Refining the role of presurgical PET/4D-CT in a large series of patients with primary hyperparathyroidism undergoing [18F]Fluorocholine PET/CT.

BACKGROUND: 4D-CT has garnered attention as complementary imaging for patients with primary hyperparathyroidism (pHPT). Herein we evaluated a diagnostic strategy using [18F]Fluorocholine Positron Emission Tomography/Computed Tomography (PET/CT), followed by 4D-CT integrated into PET/4D-CT after negative/inconclusive PET/CT results in a single-center retrospective cohort of 166 pHPT patients who underwent parathyroidectomy after [18F]Fluorocholine PET/4D-CT. METHODS: PET/CT and 4D-CT images were interpreted by three nuclear medicine physicians and one expert radiologist. Pathological findings were documented, and concordance rates were assessed. PET/CT results were categorized as positive/negative, with positive cases rated on a 3-level certitude scale: low, moderate, high. Inconclusive cases included low/moderate positivity. The added value of PET/4D-CT was assessed for negative/inconclusive cases through joint reading. RESULTS: PET/CT lesion-based analysis showed almost perfect interobserver concordance (Cohen's kappa >.8). Across the cohort, PET/CT had a sensitivity of 83%, specificity of 97%, PPV of 90% and NPV of 94%. For 4D-CT, these values were sensitivity: 53%, specificity: 84%, PPV: 56% and NPV: 82%. PET/CT was significantly more accurate than 4D-CT. Among 44 patients with negative/inconclusive results, PET/CT had sensitivity: 60%, specificity: 91%, PPV: 71% and NPV: 86%. In the same patients, sensitivity and specificity of the sequential diagnostic algorithm increased to 80% and 97%, showing significantly better global accuracy (92% vs. 83%) than standard PET/CT. CONCLUSIONS: We support a personalized imaging algorithm for pHPT, placing [18F]Fluorocholine PET/CT at the forefront, followed by 4D-CT integrated into PET/4D-CT in the same imaging session for negative/inconclusive results. When PET/CT results are clearly positive, the additional sensitivity benefit of 4D-CT is minimal.

Is clinical target volume necessary for locally advanced non-small cell lung cancer treated with 4D-CT intensity-modulated radiation therapy.

BACKGROUND: A dosimetric evaluation is still lacking in terms of clinical target volume (CTV) omission in stage III patients treated with 4D-CT Intensity-Modulated Radiation Therapy (IMRT). METHODS: 49 stage III NSCLC patients received 4D-CT IMRT were reviewed. Target volumes and organs at risk (OARs) were re-delineated. Four IMRT plans were conducted retrospectively to deliver different prescribed dose (74 Gy-60 Gy), and with or without CTV implementation. Dose and volume histogram (DVH) parameters were collected and compared. RESULTS: In the PTV-g 60 Gy plan (PTV-g refers to the PTV generated from the internal gross tumor volume), only 5 of 49 patients had the isodose ≥ 50 Gy line covering at least 95% of the PTV-c (PTV-c refers to the PTV generated from the internal CTV) volume. When the prescribed dose was elevated to 74 Gy to the PTV-g, 33 of 49 patients could have the isodose ≥ 50 Gy line covering at least 95% of the PTV-c volume. In terms of OARs protection, the SIB-IMRT plan showed the lowest value of V5, V20, and mean dose of lung, had the lowest V55 of esophagus, and the lowest estimated radiation doses to immune cells (EDIC). The V20, V30, and mean dose of heart was lower in the simultaneous integrated boost (SIB) IMRT (SIB-IMRT) plan than that of the PTV-c 60 Gy plan. CONCLUSIONS: CTV omission was not suitable for stage III patients when the prescribed dose to PTV-g was 60 Gy in the era of 4D-CT IMRT. CTV omission plus high dose to PTV-g (74 Gy for example) warranted further exploration. The SIB-IMRT plan had the best protection to normal tissue including lymphocytes, and might be the optimal choice.

Machine learning-derived clinical decision algorithm for the diagnosis of hyperfunctioning parathyroid glands in patients with primary hyperparathyroidism.

PURPOSE: To train and validate machine learning-derived clinical decision algorithm (MLCDA) for the diagnosis of hyperfunctioning parathyroid glands using preoperative variables to facilitate surgical planning. METHODS: This retrospective study included 458 consecutive primary hyperparathyroidism (PHPT) patients who underwent combined 4D-CT and sestamibi SPECT/CT (MIBI) with subsequent parathyroidectomy from February 2013 to September 2016. The study cohort was divided into training (first 400 patients) and validation sets (remaining 58 patients). Sixteen clinical, laboratory, and imaging variables were evaluated. A random forest algorithm selected the best predictor variables and generated a clinical decision algorithm with the highest performance (MLCDA). The MLCDA was trained to predict the probability of a hyperfunctioning vs normal gland for each of the four parathyroid glands in a patient. The reference standard was a four-quadrant location on operative reports and pathology. The accuracy of MLCDA was prospectively validated. RESULTS: Of 16 variables, the algorithm selected 3 variables for optimal prediction: combined 4D-CT and MIBI using (1) sensitive reading, (2) specific reading, and (3) cross-product of serum calcium and parathyroid hormone levels and outputted an MLCDA using five probability categories for hyperfunctioning glands. The MLCDA demonstrated excellent accuracy for correct classification in the training (4D-CT + MIBI: 0.91 [95% CI: 0.89-0.92]) and validation sets (4D-CT + MIBI: 0.90 [95% CI: 0.86-0.94]. CONCLUSION: Machine learning generated a clinical decision algorithm that accurately diagnosed hyperfunctioning parathyroid glands through classification into probability categories, which can be implemented for improved preoperative planning and convey diagnostic certainty. KEY POINTS: Question Can an MLCDA use preoperative variables for the diagnosis of hyperfunctioning parathyroid glands to facilitate surgical planning? Findings The developed MLCDA demonstrated excellent accuracy for correct classification in the training (0.91 [95% CI: 0.89-0.92]) and validation sets (0.90 [95% CI: 0.86-0.94]). Clinical relevance Using standard preoperative variables, an MLCDA for diagnosing hyperfunctioning parathyroid glands can be implemented to improve preoperative parathyroid localization and included in radiology reports for surgical planning.

Regional ventilation dynamics of electrical impedance tomography validated with four-dimensional computed tomography: single-center, prospective, observational study.

BACKGROUND: The dynamic regional accuracy of electrical impedance tomography has not yet been validated. We aimed to compare the regional accuracy of electrical impedance tomography with that of four-dimensional computed tomography during dynamic ventilation. METHODS: This single-center, prospective, observational study conducted in a general intensive care unit included adult patients receiving mechanical ventilation from July 2021 to February 2024. The patients were mechanically ventilated passively and underwent electrical impedance tomography and four-dimensional computed tomography on the same day. RESULTS: Overall, 45 patients were analyzed. The correlation coefficients in regional dynamic ventilation between four-dimensional computed tomography and electrical impedance tomography in each region were 0.963, 0.963, 0.835 (ventral, central, and dorsal, respectively) in the right lung and 0.947, 0.927, 0.823 (ventral, central, and dorsal, respectively) in the left lung. The correlation coefficient was low when the regional ventilation distribution detected by the electrical impedance tomography was < 2%. After excluding nine patients with a regional ventilation distribution of < 2%, the ventral, central, and dorsal correlation coefficients were 0.963, 0.963, and 0.946 in the right lung and 0.942, 0.924, and 0.951, respectively, in the left lung. CONCLUSIONS: Regional ventilation using electrical impedance tomography during dynamic ventilation was highly accurate and consistent with the time phase compared to four-dimensional computed tomography. Given the high correlation between these modalities, they can contribute significantly to further studies on regional ventilation dynamics. Trial registration number ClinicalTrials.gov (No. UMIN00044386).

Localization of Ectopic Hyperparathyroidism: Ultrasound Versus 99mTc-sestamibi, 4-Dimensional Computed Tomography, and 11C-choline Positron Emission Tomography/Computed Tomography.

OBJECTIVE: To investigate the usefulness of ultrasound (US) for the localization of ectopic hyperparathyroidism and compare it with 99mTc-sestamibi (99mTc-MIBI), 4-dimensional computed tomography (4D-CT), and 11C-choline positron emission tomography/ computed tomography (PET/CT). METHODS: Of the 527 patients with surgically confirmed primary hyperparathyroidism, 79 patients with ectopic hyperparathyroidism were enrolled. The diagnostic performance of US, 99mTc-MIBI, US + MIBI, 4D-CT, and 11C-choline PET/CT was calculated, and the factors affecting the sensitivity of US and 99mTc-MIBI were analyzed. RESULTS: Eighty-three ectopic parathyroid lesions were found in 79 patients. The sensitivity was 75.9%, 81.7%, 95.1%, 83.3%, and 100% for US, 99mTc-MIBI, US + MIBI, 4D-CT, and 11C-choline PET/CT, respectively. The difference in sensitivity among these different modalities did not achieve statistical significance (P > .05). The US sensitivity was significantly higher for ectopic lesions in the neck region than for those in the anterior mediastinum/chest wall (85.9% vs. 42.1%, P < .001). The 99mTc-MIBI and 4D-CT sensitivity was not significantly different between these two groups (84.1% vs. 94.6%, P = .193 and 81.3% vs. 85.7%, P = 1). The 11C-choline PET/CT sensitivity was 100% in both groups. CONCLUSIONS: US is a valuable tool for the localization of ectopic hyperparathyroidism, especially for ectopic lesions in the neck region.

Deep learning based automatic internal gross target volume delineation from 4D-CT of hepatocellular carcinoma patients.

BACKGROUND: The location and morphology of the liver are significantly affected by respiratory motion. Therefore, delineating the gross target volume (GTV) based on 4D medical images is more accurate than regular 3D-CT with contrast. However, the 4D method is also more time-consuming and laborious. This study proposes a deep learning (DL) framework based on 4D-CT that can achieve automatic delineation of internal GTV. METHODS: The proposed network consists of two encoding paths, one for feature extraction of adjacent slices (spatial slices) in a specific 3D-CT sequence, and one for feature extraction of slices at the same location in three adjacent phase 3D-CT sequences (temporal slices), a feature fusion module based on an attention mechanism was proposed for fusing the temporal and spatial features. Twenty-six patients' 4D-CT, each consisting of 10 respiratory phases, were used as the dataset. The Hausdorff distance (HD95), Dice similarity coefficient (DSC), and volume difference (VD) between the manual and predicted tumor contour were computed to evaluate the model's segmentation accuracy. RESULTS: The predicted GTVs and IGTVs were compared quantitatively and visually with the ground truth. For the test dataset, the proposed method achieved a mean DSC of 0.869 ± 0.089 and an HD95 of 5.14 ± 3.34 mm for all GTVs, with under-segmented GTVs on some CT slices being compensated by GTVs on other slices, resulting in better agreement between the predicted IGTVs and the ground truth, with a mean DSC of 0.882 ± 0.085 and an HD95 of 4.88 ± 2.84 mm. The best GTV results were generally observed at the end-inspiration stage. CONCLUSIONS: Our proposed DL framework for tumor segmentation on 4D-CT datasets shows promise for fully automated delineation in the future. The promising results of this work provide impetus for its integration into the 4DCT treatment planning workflow to improve hepatocellular carcinoma radiotherapy.

Clinical application of breathing-adapted 4D CT: image quality comparison to conventional 4D CT.

PURPOSE: 4D CT imaging is an integral part of 4D radiotherapy workflows. However, 4D CT data often contain motion artifacts that mitigate treatment planning. Recently, breathing-adapted 4D CT (i4DCT) was introduced into clinical practice, promising artifact reduction in in-silico and phantom studies. Here, we present an image quality comparison study, pooling clinical patient data from two centers: a new i4DCT and a conventional spiral 4D CT patient cohort. METHODS: The i4DCT cohort comprises 129 and the conventional spiral 4D CT cohort 417 4D CT data sets of lung and liver tumor patients. All data were acquired for treatment planning. The study consists of three parts: illustration of image quality in selected patients of the two cohorts with similar breathing patterns; an image quality expert rater study; and automated analysis of the artifact frequency. RESULTS: Image data of the patients with similar breathing patterns underline artifact reduction by i4DCT compared to conventional spiral 4D CT. Based on a subgroup of 50 patients with irregular breathing patterns, the rater study reveals a fraction of almost artifact-free scans of 89% for i4DCT and only 25% for conventional 4D CT; the quantitative analysis indicated a reduction of artifact frequency by 31% for i4DCT. CONCLUSION: The results demonstrate 4D CT image quality improvement for patients with irregular breathing patterns by breathing-adapted 4D CT in this first corresponding clinical data image quality comparison study.

Parathyroid Cystic Adenoma: A Systematic Review and Meta-Analysis.

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). CONCLUSION: 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.

Delayed microsurgical revascularization in an acute ischemic stroke based on perfusion study.

A 58-year-old patient presented with a severe neurological deficit due to a stroke caused by an occlusion of the left internal carotid artery siphon. Standard treatment failed and neurosurgical consult was delayed. Because of a favorable perfusion imaging finding, microsurgical revascularization via an extra-intracranial bypass (left superficial temporal artery - left middle cerebral artery) was performed 36 hours after the onset of the symptoms. The outcome of the patient was favorable. The authors want to emphasize the need to actively seek patients with a severe neurological deficit and still viable brain tissue. The time window and treatment alternatives are discussed.

Utility of 4D CT in endoleak characterization after advanced endovascular aortic repair.

OBJECTIVES: To assess the performance of dynamic or 4D CT in characterizing endoleaks in advanced endovascular aortic repair (branched and fenestrated) when other modalities fail to fully characterize the leak, most often conventional CTA. METHODS: Retrospective review of 13 patients from 2008 to 2021 who underwent 16 4D CTs to characterize endoleaks in branched and fenestrated endovascular aortic repair (FB-EVAR). The 4D CTs were performed covering up to 16 cm of the z-axis, with anywhere between 10 and 40 iterations performed every 2 s. These settings were adjusted depending on graft characteristics and type of endoleak suspected. The scans were assessed for their ability to detect the endoleak (sensitivity), and further to characterize the endoleak by type and subtype (specificity). RESULTS: Overall sensitivity in 16 scans for endoleak detection was 100%. There was a specificity of 87.5% for determining the type of endoleak (14/16). These results included two studies that were inconclusive and repeated due to technical difficulties. In patients where a specific subtype was not established, the leak was localized to the appropriate target vessel. Average dose for the 4D CT was 4724 mGy*cm (1108-11069), with the outlining higher dose scans secondary to higher iterations in those scans. CONCLUSIONS: 4D CT is a useful adjunctive tool in FB-EVAR surveillance with excellent sensitivity and specificity in characterizing endoleaks. This allows for accurate localization of leaks, which is critical for management planning.

Enhancing students' understanding of cardiac physiology by using 4D visualization.

Difficulties in achieving knowledge about physiology and anatomy of the beating heart highlight the challenges with more traditional pedagogical methods. Recent research regarding anatomy education has mainly focused on digital three-dimensional models. However, these pedagogical improvements may not be entirely applicable to cardiac anatomy and physiology due to the multidimensional complexity with moving anatomy and complex blood flow. The aim of this study was therefore to evaluate whether high quality time-resolved anatomical images combined with realistic blood flow simulations improve the understanding of cardiac structures and function. Three time-resolved datasets were acquired using time-resolved computed tomography and blood flow was computed using Computational Fluid Dynamics. The anatomical and blood flow information was combined and interactively visualized using volume rendering on an advanced stereo projection system. The setup was tested in interactive lectures for medical students. Ninety-seven students participated. Summative assessment of examinations showed significantly improved mean score (18.1 ± 4.5 vs 20.3 ± 4.9, p = 0.002). This improvement was driven by knowledge regarding myocardial hypertrophy and pressure-velocity differences over a stenotic valve. Additionally, a supplementary formative assessment showed significantly more agreeing answers than disagreeing answers (p < 0.001) when the participants subjectively evaluated the contribution of the visualizations to their education and knowledge. In conclusion, the use of simultaneous visualization of time-resolved anatomy data and simulated blood flow improved medical students' results, with a particular effect on understanding of cardiac physiology and these simulations may be useful educational tools for teaching complex anatomical and physiological concepts.

Parathyroid 4D CT in Primary Hyperparathyroidism: Exploration of Size Measurements for Identifying Multigland Disease and Guiding Biochemically Successful Parathyroidectomy.

BACKGROUND. In patients with primary hyperparathyroidism (PHPT), bilateral neck exploration is necessary for multigland disease (MGD), whereas minimally invasive parathyroidectomy is often preferred for single-gland disease (SGD). An existing system (the 4D-CT MGD score) for differentiating SGD from MGD with the use of preoperative parathyroid CT considers the size of only the largest candidate lesion. OBJECTIVE. The purpose of this study was to assess the utility of the size of the second-largest lesion on parathyroid CT for differentiating SGD from MGD as well as the utility of individual gland size for predicting the need for surgical removal and to derive optimal size thresholds for these purposes. METHODS. This retrospective study included patients with PHPT who underwent biochemically successful parathyroidectomy after preoperative parathyroid CT. Clinical radiology reports were reviewed to classify reported candidate parathyroid lesions as low-, intermediate-, or high-confidence lesions. Resected hypercellular parathyroid lesions were correlated with clinically reported candidate lesions. Patients were classified as having SGD or MGD on the basis of operative and pathology reports, independent of CT findings. One observer retrospectively determined the estimated volume (0.52 × length × width × height) and maximum diameter of clinically reported high-confidence lesions, as well as the 4D-CT MGD scores from the examinations. Diagnostic performance was assessed. RESULTS. The sample comprised 62 patients (41 women, 21 men; median age, 65 years), 47 of whom had SGD and 15 of whom had MGD, with 151 candidate lesions, including 106 high-confidence lesions. Based on the second-largest high-confidence lesions, an estimated volume threshold of 60 mm3 or greater achieved 53% sensitivity and 96% specificity, whereas a maximum diameter threshold of 7 mm or greater achieved 67% sensitivity and 96% specificity for MGD; a 4D-CT MGD score of 3 or greater achieved 47% sensitivity and 68% specificity for MGD. For predicting the need to remove a gland for successful parathyroidectomy, an estimated volume threshold of 114 mm3 or greater achieved 84% sensitivity and 97% specificity, and a threshold of 55 mm3 or greater achieved 93% sensitivity and 87% specificity; a maximum diameter threshold of 7 mm or greater achieved 93% sensitivity and 84% specificity. CONCLUSION. The estimated volume and maximum diameter of high-confidence candidate lesions can differentiate SGD from MGD and identify individual glands requiring removal for successful parathyroidectomy. Differentiating SGD from MGD may be aided by considering both the first- and second-largest high-confidence lesions. CLINICAL IMPACT. The findings will help identify patients who are likely to require bilateral neck explorations, informing preoperative patient counseling and individualized operative planning.

A comprehensive quality assurance procedure for 4D CT commissioning and periodic QA.

PURPOSE: The 4D computed tomography (CT) simulation is an essential procedure for tumors exhibiting breathing-induced motion. However, to date there are no established guidelines to assess the characteristics of existing systems and to describe meaningful performance. We propose a commissioning quality assurance (QA) protocol consisting of measurements and acquisitions that assess the mechanical and computational operation for 4D CT with both phase and amplitude-based reconstructions, for regular and irregular respiratory patterns. METHODS: The 4D CT scans of a QUASAR motion phantom were acquired for both regular and irregular breathing patterns. The hardware consisted of the Canon Aquilion Exceed LB CT scanner used in conjunction with the Anzai laser motion monitoring system. The nominal machine performance and reconstruction were demonstrated with measurements using regular breathing patterns. For irregular breathing patterns the performance was quantified through the analysis of the target motion in the superior and inferior directions, and the volume of the internal target volume (ITV). Acquisitions were performed using multiple pitches and the reconstructions were performed using both phase and amplitude-based binning. RESULTS: The target was accurately captured during regular breathing. For the irregular breathing, the measured ITV exceeded the nominal ITV parameters in all scenarios, but all deviations were less than the reconstructed slice thickness. The mismatch between the nominal pitch and the actual breathing rate did not affect markedly the size of the ITV. Phase and normalized amplitude binning performed similarly. CONCLUSIONS: We demonstrated a framework for measuring and quantifying the initial performance of 4D CT simulation scans that can also be applied during periodic QAs. The regular breathing provided confidence that the hardware and the software between the systems performs adequately. The irregular breathing data suggest that the system may be expected to capture in excess the target motion and geometry, but the deviation is expected to be within the slice thickness.

Selective venous sampling in primary hyperparathyroidism: Is it worth doing?

BACKGROUND: Accurate preoperative localization of the culprit gland is the key point for the surgical treatment of primary hyperparathyroidism. Conventional imaging techniques (ultrasound and Tc99m sestamibi scintigraphy) are usually adequate for preoperative localization. However, in some patient groups, additional imaging modalities may be required since noninvasive techniques may fail. In this study, we aimed to evaluate the diagnostic value of selective parathyroid venous sampling in patients with unclear noninvasive localization tests. METHODS: Among 513 cases who underwent parathyroidectomy due to primary hyperparathyroidism, twelve cases (2.3%) were undergone selective parathyroid venous sampling and were included in the study. Age, sex, presenting symptom, presence of a genetic disease, medical and surgical history, serum calcium (Ca)-parathormone (PTH) levels (preoperative, intraoperative, and postoperative), imaging reports (US, SM, and SVS), surgery reports, pathology reports, and complications were retrospectively reviewed. RESULTS: Seven cases (58.3%) had persistent primary hyperparathyroidism and one patient (8.3%) had past surgical history of total thyroidectomy. The remaining four patients (33.3%) had no previous neck surgery. T he sensitivity of selective venous sampling was 75%. According to the medical history, accurate localization was achieved in 85.7% of persistent cases and 60% of primary cases. Eight cases (66.6%) underwent unilateral neck exploration and four cases (33.3%) underwent four gland exploration. A single adenoma was detected in ten cases (90.9%) while one patient (9.1%) had double adenoma.

Evaluation of target volume and dose accuracy in intrafractional cases of lung cancer based on 4D-CT and 4D-CBCT images using an in-house dynamic thorax phantom.

Background: This study aimed to evaluate the target volume and dose accuracy in intrafraction cases using 4-dimensional imaging modalities and an in-house dynamic thorax phantom. Intrafraction motion can create errors in the definition of target volumes, which can significantly affect the accuracy of radiation delivery. Motion management using 4-dimensional modalities is required to reduce the risk. Materials and methods: Two variations in both breathing amplitude and target size were applied in this study. From these variations, internal target volume (ITVs) contoured in 10 phases of 4D-CT (ITV10), average intensity projection (AIP), and mid-ventilation (Mid-V) images were reconstructed from all 4D-CT datasets as reference images. Free-breathing (FB), augmentation free-breathing (Aug-FB), and static images were also acquired using the 3D-CT protocol for comparisons. In dose evaluations, the 4D-CBCT modality was applied before irradiation to obtain position correction. Then, the dose was evaluated with Gafchromic film EBT3. Results: The ITV10, AIP, and Mid-V provide GTVs that match the static GTV. The AIP and Mid-V reference images allowed reductions in ITVs and PTVs without reducing the range of target movement areas compared to FB and Aug-FB images with varying percentages in the range of 29.17% to 48.70%. In the dose evaluation, the largest discrepancies between the measured and planned doses were 10.39% for the FB images and 9.21% for the Aug-FB images. Conclusion: The 4D-CT modality can enable accurate definition of the target volume and reduce the PTV. Furthermore, 4D-CBCT provides localization images during registration to facilitate position correction and accurate dose delivery.

The EANM practice guidelines for parathyroid imaging.

INTRODUCTION: Nuclear medicine parathyroid imaging is important in the identification of hyperfunctioning parathyroid glands in primary hyperparathyroidism (pHPT), but it may be also valuable before surgical treatment in secondary hyperparathyroidism (sHPT). Parathyroid radionuclide imaging with scintigraphy or positron emission tomography (PET) is a highly sensitive procedure for the assessment of the presence and number of hyperfunctioning parathyroid glands, located either at typical sites or ectopically. The treatment of pHPT is mostly directed toward minimally invasive parathyroidectomy, especially in cases with a single adenoma. In experienced hands, successful surgery depends mainly on the exact preoperative localization of one or more hyperfunctioning parathyroid adenomas. Failure to preoperatively identify the hyperfunctioning parathyroid gland challenges minimally invasive parathyroidectomy and might require bilateral open neck exploration. METHODS: Over a decade has now passed since the European Association of Nuclear Medicine (EANM) issued the first edition of the guideline on parathyroid imaging, and a number of new insights and techniques have been developed since. The aim of the present document is to provide state-of-the-art guidelines for nuclear medicine physicians performing parathyroid scintigraphy, single-photon emission computed tomography/computed tomography (SPECT/CT), positron emission tomography/computed tomography (PET/CT), and positron emission tomography/magnetic resonance imaging (PET/MRI) in patients with pHPT, as well as in those with sHPT. CONCLUSION: These guidelines are written and authorized by the EANM to promote optimal parathyroid imaging. They will assist nuclear medicine physicians in the detection and correct localization of hyperfunctioning parathyroid lesions.

Evaluation of Dorsal Subluxation of the Scaphoid in Patients With Scapholunate Ligament Tears: A 4D CT Study.

OBJECTIVE. The purpose of this study was to evaluate the variation of the posterior radioscaphoid (RS) angle in patients with and without scapholunate ligament (SLL) tears during wrist radioulnar deviation. SUBJECTS AND METHODS. Seventy-three patients with clinically suspected scapholunate instability were prospectively evaluated with 4D CT and CT arthrography from February 2015 to April 2018. The posterior RS angle is formed between the articular surface of the scaphoid fossa of the radius and the most posterior point of the scaphoid in the sagittal plane. Two independent radiologists calculated this angle during radioulnar deviation. Posterior RS angles were correlated with the SLL status and the presence of a scapholunate diastasis on conventional stress radiographs. RESULTS. Readers 1 and 2 found mean posterior RS angles of 99° and 98°, respectively, in patients without and 107° and 111°, respectively, in patients with a scapholunate diastasis. The posterior RS angle amplitude varied 7.6-9.3° in the subgroups studied. The reproducibility of posterior RS angle measurement was considered good (intraclass correlation coefficient, 0.73). Mean posterior RS angles increased 6-10% and 12-14% when patients with an intact SLL were compared with those with partial tears and full tears, respectively (p < 0.001). These values also increased 8-13% when patients with diastasis were compared with those without (p < 0.0001). A dynamic acquisition was not necessary to assess this angle, with neutral posterior RS angles yielding a sensitivity of 64% and 72% and specificity of 79% and 94% for the diagnosis of SLL tears by readers 1 and 2, respectively. CONCLUSION. Posterior RS angle tended to increase with the severity of SLL tears and with the presence of scapholunate instability and yielded high sensitivity and specificity for the detection of SLL tears.

ACTION trial: a prospective study on diagnostic Accuracy of 4D CT for diagnosing Instable ScaphOlunate DissociatioN.

BACKGROUND: Early detection of scapholunate ligament (SLL) tears is essential after minor and major trauma to the wrist. The differentiation between stable and instable injuries determines therapeutic measures which aim to prevent osteoarthritis. Arthroscopy has since been the diagnostic gold standard in suspected SLL tears because non-invasive methods have failed to exclude instable injuries reliably. This prospective study aims to determine the diagnostic accuracy of dynamic, 4D computed tomography (CT) of the wrist for diagnosing instable SLL tears. METHODS: Single center, prospective trial including 40 patients with suspected SLL tears scheduled for arthroscopy. Diagnostic accuracy of 4D CT will be tested against the reference standard arthroscopy. Radiologists will be blinded to the results of arthroscopy and hand surgeons to radiological reports. A historical cohort of 80 patients which was diagnosed using cineradiography before implementation of 4D CT at the study site will serve as a comparative group. DISCUSSION: Static imaging lacks the ability to detect instable SLL tears after wrist trauma. Dynamic methods such as cineradiography and dynamic magnetic resonance imaging (MRI) are complex and require specific technical infrastructure in specialized centers. Modern super-fast dual source CT scanners are gaining popularity and are being installed gradually in hospitals and ambulances. These scanners enable dynamic imaging in a quick and simple manner. Establishment of dynamic 4D CT of the wrist in patients with suspected SLL tears in in- and outpatient settings could improve early detection rates. Reliable identification of instable injuries through 4D CT scans might reduce the number of unnecessary diagnostic arthroscopies in the future. TRIAL REGISTRATION: This study was registered prospectively at the German Clinical Trials Register (DRKS) DRKS00021110 . Universal Trial Number (WHO-UTN): U1111-1249-7884.

On the evaluation of mobile target trajectory between four-dimensional computer tomography and four-dimensional cone-beam computer tomography.

PURPOSE: For mobile lung tumors, four-dimensional computer tomography (4D CT) is often used for simulation and treatment planning. Localization accuracy remains a challenge in lung stereotactic body radiation therapy (SBRT) treatments. An attractive image guidance method to increase localization accuracy is 4D cone-beam CT (CBCT) as it allows for visualization of tumor motion with reduced motion artifacts. However, acquisition and reconstruction of 4D CBCT differ from that of 4D CT. This study evaluates the discrepancies between the reconstructed motion of 4D CBCT and 4D CT imaging over a wide range of sine target motion parameters and patient waveforms. METHODS: A thorax motion phantom was used to examine 24 sine motions with varying amplitudes and cycle times and seven patient waveforms. Each programmed motion was imaged using 4D CT and 4D CBCT. The images were processed to auto segment the target. For sine motion, the target centroid at each phase was fitted to a sinusoidal curve to evaluate equivalence in amplitude between the two imaging modalities. The patient waveform motion was evaluated based on the average 4D data sets. RESULTS: The mean difference and root-mean-square-error between the two modalities for sine motion were -0.35 ± 0.22 and 0.60 mm, respectively, with 4D CBCT slightly overestimating amplitude compared with 4D CT. The two imaging methods were determined to be significantly equivalent within ±1 mm based on two one-sided t tests (p < 0.001). For patient-specific motion, the mean difference was 1.5 ± 2.1 (0.8 ± 0.6 without outlier), 0.4 ± 0.3, and 0.8 ± 0.6 mm for superior/inferior (SI), anterior/posterior (AP), and left/right (LR), respectively. CONCLUSION: In cases where 4D CT is used to image mobile tumors, 4D CBCT is an attractive localization method due to its assessment of motion with respect to 4D CT, particularly for lung SBRT treatments where accuracy is paramount.

A preliminary investigation of re-evaluating the irradiation dose in hepatocellular carcinoma radiotherapy applying 4D CT and deformable registration.

PURPOSE: To investigate the effect of breathing motion on dose distribution for hepatocellular carcinoma (HCC) patients using four-dimensional (4D) CT and deformable registration. METHODS: Fifty HCC patients who were going to receive radiotherapy were enrolled in this study. All patients had been treated with transarterial chemoembolization beforehand. Three-dimensional (3D) and 4D CT scans in free breathing were acquired sequentially. Volumetric modulated arc therapy (VMAT) was planned on the 3D CT images and maximum intensity projection (MIP) images. Thus, the 3D dose (Dose-3D ) and MIP dose (Dose-MIP ) were obtained, respectively. Then, the Dose-3D and Dose-MIP were recalculated on 10 phases of 4D CT images, respectively, in which the end-inhale and end-exhale phase doses were defined as Dose-3D-EI , Dose-3D-EE , Dose-MIP-EI , and Dose-MIP-EE . The 4D dose (Dose-4D-3D and Dose-4D-MIP ) were obtained by deforming 10 phase doses to the end-exhale CT to accumulate. The dosimetric difference in Dose-3D , Dose-EI3D , Dose-EE3D , Dose-4D-3D , Dose-MIP , Dose-EIMIP , Dose-EEMIP , and Dose-4D-MIP were compared to evaluate the motion effect on dose delivery to the planning target volume (PTV) and normal liver. RESULTS: Compared with Dose-3D , PTV D99 in Dose-EI3D , Dose-EE3D and Dose-4D-3D decreased by an average of 6.02%, 1.32%, 2.43%, respectively (P < 0.05); while PTV D95 decreased by an average of 3.34%, 1.51%, 1.93%, respectively (P < 0.05). However, CI and HI of the PTV in Dose-3D was superior to the other three distributions (P < 0.05). There was no significant differences for the PTV between Dose-EI and Dose-EE , and between the two extreme phase doses and Dose-4D (P> 0.05). Negligible difference was observed for normal liver in all dose distributions (P> 0.05). CONCLUSIONS: Four-dimensional dose calculations potentially ensure target volume coverage when breathing motion may affect the dose distribution. Dose escalation can be considered to improve the local control of HCC on the basis of accurately predicting the probability of radiation-induced liver disease.