Combining Serial and Parallel Functionality in Functional Lung Avoidance Radiation Therapy.

PURPOSE: Functional lung avoidance (FLA) radiation therapy (RT) aims to minimize post-RT pulmonary toxicity by preferentially avoiding dose to high-functioning lung (HFL) regions. A common limitation is that FLA approaches do not consider the conducting architecture for gas exchange. We previously proposed the functionally weighted airway sparing (FWAS) method to spare airways connected to HFL regions, showing that it is possible to substantially reduce risk of radiation-induced airway injury. Here, we compare the performance of FLA and FWAS and propose a novel method combining both approaches. METHODS: We used breath-hold computed tomography (BHCT) and simulation 4-dimensional computed tomography (4DCT) from 12 lung stereotactic ablative radiation therapy patients. Four planning strategies were examined: (1) Conventional: no sparing other than clinical dose-volume constraints; (2) FLA: using a 4DCT-based ventilation map to delineate the HFL, plans were optimized to reduce mean dose and V13.50 in HFL; (3) FWAS: we autosegemented 11 to 13 generations of individual airways from each patient's BHCT and assigned priorities based on the relative contribution of each airway to total ventilation. We used these priorities in the optimization along with airway dose constraints, estimated as a function of airway diameter and 5% probability of collapse; and (4) FLA + FWAS: we combined information from the 2 strategies. We prioritized clinical dose constraints for organs at risk and planning target volume in all plans. We performed the evaluation in terms of ventilation preservation accounting for radiation-induced damage to both lung parenchyma and airways. RESULTS: We observed average ventilation preservation for FLA, FWAS, and FLA + FWAS as 3%, 8.5%, and 14.5% higher, respectively, than for Conventional plans for patients with ventilation preservation in Conventional plans <90%. Generalized estimated equations showed that all improvements were statistically significant (P ≤ .036). We observed no clinically relevant improvements in outcomes of the sparing techniques in patients with ventilation preservation in Conventional plans ≥90%. CONCLUSIONS: These initial results suggest that it is crucial to consider the parallel and the serial nature of the lung to improve post-radiation therapy lung function and, consequently, quality of life for patients.

X-ray interferometry without analyzer for breast CT application: a simulation study.

Purpose: We investigate an analyzer-less x-ray interferometer with a spatially modulated phase grating (MPG) that can deliver three modalities (attenuation image, phase image, and scatter images) in breast computed tomography (BCT). The system can provide three x-ray modalities while preserving the dose to the object and can achieve attenuation image sensitivity similar to that of a standard absorption-only BCT. The MPG system works with a source, a source-grating, a single phase grating, and a detector. No analyzer is necessary. Thus, there is an approximately 2x improvement in fluence at the detector for our system compared with the same source-detector distance Talbot-Lau x-ray interferometry (TLXI) because the TLXI has an analyzer after the object, which is not required for the MPG. Approach: We investigate the MPG BCT system in simulations and find a clinically feasible system geometry. First, the mechanism of MPG interferometry is conceptually shown via Sommerfeld-Rayleigh diffraction integral simulations. Next, we investigate source coherence requirements, fringe visibility, and phase sensitivity dependence on different system parameters and find clinically feasible system geometry. Results: The phase sensitivity of MPG interferometry is proportional to object-detector distance and inversely proportional to a period of broad fringes at the detector, which is determined by the grating spatial modulation period. In our simulations, the MPG interferometry can achieve about 27% fringe visibility with clinically realistic BCT geometry of a total source-detector distance of 950 mm and source-object distance of 500 mm. Conclusions: We simulated a promising analyzer-less x-ray interferometer, with a spatially sinusoidal MPG. Our system is expected to deliver the attenuation, phase and scatter image in a single acquisition without dose or fluence detriment, compared with conventional BCT.

Differentiation of Thyroid Nodules Difficult to Diagnose With Contrast-Enhanced Ultrasonography and Real-Time Elastography.

According to the 2015 American Thyroid Association (ATA), referred risk stratification and thyroid nodules with intermediate- and low-suspicion patterns are difficult to diagnose. The objective of this study is to evaluate the diagnostic performance of contrast-enhanced ultrasonography (CEUS) and elastosonography (ES) for the differentiation of these thyroid nodules. From November 2011 to June 2016, a total of 163 thyroid nodules with intermediate- and low-suspicion patterns in 150 consecutive patients at our hospital were studied before surgery. With surgical pathology as the standard, the diagnostic value of CEUS and ES was analyzed. There were 29 (17.8%) malignant lesions and 134 (82.2%) benign lesions. The enhancement patterns of CEUS, the echogenicity, and the elastography were significantly different between malignant and benign lesions (P < 0.05). Heterogenous enhancement was more common in malignant nodules, and the sensitivity, specificity, positive predictive value, negative predictive value, and odds ratio were 51.7, 88.1, 48.4, 89.4, and 10.1%, respectively. The diagnostic accuracy of CEUS was better than the conventional ultrasound [area under the curve (AUC), 0.729 vs. 0.616, P = 0.021]. The enhancement patterns of CEUS were helpful in the differential diagnosis of thyroid nodules with intermediate and low suspicion.

Performance analysis of a high-sensitivity multi-pinhole cardiac SPECT system with hemi-ellipsoid detectors.

PURPOSE: Single-photon emission computed tomography (SPECT) is a noninvasive imaging modality, used in myocardial perfusion imaging. The challenges facing the majority of clinical SPECT systems are low sensitivity, poor resolution, and the relatively high radiation dose to the patient. New generation systems (GE Discovery, DSPECT) dedicated to cardiac imaging improve sensitivity by a factor of 5-8. This improvement can be used to decrease acquisition time and/or dose. However, in the case of ultra-low dose (~3 mCi) injections, acquisition times are still significantly long, taking 10-12 min. The purpose of this work is to investigate a new gamma camera design with 21 hemi-ellipsoid detectors each with a pinhole collimator for cardiac SPECT for further improvement in sensitivity and resolution and reduced patient exposures and imaging times. METHODS: To evaluate the resolution of our hemi-ellipsoid system, GATE Monte-Carlo simulations were performed on point-sources, rod-sources, and NCAT phantoms. For average full-width-half-maximum (FWHM) equivalence with base flat-detector, the pinhole-diameter for the curved hemi-ellipsoid detector was found to be 8.68 mm, an operating pinhole-diameter nominally expected to be ~3 times more sensitive than state-of-the-art systems. Rod-sources equally spaced within the region of interest were acquired with a 21-detector system and reconstructed with our multi-pinhole (MPH) iterative OSEM algorithm with collimator resolution recovery. The results were compared with the results of a state-of-the-art system (GE Discovery) available in the literature. The system was also evaluated using the mathematical anthropomorphic NCAT (NURBS-based Cardiac Torso; Segars et al. IEEE Trans Nucl Sci. 1999;46:503-506) phantom with a full (clinical)-dose acquisition (25 mCi) for 2 min and an ultra-low dose acquisition of 3 mCi for 5.44 min. The estimated left ventricle (LV) counts were compared with the available literature on a state-of-the-art system (DSPECT). FWHM of the LV wall on MPH-OSEM-reconstructed images with collimator resolution recovery was estimated. RESULTS: On acquired rod-sources, the average resolution (FWHM) after reconstruction with resolution recovery in the entire region of interest (ROI) for cardiac imaging was on the average 4.44 mm (±2.84), compared to 6.9 mm (±1 mm) reported for GE Discovery (Kennedy et al., J Nucl Cardiol. 2014:21:443-452). For NCAT studies, improved sensitivity allowed a full-dose (25 mCi) 2-min acquisition (Ell8.68mmFD) which yielded 3.79 M LV counts. This is ~3.35 times higher compared to 1.13 M LV counts acquired in 2 min for clinical full dose for state-of-the-art DSPECT. The increased sensitivity also allowed an ultra-low dose acquisition protocol (Ell8.68 mmULD), 3 mCi (eight times less injected dose) in 5.44 min. This ultra-low dose protocol yielded ~1.23 M LV counts which was comparable to the full-dose 2-min acquisition for DSPECT. The estimated NCAT average FWHM at the LV wall after 12 iterations of the OSEM reconstruction was 4.95 and 5.66 mm around the mid-short-axis slices for Ell8.68mmFD and Ell8.68mmULD, respectively. CONCLUSION: Our Monte-Carlo simulation studies and reconstruction suggest using (inverted wineglass sized) hemi-ellipsoid detectors with pinhole collimators can increase the sensitivity ~3.35 times over the new generation of dedicated cardiac SPECT systems, while also improving the reconstructed resolution for rod-sources with an average of 4.44 mm in region of interest. The extra sensitivity may be used for ultra-low dose imaging (3 mCi) at ~5.44 min for comparable clinical counts as state-of-the-art systems.

Comparison of Ultrasound Features of Primary Metastatic Papillary Thyroid Carcinoma and Recurrent/Persistent Metastatic Cervical Lymph Nodes.

Objective To explore the ultrasound features and levels of cervical lymph node metastases in primary and recurrent/persistent papillary thyroid cancer (PTC).Methods We retrospectively analyzed the clinical data of 2181 patients who underwent cervical lymph nodes dissection for PTC from January 1st 2015 to January 1st 2016.Totally 418 PTC patients (with 622 lymph nodes) who met the inclusion criteria entered the final analysis.Patients who had not received any prior thyroid treatment (surgery with or without radioactive iodine) were categorized as the primary group (352 patients with 527 metastatic lymph nodes),and patients who had received prior treatment (thyroidectomy with or without radioactive iodine) for PTC were categorized as recurrent/persistent group (66 patients with 95 metastatic lymph nodes).Pathological results from lymph node dissections were used as the gold standards by means of level-to-level analysis.Results The mean of the minimum axis diameter of the lymph nodes in the primary group was (6.7±3.6)mm,and that of the recurrent/persistent group was (6.6±3.1)mm (U=0.180,P=0.857).The proportion of metastasis in the central area of primary group was 40.0%,which was significantly higher than that in the recurrent/persistent group (12.6%);the proportion of metastasis in the lateral area was 60.6% in the primary group,which was significantly lower than that in the recurrent/persistent group (87.4%)(χ2=26.288,P<0.001).In lateral metastatic lymph nodes,Ⅲ level was the most common place in both groups.Level Ⅴ metastatic lymph was rare in both primary group and recurrent/persistent group.Calcifications (63.1% vs. 48.2%;χ2=7.207,P=0.007) and peripheral vascularity (81.1% vs. 59.4%;χ2= 16.147, P<0.001) were more common in the recurrent/persistent group.The round shape,absence of an echogenic hilum,hyperechogenicity,and cystic aspects were not significantly different between these two groups (all P>0.05).Conclusions Primary metastatic lymph nodes often occur in the central area of lymph nodes,while lateral metastatic lymph nodes are more common in recurrent/persistent PTC.For metastatic lymph nodes,calcifications and peripheral vascularity are more common in recurrent/persistent PTC.

Cervical soft tissue recurrence of differentiated thyroid carcinoma after thyroidectomy indicates a poor prognosis.

BACKGROUND: We investigated cervical soft tissue recurrence of differentiated thyroid carcinoma (DTC) after thyroidectomy, and these lesions exhibited no evidence that they were lymph nodes (LNs). METHODS: Between January 2012 and April 2016, consecutive 6308 patients underwent thyroid surgery for DTC at our center. Among them, we encountered 21 patients with recurrent cervical soft tissue lesions, none of whom had previously undergone fine needle aspiration biopsy (FNAB). RESULTS: The 21 patients accounted for 0.33% of all 6308 patients, including twenty cases of papillary thyroid carcinoma and one case of follicular thyroid cancer. Approximately half (52.3%) of the recurrence were first detected by ultrasound (US). Eighteen lesions underwent complete preoperative US, but 6 lesions were misdiagnosed as metastatic LNs by US. Therefore, 54 age- and gender-matched recurrent or persistent LNs derived from DTC were randomly selected from the same database. The soft tissue lesions (mean size, 2.30 cm) were larger than the LNs. Fewer hyperechogenic hila and punctuations were found in the group of soft tissue recurrence (P < 0.05). During follow-up, distant metastasis was detected in 38.1% of patients in the soft tissue recurrence group. The distant metastasis rates showed that local soft tissue recurrence led to a poorer prognosis than cervical LN persistence or recurrence (P = 0.00). CONCLUSIONS: Although the incidence of DTC recurrence in cervical soft tissue was low, it may be a predictor for distant recurrence. To minimize the risk, a long-term postoperative evaluation, preferably with US, should be performed.