Tumors in pediatric patients at diffusion-weighted MR imaging: apparent diffusion coefficient and tumor cellularity

PURPOSE

To prospectively assess whether there is a relationship between the apparent diffusion coefficient (ADC) and the histopathologic cell count and whether the ADC can enable differentiation of benign and malignant extracranial mass lesions in children.

MATERIALS AND METHODS

Institutional ethics approval and parent or guardian consent were obtained. Eleven malignant and eight benign lesions in 19 children (11 girls, eight boys; median age, 3.9 years; age range, 11 days to 15.5 years) who underwent magnetic resonance (MR) imaging of extracranial mass lesions-including a diffusion-weighted sequence (with b values 0, 500, and 1000 sec/mm(2))-and histopathologic analysis to prove findings were studied. The median ADC within each mass lesion was compared with the median cell count for 10 high-power microscopic fields in the specimen. The inverse regression between cell count and ADC was calculated. The difference in ADC between benign and malignant lesions was assessed by using the Mann-Whitney U test.

RESULTS

There was an inverse relationship between ADC and cell count, expressed as ADC (in x10(-3) mm(2)/sec) = 0.56 + (66.2/cell count), with a relatively good fit to the observed data (analysis of variance R(2) = 0.541, F = 20.0, P < .001). The ADCs of benign lesions ranged from (0.84-2.83) x 10(-3) mm(2)/sec (median, 1.35 x 10(-3) mm(2)/sec; standard deviation, 0.68). The ADCs of malignant lesions ranged from (0.73-1.53) x 10(-3) mm(2)/sec (median, 1.00 x 10(-3) mm(2)/sec; standard deviation, 0.29). There was no significant difference in ADC between benign and malignant lesions (Mann-Whitney U = 22, P = .069). All highly cellular (>150 cells per high-power field) lesions had an ADC lower than 1.5 x 10(-3) mm(2)/sec.

CONCLUSION

Although there is a significant relationship between cellularity and ADC, cell count probably is not the sole determinant of the ADC. Use of the ADC cannot enable accurate differentiation of malignant and benign lesions.

MDCT of Tracheobronchial Narrowing in Pediatric Patients

Chest radiographs have been useful for the incidental detection and initial imaging evaluation of clinically suspected central airway narrowing in pediatric patients. However, cross-sectional imaging, such as computed tomography (CT), is frequently required for confirmation of diagnosis, further characterization, and preoperative evaluation of surgical lesions. Recent rapid technologic advancement in CT has allowed CT to assume a pivotal role in the noninvasive evaluation of tracheobronchial narrowing in children, in particular with multidetector computed tomography with postprocessing techniques, including multiplanar reformations and 3-dimensional reconstructions. In this article, the authors review the multidetector computed tomography technique for evaluation of central airway narrowing in children, with emphasis on the use of multiplanar reformations and 3-dimensional reconstructions in the imaging evaluation of the spectrum of intrinsic and extrinsic causes of central airway narrowing in children.

Total and intraabdominal fat distribution in preadolescents and adolescents: measurement with MR imaging

PURPOSE

To prospectively correlate single- and multisection magnetic resonance (MR) imaging measurements with clinical measurements for assessment of abdominal adipose tissue volumes in healthy (control subjects), overweight, and diabetic overweight preadolescents and adolescents.

MATERIALS AND METHODS

The study was approved by the institutional internal review board and was HIPAA compliant. Informed consent was obtained from parents, and assent was obtained from control subjects and patients. Thirty total study subjects (20 male, 10 female; age range, 10-18 years; mean, 14.5 years) underwent MR imaging, anthropometric measurement, and dual x-ray absorptiometry (DXA). A computer-assisted software program was used to quantify subcutaneous, visceral, and total abdominal adipose tissue volumes. Single-section measurements at disk space L4-L5 and whole-abdominal multisection measurements were compared, and each method was tested for correlations with anthropometric and DXA measurements with Spearman rho and Pearson correlation (r) coefficients. Single- and multisection image analyses required 5 and 25 minutes per subject, respectively.

RESULTS

There was a high degree of correlation between single- and multisection MR imaging methods for measurement of subcutaneous (r = 0.97), visceral (r = 0.96), and total abdominal fat (r = 0.97). MR imaging fat measurements strongly correlated with anthropometric measurements (rho correlation range, 0.81-0.96; P <or= .02), with overlapping 95% confidence intervals (CIs) for single- and multisection MR imaging correlations. MR imaging percentage of intraabdominal fat measurements (mean, 23%; 95% CI: 17%, 29%) highly correlated with DXA abdominal fat measurements (mean, 26%; 95% CI: 21%, 31%). Significant differences were found among healthy subjects, overweight patients, and diabetic overweight patients for total fat volumes (P < .001) but not for fat distribution patterns.

CONCLUSION

Single- and multisection MR imaging measurements for the quantitative assessment of abdominal adipose tissue strongly correlate with clinical and DXA fat measurements.

Single-versus multidetector-row CT: comparison of sedation rates, conventional angiograms and motion artefacts in young children following liver transplantation

PURPOSE

The aim of this study was to determine whether the use of multidetector computed tomography (MDCT) is associated with decreased sedation, frequency of motion artefacts and conventional angiograms compared with single-detector CT (SDCT).

MATERIALS AND METHODS

CT examinations performed in young children between January 1993 and June 2005 were reviewed retrospectively. Prior to September 2000, SDCT was used; after that period, MDCT was used. The examinations obtained during these two periods were compared for the frequency of sedation, motion artefacts, and conventional angiograms. Statistical comparison between the two groups was determined by using the chi(2) test.

RESULTS

A total of 126 infants and children younger than 6 years of age underwent 134 CT examinations. Eighty-eight were obtained with a SDCT (65%) (group 1) and 46 with a MDCT (35%) (group 2). Sedation was required in 31/88 (35%) CT examinations in group 1 and in 6/46 (13%) in group 2. Conventional angiography was performed in 20/88 (22%) cases in group 1 and in 6/46 (13%) in group 2. Motion artefacts were present in 8/88 (9%) CT examinations in group 1 and in 4/46 (8%) in group 2. There was significant statistical difference with regard to sedation and angiography rates between the two groups (p<0.001) whereas there was no significant difference with regard to motion artefacts (p>1).

CONCLUSIONS

MDCT can reduce the need for sedation and conventional angiography in children after liver transplantation. There is no effect on patient motion artefacts.

Pediatric CT angiography

Advances in CT technology are having profound impact on imaging children and have made CT angiography possible even in neonates. Even with the tiny anatomy of neonates, small volumes of contrast material, and small venous access catheters, successful CT angiography can be performed with attention to detail. Meticulous attention to patient preparation, the proper selection of technical factors, and optimal delivery of contrast material are crucial. Data post-processing and the creation of 3-D reconstructions are also essential in establishing a correct diagnosis. The applications of CT angiography are different in children than in adults and most applications in children involve assessment of congenital and postoperative vascular and cardiac diseases. The use of CT angiography offers the opportunity to eliminate the long periods of sedation associated with MR and reduce the radiation exposure associated with conventional angiography. Generally, the benefits of CT angiography in children outweigh the risk, namely that of radiation exposure. However, care must still be taken to minimize the radiation exposure.

Which MRI sequence of the spine best reveals bone-marrow metastases of neuroblastoma?

BACKGROUND

MRI is an effective tool in evaluating bone marrow metastases. However, no study has defined which MRI sequences or image characteristics best correlate with bone-marrow metastases in neuroblastoma.

OBJECTIVE

To identify and refine MRI criteria and sequence selection for the diagnosis of bone-marrow metastases in children with neuroblastoma.

MATERIALS AND METHODS

Ninety-one children (mean age: 3.2 years; standard deviation: 2.8 years) enrolled in the RDOG IV study participated in our study. Forty-five children had bone metastases determined by bone-marrow aspiration or biopsy (n=4), radionuclide imaging (n=2), or both (n=39). Spine lesions were characterized using coronal T1-weighted (T1W) sagittal short tau inversion recovery (STIR) and coronal gadolinium-enhanced T1-weighted (GAD) MR sequences. Contingency table analysis was performed to determine which MRI sequences and characteristics were associated with metastases. The MRI criteria for metastatic disease were then developed for each imaging sequence. The sensitivity, specificity, predictive values, and accuracy of these criteria were determined for the whole group, children younger than 12 months old, and children 12 months and older.

RESULTS

The MR characteristics that had significant (P<or=0.05) associations with metastases were homogeneous low T1-signal intensity, homogeneous high STIR-signal intensity, and heterogeneous pattern on T1, STIR, or GAD. Homogeneous low T1-signal had the highest sensitivity (88%), but a specificity of 62% for detecting metastases. A heterogeneous pattern on GAD was highly specific (97%), but relatively insensitive (65%) for detecting metastases. These MR characteristics were most accurate in children 12 months and older.

CONCLUSION

The combination of non-contrast-enhanced T1W and GAD sequences can be used to determine the presence of spinal metastases in children with neuroblastoma, particularly those children who are 1 year and older.

Compositional analysis of muscle in boys with Duchenne muscular dystrophy using MR imaging

OBJECTIVE

Boys with Duchenne muscular dystrophy (DMD) present by age 5 years with weakness and, untreated, stop walking unaided by age 10 or 11 years. We used magnetic resonance (MR) imaging to study age-related changes in the composition and distribution of diseased muscles.

DESIGN AND PATIENTS

Eleven boys (mean 7.1+/-1.6 years) with DMD underwent clinical and MR examinations. Quantitative muscle strength and timed functional testing was performed. Thigh muscles were scanned at three levels (hip, mid-thigh, and knee) using T1-weighted spin echo and short-tau inversion recovery (STIR) sequences. Outcome measures included intramuscular fatty infiltration, intermuscle fat deposition, edema, and muscle size.

RESULTS

Ten boys completed the study. Older boys demonstrated more prominent fatty infiltration of muscles. Fatty infiltration occurred in a characteristic pattern with the gluteus and adductor magnus muscles most commonly involved and the gracilis most commonly spared. Similarly, patchy increases in free water content suggested a pattern of intramuscular edema or inflammation. Atrophy occurred in muscles heavily infiltrated with fat, and true hypertrophy selectively occurred in those that were spared.

CONCLUSIONS

While fibrofatty changes have been described in DMD, this study further defines differential involvement and additionally suggests widespread edema or inflammation. Improved imaging techniques to quantify the degree and distribution of these changes may provide a basis for exploring mechanisms of action of medications and perhaps another means for selecting treatment regimens and monitoring their effects.

Neoplasms of the Renal Medulla: Radiologic-Pathologic Correlation

Tumors of the renal medulla cover a wide spectrum, with characteristic histomorphology and variable biologic profiles. Renal medullary tumors can be categorized into benign and malignant neoplasms based on histologic features and clinico-biologic behavior. They can be further classified into pediatric and adult tumors based on the patient age group. When small, renal medullary tumors may be differentiated from the more common renal adenocarcinomas by their central location and certain demographic characteristics. Although most large malignant medullary tumors demonstrate imaging findings that are indistinguishable from those of other renal malignancies, some tumors demonstrate imaging findings that may suggest a specific diagnosis.

Amplatzer atrial septal defect occluder for pediatric patients: radiographic appearance

PURPOSE

To describe the chest radiographic appearance of the Amplatzer septal occluder (ASO) (AGA Medical Corporation, Golden Valley, Minn) for atrial septal defects (ASDs) in pediatric patients.

MATERIALS AND METHODS

Two radiologists independently reviewed frontal and lateral chest radiographs obtained in young patients 24 hours after transcatheter ASD closure with the ASO. The appearance (flat disks or dots) and location of the ASO were recorded. The location was related to that of a thoracic vertebral body on frontal and lateral chest radiographs and to a line drawn between the anterior margin of the right hilum and the posterior margin of the inferior vena cava (hilar-caval line) on lateral radiographs; this line corresponded to the expected position of the interatrial septum. The relationship between ASO appearance and patient age was assessed with logistic regression and cumulative probability plots.

RESULTS

Sixty-eight pediatric patients (age range, 1 month to 18 years; mean age, 4.2 years; 24 boys and 44 girls) were included. On frontal radiographs, the ASO center projected between T7 and T9, either to the right of or over the spinous processes of the vertebral body. On lateral radiographs, the ASO projected over (n = 66) or anterior to (n = 2) the hilar-caval line. On frontal radiographs, it appeared as one or two flat disks (n = 61) or as two metallic dots (n = 7). On lateral radiographs, it appeared as two flat disks (n = 54) or as two metallic dots (n = 14). The relationship between increasing patient age and the metallic dot appearance on frontal and lateral radiographs and on the combination of frontal and lateral radiographs was highly significant in each case (P < .001, likelihood ratio chi(2) test), with r(2) values of 0.35, 0.20, and 0.28, respectively. ASDs were successfully occluded with the ASO in all patients except one, in whom trivial shunting was seen at 12-month follow-up.

CONCLUSION

The ASO in pediatric patients has a characteristic radiographic appearance when properly positioned.

Radiation dose and image quality in pediatric CT: effect of technical factors and phantom size and shape

PURPOSE

To evaluate effects of varying tube current and voltage on radiation dose, image noise, and image contrast with different phantom sizes and shapes.

MATERIALS AND METHODS

Four round lucite phantoms with 8-32-cm diameters were scanned with multi-detector row computed tomography (CT) and 80-120 kVp. Radiation dose was based on CT dose index, image noise, and iodine contrast and measured with constant and variable tube currents that were age appropriate for each tube voltage. Radiation dose and image noise and contrast were compared in round and oval 24-cm phantoms. For various combinations of technical factors and phantom sizes and shapes, percentage differences were calculated for radiation dose and image noise and contrast. Associations between tube voltage and radiation dose, image noise, and image contrast in round and oval phantoms were determined by fitting second-degree polynomials to data. Differences in radiation dose and image noise and contrast, which were attributable to differences in tube voltage, were tested with paired t tests.

RESULTS

With 165-mAs tube current, radiation doses with 140- and 80-kVp tube voltages were 103% ([41.9 mGy - 20.6 mGy]/20.6 mGy) and 58% ([10.2 mGy - 4.2 mGy]/10.1 mGy) higher in the 8-cm phantom than in the 32-cm phantom. When tube current was adapted for phantom size, radiation dose at 80 kVp in the 8-cm phantom was reduced by 82% ([10.1 mGy - 1.8 mGy]/10.1 mGy). In the 8-cm phantom, tube voltage was decreased from 120 to 80 kVp and tube current remained at 165 mAs, resulting in a 68% noise increase ([3.1 HU - 1.8 HU]/1.8 HU). With variable tube current, 80-kVp tube voltage in the 8-cm phantom led to a 138% noise increase ([7.3 HU - 3.1 HU]/3.1 HU). With reduced tube voltage, image contrast increased. In the 8-cm phantom, with a constant 165-mAs tube current and a decrease in tube voltage from 120 to 80 kVp, there was a 35% ([333 HU - 217 HU]/333 HU) increase in contrast. No difference was noted in radiation dose or noise between round and oval phantoms (P = .604 and P = .06, respectively), but a small statistically significant difference (1%) in contrast attenuation was demonstrated (P = .025).

CONCLUSION

Reduced tube voltage for pediatric contrast material-enhanced CT reduces radiation dose and maintains image contrast. Image noise increases, but the effect is minimal in smaller phantoms. An additional reduction in tube current further reduces radiation dose.

Congenital cystic adenomatoid malformation connected to an extralobar pulmonary sequestration in the contralateral chest: common origin?

Extralobar pulmonary sequestration (ELS) and congenital cystic adenomatoid malformation have been reported to coexist in several variations. This suggests a common embryologic origin. A 6-month-old boy presented with a history of recurrent pneumonias. The patient was diagnosed with a right lower lobe congenital cystic adenomatoid malformation (CCAM) and a left lower lobe ELS/CCAM. The diagnosis was made with the aid of a multidetector computed tomography (CT). Three-dimensional CT reconstruction showed the presence of a right lower lobe CCAM, a left lower ELS with an aberrant arterial supply from the celiac axis, and possible venous drainage into the right CCAM. The patient underwent a right thoracotomy. Intraoperatively, the lesions were discovered to be connected by a band of tissue. The right lower lobe CCAM and the left ELS were removed from the right chest. Histologic analysis confirmed the presence of a CCAM within the right lower lobe. The ELS had involvement of a type II CCAM within the sequestration. The connection between the right CCAM and left ELS/CCAM showed an anomalous conducting airway, anomalous vein, and anomalous artery connecting the 2 lesions. The authors present the first case of a CCAM connected to an ELS/CCAM in the contralateral hemithorax. The unique anatomic configuration of these lesions suggests a common embryologic origin of ELS and CCAM.

Evaluation of Angioarchitecture of Pulmonary Sequestration in Pediatric Patients Using 3D MDCT Angiography

OBJECTIVE

The goal of this study was to show the ability of 3D MDCT angiography to display the arterial and venous vascular anatomy of pulmonary sequestration in children.

CONCLUSION

MDCT angiography with 3D rendering shows the anomalous feeding artery and the draining veins that allow a diagnosis of pulmonary sequestration. These features may prove useful in distinguishing intra- and extralobar sequestration and in surgical planning.

MDCT Evaluation of Thoracic Aortic Anomalies in Pediatric Patients and Young Adults:Comparison of Axial, Multiplanar, and 3D Images

OBJECTIVE

The objective of our study was to compare accuracies of axial, multiplanar, and 3D volume-rendered images in the diagnosis of thoracic aortic anomalies in pediatric patients and young adults.

MATERIALS AND METHODS

Fourteen patients, 17 days to 20 years old, with thoracic aortic anomalies underwent MDCT using axial, multiplanar, and 3D volume-rendering imaging. All images were reviewed by three radiologists for position of the aortic arch, coarctation, vascular compression of the airway, collateral vessel formation, and aortopulmonary shunts (patent ductus arteriosus). Final diagnosis was determined by echocardiography, conventional angiography, bronchoscopy, or surgery. Diagnostic accuracy, sensitivity, and interobserver agreement were evaluated.

RESULTS

Average accuracies (average of the three observers for a correct diagnosis) were greater than or equal to 96% for diagnoses of aortic position and airway narrowing on all image types. For the diagnosis of coarctation, average sensitivities (average of the three observers for a true diagnosis) were 73% for axial, 100% for multiplanar, and 100% for 3D volume-rendered images. For the diagnosis of patent ductus arteriosus, average sensitivities were 78% for axial, 94% for multiplanar, and 89% for 3D volume-rendered images. No patients in this study had collateral vessel formation. For the diagnosis of absence of collateral vessel formation, average sensitivities were 100% for axial, 100% for multiplanar, and 100% for 3D volume-rendered images. There were no significant statistical differences in diagnostic performances, agreement with truth, or confidence scores among observers or imaging formats (p > 0.05).

CONCLUSION

Axial, multiplanar, and 3D volume-rendered images serve equally well as methods for assessing the side of the aorta to diagnose anomalies. For evaluation of coarctation and patent ductus arteriosus, multiplanar and 3D volume-rendered images perform slightly better than axial images.