What’s new in Pediatric Imaging – August 2020

2 years ago

ABDOMINAL IMAGING

 

The significance of abdominal radiographs with paucity of gas in pediatric adhesive small bowel obstruction.

Johnson BL, Campagna GA, Hyak JM, et al. The significance of abdominal radiographs with paucity of gas in pediatric adhesive small bowel obstruction. Am J Surg 2020; 220: 208–213.

https://doi.org/10.1016/j.amjsurg.2019.10.035

Question(s) What is the significance of paucity of gas on initial abdominal radiograph (AXR)?

Design Retrospective study from 2011 to 2015

Setting Single center, Texas Children’s Hospital/Baylor College of Medicine, Houston, Texas

Participants 207 patients with adhesive small bowel obstruction (ASBO)

Intervention Surgery

Outcomes Rates of AXR findings (dilated gaseous loops, paucity of gas), accuracy of AXR vs. CT scan with regards to type of obstruction (uncharacterized, low-grade, high-grade, or closed loop).

Main Results Initial AXR showed paucity of gas in 41% of cases, and surgical intervention was more common in patients with paucity of gas compared to patients with gaseous distended loops (49% vs. 32%, P=0.01). Patients with paucity of gas also more commonly had closed-loop or high-grade bowel obstruction compared to patients with gaseous loops (71% vs. 29%, P<0.001).

Commentary Abdominal radiographs often guide initial management in children with small bowel obstruction. A paucity of bowel gas is associated with more severe obstruction (high-grade and closed-loop) and operative management compared to dilated gaseous bowel loops.

 

Sedated ultrasound guided saline reduction (SUR) of Ileocolic intussusception: 20 year experience

Sacks RS, Anconina R, Farkas E, et al. Sedated ultrasound guided saline reduction (SUR) of Ileocolic intussusception: 20 year experience. Journal Pre-Proof. J Pediatr Surg 2020.

https://doi.org/10.1016/j.jpedsurg.2020.05.049

Question(s) How is ultrasound guidance used for saline reduction of ileocolic intussusception?

Design Retrospective study from 1998 to 2018

Setting Single institution, Ben Gurion University of the Negev, Be’er Sheva, Israel

Participants 414 total episodes of intussusception underwent SUR; 338 were primary episodes, and 76 were recurrent episodes.

Intervention Ultrasound-guided saline reduction (SUR)

Outcomes Technical success rate, perforation rate. Clinical and imaging associations, including patient age, absence of free fluid, and location in the right upper quadrant.

Main Results 257 of 338 primary episodes (84.3%) were successfully reduced with saline enema under ultrasound guidance. 59 of 76 recurrent episodes were successfully reduced with SUR (78%). There were no perforations during SUR. Statistically significant associations for SUR included older age at time of diagnosis (P=0.016), absence of free fluid (P=1.803e-05), and localization of the intussusception to the right upper quadrant (P=0.0048).

Commentary Reported success rates of fluoroscopic air/hydrostatic intussusception reduction range between 68-90%. The risks of these procedures include radiation exposure and a low risk of pneumatic perforation. This study demonstrates a success rate of saline enema reduction in the upper range of fluoroscopic reduction without any cases of perforation and without any radiation exposure. A major challenge of SUR includes non-visualization of the cecum and ileum in real-time as introduced air interferes with sonographic evaluation. Additionally, this technique requires anesthesia which add potential risk and is not standard practice at most hospitals. While SUR may be a useful and successful technique for reducing ileocolic intussusceptions, lack of proper sonographic and technical training may preclude its use at non-specialized hospitals.

 

CHEST IMAGING

 

Lung T1 mapping magnetic resonance imaging in the assessment of pulmonary disease in children with cystic fibrosis: a pilot study

Neemuchwala F, Mahani MG, Pang Y, et al. Lung T1 mapping magnetic resonance imaging in the assessment of pulmonary disease in children with cystic fibrosis: a pilot study. Pediatr Radiol 2020; 50: 923–934.

https://doi.org/10.1007/s00247-020-04638-9

Question(s) Can T1 lung mapping in children with cystic fibrosis (CF) detect early lung disease or monitor pulmonary exacerbations?

Design Prospective study from Sept 2017 to Jan 2018. Phase 1 was a cross-sectional evaluation and Phase 2 was a longitudinal evaluation over 2 weeks.

Setting Presumably single center

Participants 16 children: 5 patients with CF compared to 5 healthy volunteers in Phase 1 and 6 CF patients in Phase 2

Intervention Non-contrast T1 mapping, ultrashort echo time (UTE) MRI, spirometry testing

Outcomes Mean T1 value, percentage lung volume without T1 value, and MRI CF score

Main Results In Phase 1 patients, CF patients had significantly lower mean normalized T1 values of the lung (P=0.02) except in the right lower lobe (P=0.29). CF patients also had significantly higher percentage lung volume without T1 signal (P=0.006). In Phase 2, all cases except one had whole-lung T1 value increase (P=0.001) and improved perfusions scoring (P=0.02) over the course of treatment.

Commentary T1 mapping has been used in MR imaging of adults with CF. This is possible because mucus plugging and air trapping in CF result in hypoxia-induced vasoconstriction and perfusion abnormalities. Since blood has a higher T1 signal than lung parenchyma, well perfused lung will have increased T1 signal compared to hypoxic lung. This study found that, like in adults, children with CF had decreased normalized T1 signal, even when spirometry was normal. The authors state that T1 mapping may be used in children with CF to detect early lung disease and provide early treatment while minimizing radiation exposure. In CF patients with acute exacerbations, T1 mapping can help determine improvement and guide duration of antibiotic treatment. Major limitations of this study were a small sample size and the influence of artifact on T1 values.

 

CARDIAC IMAGING

 

Body fat distribution, overweight, and cardiac structures in school-age children: a population-based cardiac magnetic resonance imaging study

Toemen L, Santos S, Roest AA, et al. Body fat distribution, overweight, and cardiac structures in school-age children: a population-based cardiac magnetic resonance imaging study. JAHA 2020; 9: e014933.

https://doi.org/10.1161/JAHA.119.014933

Question(s) What are the associations of general and abdominal body fat with right and left ventricular structure and function in overweight children?

Design Population-based, prospective cohort study

Setting Generation R Study in Rotterdam, The Netherlands

Participants 2836 children of age 10 and multiple ethnicities (Dutch vs. non-Dutch, which included European, Turkish, Moroccan, Surinamese, Cape Verdian and Dutch Antilles)

Intervention Overweight, obese, and underweight children were compared to normal-weight children

Outcomes Childhood body-mass index (BMI), body composition (lean mass index, fat mass index and visceral adipose tissue index), blood pressure and cardiac measures: right ventricular end-diastolic volume (RVEDV), right ventricular ejection fraction (RVEF), left ventricular end-diastolic volume (LVEDV), left ventricular ejection fraction (LVEF), left ventricular mass (LVM),  left ventricular mass to volume ratio (LMVR) as a marker for concentric remodeling, stroke volume, and cardiac output.

Main Results Overweight and obese children had higher lean mass index, fat mass index, visceral adipose tissue index and blood pressure compared to normal weight-children. BMI was positively associated with RVEDV (0.39), LVEDV (0.41), LVM (0.39), and LMVR (0.07). Associations of lean mass index with all cardiac measures were stronger than those for BMI with the strongest association with LVEDV (0.51). To a lesser extent, fat mass index and visceral adipose tissue index also positively correlated with RVEDV (0.15 and 0.09, respectively), LVEDV (0.17 and 0.09), LVM (0.19 and 0.12), and LMVR (0.07 and 0.09). BMI and body composition ( lean mass index, fat mass index, and visceral adipose tissue index) were inversely correlated with systemic vascular resistance. Obese children had the highest cardiac volume, mass, mass to volume ratio and stroke volume and lower RVEF. No difference was seen for LVEF.

Commentary Lean mass may be a strong determinant of cardiac growth. Fat mass may also influence cardiac structure at later ages. While this study does not show an association between left heart function and BMI, other studies referenced have shown lower LVEF and increased visceral adipose tissue index. Obesity is associated with lower right heart function.

 

MUSCULOSKELETAL RADIOLOGY

 

Accuracy of ultrasound in the diagnosis of classic metaphyseal lesions using radiographs as the gold standard

Karmazyn B, Marine MB, Wanner MR et al. Accuracy of ultrasound in the diagnosis of classic metaphyseal lesions using radiographs as the gold standard. Pediatr Radiol 2020; 50: 1123–1130.
https://doi.org/10.1007/s00247-020-04671-8

Question(s) Is ultrasound (US) accurate in diagnosing classic metaphyseal lesions (CML) in suspected cases of child abuse?

Design Prospective study from 2014-2017. Two blinded radiologists (Rad1 and Rad2) reviewed US of bilateral distal femurs and either right or left proximal and distal tibia for each participant. Cases were considered positive if the child had a CML on skeletal survey and negative if CML was not definitively seen on the skeletal survey. Cases were indeterminate if the words “possible,” “concerning”, or “suggestive” were used in the skeletal survey report.

Setting Single institution, Riley Hospital for Children, Indianapolis

Participants 63 children (age < 1 year) with 241 metaphyseal sites were evaluated. All children enrolled were divided into 3 groups: control, children scheduled for skeletal surveys for possible abuse, and children already undergone skeletal survey with suspected CML.

Intervention

Outcomes Sensitivity, specificity, and accuracy of US detection between 2 interpreting radiologists, kappa (interobserver reliability).

Main Results The kappa for presence of CML on US was 0.7 with 96% agreement. US sensitivity was low (55% and 63% for Rad1 and Rad2, respectively), and US specificity was  high at 98% and 97% for Rad1 and Rad2, respectively. US accuracy was high (94% for both radiologists).

Commentary In the United States, skeletal surveys are mandated for any case of suspected abuse in a child under age 2 and are considered the reference standard for diagnosing associated fractures. Fractures can be seen on US, and this study addresses the sensitivity, specificity, and accuracy of using US to evaluate for CMLs. The inter-observer reliability in this study was higher than that reported in diagnosing CML from 2-view radiographs. Accuracy and specificity of US in diagnosing CML were high but sensitivity was low. Therefore, US could be a useful adjunct for evaluating indeterminate CMLs on radiographs.

 

Diagnostic accuracy of ultrasound for upper extremity fractures in children: a systematic review and meta-analysis.

Tsou PY, Ma YK, Wang YH, et al. Diagnostic accuracy of ultrasound for upper extremity fractures in children: a systematic review and meta-analysis. Article in Press. Am J of Emerg Med, 2020.

https://doi.org/10.1016/j.ajem.2020.04.071

Question(s) What is the diagnostic accuracy of ultrasound (US) for upper extremity fractures in children?

Design Systematic review of databases (PubMed, EMBASE, Web of Science) from November 2019 using pre-defined index terms. Random-effects bivariate model was used for the meta-analysis. Subgroup analysis of the fracture site was also performed (elbow vs. non-elbow).

Number of Studies 32 studies were included from multiple continents

Intervention US performed for upper extremity fractures

Outcomes Sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio, and the area under the ROC (AUROC) curve for US diagnosis of upper extremity fractures and subgroup analysis for elbow fractures. Meta-regression was performed to determine if the fracture site affected diagnostic accuracy.

Main Results The sensitivity, specificity, positive likelihood ratio (LR+), negative likelihood ratio (LR–), and the area under the ROC (AUROC) curve for US diagnosis were 0.95, 0.95, 21.1, 0.05, and 0.98, respectively. The sensitivity, specificity, LR+, LR–, and AUROC curve for subgroup analysis for elbow fracture were 0.95, 0.87, 7.3, 0.06, and 0.96, respectively. Meta-regression suggested that fracture site affects the diagnostic accuracy of US (P<0.01 for elbow vs. non-elbow fractures).

Commentary Current evidence shows that US has excellent diagnostic performance characteristics for upper extremity fractures in children and could serve as an alternative to plain radiographs. Interestingly, the authors also evaluated point-of-care US (POCUS) compared to radiology-performed US (RADUS) as an additional subgroup analysis and showed sensitivity, specificity, LR+, LR–, and AUROC of 0.95, 0.96, 22.7, 0.06, and 0.97, respectively. This could suggests POCUS could potentially perform similarly to RADUS; however, due to the low statistical power (17 included studies for POCUS) and the wide variation in musculoskeletal training (30 minutes of didactics with hands-on practice by clinicians to years of experience for radiologists), caution should be taken when interpreting the results, especially because US is an operator-dependent modality.

 

INTERVENTIONAL RADIOLOGY

 

Postpyloric balloon occlusion to increase technical success during pediatric percutaneous gastrostomy/gastrojejunostomy tube placement

Durand R, Cahill AM, Shellikeri S, et al. Postpyloric balloon occlusion to increase technical success during pediatric percutaneous gastrostomy/gastrojejunostomy tube placement. J Vasc Interv Radiol 2020; 31:1139–1142.

https://doi.org/10.1016/j.jvir.2020.03.004

Question(s) Does post-pyloric balloon obstruction maximize gastric insufflation in percutaneous gastrostomy/gastrojejunostomy tube placement after failure of conventional methods?

Design Single institution, Children’s Hospital of Philadelphia

Setting Retrospective study from 2016 to 2019.

Participants Cases where post-pyloric balloon occlusion was used were selected. 29 of 155 cases of feeding tube placement required balloon occlusion. The median patient age was 36 months.

Intervention Post-pyloric balloon occlusion was used if the operator felt the stomach margin was not sufficiently subcostal, did not clear the liver margin, or if there was premature loss of insufflated air.

Outcomes Technical success rate.

Main Results Balloon occlusion was successful in 23 of the 29 patients (79.3%), which increased the overall success rate of percutaneous feeding tube placement from 80.1% to 95.2%.

Commentary Post-pyloric balloon occlusion can increase the success rate of percutaneous feeding tube placement in children, particularly in cases with bowel and liver interposition. It is a simple technique and can be used in children as small as 3 kg. The authors portend that this technique could be used instead of glucagon in appropriate cases. The 6 unsuccessful cases in this study were attributed to factors that were unable to be overcome, including persistent colonic interposition, small bowel distention, and hepatomegaly. Therefore, this technique does not completely eliminate the need for surgical feeding tube placement. Limitations of this study and technique include the small sample size and additional fluoroscopy time and radiation dose to the patient.

 

NEURORADIOLOGY

 

Accuracy of MR imaging for detection of sensorineural hearing loss in infants with bacterial meningitis

Orman G, Kukreja MM, Vallejo JG, et al. Accuracy of MR imaging for detection of sensorineural hearing loss in infants with bacterial meningitis. AJNR 2020; 41: 1081–1086.

http://dx.doi.org/10.3174/ajnr.A6539

Question(s) What is the diagnostic accuracy of MRI for predicting the development of sensorineural hearing loss (SNHL) among infants with bacterial meningitis?

Design Retrospective study from 2011 to 2019.

Setting Single institution, Texas Children’s Hospital/Baylor College of Medicine, Houston, Texas

Participants 115 infants

Intervention Independent retrospective review of brain MRI performed by 2 board-certified, blinded pediatric neuroradiologists with 7-9 years of experience. Audiometric testing was the reference standard of diagnosis of SNHL in all patients.

Outcomes Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of contrasted T1-weighted imaging (T1WI+C), of FLAIR imaging, and of the combine evaluation with audiometric testing results. Laboratory findings were also evaluated, including CSF cultures, CSF glucose, CSF protein, CSF white blood cell count, and blood cultures.

Main Results For T1WI+C, the consensus sensitivity, specificity, PPV, NPV, and accuracy were 61.4%, 95.5%, 83.3%, 87.1%, and 86.3%, respectively. For FLAIR imaging, the consensus sensitivity, specificity, PPV, NPV, and accuracy were 50%, 93.6%, 75%, 83.1%, and 81.6%, respectively. The inter-observer agreement for T1WI+C, FLAIR imaging, and combined evaluation was excellent (kappa > 0.9). Factors significantly associated with SNHL were low CSF glucose, high CSF protein and positive CSF culture.

Commentary Abnormal contrast enhancement and increased FLAIR signal on MRI of the inner ear are highly specific for predicting SNHL in infants with bacterial meningitis and may be related to inflammation, break-down of the blood-brain barrier, and accumulation of abnormal proteinaceous fluid in bacterial meningitis. The findings of this study should raise awareness and encourage closer assessment of the inner ear in patients with bacterial meningitis on routine brain MRIs.

 

One-minute ultrafast brain MRI with full basic sequences: can it be a promising way forward for pediatric neuroimaging?

Ha JY, Baek HJ, Ryu KH, et al. One-minute ultrafast brain MRI with full basic sequences: can it be a promising way forward for pediatric neuroimaging? AJR 2020; 215: 198–205.

https://www.ajronline.org/doi/10.2214/AJR.19.22378

Question(s) Is a 1-minute ultrafast brain MRI protocol clinically feasible in pediatric patients?

Design Retrospective study

Setting Single center, Gyeongsang National University School of Medicine and Gyeongsang National University Changwon Hospital, Republic of Korea.

Participants 23 patients with normal and abnormal findings

Intervention 1-minute ultrafast MRI (total scan time 1 minute, 11 seconds) protocol compared to routine brain MRI (total scan time 9 minutes, 51 seconds) protocol

Outcomes 4-point Likert scale for grading of image quality, Wilcoxon signed rank test to compare the readers’ ratings, and interobserver agreement between 2 independent readers provided with percentage values

Main Results Mean scores of overall image quality and anatomic delineation in ultrafast brain MR images were significantly lower than those in routine brain MR images. However, the ultrafast brain MRIs showed sufficient overall image quality and anatomic detail with >2 points on the 4-point Likert scale. Interobserver agreement on both protocols ranged from 60-100%.

Commentary The authors conclude that the 1-minute ultrafast brain MRI protocol has sufficient image quality for diagnostic use when compared with a routine brain MRI protocol. Implications of the shorter scan time suggest lower rates of scan failure, reduced need of sedation, and decreased anxiety related to MRI examinations. However, there are several important limitations of this study, including small sample size, low interobserver reliability, and subjective analysis of image quality.

 

QUALITY & SAFETY

 

Radiation dose of chaperones during common pediatric computed tomography examinations

Overhoff D, Weis M, Riffel P, et al. Radiation dose of chaperones during common pediatric computed tomography examinations. Pediatr Radiol 2020; 50: 1078–1082.

https://doi.org/10.1007/s00247-020-04681-6

Question(s) What is the radiation dose to adult chaperones when accompanying children during CT scans?

Design Prospective study. Two protocols using 1) chest phantom, and 2) pediatric patients for routine chest scans.

Setting Single institution, University Medical Center Mannheim, Heidelberg University

Participants 3 total dosimeter measurements from 10 scans using a phantom and from 12 routine pediatric scans

Intervention The 3 dosimeters were placed at different locations around the CT scanner (at the gantry opening, 1 m away from the gantry, and beside the gantry). The radiation doses were recorded.

Outcomes Total radiation dose (μSv) of Dosimeter #1, #2, and #3

Main Results For protocol 1, Dosimeter #1 had a total radiation dose of 3 μSv, Dosimeter #2 had 1 μSv, and Dosimeter #3 had no radiation detected. For protocol 2, Dosimeter #1 had a total radiation dose of 2 μSv, Dosimeter #2 had 1 μSv, and Dosimeter #3 had no radiation detected.

Commentary Low radiation doses are recorded for all dosimeter positions for both protocols, including none when positioned next to the gantry. The difference in doses between phantom scans and real clinical scans was attributed to scatter. The study has limitations, such as measuring doses at a single height and not accounting for presence of lead aprons usually worn by chaperones. These results may not be applicable to scans of other body parts or to other types of studies, such as fluoroscopy. However, the overall low doses recorded are reassuring for allowing chaperones to safely accompany the children during CT scans.

References
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