Local reference and achievable dose levels for vascular and enterostomy access procedures in pediatric interventional radiology.

BACKGROUND: Knowledge of radiation quantities delivered in routine practice is an essential responsibility of a pediatric interventional radiology department. OBJECTIVE: To review radiation indices in frequently performed vascular and enterostomy access procedures at a quaternary pediatric hospital to formulate dosimetric reference levels and achievable levels. MATERIALS AND METHODS: A retrospective review of patient demographics, procedure information and quantitative dose metrics over a 2-year period was performed. Dosimetric details for common procedures (central line insertions, gastrostomy/gastrojejunostomy insertions and maintenance) were evaluated, correlated with demographic data and stratified across five weight groups (0-5 kg, 5-15 kg, 15-30 kg, 30-50 kg, 50-80 kg). Achievable (50th percentile) and reference (75th percentile) levels with confidence intervals were established for each procedure. RESULTS: Within the evaluation period, 3,165 studies satisfied the inclusion criteria. Five were classified as device insertions (peripherally inserted central catheter, n=1,145; port-a-catheter, n=321; central venous line, n=285; gastrostomy-tube [G-tube], n=262, and gastrojejunostomy-tube [GJ-tube], n=66), and two were classified as maintenance procedures (G-tube, n=358, and GJ-tube, n=728, checks, exchanges and reinsertions). Representative reference and achievable levels were calculated for each procedure category and weight group. CONCLUSION: This work highlights the creation of local reference and achievable levels for common pediatric interventional procedures. These data establish a dosimetric reference to understand the quantity of radiation routinely applied, allowing for improved relative radiation risk assessment and enriched communication to interventionalists, health care providers, parents and patients.

Cone-beam computed tomography-assisted percutaneous gastrostomy tube insertion in children with challenging anatomy.

BACKGROUND: Percutaneous radiological gastrostomy tube insertion is a common procedure in children. An approach using ultrasound and fluoroscopy may not be feasible in patients with challenging anatomy; therefore, advanced techniques or other imaging modalities may be required. OBJECTIVE: To describe our experience using cone-beam computed tomography (CT)-assisted percutaneous gastrostomy insertion in pediatric patients with challenging anatomy. MATERIALS AND METHODS: A retrospective review was performed in children who underwent cone-beam CT-assisted percutaneous radiologic gastrostomy between January 2015 and July 2019. Indications, technique, outcomes, complications, and radiation dose (reference-point air kerma, air kerma area product) were assessed through chart and imaging review. Descriptive statistics only were used. RESULTS: Twenty-seven procedures were attempted in 26 patients. Reasons for utilizing cone-beam CT guidance were high-positioned stomach (n = 10), interposing bowel loops and liver (n = 19), omphalocele (n = 1), severe scoliosis (n = 1), and ventriculoperitoneal shunt (n = 1). Technical success was 85% (23/27). Mean procedure time was 96 min (range 50-131 min). No safe access route into the stomach was encountered in four patients; three were referred for surgical gastrostomy and one had a successful re-attempt. Radiation dose data was obtained from 19 procedures (17 successful) with a total dose in successful procedures ranging from 8.1 to 63.6 mGy (average 26.2 mGy, median 24.9 mGy). The number of cone-beam CT acquisitions per procedure ranged from 1 to 4. Major complication frequency was 11% (3/27) (bleeding, peritonitis, and aspiration pneumonia); minor complication frequency was 3.7% (1/27). CONCLUSION: This study shows that cone-beam CT guidance can be useful for assisting percutaneous radiologic gastrostomy in children with challenging anatomy.

Clinical evaluation of reconstruction and acquisition time for pediatric 18F-FDG brain PET using digital PET/CT.

BACKGROUND: 18F-2-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) plays an important role in the diagnosis, evaluation and treatment of childhood epilepsy. The selection of appropriate acquisition and reconstruction parameters, however, can be challenging with the introduction of advanced hardware and software functionalities. OBJECTIVE: To quantify the diagnostic performance of a block-sequential regularized expectation maximization (BSREM) tool and reduced effective counts in brain PET/CT for pediatric epilepsy patients on a digital silicon photomultiplier system. MATERIALS AND METHODS: We included 400 sets of brain PET/CT images from 25 pediatric patients (0.5-16 years old) in this retrospective study. Patient images were reconstructed with conventional iterative techniques or BSREM with varied penalization factor (ß), at varied acquisition time (45 s, 90 s, 180 s, 300 s) to simulate reduced count density. Two pediatric nuclear medicine physicians reviewed images in random order - blinded to patient, reconstruction method and imaging time - and scored technical quality (noise, spatial resolution, artifacts), clinical quality (image quality of the cortex, basal ganglia and thalamus) and overall diagnostic satisfaction on a 5-point scale. RESULTS: Reconstruction with BSREM improved quality and clinical scores across all count levels, with the greatest benefits in low-count conditions. Image quality scores were greatest at 300-s acquisition times with ß=500 (overall; noise; artifacts; image quality of the cortex, basal ganglia and thalamus) or ß=200 (spatial resolution). No statistically significant difference in the highest graded reconstruction was observed between imaging at 180 s and 300 s with an appropriately implemented penalization factor (ß=350-500), indicating that a reduction in dose or acquisition time is feasible without reduction in diagnostic satisfaction. CONCLUSION: Clinical evaluation of pediatric 18F-FDG brain PET image quality was shown to be diagnostic at reductions of count density by 40% using BSREM with a penalization factor of ß=350-500. This can be accomplished while maintaining confidence of achieving a diagnostic-quality image.

Mixed-reality view of cardiac specimens: a new approach to understanding complex intracardiac congenital lesions.

Digital reality is an emerging platform for three-dimensional representation of medical imaging data. In this technical innovation paper, the authors evaluated the accuracy and utility of mixed-reality technology in the morphological evaluation of complex congenital heart disease. The authors converted CT datasets of 12 heart specimens with different subtypes of double-outlet right ventricle to stereoscopic images and interrogated them using a mixed-reality system. The morphological features identified on the stereoscopic models were compared with findings at macroscopic examination of the actual heart specimens. The results showed that the mixed-reality system provided highly accurate stereoscopic display of spatially complex congenital cardiac lesions, with interactive features that might enhance 3-D understanding of morphology. Additionally, the authors found that high-resolution digital reproduction of cardiac specimens using clinical CT scanners is feasible for preservation and educational purposes.

Dosimetric Feasibility of Cone-Beam CT in Pediatric Image-Guided Retrograde Gastrostomy Tube Insertions.

PURPOSE: Cone-beam computed tomography (CBCT) in interventional radiology allows volumetric imaging with open patient access. This work aimed to assess radiation dose metrics of CBCT in simulated image-guided retrograde gastrostomy (IGRG) tube insertions in pediatric anthropomorphic phantoms and to compare them to measured radiation dose metrics obtained using fluoroscopy during clinical IGRG tube insertions in children. METHODS: Radiation dose indices obtained from radiation dose structured reports of fluoroscopic IGRG tube insertions were retrospectively evaluated in a consecutive cohort of 30 children. Dose indices were fractionated into 3 clinical stages for each procedure (planning, insertion, and confirmation). These 3 stages in 30 patients (3 × 30 = 90 patient stages) were compared to dose indices measured from 4 CBCT acquisition protocols acquired in pediatric phantoms. RESULTS: The mean proportion of radiation dose during planning, insertion, and confirmation was 35%, 38% and 27%, with mean reference-point air kerma (range) measured to be 1.0 (0.02-6.0) mGy, 0.9 (0.03-4.1) mGy, and 0.7 (0.04-3.7) mGy, respectively. Cone-beam computed tomography dose varied greatly depending on technical parameters and protocol selection, ranging from 0.7 to 39.3 mGy. In 19% of patient stages, the most dose-sparing CBCT protocol evaluated on phantoms delivered less radiation than the radiation dose indices recorded from patient's fluoroscopy. CONCLUSIONS: From a dosimetric perspective, radiation delivered in CBCT can vary widely, yet can be appreciably low. With appropriate CBCT protocol selection, the radiation dose delivered may be sufficiently low to warrant consideration for use, if clinically needed during difficult IGRG tube insertions, and satisfy the interventionalist's benefit-risk assessment.

Quantitative color-coded digital subtraction neuroangiography for pediatric arteriovenous shunting lesions.

BACKGROUND: Several complex pediatric neurovascular conditions are amenable to endovascular treatment. Given the unique anatomical and physiological challenges in children, there is an ongoing need for tools and techniques that provide accurate information for treatment planning, while minimizing exposure to ionizing radiation and contrast. This is more so for neonates and infants with high-flow arteriovenous (AV) shunts that are challenging to assess using conventional techniques. OBJECTIVE: In this brief report, we describe, through representative cases, the potential role of quantitative color-coded digital subtraction angiography (qDSA) in neuroendovascular procedures in children with high-flow AV shunting lesions. METHODS: Images were obtained using an ArtisQ biplane system (Siemens Healthineers, Erlangen, Germany). Post-processing was performed at a dedicated workstation (Syngo, Siemens) using the iFlow module to generate color-coded maps of individual digital subtraction angiography runs. CONCLUSION: Color-coded qDSA provides real-time quantitative information in high-flow AV shunting neurovascular lesions. This can potentially help direct treatment choices, optimize endovascular treatment protocols, monitor outcomes, and determine treatment end points.

Accurately Diagnosing Uric Acid Stones from Conventional Computerized Tomography Imaging: Development and Preliminary Assessment of a Pixel Mapping Software.

PURPOSE: Preoperative determination of uric acid stones from computerized tomography imaging would be of tremendous clinical use. We sought to design a software algorithm that could apply data from noncontrast computerized tomography to predict the presence of uric acid stones. MATERIALS AND METHODS: Patients with pure uric acid and calcium oxalate stones were identified from our stone registry. Only stones greater than 4 mm which were clearly traceable from initial computerized tomography to final composition were included in analysis. A semiautomated computer algorithm was used to process image data. Average and maximum HU, eccentricity (deviation from a circle) and kurtosis (peakedness vs flatness) were automatically generated. These parameters were examined in several mathematical models to predict the presence of uric acid stones. RESULTS: A total of 100 patients, of whom 52 had calcium oxalate and 48 had uric acid stones, were included in the final analysis. Uric acid stones were significantly larger (12.2 vs 9.0 mm, p = 0.03) but calcium oxalate stones had higher mean attenuation (457 vs 315 HU, p = 0.001) and maximum attenuation (918 vs 553 HU, p <0.001). Kurtosis was significantly higher in each axis for calcium oxalate stones (each p <0.001). A composite algorithm using attenuation distribution pattern, average attenuation and stone size had overall 89% sensitivity, 91% specificity, 91% positive predictive value and 89% negative predictive value to predict uric acid stones. CONCLUSIONS: A combination of stone size, attenuation intensity and attenuation pattern from conventional computerized tomography can distinguish uric acid stones from calcium oxalate stones with high sensitivity and specificity.

CT reconstruction and MRI fusion of 3D rotational angiography in the evaluation of pediatric cerebrovascular lesions.

PURPOSE: Complex neurovascular lesions in children require precise anatomic understanding for treatment planning. Although 3DRA is commonly employed for volumetric reformation in neurointerventional procedures, the ability to reconstruct this data into CT-like images (3DRA-CT) is not widely utilized. This study demonstrates the feasibility and usefulness of 3DRA-CT and subsequent MRI fusion for problem solving in pediatric neuroangiography. METHODS: This retrospective study includes 18 3DRA-CT studies in 16 children (age 9.6 ± 3.8 years, range 2-16 years) over 1 year. After biplane 2D-digital subtraction angiography (DSA), 5-second 3DRA was performed with selective vessel injection either with or without subtraction. Images were reconstructed into CT sections which were post-processed to generate multiplanar reformation (MPR) and maximum intensity projection (MIP) images. Fusion was performed with 3D T1 MRI images to precisely demonstrate neurovascular relationships. Quantitative radiation metrics were extracted and compared against those for the entire examination and for corresponding biplane 2D-DSA acquisitions. RESULTS: In all 18 cases, the 3DRA procedure and MRI fusion were technically successful and provided clinically useful information relevant to management. The unsubtracted and subtracted 3DRA acquisitions were measured to deliver 5.9 and 132.2%, respectively, of the mean radiation dose of corresponding biplane 2D-DSA acquisitions and contributed 1.2 and 12.5%, respectively, to the total procedure dose. CONCLUSION: Lower radiation doses, high spatial resolution, and multiplanar reformatting capability make 3DRA-CT a useful adjunct to evaluate neurovascular lesions in children. Fusing 3DRA-CT data with MRI is an additional capability that can further enhance diagnostic information.

Pedicle screw accuracy placed with assistance of machine vision technology in patients with neuromuscular scoliosis.

INTRODUCTION: Pedicle screws are the primary method of vertebral fixation in scoliosis surgery, but there are lingering concerns over potential malposition. The rates of pedicle screw malposition in pediatric spine surgery vary from 10% to 21%. Malpositioned screws can lead to potentially catastrophic neurological, vascular, and visceral complications. Pedicle screw positioning in patients with neuromuscular scoliosis is challenging due to a combination of large curves, complex pelvic anatomy, and osteopenia. This study aimed to determine the rate of pedicle screw malposition, associated complications, and subsequent revision from screws placed with the assistance of machine vision navigation technology in patients with neuromuscular scoliosis undergoing posterior instrumentation and fusion. METHOD: A retrospective analysis of the records of patients with neuromuscular scoliosis who underwent thoracolumbar pedicle screw insertion with the assistance of machine-vision image guidance navigation was performed. Screws were inserted by either a staff surgeon, orthopaedic fellow, or orthopaedic resident. Post-operative ultra-low dose CT scans were used to assess pedicle screw accuracy. The Gertzbein classification was used to grade any pedicle breaches (grade 0, no breach; grade 1, <2 mm; grade 2, 2-4 mm; grade 3, >4 mm). A screw was deemed accurate if no breach was identified (grade 0). RESULTS: 25 patients were included in the analysis, with a mean age of 13.6 years (range 11 to 18 years; 13/25 (52.0%) were female. The average pre-operative supine Cobb angle was 90.0 degrees (48-120 degrees). A total of 687 screws from 25 patients were analyzed (402 thoracic, 241 lumbosacral, 44 S2 alar-iliac (S2AI) screws). Surgical trainees (fellows and orthopaedic residents) inserted 46.6% (320/687) of screws with 98.8% (4/320) accuracy. The overall accuracy of pedicle screw insertion was 98.0% (Grade 0, no breach). All 13 breaches that occurred in the thoracic and lumbar screws were Grade 1. Of the 44 S2AI screws placed, one screw had a Grade 3 breach (2.3%) noted on intra-operative radiographs following rod placement and correction. This screw was subsequently revised. None of the breaches resulted in neuromonitoring changes, vessel, or visceral injuries. CONCLUSION: Machine vision navigation technology combined with careful free-hand pedicle screw insertion techniques demonstrated high levels of pedicle screw insertion accuracy, even in patients with challenging anatomy.

Investigating the limit of detectability of a positron emission mammography device: a phantom study.

PURPOSE: A new positron emission mammography (PEM) device (PEM Flex Solo II, Naviscan Inc., San Diego, CA) has recently been introduced and its performance characteristics have been documented. However, no systematic assessment of its limit of detectability has been evaluated. The aim of this work is to investigate the limit of detectability of this new PEM system using a novel, customized breast phantom. METHODS: Two sets of F-18 infused gelatin breast phantoms of varying thicknesses (2, 4, 6, and 8 cm) were constructed with and without (blank) small, shell-less contrast objects (2 mm thick disks) of varying diameters (3-14.5 mm) [volumes: 0.15-3.3 cc] and activity concentration to background ratio (ACR) (2.7-58). For the phantom set with contrast objects, the disks were placed centrally inside the phantoms and both phantom sets were imaged for a period of 10 min on the PEM device. In addition, scans for the 2 and 6 cm phantoms were repeated at different times (0, 90, and 150 min) post phantom construction to evaluate the impact of total activity concentration (count density) on lesion detectability. Each object from each phantom scan was then segmented and placed randomly in a corresponding blank phantom image. The resulting individual images were presented blindly to seven physician observers (two nuclear medicine and five breast imaging radiologists) and scored in a binary fashion (1-correctly identified object, 0-incorrect). The sensitivity, specificity, and accuracy of lesion detectability were calculated and plots of sensitivity versus ACR and lesion diameters for different phantom thicknesses and count density were generated. RESULTS: The overall (mean) detection sensitivity across all variables was 0.68 (95% CI: [0.64, 0.72]) with a corresponding specificity of 0.93 [0.87, 0.98], and diagnostic accuracy of 0.72 [0.70, 0.75]. The smallest detectable object varied strongly as a function of ACR, as sensitivity ranged from 0.36 [0.29, 0.44] for the smallest lesion size (3 mm) to 0.80 [0.75, 0.84] for the largest (14.5 mm). CONCLUSIONS: The detectability performance of this PEM system demonstrated its ability to resolve small objects with low activity concentration ratios which may assist in the identification of early stage breast cancer. The results of this investigation can be used to correlate lesion detectability with tumor size, ACR, count rate, and breast thickness.

In-hospital resource utilization, outcome analysis and radiation exposure in children undergoing appendicostomy vs cecostomy tube placement.

INTRODUCTION AND OBJECTIVES: Continence enemas for the purpose of bowel management may be delivered via trans-anal retrograde irrigations, and via antegrade conduits including surgical appendicostomy or placement of cecostomy tube (CT). An appreciation of the relative advantages and disadvantages of each antegrade continence enema (ACE) procedure allows clinicians, parents and children to make an informed decision regarding which procedure is most appropriate in individual cases. The objective of this study was to evaluate the differences in in-hospital resource utilization, surgical outcomes and radiation exposure between children undergoing appendicostomy creation and CT placement at our institution. METHODS: We conducted a retrospective chart review of children undergoing these procedures at our institution over a 10-year period. All patients 0-18 years of age undergoing either procedure for any indication were included. Data on demographics, length of stay (LOS), radiation exposure events (REE), and surgical outcomes were collected. RESULTS: One hundred fifteen (63 appendicostomy/52 CT) patients were included. Those undergoing CT placement had significantly increased post-procedural LOS, catheter exchanges and REE compared to those undergoing appendicostomy (see Table). Reported rates of bowel control were similar between the two groups, and there was no significant difference in rates of surgical complications, although each group had unique, procedure-specific complications. DISCUSSION AND CONCLUSION: In our study, appendicostomy holds a clear advantage over CT in terms of post-procedural LOS, as well as REE. In general, children with CTs require more planned and unplanned device maintenance procedures than those with appendicostomy. These findings aside, the rates of success for bowel control between the two groups are similar, and the incidence of complications does not differ significantly between the two groups. CT remains a safe and effective conduit for delivery of ACEs, and is a particularly good option in patients whose appendix has been lost or used for another conduit. However, patients wishing to avoid repeated procedures and radiation exposure may find the option of appendicostomy more attractive.

The role of imaging in the preoperative assessment of children with inflammatory colitis.

BACKGROUND: Accurate diagnosis of Crohn's disease or ulcerative colitis is essential for surgical planning. This study compared the accuracy, safety, and utility of small bowel follow-through (SBFT) and magnetic resonance enterography (MRE) for detecting small bowel (SB) involvement preoperatively. METHODS: A retrospective review of children who underwent colectomy for inflammatory bowel disease (2000-2014) was performed. Preoperative SBFT and MRE were independently reviewed by two radiologists blinded to clinical data. Gold standard for diagnosis was surgical pathology. RESULTS: 68 patients (36 female) were included. 45 patients had SBFT prior to colectomy, 17 patients had MRE, and 6 both. Interrater reliability for radiologic interpretation was 90% (SBFT) and 91% (MRE). Mean study durations were 190min (SBFT) and 59min (MRE). Median effective dose for SBFT was 1.5mSv, while MRE involved no ionizing radiation. Specificities for diagnosing SB involvement were 87.5% (SBFT) and 94% (MRE). 54 patients underwent subtotal colectomy and ileostomy, 12 restorative proctocolectomy, and 2 colectomy with ileorectal anastomosis. Preoperative imaging correlated with surgical pathology in 83% (SBFT) and 90% (MRE). CONCLUSION: MRE is at least as effective as SBFT for assessing SB disease in children with colitis prior to colectomy. MRE requires less time and does not expose children to ionizing radiation. Retrospective Case Series, Level 4 Evidence.

Development of a high-performance dual-energy chest imaging system: initial investigation of diagnostic performance.

RATIONALE AND OBJECTIVES: The aim of this study was to assess the performance of a newly developed dual-energy (DE) chest radiographic system in comparison to digital radiographic (DR) imaging in the detection and characterization of lung nodules. MATERIALS AND METHODS: An experimental prototype was developed for high-performance DE chest imaging, with total dose equivalent to a single posterior-anterior DR image. Projections at low and high peak kilovoltage were used to decompose DE soft tissue and bone images. A cohort of 55 patients (31 men, 24 women; mean age, 65.6 years) was drawn from an ongoing trial involving patients referred for percutaneous computed tomography-guided biopsy of suspicious lung nodules. DE and DR images were acquired of each patient prior to biopsy. Image quality was assessed by means of human observer tests involving five radiologists independently rating the detection and characterization of lung nodules on a nine-point scale. Results were analyzed in terms of the fraction of cases at or above a given rating, and statistical significance was evaluated using Wilcoxon's signed-rank test. Performance was analyzed for all cases pooled as well as by stratification of nodule size, density, lung region, and chest thickness. RESULTS: The studies demonstrated a significant performance advantage for DE imaging compared to DR imaging (P < .001) in the detection and characterization of lung nodules. DE imaging improved the detection of both small and large nodules and exhibited the most significant improvement in regions of the upper lobes, where overlying anatomic noise (ribs and clavicles) are believed to reduce nodule conspicuity on DR imaging. CONCLUSIONS: DE imaging outperformed DR imaging overall, particularly in the detection of small, solid nodules. DE imaging also performed better in regions dominated by anatomic noise, such as the lung apices. The potential for improved nodule detection and characterization at radiation doses equivalent to DR imaging is encouraging and could augment the broader use of DE imaging. Future studies will extend the initial cohort and rating scale tests to a larger cohort evaluated by receiver-operating characteristic analysis and will evaluate DE imaging in comparison and as an adjuvant to low-dose computed tomography.