UNASSIGNED: Four-dimensional magnetic resonance imaging (4DMRI) has gained interest as an alternative to the current standard for motion management four-dimensional tomography (4DCT) in abdominal radiotherapy treatment planning (RTP). This review aims to assess the 4DMRI literature in abdomen, focusing on technical considerations and the validity of using 4DMRI for patients within radiotherapy protocols.
UNASSIGNED: The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A comprehensive search was performed across the Medline, Embase, Scopus, and Web of Science databases, covering all years up to December 31, 2023. The studies were grouped into two categories: 4DMRI reconstructed from 3DMRI acquisition; and 4DMRI reconstructed from multi-slice 2DMRI acquisition.
UNASSIGNED: A total of 39 studies met the inclusion criteria and were analysed to provide key findings. Key findings were 4DMRI had the potential to improve abdominal RTP for patients by providing accurate tumour definition and motion assessment compared to 4DCT. 4DMRI reconstructed from 3DMRI acquisition showed promise as a feasible approach for motion management in abdominal RTP regarding spatial resolution. Currently,the slice thickness achieved on 4DMRI reconstructed from multi-slice 2DMRI acquisitions was unsuitable for clinical purposes. Lastly, the current barriers for clinical implementation of 4DMRI were the limited availability of validated commercial solutions and the lack of larger cohort comparative studies to 4DCT for target delineation and plan optimisation.
UNASSIGNED: 4DMRI showed potential improvements in abdominal RTP, but standards and guidelines for the use of 4DMRI in radiotherapy were required to demonstrate clinical benefits.

Cone-beam CT (CBCT) is the most commonly used onboard imaging technique for target localization in radiation therapy. Conventional 3D CBCT acquires x-ray cone-beam projections at multiple angles around the patient to reconstruct 3D images of the patient in the treatment room. However, despite its wide usage, 3D CBCT is limited in imaging disease sites affected by respiratory motions or other dynamic changes within the body, as it lacks time-resolved information. To overcome this limitation, 4D-CBCT was developed to incorporate a time dimension in the imaging to account for the patient\'s motion during the acquisitions. For example, respiration-correlated 4D-CBCT divides the breathing cycles into different phase bins and reconstructs 3D images for each phase bin, ultimately generating a complete set of 4D images. 4D-CBCT is valuable for localizing tumors in the thoracic and abdominal regions where the localization accuracy is affected by respiratory motions. This is especially important for hypofractionated stereotactic body radiation therapy (SBRT), which delivers much higher fractional doses in fewer fractions than conventional fractionated treatments. Nonetheless, 4D-CBCT does face certain limitations, including long scanning times, high imaging doses, and compromised image quality due to the necessity of acquiring sufficient x-ray projections for each respiratory phase. In order to address these challenges, numerous methods have been developed to achieve fast, low-dose, and high-quality 4D-CBCT. This paper aims to review the technical developments surrounding 4D-CBCT comprehensively. It will explore conventional algorithms and recent deep learning-based approaches, delving into their capabilities and limitations. Additionally, the paper will discuss the potential clinical applications of 4D-CBCT and outline a future roadmap, highlighting areas for further research and development. Through this exploration, the readers will better understand 4D-CBCT\'s capabilities and potential to enhance radiation therapy.

Minimally invasive parathyroidectomy (MIP) is the standard of care for primary hyperparathyroidism (PHPT). Four dimensional computed tomography(4DCT) and F-18 Fluorocholine positron emission tomography/computed tomography (FCH PET/CT) localize adenomas accurately to perform MIP. We aimed to conduct a systematic review and metanalysis to evaluate the diagnostic performance of 4DCT and FCH PET/CT scan for quadrant wise localisation in PHPT patients and to do head-to-head comparison between these two modalities. DESIGN, PATIENTS AND MEASUREMENT : After searching through PubMed and EMBASE databases, 46 studies (using histology as a gold standard) of 4DCT and FCH PET/CT were included. RESULTS: Total number of patients included were 1651 and 952 for 4DCT scan (studies n = 26) and FCH PET/CT scan (studies n = 24) respectively. In per patient analysis, FCH PET/CT and 4DCT had pooled sensitivities of 92% (88-94) and 85% (73-92) respectively and in per lesion analysis, 90% (86-93) and 79% (71-84), respectively. In the subgroup with negative conventional imaging/persistent PHPT, FCH PET/CT had comparable sensitivity to 4DCT (84% [74-90] vs. 72% [46-88]). As per patient wise analysis, FCH PET/CT had better detection rates than 4DCT ([92.4 vs. 76.85], odds ratio -3.89 [1.6-9.36] p = .0024) in the subpopulation where both FCH PET/CT and 4DCT were reported. CONCLUSION: Both 4DCT and FCH PET/CT scan performed well in newly diagnosed patients, patients with persistent disease and in those with inconclusive conventional imaging results. FCH PET/CT scan had a higher pooled sensitivity than 4DCT in detecting patients with PHPT in head to head comparison.

OBJECTIVE: To review diagnostic imaging modalities for parathyroid cystic adenomas (PCA). Since PCAs are a rare (0.5%-1%) subclass of parathyroid adenomas, and due to their cystic component, imaging modalities known to be efficient for diagnosing solid adenomas might fail in localizing them.
METHODS: We conducted a systematic review using the PubMed and Cochrane databases for English articles on PCAs published between 1995 and 2020. A meta-analysis of the retrieved data was performed.
RESULTS: Overall, 39 studies, reporting on a total of 160 patients, were included in the analysis. Two thirds (68%) of the patients were female, with a mean age of 53.9 years. A single cystic adenoma was detected in 98.1% of cases. The mean blood calcium corrected for albumin level was 12.6 ± 2.7 mg/dL, and the mean parathyroid hormone level was 565.5 ± 523.8 pg/mL. The mean PCA sizes as measured by ultrasound (US), computed tomography (CT), and ex vivo measurement were 4.8 ± 3.6, 5.2 ± 3.2, and 3.5 cm, respectively. The median weight was 8.1 g. PCA was detected in 86% of US examinations; 100% of US-guided fine needle aspiration, 4-dimensional computed tomography (4D-CT), or magnetic resonance imaging examinations; and 61% of 99m-technetium sestamibi scan with single-photon emission computed tomography ((99m)Tc-SPECT). (99m)Tc-SPECT showed a significantly lower diagnostic rate than US (odds ratio, 3.589), US-guided fine needle aspiration, CT combined with 4D-CT, and the combination of US, CT, 4D-CT, and magnetic resonance imaging (P < .001).
CONCLUSIONS: Although US and 4D-CT showed a significantly high rate in diagnosing PCA, (99m)Tc-SPECT showed a lower PCA diagnostic rate. These findings suggest that larger cystic lesions suspected as PCAs should be further evaluated using 4D-CT rather than (99m)Tc-SPECT.

暂无摘要。

4D multi-image-based (4DMIB) optimization is a form of robust optimization where different uncertainty scenarios, due to anatomy variations, are considered via multiple image sets (e.g., 4DCT). In this review, we focused on providing an overview of different 4DMIB optimization implementations, introduced various frameworks to evaluate the robustness of scanned particle therapy affected by breathing motion and summarized the existing evidence on the necessity of using 4DMIB optimization clinically. Expected potential benefits of 4DMIB optimization include more robust and/or interplay-effect-resistant doses for the target volume and organs-at-risk for indications affected by anatomical variations (e.g., breathing, peristalsis, etc.). Although considerable literature is available on the research and technical aspects of 4DMIB, clinical studies are rare and often contain methodological limitations, such as, limited patient number, motion amplitude, motion and delivery time structure considerations, number of repeat CTs, etc. Therefore, the data are not conclusive. In addition, multiple studies have found that robust 3D optimized plans result in dose distributions within the set clinical tolerances and, therefore, are suitable for a treatment of moving targets with scanned particle therapy. We, therefore, consider the clinical necessity of 4DMIB optimization, when treating moving targets with scanned particle therapy, as still to be demonstrated.

OBJECTIVE: To compare the diagnostic accuracy of dual-phase 99mTc-MIBI single photon emission computed tomography/computed tomography (SPECT/CT) and 4D CT for the localization of hyperfunctioning parathyroid glands, a systematic review and meta-analysis was performed. Whether 4D CT combined to SPECT/CT [contrast-enhanced (CE)-SPECT/CT] had a better diagnostic performance than SPECT/CT alone in this scenario was also evaluated.
METHODS: PubMed and Embase databases were searched for eligible studies. To reduce interstudy heterogeneity, only studies with clear head-to-head comparison were included. Publication bias was assessed by the Deeks funnel plot. The pooled sensitivity, specificity and the area under the curve (AUC) for 4D CT, SPECT/CT and CE-SPECT/CT were determined by random-effect analysis, respectively.
RESULTS: Nine studies met the inclusion criteria, with a total of 911 participants. The sensitivity and specificity of 4D CT were 0.85 [95% confidence interval (CI), 0.69-0.94] and 0.93 (95% CI, 0.88-0.96), whereas the sensitivity and specificity for SPECT/CT were 0.68 (95% CI, 0.51-0.82; P = 0.048 compared with 4D CT) and 0.98 (95% CI, 0.95-0.99; P = 0.014 compared with 4D CT), respectively. CE-SPECT/CT is comparable to SPECT/CT in specificity and AUC, but it may improve the sensitivity (although there was a lack of statistical difference, 0.87 vs. 0.78; P = 0.125).
CONCLUSIONS: Although 4D CT shows comparable AUC and borderline better sensitivity than SPECT/CT, its clinical application is confined by relatively low specificity and high radiation exposure. CE-SPECT/CT may improve the sensitivity without compromising the specificity and AUC of SPECT/CT.

Four-dimensional computerized tomography (4DCT) is required for stereotactic ablative body radiotherapy (SABR) of mobile targets to account for tumor motion during treatment planning and delivery. In this study, we report on the impact of an image review quality assurance process performed prior to treatment planning by medical physicists for 4DCT scans used for SABR treatment. Reviews were performed of 211 4DCT scans (193 patients) over a 3-yr period (October 2014 to October 2017). Treatment sites included lung (n = 168), kidney/adrenal/adrenal gland (n = 12), rib (n = 4), mediastinum (n = 10), liver (n = 2), T-spine (n = 1), and other abdominal sites (n = 14). It was found that in 23% (n = 49) of cases patient management was altered due to the review process. The most frequent intervention involved patient-specific contouring advice (n = 35 cases, 17%) including adjustment of internal target volume (ITV) margins. In 13 cases (6%) a rescan was requested due to extensive motion artifact rendering the scan inadequate for SABR treatment planning. 4DCT review by medical physicists was found to be an effective method to improve plan quality for SABR.

OBJECTIVE: To determine whether the sensitivity and specificity of four-dimensional CTA (4D-CTA) are equivalent to digital subtraction angiography (DSA) in the detection of underlying vascular abnormalities in patients with intracerebral haemorrhage (ICH).
METHODS: A systematic review of studies comparing 4D-CTA with DSA in the detection of the underlying structural causes of ICH was performed on the literature published between 1998 and 2019.
RESULTS: We identified a total of 237 articles from PubMed, SCOPUS and Web of Science using the following Medical Subject Headings (MeSH) terms: primary intracerebral haemorrhage, 4D-CTA, DSA, cerebral haemorrhage, angiography, digital subtraction, arteriovenous malformations, 4D, CTA, dynamic-CTA and time-resolved CTA. Following the removal of duplicate publications and articles failing to meet our inclusion criteria, there were four articles potentially viable for analysis. Therefore, there were not sufficient studies to provide a statistically meaningful meta-analysis.
CONCLUSIONS: The review of current literature has demonstrated that there are few published studies comparing 4D-CTA with DSA in spontaneous ICH, with only four suitable studies identified for potential analysis. However, due to the restricted number of patients and high sensitivity and specificity of 3 studies (100%), performing a meta-analysis was not meaningful. Qualitative analysis of the data concluded that 4D-CTA has the diagnostic potential to replace invasive DSA in certain cases with vascular abnormalities. However, further research studies directly comparing 4D-CTA with DSA using larger prospective patient cohorts are required to strengthen the evidence base.

Computed Tomography Ventilation Imaging (CTVI) is an experimental imaging modality that derives regional lung function information from non-contrast respiratory-correlated CT datasets. Despite CTVI being extensively studied in cross-modality imaging comparisons, there is a lack of consensus on the state of its clinical validation in humans. This systematic review evaluates the CTVI clinical validation studies to date, highlights their common strengths and weaknesses and makes recommendations. We performed a PUBMED and EMBASE search of all English language papers on CTVI between 2000 and 2018. The results of these searches were filtered in accordance to a set of eligibility criteria and analysed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Guidelines. One hundred and forty-four records were identified, and 66 full text records were reviewed. After detailed assessment, twenty-three full text papers met the selection criteria and were included in the final review. This included thirteen prospective studies, with 579 human subjects. Studies used diverse methodologies, with a large amount of heterogeneity between different studies in terms of the reference ventilation imaging modality (e.g. nuclear medicine, hyperpolarised gas MRI), imaging parameters, DIR algorithm(s) used, and ventilation metric(s) applied. The most common ventilation metrics used deformable image registration to evaluate the exhale-to-inhale motion field Jacobian determinant (DIR-Jac) or changes in air volume content based on Hounsfield Units (DIR-HU). The strength of correlation between CTVI and the reference ventilation imaging modalities was moderate to strong when evaluated at the lobar or global level, with the average ± S.D. (number of studies) linear regression correlation coefficients were 0.73 ± 0.25 (n = 6) and 0.86 ± 0.11 (n = 12) for DIR-Jac and DIR-HU respectively, and the SPC were 0.45 ± 0.31 (n = 6) and 0.41 ± 0.11 (n = 5) for DIR-Jac and DIR-HU respectively. We concluded that it is difficult to make a broad statement about the validity of CTVI due to the diverse methods used in the validation literature. Typically, CTVI appears to show reasonable cross-modality correlations at the lobar/whole lung level but poor correlations at the voxel level. Since CTVI is seeing new implementations in prospective trials, it is clear that refinement and standardization of the clinical validation methodologies are required. CTVI appears to be of relevance in radiotherapy planning, particularly in patients whose main pulmonary impairment is not a gas exchange problem but alternative imaging approaches may need to be considered in patients with other pulmonary diseases (i.e. restrictive or gas exchange problems).