Utility of PET scans to predict disease relapse in pediatric patients with Hodgkin lymphoma

BACKGROUND: Positron emission tomography (PET) differentiates normal from abnormal cells based on metabolic activity. Numerous studies report that PET scan offers increased sensitivity, specificity and predictive values as compared to computed tomography (CT) in adult lymphoma patients. PROCEDURE: Twenty-three consecutive pediatric Hodgkin lymphoma (HL) patients were evaluated with PET scan either at diagnosis or during treatment, then at therapy completion and in follow-up. RESULTS: Twenty two of the 23 patients had a negative PET scan at the end of therapy; however, ten later developed a positive scan for a total of 11 (47.8%) patients with a positive post treatment PET scan. Six tissue biopsies were performed in five patients; four specimens were negative for disease and two confirmed HL relapse. Six patients were monitored clinically and remained asymptomatic; four had resolution of abnormalities on repeat PET while two had persistently positive, but stable PET scan findings and continue to be in remission at 11 and 40 months following treatment. Twelve (52.2%) patients of the original cohort have had consistently negative PET scans and have not relapsed. CONCLUSIONS: PET is a sensitive (100%), but not a specific (57.1%) method for evaluating post-treatment pediatric HL patients with a strong negative predictive value (NPV; 100%), but poor positive predictive value (PPV; 18.2%). We do not recommend treatment decisions be based solely on PET scan results.     

Utility of FDG-PET/CT in follow-up of children treated for Hodgkin and non-Hodgkin lymphoma

Positron emission tomography using F-flurodeoxyglucose (FDG-PET) is considered an excellent tool for staging and monitoring disease status in adults with lymphoma. We retrospectively reviewed results of PET/CT and diagnostic computed tomography (CT) scans performed during follow-up after completion of therapy in 41 children <18 years of age with Hodgkin lymphoma and non-Hodgkin lymphoma. PET/CT scan with uptake greater than that of the liver was considered positive. Uptake that increased over the background but less than in the liver was equivocal. Clinical outcomes were obtained from medical records. Thirteen (32%) had a positive PET/CT scan and an equal number had equivocal scans in a median follow-up of 2.3 years. Diagnostic CT scans revealed new findings in 13 (32%) and persistent abnormalities in 21 (51%) of the children. Five children developed recurrent disease, and one developed a second cancer. No children with equivocal positivity developed recurrent disease. PET/CT scan was 95% sensitive, with a positive predictive value (PPV) of 53%. Diagnostic CT was 79% sensitive, with a PPV of 52%. We conclude that a negative PET/CT scan during routine follow-up for lymphoma in children strongly suggests absence of recurrence but a positive PET/CT and diagnostic CT scans have low PPV and should be interpreted with caution in this setting.     

Radiographic evaluation for suspected cerebrospinal fluid shunt obstruction

OBJECTIVE: To measure the predictive value of plain radiographs (shunt series) and computed tomography (CT) scans in a group of children undergoing evaluation for suspected shunt obstruction in a tertiary care pediatric emergency department (ED). METHODS: Radiology reports were reviewed for all ED patients who underwent a shunt series over an 18-month period. Two investigators categorized all reports as normal, possibly abnormal (eg, kink in shunt tubing, no prior CT scan for comparison), or abnormal (with definite evidence of shunt dysfunction, such as shunt tubing disconnection and increase in ventricular size since prior CT scan). Studies for which there was disagreement were re-read independently by a pediatric radiologist. Medical records were reviewed to determine outcomes. RESULTS: A total of 233 patients had shunt series and CT scans ordered. Of these, 60 patients subsequently required surgery for shunt obstruction. The shunt series revealed abnormalities in 12 patients (sensitivity, 20%; negative predictive value, 22%), whereas CT scans showed definite or possible abnormalities in 50 patients (sensitivity, 83%; negative predictive value, 93%). Combined, the two tests detected 53 shunt obstructions (sensitivity, 88%; negative predictive value, 95%). Two obstructed patients had abnormalities on shunt series that would not have been suspected after physical examination or CT scan. CONCLUSIONS: Over one quarter of pediatric ED patients evaluated radiographically for suspected shunt obstruction required surgical management. One in eight obstructed patients had normal radiographic studies. Routine performance of shunt series had a low overall yield but on rare occasions detected abnormalities that were missed by CT. Prospective studies are needed to improve the use of radiographic tests for shunt evaluation and determine clinical indications for further workup when studies are normal.     

PET for staging in rhabdomyosarcoma: an evaluation of PET as an adjunct to current staging tools

BACKGROUND: Complete staging of rhabdomyosarcoma is critical to deliver appropriate therapy. We evaluated the role of F-fluorodeoxyglucose positron emission tomography (PET) in the staging of patients with rhabdomyosarcoma. METHODS: Twenty-four patients with rhabdomyosarcoma had a PET scan during staging evaluation, before or within 13 days of initiation of therapy. PET was compared with computed tomography (CT), magnetic resonance imaging (MRI), bone scan, and pathology. RESULTS: Ninety-six sites were evaluated. All patients had positive PET scans at the primary site. Thirty-one PET positive sites at primary, regional, or distant sites were biopsied. Pathology in all 31 confirmed disease. Standardized uptake value for the primary site at diagnosis ranged from 2.4 to 12.7 (mean 6.4). At 23 sites, CT or MRI was equivocal for the detection of regional or distant spread. In these cases, a negative PET helped to exclude disease in 21 of 23 patients. PET failed to capture sites of disease visualized by CT, MRI, or bone scan at 10 sites. When comparing PET with the final clinical determination of disease extent, PET was 77% sensitive and 95% specific. CONCLUSIONS: These preliminary data indicate that PET is a useful adjunct in staging rhabdomyosarcoma. A prospective study of PET for staging of rhabdomyosarcoma is warranted.     

Usefulness of bone marrow imaging in childhood malignancies

Two hundred six technetium-99m sulfur colloid bone marrow scans in 110 pediatrics patients were reviewed. The normal distribution of sulfur colloid in the lower extremities in various age groups was established. There was progressive loss of uptake with increasing age from less than two years to greater than ten years. Tumor replacement was seen as regions of decreased radioactivity, and the extent of the scan defect paralleled the response of the disease to therapy. Both chemotherapy and irradiation resulted in an extension of the Tc-99m SC to peripheral marrow sites. In irradiated areas, marrow scan defects were demonstrated and generally recovered normal activity by six months after the completion of therapy. Marrow scan abnormalities caused by tumor replacement were present in four patients despite normal bone scans and radiographs. Ultimate confirmation of tumor involvement was by needle aspiration or biopsy. Persistent marrow defects were seen in two patients with neuroblastoma who had remission of their disease: biopsy revealed myelofibrosis. Technetium-99m sulfur colloid bone marrow scanning is a sensitive monitor of altered marrow activity associated with pediatric hematologic or oncologic diseases.     

F-18 FDG-PET imaging and correlation with CT in staging and follow-up of pediatric lymphomas

Background We hypothesized that F-18 FDG-PET could be a useful, functional imaging modality for assessing the initial staging, response to therapy and follow-up of children diagnosed with lymphoma.Objective To assess the role of whole-body F-18 FDG-PET imaging in patients with lymphoma as an initial staging modality and to measure its predictive value for monitoring the response to therapy and disease recurrence compared to CT and clinical follow-up studies.Materials and methods As part of their routine clinical care, 24 patients with histologically proven lymphoma (18 Hodgkin disease and 6 non-Hodgkin lymphoma) underwent an F-18 FDG-PET and a CT scan. A total of 28 studies were performed and the entire set of scans retrospectively reviewed. Seven studies were performed for initial staging, 12 for monitoring therapy response and 9 for detecting recurrence. Initial diagnosis was confirmed by histopathology while the gold standard at follow-up was established by clinical follow-up, additional imaging modalities and/or biopsy. F-18 FDG-PET was visually compared to CT on a lesion-by-lesion basis. Fifteen anatomic regions (seven nodal and eight extranodal) were analyzed.Results Of the 414 regions analyzed, PET and CT were concordant in 366 (positive in 16 and negative in 350). Discordance was found in 48 regions. Overall sensitivities, specificities, and positive and negative predictive values were 78%, 98%, 94% and 90% for F-18 FDG-PET and 79%, 88%, 90% and 46% for CT, respectively.Conclusion F-18 FDG-PET imaging is a useful technique for the staging and follow-up of pediatric patients with lymphoma.     

18F-2-fluoro-2-deoxyglucose uptake in white adipose tissue on pediatric oncologic positron emission tomography (PET)/computed tomography (CT)

Background

Altered biodistribution of [F-18]2-fluoro-2-deoxyglucose (FDG) is sometimes encountered in pediatric patients undergoing chemotherapy for lymphoma on post-induction positron emission tomography (PET) imaging. A characteristic pattern of increased FDG uptake in white adipose tissue can be seen, particularly in the buccal regions, body wall and gluteal regions, with a shift of radiotracer away from the blood pool and liver. This altered biodistribution has been attributed to effects of corticosteroids in pediatric and adult patients and is important to recognize because of its potential for limiting the diagnostic quality of the PET scan and interfering with therapeutic response assessment.

Objective

In contrast to the well-known metabolically active brown fat seen on up to one-third of pediatric PET scans, white fat is usually non-metabolically active. We sought to determine the incidence of altered distribution of FDG in subcutaneous white adipose tissue in pediatric patients undergoing PET imaging and to assess the association with corticosteroid use.

Materials and methods

We reviewed the medical records and imaging for four children in whom altered biodistribution in white adipose tissue was present on post-induction FDG PET/CT, identified during routine clinical practice. All four were receiving corticosteroids as part of their chemotherapy. We then retrospectively reviewed oncology FDG PET/CT scans over a 2-year period (1,361 scans in 689 patients) to determine the incidence of uptake in white fat by qualitative visual assessment. In the children identified with altered biodistribution, we measured maximum standard uptake value (SUV_max) and mean standard uptake value (SUV_mean) in areas of subcutaneous white fat, the buccal regions, body wall or gluteal soft-tissue regions, liver and blood pool. We reviewed all medical records, including medication lists. We summarize the relevant clinical and imaging findings of 13 pediatric patients, including the 4 index patients.

Results

We determined the incidence of FDG uptake in white fat to be rare, found in 9 of 1,361 (0.6%) PET scans performed for pediatric cancer evaluation. FDG uptake was increased in subcutaneous adipose tissue, particularly in the buccal regions, body wall and gluteal regions, with a shift of radiotracer away from the blood pool and liver. The degree of increased uptake in peripheral white fat varied from marked to mild, and the biodistribution was distinct from that of brown adipose tissue. Children with this altered biodistribution were uniformly receiving corticosteroids as part of induction treatment for their cancer, and these findings were only identified on post-induction PET/CT. Follow-up PET/CT documented resolution of this effect after treatment with corticosteroids ceased.

Conclusion

Our findings support the current understanding that characteristic uptake of FDG in white adipose tissue is mediated by corticosteroid effect. Although this altered biodistribution is rare (<1% of PET scans) it could impair the diagnostic quality of the scan, affecting image interpretation, and should be recognized when present.

     

Pediatric Hodgkin lymphoma: are we over-scanning our patients?

Despite the favorable outcome of most pediatric patients with Hodgkin lymphoma (HL), there is rising concern about risks of carcinogenesis from both diagnostic and therapeutic radiation exposure for patients treated on study protocols. Although previous studies have investigated radiation exposure during treatment, radiation from post-treatment surveillance imaging may also increase the likelihood of secondary malignancies. All diagnostic imaging examinations involving ionizing radiation exposure performed for surveillance following completion of therapy were recorded for 99 consecutive pediatric patients diagnosed with HL from 2000 to 2010. Cumulative radiation dosage from these examinations and the frequency of relapse detection by these examinations were recorded. In the first 2 years following completion of therapy, patients in remission received a median of 11 examinations (range 0-26). Only 13 of 99 patients relapsed, 11 within 5 months of treatment completion. No relapse was detected by 1- or 2-view chest radiographs (n = 38 and 296, respectively), abdomen/pelvis computed tomography (CT) scans (n = 211), or positron emission tomography (PET) scans alone (n = 11). However, 10/391 (2.6%) of chest CT scans, 4/364 (1.1%) of neck CT scans, and 3/47 (6.4%) of PET/CT scans detected relapsed disease. Thus, only 17 scans (1.3%) detected relapse in a total of 1358 scans. Mean radiation dosages were 31.97 mSv for Stage 1, 37.76 mSv for Stage 2, 48.08 mSv for Stage 3, and 51.35 mSv for Stage 4 HL. Approximately 1% of surveillance imaging examinations identified relapsed disease. Given the very low rate of relapse detection by surveillance imaging stipulated by current protocols for pediatric HL patients, the financial burden of the tests themselves, the high cure rate, and risks of second malignancy from ionizing radiation exposure, modification of the surveillance strategy is recommended.     

Preliminary Data on the Diagnostic Accuracy of Rubidium-82 Cardiac PET Perfusion Imaging for the Evaluation of Ischemia in a Pediatric Population

Evaluation of myocardial perfusion is sometimes necessary in children with congenital heart disease or acquired coronary artery abnormalities. Limited information is available regarding the clinical utility of myocardial perfusion imaging in children. PET imaging with rubidium-82 may provide a convenient clinical means of assessing regional circulatory compromise in pediatric patients with small hearts, due to its improved spatial resolution. Clinically indicated cardiac PET studies obtained in 22 pediatric patients were reviewed by two blinded observers and assigned myocardial perfusion scores using a standard 17-segment model. PET results were correlated with coronary angiography, available in 15 cases, to determine the accuracy of PET scanning for evaluating compromise of the myocardial circulation. Reversible defects consistent with myocardial ischemia were present in 6 of 15 (40%) PET cases. The sensitivity and specificity of cardiac PET for the detection of significant coronary artery disease were 100% and 82%, respectively. The positive predictive value of cardiac PET was 67%, while the negative predictive value was 100%. Cardiac PET imaging with rubidium-82 appears promising for the noninvasive assessment of myocardial perfusion in the pediatric population. The findings from this small series suggest that prospective study in a larger patient cohort merits consideration.     

Red blood cell scintigraphy in children with acute massive gastrointestinal bleeding

Background: The main topic of the current review is the usefulness of technetium‐99m‐labeled red blood cell scintigraphy (^99mTc RBC scan) in children with acute massive gastrointestinal (GI) bleeding. Methods: The medical records of pediatric patients who experienced massive GI bleeding and who underwent ^99mTc RBC scanning between November 1991 and December 2004 were reviewed and analyzed retrospectively. Results: The study included 22 patients who underwent 23 ^99mTc RBC scans. The scans were usually performed after other diagnostic tests failed to locate the bleeding. The diagnostic sensitivity of the scans was nine out of 23 (39.1%). The test demonstrated a positive scan within the first 2 h in six patients, and three patients had positive results at 24 h. The locations of the lesions identified on scanning and surgical investigation were highly correlated in patients with a positive scan within 2 h. Conclusions: The ^99mTc RBC scan is a sensitive, albeit non‐specific, method for detecting GI bleeding. The location of a lesion as indicated by a positive scan within 2 h is helpful for guiding surgical intervention and angiography, although a definitive diagnosis should be made with other methods, particularly laparotomy.     

The value of 18F‐FDG PET in pediatric patients with post‐transplant lymphoproliferative disorder at initial diagnosis

PTLD is a serious complication of both solid organ and BMT. This study assessed whether ¹⁸F‐FDG PET, when added to CT scan, had additional value in the initial evaluation of PTLD in pediatric patients and whether PET/CT at baseline can reliably guide biopsy. This retrospective study evaluated 34 consecutive pediatric patients (14 female), aged 3.5–17.0 yr (mean age: 9.9 yr, s.d.: 4.9 yr), who had undergone ¹⁸F‐FDG PET/CT from May 2007 to December 2014 at initial diagnosis of PTLD following heart (n = 13), lung (n = 8), kidney (n = 4), liver (n = 3), liver and bowel (n = 3), and bone marrow (n = 3) transplantation. PTLD was diagnosed histopathologically in 33 patients and was based on clinical findings, elevated EBV, and imaging and follow‐up results in one patient. On lesion‐based analysis, ¹⁸F‐FDG PET showed more lesions than conventional CT scan (168 vs. 134), but CT revealed 22 lesions negative on PET. On per patient analysis, PET detected more lesions in 13 patients, CT identified more abnormalities in seven, and both showed the same number of lesions in 14. Adding ¹⁸F‐FDG PET to CT scans upstaged the disease in seven patients (20.5%). A combination of ¹⁸F‐FDG PET and CT was also useful in guiding biopsy, being positive in 36 of 39 samples (92.3%). These findings indicated that ¹⁸F‐FDG PET and CT are complementary at initial staging of pediatric PTLD and that ¹⁸F‐FDG PET/CT scanning can guide biopsies.     

Diagnostic value of physical examination and electrocardiogram in the initial evaluation of heart murmurs in children]

OBJECTIVE: To investigate the diagnostic value of the physical examination and electrocardiogram in the evaluation of heart murmur in new patients referred to the pediatric cardiologist. METHOD: From 1 April to 30 September 1998, all consecutive patients referred to the pediatric cardiology clinic for evaluation of heart murmur were included. They were prospectively categorized with no heart disease, possible heart disease or definite heart disease based on history and physical examination. They then underwent electrocardiogram with which the diagnosis was reevaluated by the pediatric cardiologist. Lastly, a doppler-echocardiography was systematically performed. RESULTS: In 120 children aged four days to 14 years (median: ten months), 72 (60%) showed abnormalities on doppler-echocardiography and 48 (40%) no heart disease. After physical examination, 52 patients were categorized with no heart disease: 45 patients had a normal doppler-echocardiography; in three of them, the diagnosis was incorrectly modified to possible heart disease on the basis of the electrocardiogram. In the other seven children, the electrocardiogram was normal and the doppler-echocardiography revealed minor (n = 5) or moderate (n = 2) heart defects. Nineteen patients were suspected of having possible heart disease, no diagnosis was modified after analysis of the electrocardiogram and six had normal doppler-echocardiography; 49 patients were correctly diagnosed as having definite heart disease. The sensibility of the physical examination was 90.3%, the specificity was 93.8%, the positive predictive value 95.6% and the negative predictive value 86.5%. CONCLUSION: The electrocardiogram is of no help in the discrimination between heart disease and no heart disease in children referred to the pediatric cardiologist for a cardiac murmur. The physical examination is able to differentiate children with or without heart disease in most of the cases.     

Bone and gallium scintigraphy in children with rhabdomyosarcoma: A 10-year review

Technetium-99m bone and Gallium-67 scintigraphy has been widely used in the management of children with solid tumors. A retrospective review of all patients with rhabdomyosarcoma (RMS) from January 1980 to December 1989 was undertaken in order to determine the sensitivity and specificity of scintigraphy in detection of metastatic disease and to determine optimum frequency of serial scans in follow up. Over the 10-year period, 40 patients were diagnosed and treated for RMS: 22 were newly diagnosed from 1980-1984 and of these 16 had a minmum 5-year disease-free period whilst 6 died of the disease, giving a cure rate of 73%. A total of 271 bone and 236 Gallium-67 scans were performed. With respect to detection of metastatic disease in all tissues, Gallium-67 scans had a sensitivity of 84%, specificity 95% and bone scans had a sensitivity of 70% and specificity 95%. Bone scan sensitivity and specificity for skeletal metastases were 100% and 95%, respectively. Considering only patients with Gallium avid primary tumors, the Gallium-67 scan sensitivity was 94%. Ten patients developed new metastatic disease or primary recurrence after starting therapy, 8/10 within 12 months of diagnosis. Frequent surveillance scanning in the treatment phase, 2 years post-diagnosis, is of value in the early detection of metastases and monitoring disease response to therapy. Surveillance scanning after completion of treatment is more difficult to justify.     

Early interim FDG PET/CT prediction of treatment response and prognosis in pediatric Hodgkin disease—added value of low-dose CT

Background

Interim 18F-FDG PET helps predict outcome and tailor treatment in adults with Hodgkin disease (HD).

Objective

The purpose of this study was to assess predictive values of interim 18F-FDG PET/CT in children with HD and to define the potential added value to interim PET of low-dose CT.

Materials and methods

Children were prospectively enrolled August 2002–April 2007. PET/low-dose CT was performed at staging, after 2 cycles, at the end of treatment and during follow-up (mean 45 months). Treatment was unchanged regardless of interim results. PET and low-dose CT were read independently.

Results

Of 34 enrolled children (ages 3–17 years), 27 achieved complete response, 4 had progressive disease and 3 had relapse. Interim PET alone had positive and negative predictive values of 67% and 89%, respectively. Interim low-dose CT alone had positive and negative predictive values of 35% and 100%, respectively. Interim PET/CT had positive and negative predictive values of 75% and 96%, respectively.

Conclusions

Early interim PET/CT was a good predictor of outcome. Integrated PET and low-dose CT improved the predictive value in children with HD.     

UTI: diagnosis and evaluation in symptomatic pediatric patients

We retrospectively reviewed data on 260 hospitalized pediatric patients with symptomatic urinary tract infection (UTI). To ascertain the colony-forming units (CFU)/mL compatible with the diagnosis of UTI, a culture from a catheterized urine specimen containing >1,000 CFU/mL was considered diagnostic of UTI and resulted in imaging by renal ultrasound, voiding cystourethrography, and renal nuclear scan with Tc99m dimercaptosuccinic acid (DMSA). A positive DMSA renal scan is indicative of pyelonephritis. We used logistic regression analysis to determine which patient characteristics were predictive of pyelonephritis. We determined that, in hospitalized pediatric patients, the colony count of the positive urine culture, the type of organism grown in culture, and the voiding cystourethrography (VCUG) result (positive or negative for vesicoureteral reflux) did not predict which patients had pyelonephritis. In females, advancing age of the patient and positive renal ultrasound results were predictive of which patients had pyelonephritis when we controlled for other factors. We feel this emphasizes the importance of a thorough evaluation of hospitalized symptomatic patients, including patients with colony counts of 1,000 to 50,000 CFU/mL, to locate the level of infection and plan appropriate therapy.     

Pretransplant functional imaging and outcome in pediatric patients with relapsed/refractory Hodgkin lymphoma undergoing autologous transplantation

1 Background

Pretransplant functional imaging (FI), particularly a negative positron emission tomography (PET), is a strong predictor of outcome in adults with relapsed or refractory Hodgkin lymphoma (HL), but data in pediatrics are limited.

2 Methods

The medical records of 49 consecutive pediatric patients, who received autologous transplant at a single institution, were retrospectively analyzed. All patients had either gallium or PET scan before transplant and were conditioned with carmustine, etoposide, cytarabine, and melphalan (BEAM). Deauville scores were retrospectively assigned for patients with PET (score ≥ 4 positive).

3 Results

Of the 49 patients (median age, 16.2 years), 41 (84%) were pretransplant FI negative and eight (16%) were pretransplant FI positive, after first‐ to fourth‐line salvage therapy, and a median of two salvage cycles. Eighteen patients (37%) received posttransplant radiation. At a median follow up of 46 months, 45 patients (92%) were alive and disease free, and there were three nonrelapse deaths and only one relapse death (Deauville score of 5). The 4‐year progression‐free survival (PFS) for the entire cohort was 92% (95% confidence interval [CI]: 78–97), and PFS based on pretransplant disease status was 95% (95% CI: 82–99%) in the negative FI group versus 75% (95% CI: 31–93) if positive FI (P = 0.057).

4 Conclusion

Our analysis revealed outstanding outcomes for children and adolescents with relapsed/refractory HL. There were too few relapses to identify the predictive value of pretransplant metabolic status, but pediatric patients with relapsed/refractory HL and a negative pretransplant FI had excellent survival.     

Reliability of splenic index to assess splenic involvement in pediatric Hodgkin's disease

The purpose of this study was to determine the reliability of the splenic index (SI) in children with Hodgkin's disease (HD). Seventeen patients who underwent staging laparotomy for HD were included in this study. Pretreatment computed tomography scans of these patients were reviewed retrospectively to determine the SI. The specificity, sensitivity, positive and negative predictive values, and accuracy of the SI were calculated. The sensitivity and specificity of the SI were 50% and 66%, respectively. The SI alone accurately identified or ruled out involvement with HD in 10 of 17 patients. Positive and negative predictive values of the SI were 57% and 60%, respectively. Even with the use of the SI, computed tomography alone remains unreliable to determine splenic involvement in children with HD. Additional imaging studies, especially fluorodeoxyglucose positron emission tomography, may improve the clinical staging of HD.     

Acute sinusitis in children: Is the Water's view sufficient?

The purpose of this study was to examine the utility of the Water's view in the diagnosis of acute sinusitis in children. The records of all pediatric (less than 18 years old) patients who underwent sinus radiography for suspected acute sinusitis between February 1991 and November 1992 were reviewed. All radiographs were reviewed by an attending radiologist and the interpretation of the Water's (occipitomental) view alone was compared to that of a three-view (anterior/posterior, lateral, Water's) series. Fifty-two three-view sinus series were obtained on pediatric patients during the study period. Twenty-eight patients were diagnosed with acute sinusitis based on the three-view series. When compared to the three-view series, the single Water's view had a sensitivity of 89%, specificity of 83%, positive predictive value of 87%, and negative predictive value of 87%. The overall accuracy of the Water's view in diagnosing childhood acute sinusitis was 87%. The authors conclude that the Water's view is usually sufficient in the evaluation of suspected acute sinusitis in children.     

Comparison between x-ray and bone scan detection of bone metastases in patients with rhabdomyosarcoma

A comparison of radiographic and 99mTechnetium methyldiphosphonate scintigraphic evaluations for extent of skeletal disease was made retrospectively in 17 pediatric patients with Group III and IV rhabdomyosarcoma. Thirteen children had evidence of skeletal metastases. Of these, four exhibited multiple sites of blastic as well as lytic skeletal involvement on x-rays that were not detected by bone scans: two at the time of initial diagnosis, and two at relapse in children with prior radiotherapy to involved bones. In three additional patients a greater extent of bony disease was evident on x-rays than on bone scan. Neither the pathology of the tumor, lytic versus blastic quality of the bone lesion, nor lesion size per se was found to correlate with the failure to detect them on the bone scan. Although bone scans have greater sensitivity than x-rays for the detection of metastatic bone involvement in several adult and pediatric neoplasms, in the case of rhabdomyosarcoma, the radiographic exam appears to be a more sensitive indicator in some patients and should be considered an essential study in the evaluation of skeletal involvement by this tumor.     

Normal patterns of 18F-FDG appendiceal uptake in children

Background

Prior to interpreting PET/CT, it is crucial to understand the normal biodistribution of fluorodeoxyglucose (FDG). It is also important to realize that the normal biodistribution can vary between adults and children. Although many studies have defined normal patterns of pediatric FDG uptake in structures like the thymus, brown fat and bone marrow, patterns of normal pediatric bowel activity, specifically uptake within the appendix, have not been well described. Active lymphoid tissue has increased FDG uptake when compared with inactive tissue. Since children have more active lymphoid tissue than adults, and because the appendix contains aggregated lymphoid tissue, we postulated that appendiceal uptake may be increased in pediatric patients.

Objective

To define the normal level of appendiceal FDG activity in children by evaluating a series of consecutive FDG PET/CT scans performed for other indications.

Materials and methods

After obtaining IRB approval, we retrospectively reviewed 128 consecutive whole-body pediatric FDG PET/CT examinations obtained for a variety of clinical indications. CT scans on which the appendix could not be visualized were excluded from analysis. CT scans on which the appendix could be visualized were evaluated for underlying appendiceal pathology. Studies with appendiceal or periappendiceal pathology by CT criteria were excluded. A region of interest (ROI) was placed over a portion of each appendix and appendiceal maximum standardized uptake value (SUVmax) was calculated. If an adjacent loop of bowel activity interfered with accurate measurements of the appendix SUVmax, the scan was excluded from the analysis. A chart review was performed on patients with elevated appendiceal SUVmax values to ensure that the patients did not have clinical symptomatology suggestive of acute appendicitis. When the appendix or a portion of the appendix could be visualized and accurately measured, the SUVmax was determined. SUVmax of the appendix was compared to the SUVmax of normal liver and ratios were recorded.

Results

A total of 128 scans were reviewed, patient ages 1 month to 21 years (mean age: 11.6 years). Thirty-one scans were excluded because of inability to visualize the appendix on CT. No scans were excluded for appendiceal/periappendiceal pathology on CT or chart review. No scans had to be excluded for inability to obtain an accurate SUVmax measurement because measurements were calculated on portions of the appendix separate from adjacent bowel using small ROIs. Maximum appendiceal SUVs ranged from 0.5 to 9.4 (mean: 2.2) with an appendix-to-liver background ratio ranging from 0.3 to 3.1 (mean: 1.1).

Conclusion

FDG uptake in the appendix is typically similar to that of background activity. However, slight variations in appendiceal FDG uptake do occur, which should not be misinterpreted as pathological.