Establishing a standard calibration methodology for MOSFET detectors in computed tomography dosimetry.

PURPOSE: The use of metal-oxide-semiconductor field-effect transistor (MOSFET) detectors for patient dosimetry has increased by ~25% since 2005. Despite this increase, no standard calibration methodology has been identified nor calibration uncertainty quantified for the use of MOSFET dosimetry in CT. This work compares three MOSFET calibration methodologies proposed in the literature, and additionally investigates questions relating to optimal time for signal equilibration and exposure levels for maximum calibration precision. METHODS: The calibration methodologies tested were (1) free in-air (FIA) with radiographic x-ray tube, (2) FIA with stationary CT x-ray tube, and (3) within scatter phantom with rotational CT x-ray tube. Each calibration was performed at absorbed dose levels of 10, 23, and 35 mGy. Times of 0 min or 5 min were investigated for signal equilibration before or after signal read out. RESULTS: Calibration precision was measured to be better than 5%-7%, 3%-5%, and 2%-4% for the 10, 23, and 35 mGy respective dose levels, and independent of calibration methodology. No correlation was demonstrated for precision and signal equilibration time when allowing 5 min before or after signal read out. Differences in average calibration coefficients were demonstrated between the FIA with CT calibration methodology 26.7 ± 1.1 mV cGy(-1) versus the CT scatter phantom 29.2 ± 1.0 mV cGy(-1) and FIA with x-ray 29.9 ± 1.1 mV cGy(-1) methodologies. A decrease in MOSFET sensitivity was seen at an average change in read out voltage of ~3000 mV. CONCLUSIONS: The best measured calibration precision was obtained by exposing the MOSFET detectors to 23 mGy. No signal equilibration time is necessary to improve calibration precision. A significant difference between calibration outcomes was demonstrated for FIA with CT compared to the other two methodologies. If the FIA with a CT calibration methodology was used to create calibration coefficients for the eventual use for phantom dosimetry, a measurement error ~12% will be reflected in the dosimetry results. The calibration process must emulate the eventual CT dosimetry process by matching or excluding scatter when calibrating the MOSFETs. Finally, the authors recommend that the MOSFETs are energy calibrated approximately every 2500-3000 mV.

Characterization of adaptive statistical iterative reconstruction algorithm for dose reduction in CT: A pediatric oncology perspective.

PURPOSE: This study demonstrates a means of implementing an adaptive statistical iterative reconstruction (ASiR™) technique for dose reduction in computed tomography (CT) while maintaining similar noise levels in the reconstructed image. The effects of image quality and noise texture were assessed at all implementation levels of ASiR™. Empirically derived dose reduction limits were established for ASiR™ for imaging of the trunk for a pediatric oncology population ranging from 1 yr old through adolescence∕adulthood. METHODS: Image quality was assessed using metrics established by the American College of Radiology (ACR) CT accreditation program. Each image quality metric was tested using the ACR CT phantom with 0%-100% ASiR™ blended with filtered back projection (FBP) reconstructed images. Additionally, the noise power spectrum (NPS) was calculated for three common reconstruction filters of the trunk. The empirically derived limitations on ASiR™ implementation for dose reduction were assessed using (1, 5, 10) yr old and adolescent∕adult anthropomorphic phantoms. To assess dose reduction limits, the phantoms were scanned in increments of increased noise index (decrementing mA using automatic tube current modulation) balanced with ASiR™ reconstruction to maintain noise equivalence of the 0% ASiR™ image. RESULTS: The ASiR™ algorithm did not produce any unfavorable effects on image quality as assessed by ACR criteria. Conversely, low-contrast resolution was found to improve due to the reduction of noise in the reconstructed images. NPS calculations demonstrated that images with lower frequency noise had lower noise variance and coarser graininess at progressively higher percentages of ASiR™ reconstruction; and in spite of the similar magnitudes of noise, the image reconstructed with 50% or more ASiR™ presented a more smoothed appearance than the pre-ASiR™ 100% FBP image. Finally, relative to non-ASiR™ images with 100% of standard dose across the pediatric phantom age spectrum, similar noise levels were obtained in the images at a dose reduction of 48% with 40% ASIR™ and a dose reduction of 82% with 100% ASIR™. CONCLUSIONS: The authors' work was conducted to identify the dose reduction limits of ASiR™ for a pediatric oncology population using automatic tube current modulation. Improvements in noise levels from ASiR™ reconstruction were adapted to provide lower radiation exposure (i.e., lower mA) instead of improved image quality. We have demonstrated for the image quality standards required at our institution, a maximum dose reduction of 82% can be achieved using 100% ASiR™; however, to negate changes in the appearance of reconstructed images using ASiR™ with a medium to low frequency noise preserving reconstruction filter (i.e., standard), 40% ASiR™ was implemented in our clinic for 42%-48% dose reduction at all pediatric ages without a visually perceptible change in image quality or image noise.

Utility of Pre-Hematopoietic Cell Transplantation Sinus CT Screening in Children and Adolescents.

BACKGROUND AND PURPOSE: The clinical benefit of pre-hematopoietic cell transplantation sinus CT screening remains uncertain, while the risks of CT radiation and anesthesia are increasingly evident. We sought to re-assess the impact of screening sinus CT on pretransplantation patient management and prediction of posttransplantation invasive fungal rhinosinusitis. MATERIALS AND METHODS: Pretransplantation noncontrast screening sinus CTs for 100 consecutive patients (mean age, 11.9 ± 5.5 years) were graded for mucosal thickening (Lund-Mackay score) and for signs of noninvasive or invasive fungal rhinosinusitis (sinus calcification, hyperattenuation, bone destruction, extrasinus inflammation, and nasal mucosal ulceration). Posttransplantation sinus CTs performed for sinus-related symptoms were similarly graded. Associations of Lund-Mackay scores, clinical assessments, changes in pretransplantation clinical management (additional antibiotic or fungal therapy, sinonasal surgery, delayed transplantation), and subsequent development of sinus-related symptoms or invasive fungal rhinosinusitis were tested (exact Wilcoxon rank sums, Fisher exact test, significance P < .05). RESULTS: Mean pretransplantation screening Lund-Mackay scores (n = 100) were greater in patients with clinical symptoms (8.07 ± 6.00 versus 2.48 ± 3.51, P < .001) but were not associated with pretransplantation management changes and did not predict posttransplantation sinus symptoms (n = 21, P = .47) or invasive fungal rhinosinusitis symptoms (n = 2, P = .59). CONCLUSIONS: Pre-hematopoietic cell transplantation sinus CT does not meaningfully contribute to pretransplantation patient management or prediction of posttransplantation sinus disease, including invasive fungal rhinosinusitis, in children. The risks associated with CT radiation and possible anesthesia are not warranted in this setting.

Full Dose-Reduction Potential of Statistical Iterative Reconstruction for Head CT Protocols in a Predominantly Pediatric Population.

BACKGROUND AND PURPOSE: A statistical iterative reconstruction algorithm provides an effective approach to reduce patient dose by compensating for increased image noise in CT due to reduced radiation output. However, after a point, the degree to which a statistical iterative algorithm is used for image reconstruction changes the image appearance. Our aim was to determine the maximum level of statistical iterative reconstruction that can be used to establish dose-reduced head CT protocols in a primarily pediatric population while maintaining similar appearance and level of image noise in the reconstructed image. MATERIALS AND METHODS: Select head examinations (brain, orbits, sinus, maxilla, and temporal bones) were investigated. Dose-reduced head protocols using an adaptive statistical iterative reconstruction were compared for image quality with the original filtered back-projection reconstructed protocols in a phantom by using the following metrics: image noise frequency (change in perceived appearance of noise texture), image noise magnitude, contrast-to-noise ratio, and spatial resolution. Dose-reduction estimates were based on CT dose index values. Patient volume CT dose index and image noise magnitude were assessed in 737 pre- and post-dose-reduced examinations. RESULTS: Image noise texture was acceptable for up to 60% adaptive statistical iterative reconstruction for the soft reconstruction kernel (at both 100 and 120 kV[peak]) and up to 40% adaptive statistical iterative reconstruction for the standard reconstruction kernel. Implementation of 40% and 60% adaptive statistical iterative reconstruction led to an average reduction in the volume CT dose index of 43% for brain, 41% for orbit, 30% for maxilla, 43% for sinus, and 42% for temporal bone protocols for patients between 1 month and 26 years of age, while maintaining an average noise magnitude difference of 0.1% (range, -3% to 5%), improving the contrast-to-noise ratio of low-contrast soft-tissue targets and the spatial resolution of high-contrast bony anatomy, compared with filtered back-projection. CONCLUSIONS: The methodology in this study demonstrates maximizing patient dose reduction and maintaining image quality by using statistical iterative reconstruction for a primarily pediatric population undergoing head CT examinations.

Estimating pediatric entrance skin dose from digital radiography examination using DICOM metadata: A quality assurance tool.

PURPOSE: To develop an automated methodology to estimate patient examination dose in digital radiography (DR) imaging using DICOM metadata as a quality assurance (QA) tool. METHODS: Patient examination and demographical information were gathered from metadata analysis of DICOM header data. The x-ray system radiation output (i.e., air KERMA) was characterized for all filter combinations used for patient examinations. Average patient thicknesses were measured for head, chest, abdomen, knees, and hands using volumetric images from CT. Backscatter factors (BSFs) were calculated from examination kVp. Patient entrance skin air KERMA (ESAK) was calculated by (1) looking up examination technique factors taken from DICOM header metadata (i.e., kVp and mA s) to derive an air KERMA (k air) value based on an x-ray characteristic radiation output curve; (2) scaling k air with a BSF value; and (3) correcting k air for patient thickness. Finally, patient entrance skin dose (ESD) was calculated by multiplying a mass-energy attenuation coefficient ratio by ESAK. Patient ESD calculations were computed for common DR examinations at our institution: dual view chest, anteroposterior (AP) abdomen, lateral (LAT) skull, dual view knee, and bone age (left hand only) examinations. RESULTS: ESD was calculated for a total of 3794 patients; mean age was 11 ± 8 yr (range: 2 months to 55 yr). The mean ESD range was 0.19-0.42 mGy for dual view chest, 0.28-1.2 mGy for AP abdomen, 0.18-0.65 mGy for LAT view skull, 0.15-0.63 mGy for dual view knee, and 0.10-0.12 mGy for bone age (left hand) examinations. CONCLUSIONS: A methodology combining DICOM header metadata and basic x-ray tube characterization curves was demonstrated. In a regulatory era where patient dose reporting has become increasingly in demand, this methodology will allow a knowledgeable user the means to establish an automatable dose reporting program for DR and perform patient dose related QA testing for digital x-ray imaging.

Type 3 Pfeiffer syndrome with normal thumbs.

We report on a male infant with extremely shallow orbits, spontaneous luxation of the eyes out of the eyelids, hypoplastic midface, broad, medially rotated great toes, and respiratory distress due to severe bilateral posterior choanal stenosis. At 4 days he had open cranial sutures (both by palpation and radiological examination). Subsequent radiologic studies demonstrated: thickening of the skull base, vertebral anomalies, flattening of the olecranon fossae with dislocated radii, and triangular shape of the proximal phalanx of the first toes. Our patient had manifestations of type 3 Pfeiffer syndrome (PS). However, the finding of normal thumbs has not been reported in type 3 PS. Point mutations in fibroblast growth factor receptor-1 (FGFR1) and fibroblast growth factor receptor-2 (FGFR2) have been reported in familial and sporadic cases of PS, but were not found in this patient. Recognizing type 3 PS, despite variability in expression, is important for genetic counseling, prognosis, and decision-making regarding craniofacial surgery.

Hallermann-Streiff syndrome with hypopituitarism contributing to growth failure.

A 35-month-old black boy with Hallermann-Streiff syndrome (HSS) was evaluated for anterior hypopituitarism when he presented with ketotic hypoglycemia, microgenitalia, and short stature. Endocrine evaluation showed a low T4 and TSH levels, suggesting hypothalamic hypothyroidism; this was confirmed by TRH stimulation. Metyrapone test confirmed ACTH deficiency as a contributing factor to the ketotic hypoglycemia. A superagonist GnRH test suggested hypothalamic GnRH deficiency. Growth hormone provocative testing conclusively demonstrated complete growth hormone deficiency. MRI investigation of the brain suggested hypopituitarism. Although facial findings were not completely classical of the HSS, we suggest these may be somewhat altered due to his racial back-ground. We recommend endocrine evaluation of HSS patients with manifestations suggesting hypopituitarism since treatment of this condition will improve the quality of life of these patients.

Neonatal progeroid (Wiedemann-Rautenstrauch) syndrome: report of five new cases and review.

The neonatal progeroid syndrome (NPS), or Wiedemann-Rautenstrauch, is a rare autosomal recessive disorder comprised of generalized lipoatrophy except for fat pads in the suprabuttock areas, hypotrichosis of the scalp hair, eyebrows, and eyelashes, relative macrocephaly, triangular face, natal teeth, and micrognathia. We report on 5 new patients who demonstrate phenotypic variability and who represent the single largest series of NPS reported to date. Two of the patients are from an African-American kindred, an ethnic occurrence not reported previously. The fact that there are 2 pairs of sibs among the 5 patients further supports that NPS is an autosomal recessive condition. This report also includes a review of the previously reported 16 patients and compares them with the 5 new patients. Abnormalities in endocrine and lipid metabolism were found in 3 of 5 patients. Skeletal findings in 2 of our patients demonstrated some new findings as well as the typical radiological abnormalities previously noted in NPS. It is apparent, based on the 21 cases, that mild to moderate mental retardation is common in NPS. Long term follow-up of patients with NPS should provide more information relative to their ultimate psychomotor development. NPS is usually lethal by 7 months; however, on rare occasions, patients have survived into the teens. Our 3 surviving patients range in age from 16-23 months. Variability in the phenotype of NPS is clear; however, the phenotype remains distinct enough to allow a secure diagnosis.

Blunt liver injury in childhood: evolution of therapy and current perspective.

One hundred eighty-eight consecutive children with serious blunt abdominal or multisystem trauma were evaluated between August 1981 and July 1985. Of the 188 patients, 53 (28%) were found to have hepatic parenchymal injuries and are the basis of this report. Four of the 53 (8%) underwent emergency laparotomy for exsanguinating hemorrhage; two patients died, both of hepatic vein lacerations, and two are alive and well after right hepatic lobectomy. Forty-nine (92%) of the children with liver injuries did not require operation for hemorrhage. Four of these 49 patients developed serious complications; hemobilia occurred in one patient and bile peritonitis occurred in three. The one case of hemobilia was resolved without surgery. One child underwent a delayed operative biliary tract reconstruction that was successful. The other two children required a combination of debridement and drainage procedures. Fifty-one of the 53 children (96%) are currently alive without morbidity related to their liver injuries. Both children who died had multiple trauma including central nervous system injuries and had exsanguinating hemorrhage that required emergency laparotomy at initial evaluation. There were no children with "late" hemorrhage and none who developed septic complications. Nonoperative management of most childhood blunt abdominal trauma is possible. Widespread use of abdominal computerized tomography scanning has made this approach practical. This large series of consecutive liver injuries from a large pediatric trauma center illustrates the advantages and the risks of a selective but primarily nonoperative approach to liver trauma in children.

Cocultured blastocyst cryopreservation: experience of more than 500 transfer cycles.

OBJECTIVE: To present our experience using cocultured cryopreserved and transferred blastocysts. DESIGN: Retrospective study of patients undergoing transfer of cryopreserved blastocysts. SETTING: Three different IVF centers. PATIENTS: Four hundred sixty-seven thawed cycles from January 1991 to June 1994. MAIN OUTCOME MEASURE: Pregnancy rate per cycle after transfer of pre-embryos developed from thawed blastocysts. RESULTS: One thousand two hundred thirty-nine blastocysts were thawed. Of these, 1,033 (83%) survived thawing and were transferred. Five hundred sixty-three thawed cycles resulted in 516 (92%) receiving intrauterine transfer. One hundred twelve clinical pregnancies were established, resulting in a 21.7% pregnancy per transfer with a 19% ongoing rate. The implantation rate of 13.4% results from 138 implanted pre-embryos. There was a higher PR in the programmed cycle (79/302; 26.2%) compared with the natural cycle (6/47;13%). CONCLUSIONS: Freezing at the blastocyst stage is a proven and reliable method in IVF technology. Although there may be fewer pre-embryos, their ability to implant appears to approach the potential of a fresh transfer.

Osteomyelitis of the distal phalanges in three children with severe atopic dermatitis.

Three children with severe, secondarily infected atopic dermatitis since infancy developed osteomyelitis of the distal phalanges of the hands. The insidious onset of one or more distal subungual black macules was followed by edema, erythema, and pain in the involved fingers. No child had an elevated erythrocyte sedimentation rate or fever, but all had roentgenographic or scintigraphic evidence of bony destruction. In two children, Staphylococcus aureus grew from skin surface cultures; S aureus also grew from nail bed and osseous cultures of the distal phalanges; Streptococcus viridans grew from one child's nail bed. All children had prolonged hospitalizations. In two children, laboratory evaluation of immunologic function disclosed normal findings. We postulate that intense scratching of infected skin coupled with minor trauma to the fingertips created distal subungual microabscesses that spread contiguously to the underlying bone.

Atlantooccipital junction: standards for measurement in normal children.

This study describes a simple method for measuring the distance between the occiput and atlas when a distraction-dislocation injury is suspected in a child. Measurements were made at five evenly spaced locations along the atlantooccipital joint on cross-table lateral skull radiographs in 100 normal children. These data were compared with similar measurements in eight patients with proved atlantooccipital dislocation. The mean normal measurement fell between 1.96-2.63 mm for all five points. For boys or girls aged 1-15 years, the normal distance should not exceed 5 mm at any point in the joint. The likelihood that any normal child will have a measurement greater than or equal to 4.5 mm at any point is between 0.4-5.85% (expected false-positive rate).

Traumatic longitudinal atlanto-occipital distraction injuries in children.

Traumatic atlanto-occipital dislocation with survival is possible and, in fact may be relatively more common than once thought. The spectrum of neurologic manifestations is broader than previously described and does not necessarily end in death or tragic neurologic deficit. Radiographic diagnosis of this injury may be difficult, particularly in the longitudinal distraction-dislocation type. Although several methods have been proposed to evaluate the atlanto-occipital relationship, none of these is infallible in the recognition of distraction injury in children. Immobilization rather than skeletal traction provides sufficient immediate stabilization when the dislocation at the atlanto-occipital junction is of the longitudinal distraction type. Three cases are reported: in one, death occurred early; in the second, recovery was partial, but sudden death occurred 2 years later; the third child recovered fully.

Ultrasonography and computed tomography in the evaluation of the acutely ill pediatric patient.

The use of diagnostic ultrasonography and CT in the investigation of the acutely ill pediatric patient has been steadily increasing because of the relative noninvasiveness of these imaging modalities and because of improvements in resolving capabilities and scanning speed of the latest equipment. In the examination of the pediatric patient, special emphasis must be given to immobilization, sedation, or both in those children too young or too ill to cooperate. Close monitoring and observation of the child throughout sedation is important and requires special personnel and equipment. The usual indications are the search for an abscess or occult infection, trauma, and acute renal failure. Because ultrasonography uses nonionizing radiation and is less expensive, it is usually the initial modality of choice for evaluating the pediatric patient. CT is reserved for situations in which greater anatomic detail and lack of compromise by the presence of bowel gas or bone are necessary. These situations include multiple abscess collections, particularly interloop abdominal abscesses, mediastinal masses and collections obscured by overlying lung, osteomyelitis, older patients with meningomyelocele and with spinal deformity when evaluating the urinary tract, and major multiorgan abdominal trauma.

Epithelioid hemangioendothelioma of the lung (intravascular bronchioloalveolar tumor) in a young girl.

This report describes a 7 year old girl who presented with scoliosis and a small right hemithorax. Findings on spine roentgenographs were pleural thickening on the right and parenchymal densities. Computed tomography of the chest and abdomen revealed multiple pulmonary nodules and two hypervascular lesions within the liver. The diagnosis established by lung biopsy was intravascular bronchioloalveolar tumor (epithelioid hemangioendothelioma of the lung). This is the youngest reported case of this rare tumor.

Osteomyelitis of the head and neck: sequential radionuclide scanning in diagnosis and therapy.

Sequential technetium and gallium scans of the head and neck were used to confirm the diagnosis of osteomyelitis and as an important therapeutic aid to delineate the transformation of active osteomyelitis to inactive osteomyelitis in 11 cases involving sites in the head and neck. Illustrative cases are presented of frontal sinus and cervical spine osteomyelitis and laryngeal osteochondritis.

Preoperative diagnosis of splenic cysts in children by gray scale ultrasonography.

Ultrasonography is a useful noninvasive modality for the diagnosis of splenic cysts in children. Characteristic features plus the typical clinical and radiographic presentation should obviate the need for further more invasive and costly techniques which add little to diagnostic accuracy. Additional advantages offered by ultrasound a minimal patient discomfort, no ionizing radiation, and immediate reassurance to parents that the mass is a cyst. We report two cases of epidermoid splenic cysts preoperatively diagnosed by ultrasonography. The typical sonographic characteristics are presented and the sonographic differential diagnosis is discussed.

Blunt hepatic injury and elevated hepatic enzymes: a clinical correlation in children.

During a recent prospective nonrandomized comparison of noninvasive imaging techniques in 100 children with suspected major blunt abdominal injury, an interesting subset of patients was defined. Of 95 hemodynamically stable patients, 44 were found to have immediate elevation of hepatic enzymes (SGOT, SGPT greater than 30 IU). Nineteen of these children (43%) were subsequently shown to have significant liver injuries. No child with a liver injury had normal enzymes on admission. The level of enzyme elevation (SGOT chi 890 +/- 142 IU, SGPT chi 536 +/- 105 IU) in those with liver injuries is significantly greater than those without injury (SGOT chi 273 +/- 44 IU, SGPT chi 115 +/- 19 IU) (P less than or equal to 0.0001 SGOT. P less than or equal to 0.0001 SGPT). Our study has allowed definition of a group of children who are at significant risk for liver injury based on immediately available serum determinations of GOT and GPT. We have begun to use this information in our institution to select children for further noninvasive imaging. We recommend that these studies be obtained emergently in all children with suspected upper abdominal trauma.

Rickets secondary to phosphate depletion. A sequela of antacid use in infancy.

Two infants presented with growth failure and were found to have generalized osteomalacia (rickets) due to phosphate depletion from prolonged administration of an aluminum-containing antacid given for the symptoms of colic. One of the infants developed bilateral proptosis due to craniosynostosis related to the underlying metabolic bone disease. The chronic use of aluminum-containing antacids in infants has potential risk for the growing skeleton and is not innocuous. Therefore, antacid therapy should be used in low doses and very cautiously, with routine monitoring of serum calcium and phosphorus in children taking medications which reduce gastrointestinal phosphate absorption.