Adult PET/CT acquisition protocols need to be modified for pediatric imaging to minimize the radiation dose while maintaining diagnostic utility. We developed pediatric PET/CT acquisition protocols customized to patient weight and estimated the dosimetry and cancer risk of these low-dose protocols to communicate basic imaging risks. Methods: Protocols were developed for whole-body 18 F-FDG imaging of patients in PET mode with a weight-based injected activity (5.3 MBq/kg) and acquisition times (3-5 min/field of view) and for CT for attenuation correction and localization with a weightbased tube current ranging from 10 to 40 mAs. Patients were categorized on the basis of the Broselow-Luten color-coded weight scale. Dosimetry and radiation-induced cancer risk for the PET and CT acquisition in each category were derived from mean patient sizes and the interpolation of factors from accepted patient models. Results: Whole-body pediatric PET/CT protocols require the customization of PET-acquisition settings and task-specific selection of CT technique. The proposed weight-based protocols result in an approximate effective dose ranging from 8.0 mSv for a 9-kg patient up to 13.5 mSv for a 63-kg patient. The radiation dose from the proposed protocols is 20%250% (depending on patient weight), the dose from PET/ CT protocols that use a fixed CT technique of 120 mAs and 120 kVp. The approximate, conservative estimate of additional lifetime attributable risk (LAR) of cancer incidence for females using the proposed protocols was approximately 3 in 1,000, with a variation of 18% across patient categories. For males, the additional LAR of cancer incidence was approximately 2 in 1,000, with a variation of 16% across categories. Conclusion: Lowdose PET/CT protocols for 11 patient weight categories were developed. The proposed protocols offer an initial set of acquisition parameters for pediatric PET/CT. The use of multiple categories allows for the continued refinement of dose-reduction parameters to minimize dose while maintaining image quality across the range of pediatric patient sizes. Thecombi nation of PETand CT is a well-established tool for adult medical imaging and has proven value for oncology, cardiology, and neurology. As the availability of these dualmodality systems increases, PET/CT is of growing importance in pediatric imaging-particularly for cancer detection, staging, therapeutic response monitoring, and outcome prediction (1). Adult PET/CT protocols should be appropriately modified for application to the pediatric population. Several works have offered recommendations on pediatric PET/CT protocols (2-4). In general, pediatric protocols are similar to adult protocols. Some variations that may require special attention include ensuring that the patient is quiescent during the uptake phase, providing a warm environment during the uptake phase, and determining whether sedation and imaging of the extremities is warranted. Development of pediatric protocols also requires the careful selection of PET and CT acquisition ...

Pediatric 18 F-FDG dosing and acquisition durations are generally based on coarse extrapolation from adult guidelines. This study sought to determine whether shorter acquisition durations or a lower 18 F-FDG injected activity could be used for pediatric 18 F-FDG PET/CT examinations while maintaining diagnostic utility. Reduction of overall scan time potentially reduces motion artifacts, improves patient comfort, and decreases length of sedation. Alternatively, decreased 18 F-FDG dose minimizes radiation risk. Methods: Fourteen whole-body 18 F-FDG PET/CT examinations were performed on 13 patients (weight, 13-109 kg; age range, 1-23 y) with a weight-based injected activity (5.3 MBq/kg [0.144 mCi/kg]), fixed acquisition durations (3 min/field of view [FOV] if , 22 kg, 5 min/FOV if . 22 kg), and list-mode acquisition. For each examination, the list-mode data were truncated to form multiple datasets with shorter acquisition durations down to a minimum of 1 min/FOV (i.e., 1, 2, 3, 4, and 5 min/FOV data were formed from single 5 min/FOV acquisition). Fifty-six image volumes were generated, randomized, and reviewed in a masked manner with corresponding CT image volumes by 5 radiologists. Overall, subjective adequacy and objective lesion detection accuracy by body region were evaluated. Results: All examinations with maximum acquisition duration were graded as adequate and were used as the reference standard for detection accuracy. For patients less than 22 kg, 1 of the 3 PET/CT examinations was graded as inadequate for clinical tasks when acquisition duration was reduced to 2 min/FOV, and all examinations were graded as inadequate when reduced to 1 min/FOV. For patients more than 22 kg, all 3-5 min/FOV studies were graded as adequate, and 2 of the 9 studies were graded as inadequate for 2 min/FOV studies. Lesion detection accuracy was perfect for acquisition times between 3 min/FOV and 5 min/FOV for all regions of the body. However, lesion detection became less accurate when imaging acquisition time was reduced more than 40%. Conclusion: Evaluation of image volumes generated from simulated shorter acquisition durations suggests that imaging times for larger patients (.22 kg) can be reduced from 5 min/FOV to 3 min/FOV without a loss of diagnostic utility. Using decreased acquisition times as a surrogate for 18 F-FDG dose, 18 F-FDG dose can be reduced by approximately 40% when all patients were scanned for 5 min/FOV.

Tuberculosis (TB) is widely prevalent in developing nations and has recently made a comeback in industrialized countries, with the rise in immunocompromized patients. Musculoskeletal TB in children presents a diagnostic challenge because it is difficult to recognize in the early stages of the disease, and imaging features mimic other entities. The clinical onset is insidious, with an indolent course and a resultant late presentation. It leads to significant morbidity; a delay in diagnosis can cause potentially serious neurological complications and bone and joint destruction. Conventional radiographs are the initial imaging modality and US, CT and MRI are used in conjunction to better delineate the disease extent and morphology. Radiologists should be familiar with the spectrum of imaging features of TB, including plain radiographs and MRI, and aid the clinician in making an early diagnosis. Aspiration or biopsy with examination for acid-fast bacillus and histological evaluation is required to confirm the diagnosis.

OBJECTIVES To determine how often neuroimaging confirms, clarifies, or contradicts initial diagnoses of late life cognitive disorders. DESIGN Retrospective case review. SETTING An outpatient clinic specializing in memory disorders. PARTICIPANTS 193 consecutively referred, cognitively impaired patients. MEASUREMENTS Diagnoses using research criteria were developed for each patient at the first visit, and ranged from cognitive impairment without dementia to dementias of single, complex, or indeterminate etiology. Structural (non-contrast MRI) and perfusion (Tc-99m ECD SPECT) images were categorized together as normal, suggestive of specific diseases, or abnormal/not diagnostic. RESULTS When a single neurodegenerative disease was suspected clinically (n=94) imaging confirmed the diagnosis in 50, contradicted the diagnosis in 32, and was abnormal/not diagnostic in 12. When more than one neurodegenerative etiology was clinically suspected (n=21) imaging assigned a single diagnosis in 13 and only cerebrovascular disease in 1, and was abnormal/not diagnostic in 7. In dementia NOS (n=33), imaging suggested a specific etiology in 23 and was abnormal/not diagnostic in 10. Abnormal/not diagnostic images were more common in cognitive disorder NOS (n=25) than in other clinical groups (68% vs. 22%, χ2 = 22.8 p < 0.001). Neuroimaging indicators of cerebrovascular disease were common (60% prevalence) but not predicted by the presence of vascular risk factors alone. CONCLUSION Overall, neuroimaging confirmed, clarified, or contradicted the initial clinical diagnosis in >80% of patients while < 20% had abnormal/not diagnostic patterns. Imaging suggested a complex dementia etiology in 21% of cases clinically thought to be caused by a single process, while 46% of complex clinical differential diagnoses appeared to reflect a single causal pattern. Further work is needed to determine whether refinement of clinical diagnoses by specialized neuroimaging improves clinical decision-making and patient outcomes.

Spontaneous or idiopathic biliary perforations are an infrequently encountered but an important cause of surgical jaundice in paediatric patients and one of the most common causes of surgical jaundice in infancy. A pre-operative diagnosis with a clinical history and physical findings may not be possible in most of the cases. The exact cause of the perforation remains unclear and the diagnosis is made at the time of laparotomy for an acute abdomen. An early, efficient and an effective surgical management is associated with a good prognosis; however, a delay in the correct diagnosis or an inappropriate management may result in bacterial contamination of the biliary ascites, with an unfavourable outcome. The relative rarity of this condition is reflected by the very few case reports, limited case studies and scarcity of published literature.