Peering Into the Future: A First Look at the CBME Transition to Practice Stage in Diagnostic Radiology

RATIONALE AND OBJECTIVES

Queen's University (Kingston, ON, Canada) adopted a competency-based medical education (CBME) curriculum for Diagnostic Radiology residency training in an accelerated manner in 2017, with the curriculum comprised of four stages of training. This article focuses on the final stage (Transition to Practice), during which assessment methods of the new national curriculum (implemented in July 2022) were piloted. This study aims to highlight the challenges and opportunities associated with the implementation of CBME in Diagnostic Radiology training and specific considerations for programs undergoing this curricular transition.

MATERIALS AND METHODS

Ethics approval was provided by the affiliated hospital Research Ethics Board. All relevant electronic assessments pertaining to all trainees who had completed the Transition to Practice stage (n = 3) were collated, deidentified, analyzed, and presented in tabulated format.

RESULTS

A total of 39 evaluations completed by 13 assessors were assessed, with an average time of 3 minutes and 6 seconds to complete an assessment form. Also, 95% of evaluations were rated as entrustments. However, no residents met the minimum number of required entrustments for all five stage-specific Entrustable Professional Activities. These 39 evaluations included 219 milestone rating scores, with 86% rated as "achieved." Following review by the residency program Competence Committee, all three residents were promoted from the Transition to Practice stage.

CONCLUSION

Challenges in CBME implementation include the number and quality of resident assessments. Strategies for success may include providing clear guidelines and training for both faculty and residents, early identification and intervention, and adopting a holistic evaluation strategy. CBME has the potential to enhance medical education quality by emphasizing learner progress toward competency and providing personalized feedback and support.

Neurological Impairment in Critically Ill Patients on Dialysis: Research Letter for the INCOGNITO-AKI Feasibility Study

Background

Acute kidney injury (AKI) resulting in kidney replacement therapy is rising among critically ill adults. Long-term kidney replacement therapy and critical illness are independently linked to acute and prolonged cognitive impairment, and structural brain pathology. Poor regional cerebral oxygenation (rSO2) may be a contributing factor.

Objective

To assess the feasibility of testing the association between intradialytic rSO2 and acute and long-term neurological outcomes.

Design

Longitudinal observational study.

Setting and Participants

We enrolled patients initiating continuous kidney replacement therapy or intermittent hemodialysis in the Kingston Health Sciences Centre (KHSC) Intensive Care Unit (ICU).

Measurements and Methods

rSO2 was monitored during the first 72 hours of continuous kidney replacement therapy or throughout each intermittent hemodialysis session. We measured acute neurological impairment by daily delirium screening and long-term neurocognitive outcomes using the Kinarm robot, Repeatable Battery for the Assessment of Neuropsychological Status, and brain magnetic resonance imaging.

Results

Of 484 ICU patients, 26 met the screening criteria. Two declined, and 13 met at least one exclusion criteria. Eleven patients were enrolled. Eight died in ICU, one died 2 months after discharge, and one declined follow-up. Data capture rates were high: rSO2/vitals (91.3%), and delirium screening and demographics (100%). Longitudinal testing was completed in 50% (1 of 2) of survivors.

Limitations

Enrollment was low due to a variety of factors, limiting our ability to evaluate long-term outcomes.

Conclusion

rSO2 and delirium data collection is feasible in critically ill patients undergoing kidney replacement therapy; high mortality limits follow-up.

Feasibility and Cost Analysis of Portable MRI Implementation in a Remote Setting in Canada

OBJECTIVE

To conduct feasibility and cost analysis of portable MRI implementation in a remote setting where MRI access is otherwise unavailable.

METHODS

Portable MRI (ultra-low field, 0.064T) was installed in Weeneebayko General Hospital, Moose Factory, Ontario. Adult patients, presenting with any indication for neuroimaging, were eligible for study inclusion. Scanning period was from November 14, 2021, to September 6, 2022. Images were sent via a secure PACS network for Neuroradiologist interpretation, available 24/7. Clinical indications, image quality, and report turnaround time were recorded. A cost analysis was conducted from a healthcare system's perspective in 2022 Canadian dollars, comparing cost of portable MRI implementation to transporting patients to a center with fixed MRI.

RESULTS

Portable MRI was successfully implemented in a remote Canadian location. Twenty-five patients received a portable MRI scan. All studies were of diagnostic quality. No clinically significant pathologies were identified on any of the studies. However, based on clinical presentation and limitations of portable MRI resolution, it is estimated that 11 (44%) of patients would require transfer to a center with fixed MRI for further imaging workup. Cost savings were $854,841 based on 50 patients receiving portable MRI over 1 year. Five-year budget impact analysis showed nearly $8 million dollars saved.

CONCLUSIONS

Portable MRI implementation in a remote setting is feasible, with significant cost savings compared to fixed MRI. This study may serve as a model to democratize MRI access, offer timely care and improved triaging in remote areas where conventional MRI is unavailable.

An Artificial Intelligence Training Workshop for Diagnostic Radiology Residents

Purpose

To develop, implement, and evaluate feedback for an artificial intelligence (AI) workshop for radiology residents that has been designed as a condensed introduction of AI fundamentals suitable for integration into an existing residency curriculum.

Materials and Methods

A 3-week AI workshop was designed by radiology faculty, residents, and AI engineers. The workshop was integrated into curricular academic half-days of a competency-based medical education radiology training program. The workshop consisted of live didactic lectures, literature case studies, and programming examples for consolidation. Learning objectives and content were developed for foundational literacy rather than technical proficiency. Identical prospective surveys were conducted before and after the workshop to gauge the participants' confidence in understanding AI concepts on a five-point Likert scale. Results were analyzed with descriptive statistics and Wilcoxon rank sum tests to evaluate differences.

Results

Twelve residents participated in the workshop, with 11 completing the survey. An average score of 4.0 ± 0.7 (SD), indicating agreement, was observed when asking residents if the workshop improved AI knowledge. Confidence in understanding AI concepts increased following the workshop for 16 of 18 (89%) comprehension questions (P value range: .001 to .04 for questions with increased confidence).

Conclusion

An introductory AI workshop was developed and delivered to radiology residents. The workshop provided a condensed introduction to foundational AI concepts, developed positive perception, and improved confidence in AI topics.Keywords: Medical Education, Machine Learning, Postgraduate Training, Competency-based Medical Education, Medical Informatics Supplemental material is available for this article. © RSNA, 2023.

Identifying neurocognitive outcomes and cerebral oxygenation in critically ill adults on acute kidney replacement therapy in the intensive care unit: the INCOGNITO-AKI study protocol

INTRODUCTION

Initiation of acute kidney replacement therapy (KRT) is common in critically ill adults admitted to the intensive care unit (ICU), and associated with increased morbidity and mortality. KRT has been linked to poor neurocognitive outcomes, leading to reduced quality of life and increased utilisation of healthcare resources. Adults on dialysis in the ICU may be particularly at risk of neurocognitive impairment, as survivors of critical illness are already predisposed to developing cerebrovascular disease and cognitive dysfunction long-term relative to healthy controls. Regional cerebral oxygen saturation may provide a critical early marker of long-term neurocognitive impairment in this population. This study aims to understand cerebral oxygenation in patients undergoing KRT (continuous or intermittent) in the ICU. These findings will be correlated with long-term cognitive and functional outcomes, and structural brain pathology.

METHODS AND ANALYSIS

108 patients scheduled to undergo treatment for acute kidney injury with KRT in the Kingston Health Sciences Centre ICU will be recruited into this prospective observational study. Enrolled patients will be assessed with intradialytic cerebral oximetry using near infrared spectroscopy. Delirium will be assessed daily with the Confusion Assessment Method-ICU (CAM-ICU) and severity quantified as cumulative CAM-ICU-7 scores. Neurocognitive impairment will be assessed at 3 and 12 months after hospital discharge using the Kinarm and Repeatable Battery for the Assessment of Neuropsychological Status. Structural brain pathology on MRI will also be measured at the same timepoints. Driving safety, adverse events and medication adherence will be assessed at 12 months to evaluate the impact of neurocognitive impairment on functional outcomes.

ETHICS AND DISSEMINATION

This study is approved by the Queen's University Health Sciences/Affiliated Teaching Hospitals Research Ethics Board (DMED-2424-20). Results will be presented at critical care conferences, and a lay summary will be provided to patients in their preferred format.

TRIAL REGISTRATION NUMBER

NCT04722939.

Ultra-High Field 7-Tesla Magnetic Resonance Imaging and Electroencephalography Findings in Epilepsy

PURPOSE

Assessment of patients for temporal lobe epilepsy (TLE) surgery requires multimodality input, including EEG recordings to ensure optimal surgical planning. Often EEG demonstrates abnormal foci not detected on 1.5T MRI. Ultra-high field MRI at 7T provides improved resolution of the brain. We investigated the utility of 7T MRI to detect potential anatomical abnormalities associated with EEG changes.

METHODS

Ultra-high field data were acquired on a 7T MRI scanner for 13 patients with history of drug resistant TLE who had had EEG telemetry recordings. Qualitative evaluation of 7T imaging for presence of focal abnormalities detected on EEG was performed. Correlation of 7T MRI findings with EEG recordings of focal slowing or interictal epileptic spikes (IEDs), and seizures was performed.

RESULTS

Assessment of 7T MRI demonstrated concordance with TLE as determined by the multidisciplinary team in 61.5% of cases (n = 8). Among these, 3 patients exhibited supportive abnormal 7T MRI abnormalities not detected by 1.5T MRI. In patients who underwent surgery, 72.7% had concordant histopathology findings with 7T MRI findings (n = 8). However, qualitative assessment of 7T images revealed focal anatomical abnormalities to account for EEG findings in only 15.4% of patients (n = 2). Other regions that were found to have localized IEDs in addition to the lesional temporal lobe, included the contralateral temporal lobe (n = 5), frontal lobe (n = 3), and parieto-occipital lobe (n = 2).

CONCLUSION

Ultra-high field 7T MRI findings show concordance with clinical data. However, 7T MRI did not reveal anatomical findings to account for abnormalities detected by EEG.

Creating a Competency-Based Medical Education Curriculum for Canadian Diagnostic Radiology Residency (Queen's Fundamental Innovations in Residency Education)-Part 2: Core of Discipline Stage

PURPOSE

All postgraduate residency programs in Canada are transitioning to a competency-based medical education (CBME) model divided into 4 stages of training. Queen's University has been the first Canadian institution to mandate transitioning to CBME across all residency programs, including Diagnostic Radiology. This study describes the implementation of CBME with a focus on the third developmental stage, Core of Discipline, in the Diagnostic Radiology residency program at Queen's University. We describe strategies applied and challenges encountered during the adoption and implementation process in order to inform the development of other CBME residency programs in Diagnostic Radiology.

METHODS

At Queen's University, the Core of Discipline stage was developed using the Royal College of Physicians and Surgeons of Canada's (RCPSC) competence continuum guidelines and the CanMEDS framework to create radiology-specific entrustable professional activities (EPAs) and milestones for assessment. New committees, administrative positions, and assessment strategies were created to develop these assessment guidelines. Currently, 2 cohorts of residents (n = 6) are enrolled in the Core of Discipline stage.

RESULTS

EPAs, milestones, and methods of evaluation for the Core of Discipline stage are described. Opportunities during implementation included tracking progress toward educational objectives and increased mentorship. Challenges included difficulty meeting procedural volume requirements, inconsistent procedural tracking, improving feedback mechanisms, and administrative burden.

CONCLUSION

The transition to a competency-based curriculum in an academic Diagnostic Radiology residency program is significantly resource and time intensive. This report describes challenges faced in developing the Core of Discipline stage and potential solutions to facilitate this process.

An evaluation of the diagnostic equivalence of 18F-FDG-PET between hybrid PET/MRI and PET/CT in drug-resistant epilepsy: A pilot study

OBJECTIVE

Hybrid PET/MRI may improve detection of seizure-onset zone (SOZ) in drug-resistant epilepsy (DRE), however, concerns over PET bias from MRI-based attenuation correction (MRAC) have limited clinical adoption of PET/MRI. This study evaluated the diagnostic equivalency and potential clinical value of PET/MRI against PET/CT in DRE.

MATERIALS AND METHODS

MRI, FDG-PET and CT images (n = 18) were acquired using a hybrid PET/MRI and a CT scanner. To assess diagnostic equivalency, PET was reconstructed using MRAC (RESOLUTE) and CT-based attenuation correction (CTAC) to generate PET/MRI and PET/CT images, respectively. PET/MRI and PET/CT images were compared qualitatively through visual assessment and quantitatively through regional standardized uptake value (SUV) and z-score assessment. Diagnostic accuracy and sensitivity of PET/MRI and PET/CT for SOZ detection were calculated through comparison to reference standards (clinical hypothesis and histopathology, respectively).

RESULTS

Inter-reader agreement in visual assessment of PET/MRI and PET/CT images was 78 % and 81 %, respectively. PET/MRI and PET/CT were strongly correlated in mean SUV (r = 0.99, p < 0.001) and z-scores (r = 0.92, p < 0.001) across all brain regions. MRAC SUV bias was <5% in most brain regions except the inferior temporal gyrus, temporal pole, and cerebellum. Diagnostic accuracy and sensitivity were similar between PET/MRI and PET/CT (87 % vs. 85 % and 83 % vs. 83 %, respectively).

CONCLUSION

We demonstrate here that PET/MRI with optimal MRAC can yield similar diagnostic performance as PET/CT. Nevertheless, further exploration of the potential added value of PET/MRI is necessary before clinical adoption of PET/MRI for epilepsy imaging.

A Pilot Study on Diagnostic Radiology Residency Case Volumes From a Canadian Perspective: A Marker of Resident Knowledge

Purpose:

New guidelines from the Accreditation Council for Graduate Medical Education (ACGME) have proposed minimum case volumes to be obtained during residency. While radiology residency programs in Canada are accredited by the Royal College of Physicians and Surgeons of Canada, there are currently no minimum case volumes standards for radiology residency training in Canada. New changes in residency training throughout Canada are coming in the form of competency-based medical education. Using data from a pilot study, this article examines radiology resident case volumes among recently graduated cohorts of residents and determines whether there is a correlation between case volumes and measures of resident success.

Materials and Methods:

Resident case volumes for 3 cohorts of graduated residents (2016-2018) were extracted from the institutional database. Achievement of minimum case volumes based on the ACGME guidelines was performed for each resident. Pearson correlation analysis (n = 9) was performed to examine the relationships between resident case volumes and markers of resident success including residents’ relative knowledge ranking and their American College of Radiology (ACR) in-training exam scores.

Results:

A statistically significant, positive correlation was observed between residents’ case volume and their relative knowledge ranking ( r = 0.682, P < .05). Residents’ relative knowledge ranking was also statistically significant and positively correlated with their ACR in-training percentile score ( r = 0.715, P < .05).

Conclusions:

This study suggests that residents who interpret more cases are more likely to demonstrate higher knowledge, thereby highlighting the utility of case volumes as a prognostic marker of resident success. As well, the results underscore the potential use of ACGME minimum case volumes as a prognostic marker. These findings can inform future curriculum planning and development in radiology residency training programs.

18F-FDG PET-guided diffusion tractography reveals white matter abnormalities around the epileptic focus in medically refractory epilepsy: implications for epilepsy surgical evaluation

BACKGROUND

Hybrid PET/MRI can non-invasively improve localization and delineation of the epileptic focus (EF) prior to surgical resection in medically refractory epilepsy (MRE), especially when MRI is negative or equivocal. In this study, we developed a PET-guided diffusion tractography (PET/DTI) approach combining ¹⁸F-fluorodeoxyglucose PET (FDG-PET) and diffusion MRI to investigate white matter (WM) integrity in MRI-negative MRE patients and its potential impact on epilepsy surgical planning.

METHODS

FDG-PET and diffusion MRI of 14 MRI-negative or equivocal MRE patients were used to retrospectively pilot the PET/DTI approach. We used asymmetry index (AI) mapping of FDG-PET to detect the EF as brain areas showing the largest decrease in FDG uptake between hemispheres. Seed-based WM fiber tracking was performed on DTI images with a seed location in WM 3 mm from the EF. Fiber tractography was repeated in the contralateral brain region (opposite to EF), which served as a control for this study. WM fibers were quantified by calculating the fiber count, mean fractional anisotropy (FA), mean fiber length, and mean cross-section of each fiber bundle. WM integrity was assessed through fiber visualization and by normalizing ipsilateral fiber measurements to contralateral fiber measurements. The added value of PET/DTI in clinical decision-making was evaluated by a senior neurologist.

RESULTS

In over 60% of the patient cohort, AI mapping findings were concordant with clinical reports on seizure-onset localization and lateralization. Mean FA, fiber count, and mean fiber length were decreased in 14/14 (100%), 13/14 (93%), and 12/14 (86%) patients, respectively. PET/DTI improved diagnostic confidence in 10/14 (71%) patients and indicated that surgical candidacy be reassessed in 3/6 (50%) patients who had not undergone surgery.

CONCLUSIONS

We demonstrate here the utility of AI mapping in detecting the EF based on brain regions showing decreased FDG-PET activity and, when coupled with DTI, could be a powerful tool for detecting EF and assessing WM integrity in MRI-negative epilepsy. PET/DTI could be used to further enhance clinical decision-making in epilepsy surgery.

Minimally Invasive Unilateral Percutaneous Transfracture Fixation of a Hangman's Fracture Using Neuronavigation and Intraoperative Fluoroscopy

BACKGROUND

Traumatic spondylolisthesis or hangman's fracture is a common cervical spine fracture. Most cases of traumatic spondylolisthesis are treated nonoperatively with external immobilization. The indications for surgery have generally included fracture instability or failed nonoperative management. Operative stabilization can be performed through either anterior or posterior approaches and has generally required instrumentation using open methods. We propose a technique for surgical repair of hangman's fracture that is minimally invasive and motion preserving using recent advances in 3-dimensional image-guidance technology. We believe this method represents another option in the treatment of hangman's fractures, because it allows for immediate stabilization, prompt recovery, and quick mobilization.

CASE DESCRIPTION

We present the case of 2 patients with hangman's fractures who had undergone surgical unilateral transfixation with minimally invasive percutaneous screw placement. In both cases, we used 3-dimensional neuronavigation and bidirectional intraoperative fluoroscopy. The operative time from incision to closure was <30 minutes. Preparation and positioning after intubation varied from 40 to 150 minutes. No intraoperative complications occurred. Both patients were discharged within 48 hours postoperatively. The follow-up examinations at 3 months, 12 months, and 5 years revealed healthy bony fusion on computed tomography imaging and an excellent clinical recovery.

CONCLUSION

We have provided 2 examples in which minimally invasive unilateral fixation of hangman's fractures proved to be safe and effective. In both cases, the patients were immediately relieved of their pain, quickly mobilized, and promptly discharged. The achievement of successful fusion confirmed at the follow-up examinations.

Morphology-Specific Discrimination between MS White Matter Lesions and Benign White Matter Hyperintensities Using Ultra-High-Field MRI

BACKGROUND AND PURPOSE

Recently published North American Imaging in Multiple Sclerosis guidelines call for derivation of a specific radiologic definition of MS WM lesions and mimics. The purpose of this study was to use SWI and magnetization-prepared FLAIR images for sensitive differentiation of MS from benign WM lesions using the morphologic characteristics of WM lesions.

MATERIALS AND METHODS

Seventeen patients with relapsing-remitting MS and 18 healthy control subjects were enrolled retrospectively. For each subject, FLAIR and multiecho gradient-echo images were acquired using 7T MR imaging. Optimized postprocessing was used to generate single-slice SWI of cerebral veins. SWI/FLAIR images were registered, and 3 trained readers performed lesion assessment. Morphology, location of lesions, and the time required for assessment were recorded. Analyses were performed on 3 different pools: 1) lesions of >3 mm, 2) nonconfluent lesions of >3 mm, and 3) nonconfluent lesions of >3 mm with no or a single central vein.

RESULTS

The SWI/FLAIR acquisition and processing protocol enabled effective assessment of central veins and hypointense rims in WM lesions. Assessment of nonconfluent lesions with ≥1 central vein enabled the most specific and sensitive differentiation of patients with MS from controls. A threshold of 67% perivenous WM lesions separated patients with MS from controls with a sensitivity of 94% and specificity of 100%. Lesion assessment took an average of 12 minutes 10 seconds and 4 minutes 33 seconds for patients with MS and control subjects, respectively.

CONCLUSIONS

Nonconfluent lesions of >3 mm with ≥1 central vein were the most sensitive and specific differentiators between patients with MS and control subjects.

Investigation of hippocampal substructures in focal temporal lobe epilepsy with and without hippocampal sclerosis at 7T

PURPOSE

To provide a more detailed investigation of hippocampal subfields using 7T magnetic resonance imaging (MRI) for the identification of hippocampal sclerosis in temporal lobe epilepsy (TLE).

MATERIALS AND METHODS

Patients (n = 13) with drug-resistant TLE previously identified by conventional imaging as having hippocampal sclerosis (HS) or not (nine without HS, four HS) and 20 age-matched healthy controls were scanned and compared using a 7T MRI protocol. Using a manual segmentation scheme to delineate hippocampal subfields, subfield-specific volume changes and apparent transverse relaxation rate ( R2*) were studied between the two groups. In addition, qualitative assessment at 7T and clinical outcomes were correlated with measured subfield changes.

RESULTS

Volumetry of the hippocampus at 7T in HS patients revealed significant ipsilateral subfield atrophy in CA1 (P = 0.001) and CA4+DG (P < 0.001). Volumetry also uncovered subfield atrophy in 33% of patients without HS, which had not been detected using conventional imaging. R2* was significantly lower in the CA4+DG subfields (P = 0.001) and the whole hippocampus (P = 0.029) of HS patients compared to controls but not significantly lower than the group without HS (P = 0.077, P = 0.109). No correlation was found between quantitative volumetry and qualitative assessment as well as surgical outcomes (Sub, P = 0.495, P = 0.567, P = 0.528; CA1, P = 0.104 ± 0.171, P = 0.273, P = 0.554; CA2+CA3, P = 0.517, P = 0.952, P = 0.130 ± 0.256; CA4+DG, P = 0.052 ± 0.173, P = 0.212, P = 0.124 ± 0.204; WholeHipp, P = 0.187, P = 0.132 ± 0.197, P = 0.628).

CONCLUSION

These preliminary findings indicate that hippocampal subfield volumetry assessed at 7T is capable of identifying characteristic patterns of hippocampal atrophy in HS patients; however, difficulty remains in using imaging to identify hippocampal pathologies in cases without HS.

LEVEL OF EVIDENCE

2 J. MAGN. RESON. IMAGING 2017;45:1359-1370.

Usage of SWI (susceptibility weighted imaging) acquired at 7T for qualitative evaluation of temporal lobe epilepsy patients with histopathological and clinical correlation: An initial pilot study

OBJECTIVES

Ultra high field MRI at 7T is able to provide much improved spatial and contrast resolution which may aid in the diagnosis of hippocampal abnormalities. This paper presents a preliminary experience on qualitative evaluation of 7T MRI in temporal lobe epilepsy patients with a focus on comparison to histopathology.

METHODS

7T ultra high field MRI data, using T1-weighted, T2*-weighted and susceptibility-weighted images (SWI), were acquired for 13 patients with drug resistant temporal lobe epilepsy (TLE) during evaluation for potential epilepsy surgery. Qualitative evaluation of the imaging data for scan quality and presence of hippocampal and temporal lobe abnormalities were scored while blinded to the clinical data. Correlation of imaging findings with the clinical data was performed. Blinded evaluation of 1.5T scans was also performed.

RESULTS

On the 7T MRI findings, eight out of 13 cases demonstrated concordance with the clinically suspected TLE. Among these concordant cases, three exhibited supportive abnormal 7T MRI findings which were not detected by the clinical 1.5T MRI. Of the ten cases that progressed to epilepsy surgery, seven showed concordance between 7T MRI findings and histopathology; of these, four cases had hippocampal sclerosis. SWI had the highest concordance with the clinical and histopathological findings. Similar clinical and histopathological concordance was found with 1.5T MRI.

CONCLUSIONS

There was moderate and high concordance between the 7T imaging findings with the clinical data and histopathology respectively.

Retrospective review of percutaneous synovial cyst ruptures: increased thickness of the T2 hypointense rim on post-rupture MRI may be associated with need for subsequent surgery

OBJECTIVE

To analyze MRI characteristics of lumbar facet synovial cysts and distinguish those requiring subsequent surgical management for recurrence, after percutaneous synovial cyst rupture.

METHODS AND MATERIALS

Retrospective chart review conducted in patients undergoing percutaneous synovial cyst rupture between February 2012 and April 2015. Pre- and post-percutaneous rupture procedure MRI spine studies were serially reviewed. Synovial cyst sizes, T1 and T2 signal characteristics and changes therein, T2 hypointense (or 'dark rim') thickness and change, and changes in the complexity of cyst signals were compared. Operative notes for patients who underwent subsequent surgical removal of recurrent synovial cysts were reviewed.

RESULTS

24 patients received 41 percutaneous synovial cyst rupture procedures, with a technical success rate of 82.9%. There was a significant difference in the mean increased thickness of the T2 hypointense rim on the first post-rupture MRI scan (p=0.0411) between patients requiring subsequent surgery and those who did not. There was a significant difference in the average sizes of synovial cysts before the procedure (p=0.0483) in those requiring subsequent surgery and those who did not. Five complications were noted (12.2%), mostly involving leg pain or weakness. Of the nine patients who underwent subsequent surgery post-synovial cyst rupture, six of the surgeries had recorded difficulty pertaining to scarring and/or adherence of the cyst to dura.

CONCLUSIONS

A larger increase in thickness of the T2 hypointense rim on the first post-rupture MRI scan and a larger synovial cyst size were associated with the need for subsequent surgical resection.

Retrospective review of efficacy of radiofrequency ablation for treatment of colorectal cancer liver metastases from a Canadian perspective

PURPOSE

A retrospective single-center review of ultrasound-guided radiofrequency ablation (RFA) treatment of colorectal cancer liver metastases was performed. This study reviews the primary and secondary technical effectiveness, overall survival of patients, recurrence-free survival, tumour-free survival, rates of local recurrence, and postprocedural RFA complications. Technical effectiveness and rates of complication with respect to tumour location and size were evaluated. Our results were compared with similar studies from Europe and North America.

METHODS

A total of 63 patients (109 tumours) treated with RFA between February 2004 and December 2009 were reviewed. Average and median follow-up time was 19.4 and 16.5 months, respectively (range, 1-54 months). Data from patient charts, pathology, and Picture Archiving and Communication System was integrated into an Excel database. Statistical Analysis Software was used for statistical analysis.

RESULTS

Primary and secondary technical effectiveness of percutaneous and intraoperative RFA were 90.8% and 92.7%, respectively. Average (SE) tumour-free survival was 14.4 ± 1.4 months (range, 1-43 months), and average (SE) recurrence-free survival was 33.5 ± 2.3 months (range, 2-50 months). Local recurrence was seen in 31.2% of treated tumours (range, 2-50 months) (34/109). Overall survival was 89.4% at 1 year, 70.0% at 2 years, and 38.1% at 3 years, with an average (SE) overall survival of 37.0 ± 2.8 months. There were 14 postprocedural complications. There was no statistically significant difference in technical effectiveness for small tumours (1-2 cm) vs intermediate ones (3-5 cm). There was no difference in technical effectiveness for peripheral vs parenchymal tumours.

CONCLUSIONS

This study demonstrated good-quality outcomes for RFA treatment of colorectal cancer liver metastases from a Canadian perspective and compared favorably with published studies.

Human PTCHD3 nulls: rare copy number and sequence variants suggest a non-essential gene

Background

Copy number variations (CNVs) can contribute to variable degrees of fitness and/or disease predisposition. Recent studies show that at least 1% of any given genome is copy number variable when compared to the human reference sequence assembly. Homozygous deletions (or CNV nulls) that are found in the normal population are of particular interest because they may serve to define non-essential genes in human biology.

Results

In a genomic screen investigating CNV in Autism Spectrum Disorders (ASDs) we detected a heterozygous deletion on chromosome 10p12.1, spanning the Patched-domain containing 3 (PTCHD3) gene, at a frequency of ~1.4% (6/427). This finding seemed interesting, given recent discoveries on the role of another Patched-domain containing gene (PTCHD1) in ASD. Screening of another 177 ASD probands yielded two additional heterozygous deletions bringing the frequency to 1.3% (8/604). The deletion was found at a frequency of ~0.73% (27/3,695) in combined control population from North America and Northern Europe predominately of European ancestry. Screening of the human genome diversity panel (HGDP-CEPH) covering worldwide populations yielded deletions in 7/1,043 unrelated individuals and those detected were confined to individuals of European/Mediterranean/Middle Eastern ancestry. Breakpoint mapping yielded an identical 102,624 bp deletion in all cases and controls tested, suggesting a common ancestral event. Interestingly, this CNV occurs at a break of synteny between humans and mouse. Considering all data, however, no significant association of these rare PTCHD3 deletions with ASD was observed. Notwithstanding, our RNA expression studies detected PTCHD3 in several tissues, and a novel shorter isoform for PTCHD3 was characterized. Expression in transfected COS-7 cells showed PTCHD3 isoforms colocalize with calnexin in the endoplasmic reticulum. The presence of a patched (Ptc) domain suggested a role for PTCHD3 in various biological processes mediated through the Hedgehog (Hh) signaling pathway. However, further investigation yielded one individual harboring a homozygous deletion (PTCHD3 null) without ASD or any other overt abnormal phenotype. Exon sequencing of PTCHD3 in other individuals with deletions revealed compound point mutations also resulting in a null state.

Conclusion

Our data suggests that PTCHD3 may be a non-essential gene in some humans and characterization of this novel CNV at 10p12.1 will facilitate population and disease studies.