Non-diagnostic Scans Research Articles

Applying Wells score to inconclusive perfusion only modified PIOPED II (Prospective Investigation of Pulmonary Embolism Diagnosis II) readings in orderto optimize the lung scintigraphy diagnostic yield in acute pulmonary embolism detection.

When using perfusion only modified PIOPED II criteria for PE detection, generated non-diagnostic scans are found to be the main diagnostic restriction. The objective of current study is to identify the role of Wells criteria added to inconclusive readings with the intent of enhancing the lung scintigraphy diagnostic yield. CTPA was performed in 34 suspected PE patients with inconclusive lung scintigraphy. They also were evaluated by Wells score and classified as low, intermediate and high probability. Overall prevalence and the rate of PE for each probability were calculated. Furthermore, NPV for scores < 2 and PPV for scores > 6 were computed. Having a mean age of 59.75 ± 17.38years, 7 (20.6%), 23 (67.6%) and 4 (11.8%) of cases had total criteria point count < 2, 2-6 and > 6, respectively. Using CTPA, 5 patients (14.7%) were diagnosed with PE. None of the patients with scores < 2 had PE with an associated NVP of 100%. Patients with scores 2-6 had a PE rate of 4.3% and 100% of patients with scores > 6 were diagnosed with PE, implying that the PPV of scores > 6 was 100%. Adding Wells score to non-diagnostic scans allowed identification of PE to be done reliably, and provided further insight into how lung scintigraphy in conjunction with clinical assessment is a practical strategy not only for the patients unfit for performing CTPA but also in all the patients referred for PE evaluation.

Validation of semi-automated flow-mediated dilation measurement in healthy volunteers.

Flow-mediated dilation (FMD) is a non-invasive imaging modality used to measure endothelial function but has significant intra- and inter-observer variability. The use of semi-automated FMD devices could overcome this limitation. We assessed the reproducibility of same-day semi-automated FMD measurements by investigators who received basic training on the correct use of the device. Forty-three healthy volunteers had two brachial artery FMD measurements performed 20 minutes apart using the UNEX EF 38G device, and automated outputs were produced. Images were also manually analysed using edge-detection software. The reproducibility of repeat FMD measurements within individuals was compared for automated and manual readings, and the correlation between analytical techniques was calculated. Twenty-five percent of scans were of non-diagnostic quality (n = 32). Automated analyses demonstrated sub-optimal reproducibility and measurement variability [intraclass correlation coefficient (ICCC) = 0.334, coefficient of variation (CV) = 45.87%]. In contrast, manually analysed scans had excellent reproducibility and low measurement variance (ICCC = 0.815, CV = 11.40%). FMD values obtained from automated and manual analysis correlated poorly (r = 0.164), whereas resting (r = 0.955) and maximal brachial artery diameters demonstrated excellent correlation (r = 0.867). Manually evaluated serial UNEX EF readings have good reproducibility and therefore, the optimal FMD workflow involves manual analyses prior to independent automated interrogation. The high non-diagnostic scan rate is most likely the result of insufficient training and indicates that semi-automatic devices such as UNEX EF should be used by experienced investigators to achieve optimal results.

DIAGNOSTIC IMAGE QUALITY ASSESSMENT AND CLASSIFICATION IN MEDICAL IMAGING: OPPORTUNITIES AND CHALLENGES.

Magnetic Resonance Imaging (MRI) suffers from several artifacts, the most common of which are motion artifacts. These artifacts often yield images that are of non-diagnostic quality. To detect such artifacts, images are prospectively evaluated by experts for their diagnostic quality, which necessitates patient-revisits and rescans whenever non-diagnostic quality scans are encountered. This motivates the need to develop an automated framework capable of accessing medical image quality and detecting diagnostic and non-diagnostic images. In this paper, we explore several convolutional neural network-based frameworks for medical image quality assessment and investigate several challenges therein.

Evaluating the success of a newly introduced Feed and Wrap protocol in magnetic resonance imaging scanning of the temporal bone for the evaluation of congenital sensorineural hearing loss

ObjectivesMagnetic resonance imaging (MRI) of the temporal bones, specifically of the cochlea and retro-cochlear pathway, is an important investigation in the diagnostic workup and management of congenital hearing loss. However, obtaining a diagnostic quality MRI scan depends upon the need for the infant to remain still for the duration of the scan. The Feed and Wrap (F + W) technique is a method that has been used successfully in infants for scans of other parts of the body, but has not been properly studied in MRI scans performed for hearing loss.The primary aim was to evaluate the diagnostic success rate of a newly introduced Feed and Wrap MRI scanning protocol used for assessment of sensorineural hearing loss in infants at Western Australia's Tertiary Paediatric hospital over the last three years. The secondary aims were to discuss the advantages and disadvantages of this technique and to review the available published literature on this technique and compare it to our case series. MethodsAll F + W MRI scans performed for the investigation of congenital hearing loss between 2016 and 2019 at the King Edward Memorial Hospital for Women and Perth Children's Hospital were retrospectively reviewed. The primary outcome was the diagnostic utility of the MRI scan with a diagnostic scan defined as the ability to diagnose or exclude radiological causes of sensorineural hearing loss. Results53 MRI scans of the temporal bone and brain were identified. 86.8% of scans were diagnostic. The mean age of infants who underwent diagnostic scans was 6.8 weeks old compared to 10.9 weeks (p = 0.01) for those who had non-diagnostic scans. The optimal age cut off for F + W technique was ≤10 weeks. The odds of failure are 16.7 (95%CI 6.5–42.8, p = 0.003) times higher above the cut of age of 10 weeks compared to ≤10 weeks. ConclusionThe F + W technique is a viable method for obtaining diagnostic quality MRI scans of the inner ear structures in infants with hearing loss, with a greater likelihood of success when applied in younger infants.

Accuracy of unenhanced, non-sedated MRI in the diagnosis of acute appendicitis in children

BackgroundChildren with suspected appendicitis generally undergo an ultrasound (most commonly) or a CT scan (rarely) as the first imaging study. At our hospital, patients with non-diagnostic ultrasound or CT scan results undergo a non-contrast (unenhanced), non-sedated MRI. We aimed to determine the accuracy of this study for this purpose in a large cohort of children. MethodsA retrospective review of all unenhanced, non-sedated MRIs done for suspected appendicitis was performed from January 2014 to December 2018. MRI reports were correlated with pathology reports in cases that underwent appendectomy, and with clinical outcomes if no operation was done (clinical follow up: 30d). No patient was treated for appendicitis non-operatively. ResultsThree hundred fifty unenhanced, non-sedated MRIs were done and reviewed with median age: 12 (3 to 18) years. Sixty-five (18.6%) MRIs were positive for appendicitis, and 62 of those underwent appendectomy (3 excluded clinically). Pathology was positive in 59/62 cases. 256 (73.1%) MRIs were negative for appendicitis. Six cases underwent appendectomy (persistent symptoms). Pathology was positive in 2/6 cases. The overall diagnostic accuracy was: sensitivity 96.7% (95% CI: 88.6–99.6), specificity 97.7% (95% CI: 95.0–99.1), PPV: 90.8% (95% CI: 81.6–95.6; false positives 6/65), and NPV: 99.2% (95% CI: 97.0–99.8; false negatives 2/254). Twenty-nine (8.3%) MRIs were non-diagnostic. None of those 29 cases had appendicitis (4 negative pathology, 25 excluded clinically). ConclusionsThe unenhanced, non-sedated MRI is highly accurate for the diagnosis of appendicitis in children. It should be considered as an alternative to CT in the work-up of patients with suspected appendicitis to eliminate the risks associated with ionizing radiation. Level of EvidenceLevel IV.

Adoption of the Coronary Artery Disease-reporting and Data System: Reduced Downstream Testing and Cardiology Referral Rates in Patients with Non-obstructive Coronary Artery Disease.

IntroductionThe coronary artery disease-reporting and data system (CAD-RADS) was developed to standardize communication of per-patient maximal stenosis and provide treatment recommendations that may affect downstream testing.MethodsDownstream testing, cardiology referral, and cost were abstracted for 1,796 consecutive patients undergoing coronary CT angiography (CCTA) before and after the adoption of the CAD-RADS reporting template at a single-center closed referral hospital system. Cost analysis was based on direct invasive and non-invasive testing utilizing the Center for Medicare & Medicaid Services (CMS) outpatient prospective payment system (OPPS) final rule for 2018.ResultsBaseline cardiovascular risk factors were balanced between the groups. Overall, referrals for downstream testing were similar between cohorts (10.7% vs 10.8%; p = 0.939). Referral for downstream testing was reduced in the CAD-RADS 1 & 2 cohort compared to non-obstructive coronary artery disease (CAD) by non-standardized reporting (NSR; 5.1% vs 14.4%, p < 0.001). This was offset by more non-diagnostic scans in the CAD-RADS cohort (9.7% vs 4.2%, p < 0.001), resulting in increased downstream testing (28.8% vs 11.4%, p = 0.038). Overall, cardiology referral rates by primary care providers (PCPs) were similar between the groups (12.2% vs 15.8%, p = 0.197). Cardiology referral rates were increased among patients with non-obstructive CAD in the NSR cohort compared with CAD-RADS 1 & 2 patients (20.5% vs 8.6%, p = 0.021). Referrals for invasive coronary angiography were low in both groups overall (3.5% vs 3.2%, p = 0.726). Median downstream testing costs were similar between the groups (p = 0.554).ConclusionsAdoption of the CAD-RADS reporting template was associated with a reduction in downstream testing and cardiology referral rates among non-obstructive CAD (CAD-RADS 1 & 2) patients. Thus, CAD-RADS may impact downstream testing in patients in whom further testing can typically be deferred.

Cone-beam computed tomography of the head in standing equids

BackgroundComputed tomography in standing horses has revolutionized diagnostic imaging. The O-arm®, a cone beam computed tomography (CBCT) scanner with a gantry opening of 96.5 cm is routinely used for image-guided spine and neurosurgery in humans. The aim of this study is to describe the set-up and first experiences using the O-arm® to achieve CBCT imaging of the head in standing horses.CT imaging of the predefined region of interest (ROI) was tested on 2 cadaveric heads, concentrating on centering issues within the gantry, as well as determining the number of scans needed per ROI. All horses presented with head-related diseases and subjected to a CBCT examination between February 2015 and November 2016 for CBCT were included. Per scan, a limited field of view, i.e. a cylindrical volume of 21 cm in diameter and 16 cm in height was acquired within 13 s. Depending on the dimensions of the ROI, the minimum number of scans could range from one to six, if the entire equine head is to be examined in an adult horse.ResultsSixty-eight horses were included, five of which had a follow-up CBCT exam, and two of which were presented twice for two different indications (75 clinical cases). A total number of 449 acquired three-dimensional (3D) scans were recorded for these 75 cases. Two-hundred and forty-two 3D scans (54%) were considered as diagnostic quality. The imaging procedure was generally well tolerated by the sedated, standing equid, and diagnostic studies were performed in 73 out of 75 cases (97.3%). Motion artefacts and inadequate centering of the ROI were the most common reasons for non-diagnostic quality images and repeat scans of the same ROI.ConclusionsCBCT is a valuable imaging modality for the equine head. Advantages of the O-arm® compared to a conventional multi-slice helical CT for imaging of the head in standing equids include the rapid image acquisition, the gantry’s mobility in all dimensions, and the free movability of the entire imaging unit. Disadvantages include the considerable sensitivity to motion artefact, increased scatter, low soft tissue contrast and the limited dimensions of the field of view.

Impact of heart rate on coronary computed tomographic angiography interpretability with a third-generation dual-source scanner

BackgroundGuidelines suggest coronary computed tomography angiography (CCTA) should be performed with a heart rate (HR) below 60. Third-generation dual-source CT (DSCT) scanners, with improved temporal resolution, and end-systolic acquisition may facilitate imaging at higher HRs. We determined the influence of HR and end-systolic acquisition on image interpretability and quality with a third-generation DSCT. MethodsPatients who underwent CCTA between July 2017 and December 2018 were retrospectively identified. All images were acquired using a SOMATOM Force scanner (Siemens Healthcare). The primary outcome was the presence of any uninterpretable coronary segment. The association between HR and CCTA with uninterpretable segments was assessed with multivariable logistic regression, correcting for demographics and imaging variables. ResultsIn total, 2620 patients were included, mean age 61.4 ± 12.9 years and 61.2% male, with uninterpretable segments present in 229 (8.7%) scans. In multivariable analysis, HR 80–89 was associated with an increased likelihood of having a scan with uninterpretable segments (adjusted odds ratio [OR] 4.53, p < 0.001). However, no significant association was present with end-systolic acquisition (HR 80–89, adjusted OR 2.32, p = 0.125). HR ≥ 90 was associated with a decreased likelihood of good or excellent image quality (adjusted OR 0.26, 95% CI 0.11–0.63, p = 0.003). ConclusionsWith third-generation dual-source CT scanners, patients with HR 60–80 can be imaged without impacting image interpretability. End-systolic image acquisition facilitates imaging at HRs > 80 without increasing non-diagnostic scans. Routine use of systolic gating could omit the need for strict HR control and pre-test beta blockade currently required for CCTA.

Bone densitometry by radiofrequency echographic multi-spectrometry (REMS) in the diagnosis of osteoporosis

The paper summarises the present knowledge of the new bone densitometry method called radiofrequency echographic multi-spectrometry (REMS). This ultrasound-based approach enables the evaluation of bone mineral density (BMD) in the hip and the lumbar spine. During REMS densitometry, a fully automatic algorithm performs a series of spectral and statistical analyses involving both echographic images and corresponding “raw” (unfiltered) radiofrequency signals. This provides the identification of the region of interest (ROI) and the calculation of standard densitometric parameters: BMD, T-score and Z-score. Nondiagnostic scans and artifacts are automatically excluded by the algorithm, reducing the risk of false results. A recently published multi-center study has demonstrated high diagnostic sensitivity, specificity and accuracy of this innovative method in the diagnosis of osteoporosis. To the authors’ best knowledge, this is the first Polish paper on REMS densitometry. Forum Reumatol. 2019, tom 5, nr 2: 81–88

MRI Safety for Patients Implanted With the MRI Ready ICD System

A prospective, multicenter study was performed to assess the safety and efficacy of the Durata and Optisure HV leads and the Ellipse VR implantable cardioverter-defibrillator (ICD) (St. Jude Medical, Sylmar, California) in a 1.5-T magnetic resonance imaging (MRI) environment. The primary safety objective was >90% freedom from MRI scan-related complications. The primary efficacy objectives were absence of change in capture threshold and absence of decrease of sensing amplitude from pre-MRI examination to 1 month after MRI. MRI scanning of patients has been shown to be safe in patients with magnetic resonance-conditional implantable cardioverter-defibrillators (ICD) systems. Patients with a previously implanted magnetic resonance-conditional system underwent a nondiagnostic MRI scan. After the scan, a questionnaire was given to investigators and patients who returned for 1-month follow-up examination. A subset of patients underwent ventricular tachyarrhythmia or ventricular fibrillation (VT/VF) induction testing after the MRI to evaluate defibrillation function. There were 220 patients (81% male; 62.1 ± 11.2 years of age) enrolled who received an MRI scans from 29centers. All primary safety and efficacy endpoints were met (p<0.0001). No significant detection delays were found in 34 patients who had VT/VF episodes after the MRI scan was performed. Most physicians reported easy and acceptable programming and ease of MRI scheduling. The MRI Ready MRI-conditional ICD system is safe, and electrical performance was not affected in patients receiving a 1.5-T whole-body MRI scan. Investigators reported favorable collaboration between cardiologists and radiologists in the MRI Ready IDE clinical trial. (A Clinical Evaluation of the Durata or Optisure High Voltage Leads and Ellipse VR ICD Undergoing MRI, an IDE Study [MRI Ready IDE]; NCT02787291).

Low-dose computed tomography of urolithiasis in obese patients: a feasibility study to evaluate image reconstruction algorithms.

Purpose: Retrospective evaluation and comparison of image quality generated by low-dose computed tomography (LDCT) from obese patients with urolithiasis using alternative reconstruction algorithms.Materials and methods: Twenty-five obese patients (body mass index [BMI]>25 kg/m2) underwent LDCT scans for suspected urolithiasis. The scans were recompiled using filtered-back projection (FBP), statistical iterative reconstruction (iDose) and iterative model-based reconstruction (IMR). Dose-length product (DLP) and patient details were obtained from the CT dose report and clinical charts, respectively. Objective image noise was assessed by measuring the SD of Hounsfield units (HUs) in defined locations. Additionally, subjective image evaluation was independently performed by two radiologists using a 3-point Likert scale. The inter-reviewer agreement of image quality was calculated.Results: Ureteral concretions were observed in all CT scans, two of which revealed bilateral stones. The assessed patients’ mean BMI was 29.29±3.74 kg/m2, and the DLP of the CT scans was 100.04±10.00 mGy*cm. All scans were rated diagnostic with the iDose and iterative model-based reconstructions, whereas 41% of the scans performed with FBP reconstruction were nondiagnostic. With respect to image quality, IMR was superior to iDose and FBP, both in the objective (P<0.001) and overall subjective (P≤0.008) evaluation of the respective data sets. The inter-reviewer agreement for overall image quality was “almost perfect” for IMR, “substantial” for iDose and “moderate” for FBP (κ values of 1.0, 0.6 and 0.46, respectively).Conclusion: Using iterative image reconstruction algorithms, LDCT of urolithiasis is feasible in overweight patients with a BMI between 25 and 35 kg/m2. Due to higher image quality, IMR is the preferred algorithm for scan reconstruction as it may help to avoid repeated examinations due to initial nondiagnostic scans.

Diagnostic Performance of a Novel Coronary CT Angiography Algorithm: Prospective Multicenter Validation of an Intracycle CT Motion Correction Algorithm for Diagnostic Accuracy.

Motion artifact can reduce the diagnostic accuracy of coronary CT angiography (CCTA) for coronary artery disease (CAD). The purpose of this study was to compare the diagnostic performance of an algorithm dedicated to correcting coronary motion artifact with the performance of standard reconstruction methods in a prospective international multicenter study. Patients referred for clinically indicated invasive coronary angiography (ICA) for suspected CAD prospectively underwent an investigational CCTA examination free from heart rate-lowering medications before they underwent ICA. Blinded core laboratory interpretations of motion-corrected and standard reconstructions for obstructive CAD (≥ 50% stenosis) were compared with ICA findings. Segments unevaluable owing to artifact were considered obstructive. The primary endpoint was per-subject diagnostic accuracy of the intracycle motion correction algorithm for obstructive CAD found at ICA. Among 230 patients who underwent CCTA with the motion correction algorithm and standard reconstruction, 92 (40.0%) had obstructive CAD on the basis of ICA findings. At a mean heart rate of 68.0 ± 11.7 beats/min, the motion correction algorithm reduced the number of nondiagnostic scans compared with standard reconstruction (20.4% vs 34.8%; p < 0.001). Diagnostic accuracy for obstructive CAD with the motion correction algorithm (62%; 95% CI, 56-68%) was not significantly different from that of standard reconstruction on a per-subject basis (59%; 95% CI, 53-66%; p = 0.28) but was superior on a per-vessel basis: 77% (95% CI, 74-80%) versus 72% (95% CI, 69-75%) (p = 0.02). The motion correction algorithm was superior in subgroups of patients with severely obstructive (≥ 70%) stenosis, heart rate ≥ 70 beats/min, and vessels in the atrioventricular groove. The motion correction algorithm studied reduces artifacts and improves diagnostic performance for obstructive CAD on a per-vessel basis and in selected subgroups on a per-subject basis.

GRASE Revisited: breath-hold three-dimensional (3D) magnetic resonance cholangiopancreatography using a Gradient and Spin Echo (GRASE) technique at 3T.

To evaluate the clinical feasibility and image quality of breath-hold (BH) three-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP) using a gradient and spin-echo (GRASE) technique compared to the conventional 3D respiratory-triggered (RT)-MRCP using a turbo spin-echo (TSE) sequence at 3 T. Sixty-six patients underwent both 3D RT-TSE-MRCP and 3D BH-GRASE-MRCP at 3 T. Three radiologists independently reviewed the visualisation of biliary and pancreatic ducts, image blurring, and overall image quality of the two data sets using four- or five-point scales. The numbers of scans with non-diagnostic or poor image quality were compared between the two scans. The 3D BH-GRASE-MRCP had a significantly better image quality (3.69 ± 0.77 vs. 3.30 ± 1.18, p = 0.005) and less image blurring (3.23 ± 0.94 vs. 3.65 ± 0.57, p = 0.0003) than the 3D RT-TSE-MRCP. In detail, 3D BH-GRASE-MRCP better depicted the common bile duct, cystic duct, and bilateral first intrahepatic duct (all ps < 0.05). The number of scans with non-diagnostic or poor image quality significantly decreased with 3D BH-GRASE-MRCP compared with 3D RT-TSE-MRCP [19.7% (13/66) vs. 1.5% (1/66), p = 0.002]. The 3D BH-GRASE-MRCP provided better image quality and a reduced number of non-diagnostic images compared to 3D RT-TSE-MRCP. • The GRASE technique enabled 3D MRCP acquisition within a single breath-hold. • The short acquisition time of 3D BH-GRASE-MRCP significantly reduced image blurring. • The 3D BH-GRASE-MRCP had a better image quality than 3D RT-TSE-MRCP. • The number of non-diagnostic scans was reduced with 3D BH-GRASE-MRCP.

Clinical safety and performance of a MRI conditional pacing system in patients undergoing cardiac MRI.

Utilization of cardiac magnetic resonance imaging (cMRI) as an imaging modality in clinical practice is rapidly increasing. More evidence from randomized studies establishing clinical safety and performance of pacing systems in patients undergoing a cMRI scan is needed. The purpose of this prospective, multicenter, randomized study was to demonstrate safety and efficacy of the Accent MRI™ conditional pacing systems (St. Jude Medical, St. Paul, MN, USA) in patients undergoing cMRI scan. Patients (n=283) indicated for dual-chamber pacemaker implant were randomized to either the MRI Group (MG) (n=140) or the Control Group (CG) (n=143) after successful device implantation of the Accent MRI™ system. Clinical evaluation and device interrogation were performed at pre- and post-MRI scan, and 1 month post-MRI for all patients. At 9-12weeks postimplant, patients in MG underwent a nondiagnostic cMRI scan at 1.5 Tesla (T), while patients in CG underwent device interrogation and clinical evaluation twice with a 45-minute waiting period in between. The safety endpoint was freedom from MRI scan-related complications and that for efficacy was significant changes in right atrial/ventricular capture threshold and sensing amplitude between right before MRI, immediately after MRI, and 1 month post-MRI. Results showed 100% freedom from MRI scan-related complications. There were no significant changes in device performance between pre-MRI scan and 1 month post-MRI scan time points in both study groups. cMRI scanning with 1.5 T scanners is safe in patients implanted with the Accent MRI™ conditional pacing system and has no significant effect on the electrical parameters of the device and leads.

Evaluating the risk of appendiceal perforation when using ultrasound as the initial diagnostic imaging modality in children with suspected appendicitis.

Ultrasound scan has gained attention for diagnosing appendicitis due to its avoidance of ionizing radiation. However, studies show that ultrasound scan carries inferior sensitivity to computed tomography scan. A non-diagnostic ultrasound scan could increase the time to diagnosis and appendicectomy, particularly if follow-up computed tomography scan is needed. Some studies suggest that delaying appendicectomy increases the risk of perforation. To investigate the risk of appendiceal perforation when using ultrasound scan as the initial diagnostic imaging modality in children with suspected appendicitis. We retrospectively reviewed 1411 charts of children ≤17 years old diagnosed with appendicitis at two urban academic medical centers. Patients who underwent ultrasound scan first were compared to those who underwent computed tomography scan first. In the sub-group analysis, patients who only received ultrasound scan were compared to those who received initial ultrasound scan followed by computed tomography scan. Main outcome measures were appendiceal perforation rate and time from triage to appendicectomy. In 720 children eligible for analysis, there was no significant difference in perforation rate between those who had initial ultrasound scan and those who had initial computed tomography scan (7.3% vs. 8.9%, p = 0.44), nor in those who had ultrasound scan only and those who had initial ultrasound scan followed by computed tomography scan (8.0% vs. 5.6%, p = 0.42). Those patients who had ultrasound scan first had a shorter triage-to-incision time than those who had computed tomography scan first (9.2 (IQR: 5.9, 14.0) vs. 10.2 (IQR: 7.3, 14.3) hours, p = 0.03), whereas those who had ultrasound scan followed by computed tomography scan took longer than those who had ultrasound scan only (7.8 (IQR: 5.3, 11.6) vs. 15.1 (IQR: 10.6, 20.6), p < 0.001). Children < 12 years old receiving ultrasound scan first had lower perforation rate (p = 0.01) and shorter triage-to-incision time (p = 0.003). Children with suspected appendicitis receiving ultrasound scan as the initial diagnostic imaging modality do not have increased risk of perforation compared to those receiving computed tomography scan first. We recommend that children <12 years of age receive ultrasound scan first.

216-37: A prospective, randomized clinical evaluation of the safety and efficacy of an MR Conditional pacing system in subjects undergoing Cardiac Magnetic Resonance Imaging (MRI)

Purpose: There are limited published data from controlled studies on pacemaker implanted patients who underwent a Cardiac MRI scan. The purpose of this prospective, international, multi-center, randomized study was to demonstrate safety and efficacy of the SJM MRI conditional pacing system in patients undergoing cardiac MRI scan. Methods: Patients (n = 283) indicated for dual chamber pacemaker implant were invited to provide voluntary consent at 15 centers across Asia and randomized either to the MRI scan group (SG; n = 140) or the Control group (CG; n = 143) post successful device implantation (Accent MRITM DDDR, Tendril MRITM lead, St. Jude Medical). Each patient in SG (within 9 – 12 weeks post-implant) underwent an elective, prespecificed, non-diagnostic cardiac MRI scan in a 1.5 Tesla horizontal cylindrical bore scanning machine with total magnet exposure time of approximately 60 minutes, maximized gradient slew rate of up to 200 T/m/s and whole body SAR < 4W/kg. Clinical evaluation and device interrogation were performed at baseline, pre and post MRI scan visit and 1-month post MRI for all enrolled patients. The primary endpoint for device safety was freedom from MRI-related complications. The primary endpoint for device efficacy was change in RA/RV capture threshold and sensing amplitude from the MRI visit to 1 month post-MRI visit. Summary of results: The study achieved both safety and efficacy endpoints with 118 patients completing the 1 month post MRI scan visit reporting 100% freedom from MRI scan related complications at the 1 Month post Cardiac MRI Scan follow-up visit (95% LCB: 97.4%). The study reported 12 SADEs & 28 SAEs all of which were found to be not related to MRI scan. No significant changes in device performance with respect to RA/RV capture threshold and RA/RV sensing amplitude from the MRI visit to 1 month post-MRI visit were observed between CG and SG groups (Table 1). Change in RA/RV lead efficacy parameters# #Minimum 113 subjects were required in each group to achieve more than 90% of power at a one sided significant level of 5% to show the non-inferiority with a margin of 10% *n - Number of subjects who experienced an increase in RA capture threshold @ 0.5 ms at 1 M post-MRI scan ≤ 0.5V compared to pre-MRI testing *n - Number of subjects who experienced a decrease in RA sensing amplitude ≤ 50% and ≥ 1.5 mV at 1 M post-MRI scan compared to pre-MRI testing Change in RA/RV lead efficacy parameters# #Minimum 113 subjects were required in each group to achieve more than 90% of power at a one sided significant level of 5% to show the non-inferiority with a margin of 10% *n - Number of subjects who experienced an increase in RA capture threshold @ 0.5 ms at 1 M post-MRI scan ≤ 0.5V compared to pre-MRI testing *n - Number of subjects who experienced a decrease in RA sensing amplitude ≤ 50% and ≥ 1.5 mV at 1 M post-MRI scan compared to pre-MRI testing Conclusions: This study of the St. Jude Medical Accent MRITM pacemaker system in patients undergoing 1.5T cardiac MRI scans at up to 4W/kg successfully met the safety and efficacy endpoints.

Abstract WP37: Whole Brain CT Perfusion Identifies Ischemic Events in Patients With Mild Neurological Symptoms

Introduction: More than half of ischemic stroke patients present as minor strokes (NIHSS&lt;6). A lack of thrombolysis guidelines for this population leads to untreated strokes and erroneously treated stroke mimics, producing adverse outcomes. Data suggest that whole brain CT perfusion (WB-CTP) improves detection of ischemia, offering a potential method of ameliorating diagnostic uncertainty in these patients. Hypothesis: WB-CTP can guide clinical decisions by identifying patients with ischemic episodes that would benefit from thrombolysis or early intervention. Methods: This retrospective chart review enrolled 524 consecutive patients receiving WB-CTP with a Toshiba 320 detector scanner between 08/2008 and 06/2015, for acute stroke less than 6 hours from onset and NIHSS&lt;6, and who showed no evidence of intracranial hemorrhage. Patients were excluded for non-diagnostic (n=25) or unreported (n=8) scans and non-ischemic findings (7). For diagnostic accuracy calculations, the reference standard was the final clinical impression suggesting ischemic events, as only 52% had follow-up imaging. Subgroup analyses were performed in patients receiving follow-up imaging. Results: A total of 484 patients (age 17-101, 54% men, mean NIHSS 2.47) were included. Follow-up imaging was performed in 251 patients; 150 underwent MRI with diffusion-weighted imaging (DWI). A summary of diagnostic accuracy values is shown in table below. WB-CTP is highly specific with a high positive predictive value in all groups and has moderate to high negative predictive value. Positive and negative likelihood ratios were 21.24 and 0.5 in the whole group analysis. Conclusions: Positive WB-CTP findings may warrant early intervention, including thrombolysis, while negative findings alone are not a sufficient basis upon which to confidently withhold interventions.

Quantitative high-efficiency cadmium-zinc-telluride SPECT with dedicated parallel-hole collimation system in obese patients: Results of a multi-center study

BackgroundObesity is a common source of artifact on conventional SPECT myocardial perfusion imaging (MPI). We evaluated image quality and diagnostic performance of high-efficiency (HE) cadmium-zinc-telluride parallel-hole SPECT MPI for coronary artery disease (CAD) in obese patients. Methods and Results118 consecutive obese patients at three centers (BMI 43.6 ± 8.9 kg·m−2, range 35-79.7 kg·m−2) had upright/supine HE-SPECT and invasive coronary angiography > 6 months (n = 67) or low likelihood of CAD (n = 51). Stress quantitative total perfusion deficit (TPD) for upright (U-TPD), supine (S-TPD), and combined acquisitions (C-TPD) was assessed. Image quality (IQ; 5 = excellent; < 3 nondiagnostic) was compared among BMI 35-39.9 (n = 58), 40-44.9 (n = 24) and ≥45 (n = 36) groups. ROC curve area for CAD detection (≥50% stenosis) for U-TPD, S-TPD, and C-TPD were 0.80, 0.80, and 0.87, respectively. Sensitivity/specificity was 82%/57% for U-TPD, 74%/71% for S-TPD, and 80%/82% for C-TPD. C-TPD had highest specificity (P = .02). C-TPD normalcy rate was higher than U-TPD (88% vs 75%, P = .02). Mean IQ was similar among BMI 35-39.9, 40-44.9 and ≥45 groups [4.6 vs 4.4 vs 4.5, respectively (P = .6)]. No patient had a nondiagnostic stress scan. ConclusionsIn obese patients, HE-SPECT MPI with dedicated parallel-hole collimation demonstrated high image quality, normalcy rate, and diagnostic accuracy for CAD by quantitative analysis of combined upright/supine acquisitions.

The Correct Selection of Pitch for Optimal CT Scanning: Avoiding Common Misconceptions

Today’s state-of-the-art CT scanners include many features that aid in the selection of optimal technique parameters. Vendors offer solutions for choosing the optimal beam energy (tube voltage), automatic exposure control (AEC) via tube current modulation control, patient positioning within the gantry, and patient-specific contrast injection protocols. The trend seems to be leading to a “push button” CT scanner in which only the dose, noise level, and image sharpness, determined by the clinical indication, need to be prescribed. This trend will likely decrease the frequency of nondiagnostic CT scans. However, it should not mitigate the need to understand some of the fundamental relationships between acquisition parameters and dose. We illustrate the most common misconceptions concerning the selection of pitch in this article.

Cardiac CT and Stent Imaging: Update 2014

Percutaneous coronary intervention with stent implantation is a common technique for coronary revascularization. Despite the widespread use of drug-eluting stents in-stent restenosis (ISR) is still a major issue. Multidetector row computed tomography angiography of the coronary arteries is a well-established, noninvasive tool for the assessment of the coronary arteries. Stent imaging, however, is a challenging task with relevant rates of nondiagnostic scans due to motion and beam-hardening artifacts. Nevertheless, recent scanners provide excellent results for the exclusion of ISR with a negative predictive value of about 97 %. Further indications for CT imaging of coronary stents include the detection and visualization of stent-related complications such as stent fracture. During the last couple of years there have been some major advances in CT imaging of coronary stents relating to hardware and imaging protocols. This review describes recent advances in CT imaging of coronary stents and summarizes current results