranial to the penile bulb (range 0-10.3 mm). Conclusion: We show marked variability in the distance between penile bulb and the tip of the urethrogram cone. In all sixteen patients, placing the inferior border of the CTV 15mm cranial to the penile bulb would have failed to treat the caudal aspect of the anastomosis, a frequent site of local relapse, that cannot be reliably landmarked by any other anatomic structure. Individualizing the treatment volume to patient anatomy is the only way to ensure consistent coverage without treating a larger than necessary volume in many patients. We recommend the use of planning urethrogram to minimize the potential for geographic miss.

An evaluation of the BrainLAB 6D ExacTrac/Novalis Tx System for image-guided intracranial radiotherapy

PurposeStereotactic-fractionated radiotherapy and radiosurgery (RS) for benign and malignant intracranial lesions relies on a very high degree of accuracy in dose alignment due to the ablative dose delivered, and therefore requires a high-precision image guidance modality. The aim of this review is to investigate the localisation and verification accuracy performance of ExacTrac (ET) and Novalis Tx System.Materials and methodsA systematic review of the database Science Direct was carried out using search terms ‘stereotactic radiotherapy (SRT)’ and ‘ET’. All articles before 2000 were excluded. Only articles that involved intracranial lesions, with the exception of one article, were included in the final review.ResultsResults from gold standard Hidden Target Tests and patient data show that patient position can be reproduced within 1·0 mm with the use of ET imaging. In addition, the 6 degrees of freedom algorithm function of ET allows for better translational accuracy as well optimal positioning when rotations are corrected for. Studies showed excellent correlation (p<0·01) between bony ET images and cone beam computed tomography (CBCT) soft tissue registration, evidencing the safe reliance of bony anatomy for image guidance via ET. Shifts were found to be comparable between CBCT and ET.ConclusionThere is the need for regular calibration to prevent systematic errors and potential geographic miss. However, due to ET’s additional benefits, including reduced concomitant dose and faster imaging time, ET is the superior image guidance modality for RS/SRT in the treatment of intracranial lesions.

Practical guidance in the use of image-guided radiotherapy systems

From mega-voltage portal images acquired on an electronic system (EPID), technological research has developed 3D and recently 4D volumetric verification modalities, allowing a direct visualization of the target, a direct comparison with the planning-TC and an optimization of the treatment (reduction of set-up errors, verification of the need for re-planning), leading to the very modern Image Guided RadioTherapy (IGRT). IGRT allows different technical solutions through direct or indirect visualization of the tumor and the acquisition of pre-treatment verification images, allowing to identify, quantify and correct errors related to set-up and organ-tumor motion, obtaining a greater compliance of the delivered dose, decreasing the risk of "geographic miss" and toxicity to healthy tissues and reducing the margins from CTV to PTV for the implementation of "dose escalation" protocols.