Improved guided image fusion for magnetic resonance and computed tomography imaging.
Ontology highlight
ABSTRACT:
SUBMITTER: Jameel A
PROVIDER: S-EPMC3947728 | biostudies-other | 2014
REPOSITORIES: biostudies-other
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Project description:A preschool male patient with an extensive cardiac surgical history developed refractory chylothorax after a total cavopulmonary connection. Neither lymphoscintigraphy nor single-photon emission computed tomography (SPECT)/computed tomography could identify the lymphatic system leakage sites. Non-contrast heavy T2-weighted magnetic resonance lymphangiography (MRL) was performed to visualize the lymphatic system. Nevertheless, distinguishing lymphatic ducts from other watery structures of the patient remained difficult. Therefore, non-contrast MRL and SPECT images were fused. This hybrid diagnostic tool elucidated the pathophysiology of the prolonged chylothorax; pulmonary lymphatic perfusion syndrome and illustrated the anatomical connection of the thoracic duct and an abnormally dilated lymphatic network in the neck and left hilar regions. Subsequent intranodal lymphangiography with ethiodized oil confirmed these findings. SPECT/MRL may become an alternative modality for revealing the mechanism of prolonged chylothorax by visualizing the lymphatic system when dynamic contrast-enhanced magnetic resonance lymphangiography is unavailable.
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Project description:ImportanceMagnetic resonance imaging (MRI) guidance offers multiple theoretical advantages in the context of stereotactic body radiotherapy (SBRT) for prostate cancer. However, to our knowledge, these advantages have yet to be demonstrated in a randomized clinical trial.ObjectiveTo determine whether aggressive margin reduction with MRI guidance significantly reduces acute grade 2 or greater genitourinary (GU) toxic effects after prostate SBRT compared with computed tomography (CT) guidance.Design, setting, and participantsThis phase 3 randomized clinical trial (MRI-Guided Stereotactic Body Radiotherapy for Prostate Cancer [MIRAGE]) enrolled men aged 18 years or older who were receiving SBRT for clinically localized prostate adenocarcinoma at a single center between May 5, 2020, and October 1, 2021. Data were analyzed from January 15, 2021, through May 15, 2022. All patients had 3 months or more of follow-up.InterventionsPatients were randomized 1:1 to SBRT with CT guidance (control arm) or MRI guidance. Planning margins of 4 mm (CT arm) and 2 mm (MRI arm) were used to deliver 40 Gy in 5 fractions.Main outcomes and measuresThe primary end point was the incidence of acute (≤90 days after SBRT) grade 2 or greater GU toxic effects (using Common Terminology Criteria for Adverse Events, version 4.03 [CTCAE v4.03]). Secondary outcomes included CTCAE v4.03-based gastrointestinal toxic effects and International Prostate Symptom Score (IPSS)-based and Expanded Prostate Cancer Index Composite-26 (EPIC-26)-based outcomes.ResultsBetween May 2020 and October 2021, 156 patients were randomized: 77 to CT (median age, 71 years [IQR, 67-77 years]) and 79 to MRI (median age, 71 years [IQR, 68-75 years]). A prespecified interim futility analysis conducted after 100 patients reached 90 or more days after SBRT was performed October 1, 2021, with the sample size reestimated to 154 patients. Thus, the trial was closed to accrual early. The incidence of acute grade 2 or greater GU toxic effects was significantly lower with MRI vs CT guidance (24.4% [95% CI, 15.4%-35.4%] vs 43.4% [95% CI, 32.1%-55.3%]; P = .01), as was the incidence of acute grade 2 or greater gastrointestinal toxic effects (0.0% [95% CI, 0.0%-4.6%] vs 10.5% [95% CI, 4.7%-19.7%]; P = .003). Magnetic resonance imaging guidance was associated with a significantly smaller percentage of patients with a 15-point or greater increase in IPSS at 1 month (6.8% [5 of 72] vs 19.4% [14 of 74]; P = .01) and a significantly reduced percentage of patients with a clinically significant (≥12-point) decrease in EPIC-26 bowel scores (25.0% [17 of 68] vs 50.0% [34 of 68]; P = .001) at 1 month.Conclusions and relevanceIn this randomized clinical trial, compared with CT-guidance, MRI-guided SBRT significantly reduced both moderate acute physician-scored toxic effects and decrements in patient-reported quality of life. Longer-term follow-up will confirm whether these notable benefits persist.Trial registrationClinicalTrials.gov Identifier: NCT04384770.
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Project description:In this article, a heterogeneous multimodal anthropomorphic breast phantom with carcinoma is introduced to meet the response of the natural breast tissue when imaged using ionizing and non-ionizing machines. The skin, adipose, fibroglandular, pectoral muscle, and carcinoma tissue were mimicked. A T1-weighted breast magnetic resonance image with BI-RADS I tissue segmentation was used for molds creation. The tissue-mimicking materials (TMMs) were tailored in terms of their elemental composition weight fractions and their response to ionization radiation parameters. These are the mass attenuation coefficient (MAC), electron density (ne) and effective atomic number (Zeff). The behaviour of the TMMs, when exposed to a wide range of ionization radiation energy, was investigated analytically and numerically using X-COM. The achieved results showed an excellent agreement with the corresponding properties of the natural breast elemental compositions as reported by the International Commission on Radiation Units and Measurements (ICRU). The MAC of the TMMs and the ICRU-based breast tissue were found to be consistent. The maximum percentage of error in ne and Zeff amounts to only 2.93% and 5.76%, respectively. For non-ionizing imaging, the TMMs were characterized in term of T1 and T2 relaxation times. Using our preclinical MRI unit, the TMMs relaxation times were measured and compared to the natural tissue. The fabricated phantom was validated experimentally using CT, MRI, and Mammographic machines. The achieved images of the TMMs were in alignment with the real tissue in terms of CT HU values and grayscale colors. T1W and T2W images on MRI revealed the expected contrast between TMMs as in natural tissue.
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Project description:IntroductionChildren with ventricular shunts undergo frequent neuroimaging, and therefore, radiation exposures, to evaluate shunt malfunctions. The objective of this study was to safely reduce radiation exposure in this population by reducing computed tomography (CT) and increasing "rapid" magnetic resonance imaging (rMRI-shunt) among patients warranting neuroimaging for possible shunt malfunction.MethodsThis was a single-center quality improvement study in a tertiary care pediatric emergency department (ED). We implemented a multidisciplinary guideline for ED shunt evaluation, which promoted the use of rMRI-shunt over CT. We included patients younger than 18 years undergoing an ED shunt evaluation during 11 months of the preintervention and 25 months of the intervention study periods. The primary outcome was the CT rate, and we evaluated the relevant process and balancing measures.ResultsThere were 266 encounters preintervention and 488 during the intervention periods with similar neuroimaging rates (80.7% versus 81.5%, P = 0.8.) CT decreased from 90.1% to 34.8% (difference -55.3%, 95% confidence interval [CI]: -71.1, -25.8), and rMRI-shunt increased from 9.9% to 65.2% (difference 55.3%, 95% CI: 25.8, 71.1) during the preintervention and intervention periods, respectively. There were increases in the mean time to neuroimaging (53.1 min; [95% CI: 41.6, 64.6]) and ED length of stay (LOS) (52.3 min; [95% CI: 36.8, 67.6]), without changes in total neuroimaging, 72-hour revisits, or follow-up neuroimaging.ConclusionsMultidisciplinary implementation of a standardized guideline reduced CT and increased rMRI-shunt use in a pediatric ED setting. Clinicians should balance the reduction in radiation exposure with ED rMRI-shunt for patients with ventricular shunts against the increased time of obtaining imaging and LOS.
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Project description:BackgroundComplications might occur after great vessel stent implantation in children. Therefore follow-up using imaging is warranted.PurposeTo determine the optimal imaging modality for the assessment of stents used to treat great vessel obstructions in children.Material and methodsFive different large vessel stents were evaluated in an in-vitro setting. All stents were expanded to the maximal vendor recommended diameter (20mm; n = 4 or 10mm; n = 1), placed in an anthropomorphic chest phantom and imaged with a 256-slice CT-scanner. MRI images were acquired at 1.5T using a multi-slice T2-weighted turbo spin echo, an RF-spoiled three-dimensional T1-weighted Fast Field Echo and a balanced turbo field echo 3D sequence. Two blinded observers assessed stent lumen visibility (measured diameter/true diameter *100%) in the center and at the outlets of the stent. Reproducibility of diameter measurements was evaluated using the intraclass correlation coefficient for reliability and 95% limits of agreement for agreement analysis.ResultsMedian stent lumen visibility was 88 (IQR 86-90)% with CT for all stents at both the center and outlets. With MRI, the T2-weighted turbo spin echo sequence was preferred which resulted in 82 (78-84%) stent lumen visibility. Interobserver reliability and agreement was good for both CT (ICC 0.997, mean difference -0.51 [-1.07-0.05] mm) and MRI measurements (ICC 0.951, mean difference -0.05 [-2.52 --2.41] mm).ConclusionGood in-stent lumen visibility was achievable in this in-vitro study with both CT and MRI in different great vessel stents. Overall reliability was good with clinical acceptable limits of agreement for both CT and MRI. However, common conditions such as in-stent stenosis and associated aneurysms were not tested in this in-vitro study, limiting the value of the in-vitro study.
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Project description:The application of magnetic resonance image (MRI)-guided brachytherapy has demonstrated significant growth during the past 2 decades. Clinical improvements in cervix cancer outcomes have been linked to the application of repeated MRI for identification of residual tumor volumes during radiotherapy. This has changed clinical practice in the direction of individualized dose administration, and resulted in mounting evidence of improved clinical outcome regarding local control, overall survival as well as morbidity. MRI-guided prostate high-dose-rate and low-dose-rate brachytherapies have improved the accuracy of target and organs-at-risk delineation, and the potential exists for improved dose prescription and reporting for the prostate gland and organs at risk. Furthermore, MRI-guided prostate brachytherapy has significant potential to identify prostate subvolumes and dominant lesions to allow for dose administration reflecting the differential risk of recurrence. MRI-guided brachytherapy involves advanced imaging, target concepts, and dose planning. The key issue for safe dissemination and implementation of high-quality MRI-guided brachytherapy is establishment of qualified multidisciplinary teams and strategies for training and education.
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Project description:The aim of this study was to analyze the computed tomography (CT) and magnetic resonance imaging (MRI) findings of dermatofibrosarcoma protuberans (DFSP), with a view to improving the diagnosis of this kind of tumor. A total of 27 cases of histopathologically confirmed DFSP were analyzed retrospectively. Of these, 18 patients underwent a CT scan and 9 patients underwent an MRI. All patients underwent unenhanced and contrast-enhanced examinations; 1 patient underwent multiphrase CT enhancement examination. Imaging characteristics, including location, shape, size, number, edge, and attenuation or intensity of each lesion, both unenhanced and contrast enhanced, were analyzed. Of the 27 cases, 24 were solitary, 2 had 2 nodules, and 1 had multiple confluent tumors. The lesion with multiple confluent tumors was ill defined and irregular; the other lesions were oval or round, well-defined nodules or masses. The unenhanced CT images showed 19 homogenous isodense lesions. There was no calcification in any of the patients. The contrast-enhanced CT images showed intermediate and marked nonhomogeneous enhancement in 13 lesions, intermediate homogeneous enhancement in 4 lesions, and a mild heterogeneous enhancement in 2 lesions. MR T1-weighted images revealed 1 ill-defined and 9 well-defined homogeneous isointense lesions. T2-weighted images showed homogeneous hyperintensity to the muscles in 6 lesions, 3 mild hyperintense lesions with hypointense lesions, and 1 mixed, mild hyperintense and isointense lesion. Contrast-enhanced T1-weighted images demonstrated intermediate and marked nonhomogeneous enhancement in 9 lesions and intermediate homogeneous enhancement in 1 lesion. DFSP is characterized by a subcutaneous well-defined soft tissue nodule or mass on plain CT/MR scans, and shows intermediate-to-marked enhancement on contrast-enhanced CT/MR scans. The imaging findings for DFSP are nonspecific, but may help to define the diagnosis in an appropriate clinical setting.
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Project description:Background and purposeThe requirement of computed tomography (CT) for radiotherapy planning may be bypassed by synthetic CT (sCT) generated from magnetic resonance (MR), which has recently led to the clinical introduction of MR-only radiotherapy for specific sites. Further developments are required for abdominal sCT, mostly due to the presence of mobile air pockets affecting the dose calculation. In this study we aimed to overcome this limitation for abdominal sCT at a low field (0.35 T) hybrid MR-Linac.Materials and methodsA retrospective analysis was conducted enrolling 168 patients corresponding to 215 MR-CT pairs. After the exclusion criteria, 152 volumetric images were used to train the cycle-consistent generative adversarial network (CycleGAN) and 34 to test the sCT. Image similarity metrics and dose recalculation analysis were performed.ResultsThe generated sCT faithfully reproduced the original CT and the location of the air pockets agreed with the MR scan. The dose calculation did not require manual bulk density overrides and the mean deviations of the dose-volume histogram dosimetric points were within 1 % of the CT, without any outlier above 2 %. The mean gamma passing rates were above 99 % for the 2 %/ 2 mm analysis and no cases below 95 % were observed.ConclusionsThis study presented the implementation of CycleGAN to perform sCT generation in the abdominal region for a low field hybrid MR-Linac. The sCT was shown to correctly allocate the electron density for the mobile air pockets and the dosimetric analysis demonstrated the potential for future implementation of MR-only radiotherapy in the abdomen.
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