Frameless Stereotaxy for Pre-treatment Planning and Post-treatment Evaluation of Radiosurgery

Abstract:In our centre, 111 patients have been treated with linear accelerator stereotactic radiosurgery. Angiographic, CT and MRI images are generated and the target coordinates calculated in 3 dimensions. For CT scanning, cross sections of perpendicular and oblique fiducial markers are seen. For follow-up CT scans done without the frame, a virtual frame is generated by means of a computer program that places fiducial markers on each CT scan cut, as if the patient had been wearing the OBT frame and the scan produced with the gantry parallel to the base of the frame. The position of the oblique marker may be calculated by knowing the thickness and position of each CT cut. Various natural fiducial markers (bony landmarks) are identified by coordinates in the scan with the patient wearing the real frame and in the scan with the virtual frame applied. A transformation matrix is utilized to establish the equivalence between the original CT scan with the real frame applied and subsequent scans without the real frame but with the virtual frame applied. In effect, the virtual frame is re-applied in exactly the same position as the real frame. Lesion measurements may then be duplicated and growth or regression accurately established. The uncertainty in this system of re-application resides in possible patient movement, CT scan slice thickness and inter-observer error in the identification of natural fiducial markers.

Download Full-text

Precision of navigated stereotactic probe implantation into the brainstem

Journal of Neurosurgery Pediatrics ◽

10.3171/2009.10.peds09292 ◽

2010 ◽

Vol 5 (4) ◽

pp. 350-359 ◽

Cited By ~ 20

Author(s):

Henrik Giese ◽

Karl-Titus Hoffmann ◽

Andreas Winkelmann ◽

Florian Stockhammer ◽

George I. Jallo ◽

...

Keyword(s):

Mr Imaging ◽

Ct Scan ◽

Ct Scanning ◽

Frameless Stereotaxy ◽

Imaging Data ◽

Stereotactic System ◽

Brainstem Tumors ◽

Probe Placement ◽

Stereotactic Biopsies

Object The indications for stereotactic biopsies or implantation of probes for local chemotherapy in diffuse brainstem tumors have recently come under debate. The quality of performing these procedures significantly depends on the precision of the probes' placement in the brainstem. The authors evaluated the precision of brainstem probe positioning using a navigated frameless stereotactic system in an experimental setting. Methods Using the VarioGuide stereotactic system, 33 probes were placed into a specially designed model filled with agarose. In a second experimental series, 8 anatomical specimens were implanted with a total of 32 catheters into the pontine brainstem using either a suboccipital or a precoronal entry point. Before intervention in both experimental settings, a thin-sliced CT scan for planning was obtained and fused to volumetric T1-weighted MR imaging data. After the probe positioning procedures, another CT scan and an MR image were obtained to compare the course of the catheters versus the planned trajectory. The deviation between the planned and the actual locations was measured to evaluate the precision of the navigated intervention. Results Using the VarioGuide system, mean total target deviations of 2.8 ± 1.2 mm on CT scanning and 3.1 ± 1.2 mm on MR imaging were detected with a mean catheter length of 151 ± 6.1 mm in the agarose model. The catheter placement in the anatomical specimens revealed mean total deviations of 1.95 ± 0.6 mm on CT scanning and 1.8 ± 0.7 mm on MR imaging for the suboccipital approach and a mean catheter length of 59.5 ± 4.1 mm. For the precoronal approach, deviations of 2.2 ± 1.2 mm on CT scanning and 2.1 ± 1.1 mm on MR imaging were measured (mean catheter length 85.9 ± 4.7 mm). Conclusions The system-based deviation of frameless stereotaxy using the VarioGuide system reveals good probe placement in deep-seated locations such as the brainstem. Therefore, the authors believe that the system can be accurately used to conduct biopsies and place probes in patients with brainstem lesions.

Download Full-text

Accuracy of an MR-only workflow for prostate radiotherapy using semi-automatically burned-in fiducial markers

Radiation Oncology ◽

10.1186/s13014-021-01768-8 ◽

2021 ◽

Vol 16 (1) ◽

Author(s):

Karin Goudschaal ◽

F. Beeksma ◽

M. Boon ◽

M. Bijveld ◽

J. Visser ◽

...

Keyword(s):

Medical Center ◽

Academic Medical Center ◽

Slice Thickness ◽

Fiducial Markers ◽

Mr Image ◽

Target Delineation ◽

Observer Error ◽

Prostate Radiotherapy ◽

Significant Difference ◽

Image Registrations

Abstract Background The benefit of MR-only workflow compared to current CT-based workflow for prostate radiotherapy is reduction of systematic errors in the radiotherapy chain by 2–3 mm. Nowadays, MRI is used for target delineation while CT is needed for position verification. In MR-only workflows, MRI based synthetic CT (sCT) replaces CT. Intraprostatic fiducial markers (FMs) are used as a surrogate for the position of the prostate improving targeting. However, FMs are not visible on sCT. Therefore, a semi-automatic method for burning-in FMs on sCT was developed. Accuracy of MR-only workflow using semi-automatically burned-in FMs was assessed and compared to CT/MR workflow. Methods Thirty-one prostate cancer patients receiving radiotherapy, underwent an additional MR sequence (mDIXON) to create an sCT for MR-only workflow simulation. Three sources of accuracy in the CT/MR- and MR-only workflow were investigated. To compare image registrations for target delineation, the inter-observer error (IOE) of FM-based CT-to-MR image registrations and soft-tissue-based MR-to-MR image registrations were determined on twenty patients. Secondly, the inter-observer variation of the resulting FM positions was determined on twenty patients. Thirdly, on 26 patients CBCTs were retrospectively registered on sCT with burned-in FMs and compared to CT-CBCT registrations. Results Image registration for target delineation shows a three times smaller IOE for MR-only workflow compared to CT/MR workflow. All observers agreed in correctly identifying all FMs for 18 out of 20 patients (90%). The IOE in CC direction of the center of mass (COM) position of the markers was within the CT slice thickness (2.5 mm), the IOE in AP and RL direction were below 1.0 mm and 1.5 mm, respectively. Registrations for IGRT position verification in MR-only workflow compared to CT/MR workflow were equivalent in RL-, CC- and AP-direction, except for a significant difference for random error in rotation. Conclusions MR-only workflow using sCT with burned-in FMs is an improvement compared to the current CT/MR workflow, with a three times smaller inter observer error in CT-MR registration and comparable CBCT registration results between CT and sCT reference scans. Trial registry Medical Research Involving Human Subjects Act (WMO) does apply to this study and was approved by the Medical Ethics review Committee of the Academic Medical Center. Registration number: NL65414.018.18. Date of registration: 21–08-2018.

Download Full-text

How precise are oral splints for frameless stereotaxy in guided ear, nose, throat, and maxillofacial surgery: a cadaver study

European Radiology Experimental ◽

10.1186/s41747-021-00223-3 ◽

2021 ◽

Vol 5 (1) ◽

Author(s):

Manfred Nilius ◽

Minou Hélène Nilius

Keyword(s):

Bone Markers ◽

Maxillofacial Surgery ◽

Computer Assisted Surgery ◽

Ct Scanning ◽

Cadaver Study ◽

Computer Assisted ◽

Frameless Stereotaxy ◽

Fiducial Markers ◽

Linear Regression Models ◽

Non Invasive

Abstract Background Computer-assisted surgery optimises accuracy and serves to improve precise surgical procedures. We validated oral splints with fiducial markers by testing them against rigid bone markers. Methods We screwed twenty bone anchors as fiducial markers into different regions of a dried skull and measured the distances. After computed tomography (CT) scanning, the accuracy was evaluated by determining the markers’ position using frameless stereotaxy on a dry cadaver and indicated on the CT scan. We compared the accuracy of chairside fabricated oral splints to standard registration with bone markers immediately after fabrication and after a ten-time use. Accuracy was calculated as deviation (mean ± standard deviation). For statistical analysis, t test, Kruskal-Wallis, Tukey's, and various linear regression models, such as the Pearson's product–moment correlation coefficient, were used. Results Oral splints showed an accuracy of 0.90 mm ± 0.27 for viscerocranium, 1.10 mm ± 0.39 for skull base, and 1.45 mm ± 0.59 for neurocranium. We found an accuracy of less than 2 mm for both splints for a distance of up to 152 mm. The accuracy persisted even after ten times removing and reattaching the splints. Conclusions Oral splints offer a non-invasive indicator to improve the accuracy of image-guided surgery. The precision is dependent on the distance to the target. Up to 150-mm distance, a precision of fewer than 2 mm is possible. Dental splints provide sufficient accuracy than bone markers and may opt for higher precision combined with other non-invasive registration methods.

Download Full-text

Accuracy of an MR-only workflow for prostate radiotherapy using semi-automatically burned-in fiducial markers

10.21203/rs.3.rs-127932/v1 ◽

2020 ◽

Author(s):

Karin Goudschaal ◽

F. Beeksma ◽

M. Boon ◽

M. Bijveld ◽

J. Visser ◽

...

Keyword(s):

Medical Center ◽

Academic Medical Center ◽

Slice Thickness ◽

Fiducial Markers ◽

Mr Image ◽

Target Delineation ◽

Observer Error ◽

Prostate Radiotherapy ◽

Significant Difference ◽

Image Registrations

Abstract BackgroundThe benefit of MR-only workflow compared to current CT-based workflow for prostate radiotherapy is reduction of systematic errors in the radiotherapy chain by 2 – 3 mm. Nowadays, MRI is used for target delineation while CT is needed for position verification. In MR-only workflows, MRI based synthetic CT (sCT) replaces CT.Intraprostatic fiducial markers (FMs) are used as a surrogate for the position of the prostate improving targeting. However, FMs are not visible on sCT. Therefore, a semi-automatic method for burning-in FMs on sCT was developed. Accuracy of MR-only workflow using semi-automatically burned-in FMs was assessed and compared to CT/MR workflow.MethodsThirty-one prostate cancer patients receiving radiotherapy, underwent an additional MR sequence (mDIXON) to create an sCT for MR-only workflow simulation. Three sources of accuracy in the CT/MR- and MR-only workflow were investigated. To compare image registrations for target delineation, the inter-observer error (IOE) of FM-based CT-to-MR image registrations and soft-tissue-based MR-to-MR image registrations were determined on twenty patients. Secondly, the inter-observer variation of the resulting FM positions was determined on twenty patients. Thirdly, on 31 patients CBCTs were retrospectively registered on sCT with burned-in FMs and compared to CT-CBCT registrations.ResultsImage registration for target delineation shows a three times smaller IOE for MR-only workflow compared to CT/MR workflow. All observers agreed in correctly identifying all FMs for 18 out of 20 patients (90%). The IOE in CC direction of the center of mass (COM) position of the markers was within the CT slice thickness (2.5mm), the IOE in AP and RL direction were below 1.0 mm and 1.5 mm, respectively. Registrations for IGRT position verification in MR-only workflow compared to CT/MR workflow were equivalent in RL-, CC- and AP-direction, except for a significant difference for random error in rotation.ConclusionsMR-only workflow using sCT with burned-in FMs is an improvement compared to the current CT/MR workflow, with a three times smaller inter observer error in CT-MR registration and comparable CBCT registration results between CT and sCT reference scans.Trial registrationMedical Research Involving Human Subjects Act (WMO) does apply to this study and was approved by the Medical Ethics review Committee of the Academic Medical Center. Registration number: NL65414.018.18. Date of registration: 21-08-2018.

Download Full-text

Morphology and Affinities of Ampelocissites Seeds (Vitaceae: Ampelopsis clade) from the Paleogene of Texas, USA

Systematic Botany ◽

10.1600/036364420x15935294613400 ◽

2020 ◽

Vol 45 (3) ◽

pp. 478-482

Author(s):

Steven R. Manchester

Keyword(s):

Computed Tomography ◽

Cross Sections ◽

Seed Coat ◽

Ct Scanning ◽

Seed Morphology ◽

Early Eocene ◽

Micro Computed Tomography ◽

X Ray ◽

Fossil Seeds ◽

Fossil Genus

Abstract—The type material on which the fossil genus name Ampelocissites was established in 1929 has been reexamined with the aid of X-ray micro-computed tomography (μ-CT) scanning and compared with seeds of extant taxa to assess the relationships of these fossils within the grape family, Vitaceae. The specimens were collected from a sandstone of late Paleocene or early Eocene age. Although originally inferred by Berry to be intermediate in morphology between Ampelocissus and Vitis, the newly revealed details of seed morphology indicate that these seeds represent instead the Ampelopsis clade. Digital cross sections show that the seed coat maintains its thickness over the external surfaces, but diminishes quickly in the ventral infolds. This feature, along with the elliptical chalaza and lack of an apical groove, indicate that Ampelocissites lytlensis Berry probably represents Ampelopsis or Nekemias (rather than Ampelocissus or Vitis) and that the generic name Ampelocissites may be useful for fossil seeds with morphology consistent with the Ampelopsis clade that lack sufficient characters to specify placement within one of these extant genera.

Download Full-text

Image Registration of 18F-FDG PET/CT Using the MotionFree Algorithm and CT Protocols through Phantom Study and Clinical Evaluation

Healthcare ◽

10.3390/healthcare9060669 ◽

2021 ◽

Vol 9 (6) ◽

pp. 669

Author(s):

Deok-Hwan Kim ◽

Eun-Hye Yoo ◽

Ui-Seong Hong ◽

Jun-Hyeok Kim ◽

Young-Heon Ko ◽

...

Keyword(s):

Ct Scan ◽

Ct Scanning ◽

Motion Artifacts ◽

Scanning Time ◽

Pet Ct ◽

Static Images ◽

Type C ◽

Natural Breathing ◽

Fdg Pet Ct ◽

Patient Studies

We evaluated the benefits of the MotionFree algorithm through phantom and patient studies. The various sizes of phantom and vacuum vials were linked to RPM moving with or without MotionFree application. A total of 600 patients were divided into six groups by breathing protocols and CT scanning time. Breathing protocols were applied as follows: (a) patients who underwent scanning without any breathing instructions; (b) patients who were instructed to hold their breath after expiration during CT scan; and (c) patients who were instructed to breathe naturally. The length of PET/CT misregistration was measured and we defined the misregistration when it exceeded 10 mm. In the phantom tests, the images produced by the MotionFree algorithm were observed to have excellent agreement with static images. There were significant differences in PET/CT misregistration according to CT scanning time and each breathing protocol. When applying the type (c) protocol, decreasing the CT scanning time significantly reduced the frequency and length of misregistrations (p < 0.05). The MotionFree application is able to correct respiratory motion artifacts and to accurately quantify lesions. The shorter time of CT scan can reduce the frequency, and the natural breathing protocol also decreases the lengths of misregistrations.

Download Full-text

Selective non-operative management of anterior abdominal stab wounds with emphasis on the value of follow-up abdominal CT scanning

Trauma ◽

10.1177/1460408617706389 ◽

2017 ◽

Vol 20 (3) ◽

pp. 194-202

Author(s):

El Yamani Fouda ◽

Alaa Magdy ◽

Sameh Hany Emile

Keyword(s):

Ct Scan ◽

Ct Scanning ◽

Operative Management ◽

Abdominal Ct ◽

Management Group ◽

Abdominal Ct Scan ◽

Laparotomy Group ◽

Abdominal Stab Wounds ◽

Non Operative Management

Background and aim Selective non-operative management of patients with penetrating abdominal stabs is the preferred treatment strategy. The present study aimed to assess the efficacy and safety of non-operative management with emphasis on the value of follow-up abdominal CT scanning in management of patients with penetrating anterior abdominal stab. Patients and methods This is a retrospective chart review of stable patients with anterior abdominal stab wounds. Patients were divided in terms of initial decisions into two groups: laparotomy group and non-operative management group. Abdominal CT scan was performed for patients in the non-operative management group on admission and follow-up CT scanning was performed in cases of clinical and/or biochemical deterioration. Results The laparotomy group included 82 patients and 68.2% of them had unnecessary laparotomies. The non-operative management group comprised 97 patients and 90.7% of them did not require subsequent laparotomy. Abdominal CT scan had a sensitivity of 88.9% and specificity of 100% in detection of intra-abdominal injuries. Follow-up CT scanning detected bowel injuries missed by initial CT scan in three patients. The non-operative management group had significantly lower post-operative complication rate than the laparotomy group (4.1% vs. 18.3%), with a significantly shorter length of stay. Conclusions Non-operative management is the optimal management strategy for stable patients with penetrating anterior abdominal stab to decrease unnecessary laparotomy rates, hospital stay and costs. Follow-up abdominal CT scanning facilitated the decision making for patients selected for non-operative management and is highly sensitive in the diagnosis of patients who require subsequent exploration.

Download Full-text

Incidence of silent hemorrhage and delayed deterioration after stereotactic brain biopsy

Journal of Neurosurgery ◽

10.3171/jns.1998.89.1.0031 ◽

1998 ◽

Vol 89 (1) ◽

pp. 31-35 ◽

Cited By ~ 83

Author(s):

Abhaya V. Kulkarni ◽

Abhijit Guha ◽

Andres Lozano ◽

Mark Bernstein

Keyword(s):

Ct Scan ◽

Neurological Deficit ◽

Stereotactic Biopsy ◽

Brain Biopsy ◽

Ct Scanning ◽

Ct Scans ◽

Stereotactic Brain Biopsy ◽

Content Type ◽

Fine Print

Object. Many neurosurgeons routinely obtain computerized tomography (CT) scans to rule out hemorrhage in patients after stereotactic procedures. In the present prospective study, the authors investigated the rate of silent hemorrhage and delayed deterioration after stereotactic biopsy sampling and the role of postbiopsy CT scanning. Methods. A subset of patients (the last 102 of approximately 800 patients) who underwent stereotactic brain biopsies at the Toronto Hospital prospectively underwent routine postoperative CT scanning within hours of the biopsy procedure. Their medical charts and CT scans were then reviewed. A postoperative CT scan was obtained in 102 patients (aged 17–87 years) who underwent stereotactic biopsy between June 1994 and September 1996. Sixty-one patients (59.8%) exhibited hemorrhages, mostly intracerebral (54.9%), on the immediate postoperative scan. Only six of these patients were clinically suspected to have suffered a hemorrhage based on immediate postoperative neurological deficit; in the remaining 55 (53.9%) of 102 patients, the hemorrhage was clinically silent and unsuspected. Among the clinically silent intracerebral hemorrhages, 22 measured less than 5 mm, 20 between 5 and 10 mm, five between 10 and 30 mm, and four between 30 and 40 mm. Of the 55 patients with clinically silent hemorrhages, only three demonstrated a delayed neurological deficit (one case of seizure and two cases of progressive loss of consciousness) and these all occurred within the first 2 postoperative days. Of the neurologically well patients in whom no hemorrhage was demonstrated on initial postoperative CT scan, none experienced delayed deterioration. Conclusions. Clinically silent hemorrhage after stereotactic biopsy is very common. However, the authors did not find that knowledge of its existence ultimately affected individual patient management or outcome. The authors, therefore, suggest that the most important role of postoperative CT scanning is to screen for those neurologically well patients with no hemorrhage. These patients could safely be discharged on the same day they underwent biopsy.

Download Full-text

Management of the Orbital Floor in Silent Sinus Syndrome

American Journal of Rhinology ◽

10.1177/194589240301700206 ◽

2003 ◽

Vol 17 (2) ◽

pp. 97-100 ◽

Cited By ~ 50

Author(s):

Robert D. Thomas ◽

Scott M. Graham ◽

Keith D. Carter ◽

Jeffrey A. Nerad

Keyword(s):

Ct Scan ◽

Maxillary Sinus ◽

Current Trend ◽

Ct Scanning ◽

Volumetric Analysis ◽

Orbital Floor ◽

Second Stage ◽

Silent Sinus Syndrome ◽

Orbital Floor Reconstruction ◽

Preoperative Ct

Background Enophthalmos in a patient with an opacified hypoplastic maxillary sinus, without sinus symptomatology, describes the silent sinus syndrome. A current trend is to perform endoscopic maxillary antrostomy and orbital floor reconstruction as a single-staged operation. A two-staged approach is performed at our institution to avoid placement of an orbital floor implant in the midst of potential infection and allow for the possibility that enophthalmos and global ptosis may resolve with endoscopic antrostomy alone, obviating the need for orbital floor reconstruction. Methods A retrospective review identified four patients with silent sinus syndrome evaluated between June 1999 and August 2001. Patients presented to our ophthalmology department with ocular asymmetry, and computerized tomography (CT) scanning confirmed the diagnosis in each case. Results There were three men and one woman, with ages ranging from 27 to 40 years. All patients underwent endoscopic maxillary antrostomy. Preoperative enophthalmos determined by Hertel's measurements ranged from 3 to 4 mm. After endoscopic maxillary antrostomy, the range of reduction in enophthalmos was 1–2 mm. Case 2 had a preoperative CT scan and a CT scan 9 months after left endoscopic maxillary antrostomy. Volumetric analysis of the left maxillary sinus revealed a preoperative volume of 16.85 ± 0.06 cm3 and a postoperative volume of 19.56 ± 0.07 cm3. This represented a 16% increase in maxillary sinus volume postoperatively. Orbital floor augmentation was avoided in two patients because of satisfactory improvement in enophthalmos. In the other two patients, orbital reconstruction was performed as a second-stage procedure. There were no complications. Conclusion Orbital floor augmentation can be offered as a second-stage procedure for patients with silent sinus syndrome. Some patients’ enophthalmos may improve with endoscopic antrostomy alone.

Download Full-text

Elastic scattering and breakup reactions with light proton- and neutron-rich exotic nuclei

EPJ Web of Conferences ◽

10.1051/epjconf/201819407002 ◽

2018 ◽

Vol 194 ◽

pp. 07002

Author(s):

M.K. Gaidarov ◽

V.K. Lukyanov ◽

D.N. Kadrev ◽

E.V. Zemlyanaya ◽

A.N. Antonov ◽

...

Keyword(s):

Experimental Data ◽

Elastic Scattering ◽

Cross Sections ◽

Cluster Model ◽

Microscopic Analysis ◽

High Energy ◽

The Real ◽

Optical Potentials ◽

Generator Coordinate ◽

Energy Approximation

A microscopic analysis of the optical potentials (OPs) and cross sections of elastic scattering of 8B on 12C, 58Ni, and 208Pb targets at energies 20 < E < 170 MeV and 12,14Be on 12C at 56 MeV/nucleon is carried out. The real part of the OP is calculated by a folding procedure and the imaginary part is obtained on the base of the high-energy approximation (HEA). The density distributions of 8B evaluated within the variational Monte Carlo (VMC) model and the three-cluster model (3CM) are used to construct the potentials. The 14Be densities obtained in the framework of the the generator coordinate method (GCM) are used to calculate the optical potentials, while for the same purpose both the VMC model and GCM densities of 12Be are used. In the hybrid model developed and explored in our previous works, the only free parameters are the depths of the real and imaginary parts of OP obtained by fitting the experimental data. The use of HEA to estimate the imaginary OP at energies just above the Coulomb barrier is discussed. In addition, cluster model, in which 8B consists of a p-halo and the 7Be core, is applied to calculate the breakup cross sections of 8B nucleus on 9Be, 12C, and 197Au targets, as well as momentum distributions of 7Be fragments. A good agreement of the theoretical results with the available experimental data is obtained. It is concluded that the reaction studies performed in this work may provide supplemental information on the internal spatial structure of the proton- and neutron-halo nuclei.

Download Full-text