Half-dose non-contrast CT in the investigation of urolithiasis: image quality improvement with third-generation integrated circuit CT detectors.

PURPOSE: The objective of this study is to establish the effect of third-generation integrated circuit (IC) CT detector on objective image quality in full- and half-dose non-contrast CT of the urinary tract. METHODS: 51 consecutive patients with acute renal colic underwent non-contrast CT of the urinary tract using a 128-slice dual-source CT before (n = 24) and after (n = 27) the installation of third-generation IC detectors. Half-dose images were generated using projections from detector A using the dual-source RAW data. Objective image noise in the liver, spleen, right renal cortex, and right psoas muscle was compared between DC and IC cohorts for full-dose and half-dose images reconstructed with FBP and IR algorithms using 1 cm(2) regions of interest. Presence and size of obstructing ureteric calculi were also compared for full-dose and half-dose reconstructions using DC and IC detectors. RESULTS: No statistical difference in age and lateral body size was found between patients in the IC and DC cohorts. Radiation dose, as measured by size-specific dose estimates, did not differ significantly either between the two cohorts (10.02 ± 4.54 mGy IC vs. 12.28 ± 7.03 mGy DC). At full dose, objective image noise was not significantly lower in the IC cohort as compared to the DC cohort for the liver, spleen, and right psoas muscle. At half dose, objective image noise was lower in the IC cohort as compared to DC cohort at the liver (21.32 IC vs. 24.99 DC, 14.7% decrease, p < 0.001), spleen (19.33 IC vs. 20.83 DC, 7.20% decrease, p = 0.02), and right renal cortex (20.28 IC vs. 22.98 DC, 11.7% decrease, p = 0.005). Mean obstructing ureteric calculi size was not significantly different when comparison was made between full-dose and half-dose images, regardless of detector type (p > 0.05 for all comparisons). CONCLUSIONS: Third-generation IC detectors result in lower objective image noise at full- and half-radiation dose levels as compared with traditional DC detectors. The magnitude of noise reduction was greater at half-radiation dose indicating that the benefits of using novel IC detectors are greater in low and ultra-low-dose CT imaging.

Gadolinium Enhanced T2 FLAIR is an Imaging Biomarker of Radiation Necrosis and Tumor Progression in Patients with Brain Metastases.

BACKGROUND AND PURPOSE: Differentiating radiation necrosis (RN) from tumor progression (TP) after radiotherapy for brain metastases is an important clinical problem requiring advanced imaging techniques which may not be widely available and are challenging to perform at multiple time points. The ability to leverage conventional MRI for this problem, could have meaningful clinical impact. The purpose of this study was to explore contrast enhanced T2 FLAIR (T2FLAIRc) as a new imaging biomarker of RN and TP. MATERIALS AND METHODS: This single-institution retrospective study included patients with treated brain metastases undergoing DSC-MRI between January 2021 and June 2023. Reference standard assessment was based on histopathology or serial follow-up including results of DSC-MRI for a minimum of 6 months from the first DSC-MRI. The index test was implemented as part of the institutional brain tumor MRI protocol and preceded the first DSC-MRI. T2FLAIRc and gadolinium enhanced T1 MPRAGE (T1c) signal were normalized against normal brain parenchyma and expressed as z-score. Mean signal intensity of enhancing disease for RN and TP groups were compared using unpaired t-test. Receiver operator characteristic (ROC) curves and area under the ROC curve (AUC) were derived by bootstrapping. DeLong test was used to compare AUC. RESULTS: 56 participants (mean age, 62 years +/-12.7 [SD]; 39 females); 28 RN, 28 TP were evaluated. The index MRI was performed on average 73 days +/-34 [SD] before the first DSC-MRI. Significantly higher z-scores were found for RN using T2FLAIRc (8.3 versus 5.8, p<0.001) and T1c (4.1 versus 3.5, p=0.02). AUC for T2FLAIRc (0.83, 95% CI, 0.72-0.92) was greater than T1c (0.70, 95% CI, 0.560.83) (p = 0.04). The AUC of DSC derived rCBV (0.82, 95% CI, 0.70-0.93) was not significantly different from T2FLAIRc (p = 0.9). CONCLUSIONS: A higher normalized T1c and T2FLAIRc signal intensity was found for RN. In a univariable test, mean T2FLAIRc signal intensity of enhancing voxels showed good discrimination performance for distinguishing RN from TP. The results of this work demonstrate the potential of T2FLAIRc as an imaging biomarker in the work-up of RN in patients with brain metastases. ABBREVIATIONS: AUC = area under the receiver operating characteristic curve; RN = radiation necrosis; ROC = receiver operating characteristic; SRS = stereotactic radiosurgery; T1c = contrast enhanced T1; T2FLAIRc = contrast enhanced T2 FLAIR; TP = tumor progression.

Combining Feature Correspondence With Parametric Chamfer Alignment: Hybrid Two-Stage Registration for Ultra-Widefield Retinal Images.

We propose a novel hybrid framework for registering retinal images in the presence of extreme geometric distortions that are commonly encountered in ultra-widefield (UWF) fluorescein angiography. Our approach consists of two stages: a feature-based global registration and a vessel-based local refinement. For the global registration, we introduce a modified RANSAC (random sample and consensus) that jointly identifies robust matches between feature keypoints in reference and target images and estimates a polynomial geometric transformation consistent with the identified correspondences. Our RANSAC modification particularly improves feature point matching and the registration in peripheral regions that are most severely impacted by the geometric distortions. The second local refinement stage is formulated in our framework as a parametric chamfer alignment for vessel maps obtained using a deep neural network. Because the complete vessel maps contribute to the chamfer alignment, this approach not only improves registration accuracy but also aligns with clinical practice, where vessels are typically a key focus of examinations. We validate the effectiveness of the proposed framework on a new UWF fluorescein angiography (FA) dataset and on the existing narrow-field FIRE (fundus image registration) dataset and demonstrate that it significantly outperforms prior retinal image registration methods in accuracy. The proposed approach enhances the utility of large sets of longitudinal UWF images by enabling: (a) automatic computation of vessel change metrics such as vessel density and caliber, and (b) standardized and co-registered examination that can better highlight changes of clinical interest to physicians.

Gonioscopy-Assisted Transluminal Trabeculotomy for the Treatment of Glaucoma in Uveitic Eyes.

PURPOSE: To evaluate the outcomes of gonioscopy-assisted transluminal trabeculotomy (GATT) in adult eyes with uncontrolled uveitic glaucoma. METHODS: We reviewed 16 eyes from 13 patients. Surgical success was defined as intraocular pressure (IOP) reduction >20% from baseline or IOP between 5 and 21 mmHg by the 3-month visit while on a stable number or fewer IOP-lowering agents and no need for additional glaucoma surgery. RESULTS: At 12 months, the cumulative success rate was 81%. Mean IOP was 37.8 ± 13.0 mmHg at baseline and 12.2 ± 3.0 mmHg at 12 months (68% reduction; p < .0001). The average number of glaucoma medications was 4.6 ± 1.3 at baseline and 2.2 ± 0.7 at 12 months (52% reduction; p < .0001). Transient hyphema was seen in 44% of eyes at 1 week. CONCLUSIONS: This small retrospective study suggests that GATT is effective and safe as an initial surgical treatment for medically refractory glaucoma in uveitic adult eyes.

Segmentation of Brain Metastases Using Background Layer Statistics (BLAST).

BACKGROUND AND PURPOSE: Accurate segmentation of brain metastases is important for treatment planning and evaluating response. The aim of this study was to assess the performance of a semiautomated algorithm for brain metastases segmentation using Background Layer Statistics (BLAST). MATERIALS AND METHODS: Nineteen patients with 48 parenchymal and dural brain metastases were included. Segmentation was performed by 4 neuroradiologists and 1 radiation oncologist. K-means clustering was used to identify normal gray and white matter (background layer) in a 2D parameter space of signal intensities from postcontrast T2 FLAIR and T1 MPRAGE sequences. The background layer was subtracted and operator-defined thresholds were applied in parameter space to segment brain metastases. The remaining voxels were back-projected to visualize segmentations in image space and evaluated by the operators. Segmentation performance was measured by calculating the Dice-Sørensen coefficient and Hausdorff distance using ground truth segmentations made by the investigators. Contours derived from the segmentations were evaluated for clinical acceptance using a 5-point Likert scale. RESULTS: The median Dice-Sørensen coefficient was 0.82 for all brain metastases and 0.9 for brain metastases of ≥10 mm. The median Hausdorff distance was 1.4 mm. Excellent interreader agreement for brain metastases volumes was found with an intraclass correlation coefficient = 0.9978. The median segmentation time was 2.8 minutes/metastasis. Forty-five contours (94%) had a Likert score of 4 or 5, indicating that the contours were acceptable for treatment, requiring no changes or minor edits. CONCLUSIONS: We show accurate and reproducible segmentation of brain metastases using BLAST and demonstrate its potential as a tool for radiation planning and evaluating treatment response.

Illness Perceptions, Medication Beliefs, and Adherence to Antiretrovirals and Medications for Comorbidities in Adults With HIV Infection and Hypertension or Chronic Kidney Disease.

BACKGROUND: Mortality in patients with HIV infection is increasingly due to comorbid medical conditions. Research on how adherence to medications for comorbidities relates to antiretroviral (ARV) medication adherence and how interrelations between illness perceptions and medication beliefs about HIV and comorbidities affect medication adherence is needed to inform adherence interventions. METHODS: HIV-infected adults with hypertension (HTN) (n = 151) or chronic kidney disease (CKD; n = 41) were recruited from ambulatory practices at an academic medical center. Illness perceptions and medication beliefs about HIV and HTN or CKD were assessed and adherence to one ARV medication and one medication for either HTN or CKD was electronically monitored for 10 weeks. RESULTS: Rates of taking, dosing, and timing adherence to ARV medication did not differ from adherence to medication for HTN or CKD, with the exception that patients were more adherent to the timing of their ARV (78%) than to the timing of their antihypertensive (68%; P = 0.01). Patients viewed HIV as better understood, more chronic, having more negative consequences, and eliciting more emotions, compared with HTN. Patients viewed ARVs as more necessary than medication for HTN or CKD. Having a realistic view of the efficacy of ARVs (r = -0.20; P < 0.05) and a high level of perceived HIV understanding (r = 0.21; P < 0.05) correlated with better ARV adherence. CONCLUSIONS: Patients with HIV showed similar rates of adherence to ARVs as to medications for comorbidities, despite perceiving HIV as more threatening and ARVs as more important. This can be used in adapting existing interventions for ARV adherence to encompass adherence to medications for comorbid conditions.