Objectives
To present the results of a systematic literature search aimed at determining to what extent the radiation dose can be reduced with iterative reconstruction (IR) for cardiopulmonary and ...body imaging with computed tomography (CT) in the clinical setting and what the effects on image quality are with IR versus filtered back-projection (FBP) and to provide recommendations for future research on IR.
Methods
We searched Medline and Embase from January 2006 to January 2012 and included original research papers concerning IR for CT.
Results
The systematic search yielded 380 articles. Forty-nine relevant studies were included. These studies concerned: the chest(
n
= 26), abdomen(
n
= 16), both chest and abdomen(
n
= 1), head(
n
= 4), spine(
n
= 1), and no specific area (
n
= 1). IR reduced noise and artefacts, and it improved subjective and objective image quality compared to FBP at the same dose. Conversely, low-dose IR and normal-dose FBP showed similar noise, artefacts, and subjective and objective image quality. Reported dose reductions ranged from 23 to 76 % compared to locally used default FBP settings. However, IR has not yet been investigated for ultra-low-dose acquisitions with clinical diagnosis and accuracy as endpoints.
Conclusion
Benefits of IR include improved subjective and objective image quality as well as radiation dose reduction while preserving image quality. Future studies need to address the value of IR in ultra-low-dose CT with clinically relevant endpoints.
Key Points
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Iterative reconstruction improves image quality of CT images at equal acquisition parameters.
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IR preserves image quality compared to normal-dose filtered back-projection.
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The reduced radiation dose made possible by IR is advantageous for patients.
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IR has not yet been investigated with clinical diagnosis and accuracy as endpoints.
Objectives
To explain the technical principles of and differences between commercially available iterative reconstruction (IR) algorithms for computed tomography (CT) in non-mathematical terms for ...radiologists and clinicians.
Methods
Technical details of the different proprietary IR techniques were distilled from available scientific articles and manufacturers' white papers and were verified by the manufacturers. Clinical results were obtained from a literature search spanning January 2006 to January 2012, including only original research papers concerning IR for CT.
Results
IR for CT iteratively reduces noise and artefacts in either image space or raw data, or both. Reported dose reductions ranged from 23 % to 76 % compared to locally used default filtered back-projection (FBP) settings, with similar noise, artefacts, subjective, and objective image quality.
Conclusion
IR has the potential to allow reducing the radiation dose while preserving image quality. Disadvantages of IR include blotchy image appearance and longer computational time. Future studies need to address differences between IR algorithms for clinical low-dose CT.
Key Points
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Iterative reconstruction technology for CT is presented in non-mathematical terms
.
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IR reduces noise and artefacts compared to filtered back-projection
.
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IR can improve image quality in routine-dose CT and lower the radiation dose
.
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IR's disadvantages include longer computation and blotchy appearance of some images
.
Purpose
To systematically review and meta-analyse published data on the diagnostic performance of
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F-FDG PET/CT in detecting bone marrow involvement in patients with newly diagnosed diffuse large ...B-cell lymphoma (DLBCL).
Methods
PubMed/MEDLINE and Embase were systematically searched for relevant studies. The methodological quality of each study was assessed. Sensitivities and specificities of FDG PET/CT in individual studies were calculated and meta-analysed with a random effects model. A summary receiver operating characteristic curve (sROC) was constructed with the Moses-Shapiro-Littenberg method. Weighted summary proportions of discrepancies between the FDG PET/CT and (blind) bone marrow biopsy (BMB) results among all patients were calculated.
Results
Seven studies, with a total of 654 patients with newly diagnosed DLBCL, were included. Overall, the quality of the included studies was moderate. The sensitivity and specificity of FDG PET/CT for detecting bone marrow involvement ranged from 70.8 % to 95.8 % and from 99.0 % to 100 %, with pooled estimates of 88.7 % (95 % confidence interval, CI, 82.5 – 93.3 %) and 99.8 % (95 % CI 98.8 – 100 %), respectively. The area under the sROC curve was 0.9983. The weighted summary proportion of FDG PET/CT-negative patients with positive BMB findings among all patients was 3.1 % (95 % CI 1.8 – 5.0 %) and the weighted summary proportion of FDG PET/CT-positive patients with negative BMB findings among all patients was 12.5 % (95 % CI 8.4 – 17.3 %).
Conclusion
FDG PET/CT is accurate and complementary to BMB for detecting bone marrow involvement in patients with newly diagnosed DLBCL. A negative FDG PET/CT scan cannot rule out the presence of bone marrow involvement, but positive FDG PET/CT findings obviate the need for BMB for the detection of bone marrow involvement in these patients.
Diffusion-weighted magnetic resonance imaging (DWI) provides functional information and can be used for the detection and characterization of pathologic processes, including malignant tumors. The ...recently introduced concept of “diffusion-weighted whole-body imaging with background body signal suppression” (DWIBS) now allows acquisition of volumetric diffusion-weighted images of the entire body. This new concept has unique features different from conventional DWI and may play an important role in whole-body oncological imaging. This review describes and illustrates the basics of DWI, the features of DWIBS, and its potential applications in oncology.
Computed tomography (CT), a strong diagnostic tool, delivers higher radiation doses than most imaging modalities. As CT use has increased rapidly, radiation protection is important, particularly ...among children. We evaluate leukemia and brain tumor risk following exposure to low-dose ionizing radiation from CT scans in childhood.
For a nationwide retrospective cohort of 168 394 children who received one or more CT scans in a Dutch hospital between 1979 and 2012 who were younger than age 18 years, we obtained cancer incidence, vital status, and confounder information by record linkage with external registries. Standardized incidence ratios were calculated using cancer incidence rates from the general Dutch population. Excess relative risks (ERRs) per 100 mGy organ dose were calculated with Poisson regression. All statistical tests were two-sided.
Standardized incidence ratios were elevated for all cancer sites. Mean cumulative bone marrow doses were 9.5 mGy at the end of follow-up, and leukemia risk (excluding myelodysplastic syndrome) was not associated with cumulative bone marrow dose (44 cases). Cumulative brain dose was on average 38.5 mGy and was statistically significantly associated with risk for malignant and nonmalignant brain tumors combined (ERR/100 mGy: 0.86, 95% confidence interval = 0.20 to 2.22, P = .002, 84 cases). Excluding tuberous sclerosis complex patients did not substantially change the risk.
We found evidence that CT-related radiation exposure increases brain tumor risk. No association was observed for leukemia. Compared with the general population, incidence of brain tumors was higher in the cohort of children with CT scans, requiring cautious interpretation of the findings.
Purpose
Diffuse large B-cell lymphoma (DLBCL) represents the most common subtype of non-Hodgkin lymphoma. Most relapses occur in the first 2 years after diagnosis. Early response assessment with
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...F-fluoro-2-deoxy-D-glucose (
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F-FDG) positron emission tomography (PET) may facilitate early change of treatment, thereby preventing ineffective treatment and unnecessary side effects. We aimed to assess the predictive value of visually-assessed interim
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F-FDG PET on progression-free survival (PFS) or event-free survival (EFS) in DLBCL patients treated with first-line immuno-chemotherapy regimens.
Methods
For this systematic review and meta-analysis Pubmed, Embase, and the Cochrane Library were searched until July 11, 2017. Prospective and retrospective studies investigating qualitative interim PET response assessment without treatment adaptation based on the interim PET result were eligible. The primary outcome was two-year PFS or EFS. Prognostic and diagnostic measures were extracted and analysed with pooled hazard ratios and Hierarchical Summary Receiver Operator Characteristic Curves, respectively. Meta-regression was used to study covariate effects.
Results
The pooled hazard ratio for 18 studies comprising 2,255 patients was 3.13 (95%CI 2.52–3.89) with a 95% prediction interval of 1.68–5.83. In 19 studies with 2,366 patients, the negative predictive value for progression generally exceeded 80% (64–95), but sensitivity (33–87), specificity (49–94), and positive predictive values (20–74) ranged widely.
Conclusions
These findings showed that interim
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F-FDG PET has predictive value in DLBCL patients. However, (subgroup) analyses were limited by lack of information and small sample sizes. Some diagnostic test characteristics were not satisfactory, especially the positive predictive value should be improved, before a successful risk stratified treatment approach can be implemented in clinical practice.
Computed tomography (CT) is currently the most commonly used means for staging malignant lymphoma. 18F-fluoro-2-deoxyglucose positron emission tomography (FDG-PET), FDG-PET/CT fusion, and whole-body ...magnetic resonance imaging (WB-MRI) are potential alternatives. The purpose of this study was to systematically review published data on the diagnostic performance of CT, FDG-PET, FDG-PET/CT fusion, and WB-MRI in staging of malignant lymphoma. In addition, technical aspects, procedures, advantages, and drawbacks of each imaging modality are outlined. Three CT studies, 17 FDG-PET studies, and 4 FDG-PET/CT fusion studies were included in this systematic review. The studies were of moderate methodological quality and used different scoring systems to stage malignant lymphoma. CT remains the standard imaging modality for initial staging of malignant lymphoma, while FDG-PET has an essential role in restaging after treatment. Early results suggest that FDG-PET/CT fusion outperforms both CT alone and FDG-PET alone. Data on the diagnostic performance of WB-MRI are lacking. Future well-designed studies, expressing their results according to the Ann Arbor staging system, are needed to determine which imaging modality is most accurate and cost-effective in staging malignant lymphoma.
Summary
This study systematically reviewed and meta‐analysed the prognostic value of complete remission status at end‐of‐treatment 18F‐fluoro‐2‐deoxy‐d‐glucose positron emission tomography (FDG‐PET) ...in diffuse large B‐cell lymphoma (DLBCL) patients treated with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R‐CHOP). The systematic PubMed/MEDLINE search yielded seven suitable studies comprising a total of 737 R‐CHOP‐treated DLBCL patients who were in complete remission at end‐of‐treatment FDG‐PET. Overall, the methodological quality of included studies was reasonable. The disease relapse rate among all patients with complete remission status according to end‐of‐treatment FDG‐PET ranged from 7·0% to 20·0%, with a weighted summary proportion of 13·7%. Five of seven studies reported progression‐free survival (PFS) of these patients at various specific time points, i.e., 2‐year PFS (n = 1), estimated 3‐year PFS (n = 3) and 5‐year PFS (n = 1), which was 83%, 85–86·4% and 75%, respectively. Three of seven studies reported overall survival (OS) of these patients at various specific time points, i.e., estimated 3‐year OS (n = 2) and estimated 5‐year OS (n = 1), which were 90%, 93·6% and 83%, respectively. In conclusion, a non‐negligible proportion of R‐CHOP‐treated DLBCL patients who achieve complete remission according to end‐of‐treatment FDG‐PET experiences disease relapse during follow‐up.
Objective To assess the relation between patterns of brain injury on neonatal and childhood magnetic resonance imaging (MRI) and long-term neurodevelopmental outcome. Study design Neonatal (n = 34) ...and childhood MRIs (n = 77) were analyzed for 80 children with neonatal encephalopathy and for 51 control subjects during childhood. MRIs were graded as normal, mildly abnormal (white matter lesions), or moderately/severely abnormal (watershed injury, lesions in basal ganglia/thalamus or focal infarction). Severity of brain injury was related to different aspects of neurologic outcome: Total impairment score of the Movement Assessment Battery for Children, intelligence quotient score, cerebral palsy, postneonatal epilepsy, and need for special education. Seven children with neonatal encephalopathy required extracorporeal membrane oxygenation treatment. Results Neonatal and childhood MRI were comparable in 25/33 children (75.8%, P < .001). Children with moderate/severe lesions on neonatal or childhood MRI more often had a total impairment score ≤ 15th percentile, an intelligence quotient ≤ 85, and cerebral palsy, and attended special education. Conclusion Different patterns of injury seen on neonatal MRI after neonatal encephalopathy can still be recognized on childhood MRI. Children with moderate to severe brain lesions on neonatal or childhood MRI significantly more often have impaired motor and cognitive outcomes.
With the increased use of MRI in preterm infants, punctate white matter lesions (PWML) are more often recognized. The aim of this study was to describe the incidence and characteristics of these ...lesions as well as short-term outcome in a cohort of serially scanned preterm infants, using both conventional imaging, diffusion (DWI) and susceptibility (SWI) weighted imaging.
112 preterm infants with 2 MRIs in the neonatal period, with evidence of punctate white matter lesions, were included. Appearance, lesion load, location, and abnormalities on DWI and SWI were scored and outcome data were collected.
Different patterns of punctate white matter lesions did appear: a linear appearance associated with signal loss on SWI, and a cluster appearance associated with restricted diffusion on DWI on the first MRI. Cluster and mixed lesions on the first scan changed in appearance in over 50% on the second scan, whereas linear lesions generally kept their appearance. Lesions were only visible on the early scan in 33%, and were only seen at term equivalent age in 20%. Nine infants developed cerebral palsy, due to additional overt white matter lesions in six.
Two patterns of punctate white matter lesions were identified: one with loss of signal on SWI in a linear appearance, and the other with DWI lesions with restricted diffusion in a cluster appearance. These different patterns are suggestive of a difference in underlying pathophysiology. To reliably classify PWML in the preterm infant in either pattern, an early MRI with DWI and SWI sequences is required.
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