Pediatric CT: Understanding of Radiation Dose and Optimization of Imaging Techniques

The number of CT examinations is dramatically increasing due to recent technical advances including multi-slice spiral CT. Although the benefits of CT outweigh the risks of radiation exposure of CT, radiologists should alert to the potential harmful effects of CT and avoid unnecessarily high CT dose, especially for pediatric CT examinations. To accomplish this, we should understand CT radiation dose and be familiar with imaging techniques of reducing CT dose without degrading diagnostic image quality. In addition, it is important to spread this balanced and useful information into CT referring clinicians, radiologists in training, and medical students.

Multi-Slice Spiral CT of Living-Related Liver Transplantation in Children: Pictorial Essay

In pediatric living-related liver transplantation, preoperative evaluation of the recipient is important for surgical planning, while the accurate diagnosis of postoperative complications is essential for graft salvage. Multiplanar and three-dimensional imaging using multi-slice spiral CT can be used for preoperative vascular imaging, as well as for evaluating postoperative complications. In this essay, we describe the usefulness of multi-slice CT, combined with a variety of different reconstruction techniques, for the preoperative evaluation of transplant recipients. In addition, we demonstrate the multi-slice CT findings of postoperative complications, including vascular stenosis or thrombosis, bile duct leak or stricture, and extrahepatic fluid collection.

CT Numbers of Liver and Spleen in Normal Children

PURPOSE: To determine the mean liver CT numbers, and differences between liver and spleen, and liver and back muscle CT numbers in normal children, and to correlate the findings with sex and age. MATERIALS AND METHODS: One hundred and five normal children aged 2-14 years underwent pre-contrast CT scanning. Mean CT numbers of the liver, spleen, and back muscles were calculated, as well as the differences in CT numbers between the liver and spleen (liver-spleen CT numbers), and between the liver and back muscles (liver-back muscles CT numbers). The results were correlated with age and sex. RESULTS: For all children, mean liver, spleen, and back muscle, and liver-spleen and liver-back muscle CT numbers were 70.22+/-6.51 HU, 53.28+/-3.0 HU, 58.31+/-3.57 HU, 17.13+/-6.57 HU, and 11.88+/-5.94 HU, respectively. Mean liver CT numbers and the difference between liver and spleen CT numbers were high in children aged less than seven, bet mean spleen and back CT numbers, and the difference between liver and back muscle CT numbers were not different by age. By sex, all the CT numbers did not vary according to age. The sex of a subject did not affect the CT number. CONCLUSION: The children's mean liver CT number was 70.22+/-6.51 HU and the difference between liver and spleen CT numbers was 17.13+/-6.57 HU. Younger children had higher liver CT and liver-spleen CT numbers than older children. No CT numbers varied according to sex.

Localized Fluid Collection of Hepatic Bare Area in Children with Blunt Abdominal Trauma

PURPOSE: To investigate the incidence and significance of localized fluid collection in the hepatic bare area re-sulting from blunt abdominal trauma in children. Materias and Methods:We retrospectively reviewed the CT scans and medical records of eighty children with blunt abdominal trauma and evaluated the incidence of fluid collection in the hepatic bare area. The findings were correlated with the presence of injury to adjacent organs. RESULTS: Fluid collection in the hepatic bare area was noted in 23 of 80 patients (28.7%). Associated organ in-juries included liver laceration (17/23), contusion of the right hemidiaphragm (7/23), right adrenal injury (5/23), and right renal injury (5/23). In one patient, organic injury was not detected in spite of fluid collection in the hepatic bare area. Eight of 23 patients (34.8%) showed fluid collection in this area, but not intraperitoneally. CONCLUSION: Fluid collection in the hepatic bare area after blunt abdominal trauma was noted in about 30% of patients and was frequently accompanied by injury to adjacent organs. Since right hemidiaphragmatic contusion associated with fluid collection in the bare area was a not uncommon CT finding, close observation of the condition is warranted.

CT and MR Findings of Neonatal Dermoid ("Hairy Polyp")Developed at Eustachian Tube: A Case Report

Nasopharyngeal dermoid is a rare disease which in neonates leads to respiratory failure. We report the CT and MR imaging findings of a case of neonatal dermoid which developed in the Eustachian tube. The neonate involved was referred to our hospital because of respiratory difficulties and cyanosis.

CT of Normal Variations of the Minute Central Skull Base Foramina

PURPOSE: To evaluate the CT appearance of normal variations in the minute central skull base foramina in infants and children. MATERIALS AND METHODS: One hundred and fourteen children under the age of 17 years without skull base abnormality underwent CT scanning. A high spatial frequency algorithm was used, and contiguous axial scanning parallel to the orbitomeatal line was performed from the foramen magnum to the orbital roof, with a 1-mm slice thickness. The presence or absence of eight foramina, pseudoforamina, or ossification centers including anterior presphenoidal foramen, posterior presphenoidal foramen, rostro-orbital pseudoforamen, intralateromedial postsphenoidal pseudoforamen, intrapostsphenoidal pseudoforamen, spheno-occipital pseudo-foramen, canalis basilaris medianus and intrasynchondral ossified bodies was analysed according to age. The presence of foramina or pseudoforamina was indicated if a ring-shaped structure was seen on two or more CT scans at the location anatomically predicted, and intrasynchondral ossified bodies were indicated if linear or dot-like structures with high attenuation accompanied spheno-occipital synchondrosis. RESULTS: CT indicated that within a certain age range, various kinds of foramina, pseudoforamina, and ossification centers were frequent. The anterior presphenoidal foramen was most commonly seen in infants aged 1-12 months (16/17, 94 %); the posterior presphenoidal foramen in children less than 2 years old(27/37, 73 % ) ; the rostro-orbital pseudoforamen in children aged 2 -5 years (9/17, 53%); intrapostsphenoidal pseudoforamen in children 6 -12 years old(20/37, 54%) and spheno-occipital pseudoforamen and intrasynchondral ossified bodies in children aged 13 -16 years. The canalis basilaris medianus was identified in about 20 % of all subjects regardless of age. CONCLUSION: Development of the minute central skull base foramina varied greatly according to age. Knowledge of the CT appearances of such embryologic variants of the central skull base should not only help Provide an understanding of complex skull base anatomy but also identify abnormal skull base development.

Intracranial Tuberculosis in Children: CT Findings before and after Treatment

OBJECT: To analyze the CT findings of intracranial tuberculosis in children at initial stage and during follow-up after treatment. MATERIALS AND METHODS: We evaluated 25 patients who were diagnosed by CSF analysis or response to anti-tuberculous medication as suffering from intracranial tuberculosis. There were 13 boys and 12 girls aged between 4 months and 14 years. Twenty-five initial and sixty-three follow-up CT scans were retrospectively analyzed. We evaluated the pattern of cisternal enhancement, the locations of infarction, and the presence of calcification and parenchymal granuloma. The changes of hydrocephalus and related complications, aswell as cisternal abnormality during anti-tuberculous medication were also evaluated. RESULTS: The initial findings on CT scan were hydrocephalus(75%), cisternal obliteration in precontrast study(64%), thick-line orring-shaped cisternal enhancement on postcontrast study(44%), infarctions(32%), calcifications(32%), periventricular edema(28%), and parenchymal granulomas(16%). On follow-up CT scan, hydrocephalus and cisternal enhancement had decreased to 35% and 82%, respectively, and the granulomas had changed to calcified nodules(100%). Ventriculo-peritoneal shunt or external ventricular drainage was needed in nine patients, and ventriculitis or complication of shunt procedure developed in four. CONCLUSION: Intracranial tuberculosis in children presented predominantly as meningitis involving basal cisterns and was associated with hydrocephalus. Infarction and calcification may be seen as parenchymal lesion. In spite of medical treatment, drainage was needed in about half the patients. During this treatment, the resolution of hydrocephalus, decreased cisternal enhancement, and calcification of the granulomas were seen.