Fluorination/Dearomatization of C6F5 Groups: An FLP Route to an Electrophilic Borane and Non-Coordinating Anions.

B(C6F5)3 and the corresponding anion [B(C6F5)4]- are ubiquitous in main group and transition metal chemistry. Known derivatives are generally limited to the incorporation of electron donating substituents. Herein we describe electrophilic fluorination and dearomatization of such species using XeF2 in the presence of BF3 or Lewis acidic cations. In this fashion the anions [HB(C6F5)3]-, [B(C6F5)4]- and [(C6F5)3BC≡NB(C6F5)3]-, are converted to [FB(C6F7)3]-, [B(C6F7)4]-, and [(C6F7)3BC≡NB(C6F7)3]-, respectively. Similarly, the borane adducts (L)B(C6F7)3 (L=MeCN, OPEt3) are produced. These rare examples of electrophilic attack of electron deficient rings proceed as [XeF][BF4] acts as a frustrated Lewis pair effecting fluorination and dearomatization of C6F5 rings.

Cervical carcinomas with serous-like papillary and micropapillary components: illustrating the heterogeneity of primary cervical carcinomas.

Recent changes in the classification of cervical adenocarcinomas have re-categorized serous carcinoma as potentially nonexistent. However, clinical and pathological profiles of cervical adenocarcinomas with serous-like morphological features have not been systematically evaluated using the latest taxonomy and biomarkers. We studied 14 cases of primary cervical carcinomas with serous-like morphologies (papillary and micropapillary patterns). None of these cases exhibited evidence of serous carcinoma involving the upper tracts. Patient ages ranged between 34 and 86 years, most presented with abnormal uterine bleeding. Histologically, ten cases were classified as human papillomavirus (HPV)-associated carcinomas (eight usual-type endocervical adenocarcinomas and two adenosquamous carcinomas), of which six exhibited a papillary pattern and four had a micropapillary pattern. The four remaining cases were HPV-independent gastric-type adenocarcinomas, which displayed a papillary pattern in one case and a micropapillary pattern in three others. All ten HPV-associated carcinomas displayed block positive p16 and wild-type p53 by immunohistochemistry, with nine of them confirmed by HPV testing. Two of the four gastric-type adenocarcinomas had mutation-type p53, one of which also being p16 block positive. HER2 overexpression was demonstrated in 3/14 (21.4%) cases (2 HPV-associated and 1 HPV-independent). PD-L1 expression was identified in 4/10 (40%) cases, all HPV-associated. Targeted next-generation sequencing was performed in two cases with a micropapillary pattern, revealing a missense variant in ATM in an HPV-associated tumor and missense variants in TP53 and SMARCB1 in an HPV-independent tumor. The results demonstrated that primary endocervical adenocarcinomas can mimic the appearance of serous carcinoma, while not representing serous carcinoma. Serous-like papillary and micropapillary patterns may be present in both HPV-associated and HPV-independent cervical carcinomas, but none of the cases studied were unequivocally serous upon detailed analysis. Our findings support the exclusion of "cervical serous carcinoma" from existing classifications of cervical adenocarcinoma.

Endovascular Stent Placement for May-Thurner Syndrome in the Absence of Acute Deep Vein Thrombosis.

PURPOSE: To assess the clinical utility of iliac vein stent placement for patients with chronic limb edema or pelvic congestion presenting with nonocclusive May-Thurner physiology. MATERIALS AND METHODS: All patients (N = 45) undergoing stent placement for May-Thurner syndrome (MTS) without an associated acute thrombotic event between 2007 and 2014 were retrospectively reviewed; 11 were excluded for poor follow-up. A total of 34 patients (28 female) were studied (mean age, 44 y; range, 19-80 y). Average follow-up time was 649 days (median, 488 d; range, 8-2,499 d). RESULTS: The technical success rate was 100% (34 of 34). No major and two minor (5%) complications occurred, and 68% of patients (23 of 34) had clinical success with relief of presenting symptoms on follow-up visits. Technical parameters including stent size and number, stent type, concurrent angioplasty, access site, and resolution of collateral iliolumbar vessels were not found to be statistically related to clinical success (P > .05). Similarly, no significant relation to clinical success was seen for clinical factors such as the type of symptoms, presence of chronic deep vein thrombosis (DVT), or concurrent coagulopathy (P > .05). Female sex was found to correlate with clinical success (82% vs 18%; P = .04). CONCLUSIONS: Iliac stent placement in patients presenting with chronic limb or pelvic symptoms from MTS without acute DVT is associated with clinical success in the majority of patients.

Compact lensless digital holographic microscopy using a curved mirror for an enlarged working distance.

Digital holographic microscopy (DHM) has a wide range of applications from the analysis of microelectronic mechanical systems (MEMS) to the measurement of cells. We intend on making the system more compact to improve the portability of the device. A concave mirror has been presented to be used in a lensless DHM system to effectively enlarge the working distance and at the same time maintain the compact size of the whole system. A theoretical analysis of the phase compensation between the object wave and the wave reflected from curved reference mirrors is given. Experimental demonstrations of the curved reference mirrors used in the DHM system have been obtained to support our idea. This would change the overall size and adaptability of the DHM system and provide a better understanding of the effects of phase reflected off a curved mirror.

GLI1-Altered Soft Tissue Tumor in the Tongue-A Case Report and Literature Review.

Background: Soft tissue tumors with fusions or amplifications of the GLI1 gene have distinctive molecular characteristics and have recently been considered a unique pathological entity, thus named "GLI1-altered soft tissue tumors." It is a rare mesenchymal neoplasm that involves soft tissues at any site. Case presentation: We report an example of this condition in a 13-year-old Chinese male patient who presented with a mass in the tongue. The tumor was multilobulated; the tumor cells were arranged in nests and sheets, had a rich, delicate fibrovascular network, and were separated by a hyalinized fibrous stroma. The tumor cells were epithelioid to ovoid, with variable eosinophilic to pale vacuolated cytoplasm and round to oval nuclei. Immunostaining revealed that the tumor cells were positive for CDK4 and CD56. Fluorescence in situ hybridization (FISH) for GLI1 translocation was positive, with a high level of amplification of the translocated segment. Literature review: We present a comprehensive literature review of this condition, focusing on its clinical presentation, histological features, immunohistochemical profile, molecular characteristics, and prognosis.

The establishment of kidney cancer organoid line in drug testing.

INTRODUCTION: Kidney cancer is a common urological malignancy worldwide with an increasing incidence in recent years. Among all subtypes, renal cell carcinoma (RCC) represents the most predominant malignancy in kidney. Clinicians faced a major challenge to select the most effective and suitable treatment regime for patients from a wide range of modalities, despite improved understanding and diagnosis of RCC. OBJECTIVE: Recently, organoid culture gained more interest as the 3D model is shown to be highly patient specific which is hypothetically beneficial to the investigation of precision medicine. Nonetheless, the development and application of organotypic culture in RCC is still immature, therefore, the primary objective of this study was to establish an organoid model for RCC. MATERIALS AND METHODS: Patients diagnosed with renal tumor and underwent surgical intervention were recruited. RCC specimen was collected and derived into organoids. Derived organoids were validated by histological examminations, sequencing and xenograft. Drug response of organoids were compared with resistance cell line and patients' clinical outcomes. RESULTS: Our results demonstrated that organoids could be successfully derived from renal tumor and they exhibited high concordance in terms of immunoexpressional patterns. Sequencing results also depicted concordant mutations of driver genes in both organoids and parental tumor tissues. Critical and novel growth factors were discovered during the establishment of organoid model. Besides, organoids derived from renal tumor exhibited tumorigenic properties in vivo. In addition, organoids recapitulated patient's in vivo drug resistance and served as a platform to predict responsiveness of other therapeutic agents. CONCLUSION: Our RCC organoid model recaptiluated histological and genetic features observed in primary tumors. It also served as a potential platform in drug screening for RCC patients, though future studies are necessary before translating the outcomes into clinical practices.

The Malignant Potential of Ovarian Steroid Cell Tumors Revisited: A Multi-institutional Clinicopathologic Analysis of 115 Cases.

Steroid cell tumors (SCTs) of the ovary are rare and understudied, and as such, uncertainties remain about their malignant potential, as well as clinicopathologic predictors of patient outcome. Based on a multi-institutional cohort of cases, we present findings from the largest study of SCT reported to date. Clinicopathologic data were documented on 115 cases of SCT that were assembled from 17 institutions. The median patient age was 55 years (range: 9 to 84). When measured, preoperative androgen levels were elevated in 84.2% (48/57) of patients. A total of 111 (96.5%) cases were classified as stage I (103 stage IA; 2 stage IB; 6 stage IC). The stage distribution for the remaining 4 patients was as follows: stage II (n = 1), III (n = 3; 1 IIIA, 1 IIIB, 1 IIIC). The median tumor size was 3 cm (range: 0.2 to 22). Cytologic atypia, microscopic tumor necrosis, microscopic tumor hemorrhage, and a mitotic index of >1 mitotic figure/10 high-power fields were present in 52% (60/115), 9.6% (11/115), 37% (43/115), and 19% (22/115) of cases, respectively. Of 115 patients, 7 (6.1%) recurred postexcision, 4 (3.5%) ultimately died of disease, and 10 (8.7%) either recurred, died of disease, or were advanced stage at presentation. The median duration to recurrence postresection was 33 months (range: 23 to 180). Four of the 7 recurrences were stage IA at baseline. Tumor size >4 cm, International Federation of Gynecology and Obstetrics (FIGO) stage ≥IB, tumor necrosis, and tumor hemorrhage were each significantly associated with reduced recurrence-free survival in log-rank tests and univariable Cox models, with age older than 65 years being of marginal significance (hazard ratio [HR]: 5.4, 95% CI: 1.0-30.0, P = 0.05). Multivariable analyses suggested that FIGO stage ≥IB (HR: 27.5, 95% CI: 2.6-290.5), and age older than >65 years (HR: 21.8, 95% CI: 1.6-303.9) were the only parameters that were independently associated with recurrence. Cross-section analyses showed that tumor necrosis, tumor hemorrhage, and larger tumor size were significantly associated with a FIGO stage ≥IB status, which bolstered the conclusion that they are not independent predictors of recurrence. In summary, <10% of SCTs are clinically malignant, a substantially lower frequency than has previously been reported in the literature. Clinicopathologic predictors of patient outcomes that are prospectively applicable in practice could not be definitively established. Recurrences may occur many years (up to 15 y in this study) after primary resection, even in stage IA cases.

US and MR imaging of the extensor compartment of the ankle.

Injuries to the extensor compartment of the ankle are uncommon and often are overlooked or misinterpreted at clinical presentation. Ultrasonography (US) and magnetic resonance (MR) imaging play a critical role in the diagnosis and evaluation of these injuries. US is a dynamic, quick, cost-effective imaging method for assessing ankle extensor compartment injuries as an alternative or adjunct to MR imaging. MR imaging provides multiplanar cross-sectional delineation of regional anatomic structures and also can be used to assess the predisposing cause, estimate the extent of injury, and aid in preoperative planning for requisite surgical repair. The spectrum of pathologic conditions affecting the ankle extensor compartment ranges from tendinosis secondary to degenerative, inflammatory, or depositional disease to traumatic tendon or retinacular rupture and entrapment neuropathy. Major components of the ankle extensor compartment at risk for injury include the anterior tibial, extensor hallucis longus, and extensor digitorum longus tendons; the extensor retinacular mechanism; and the anterior tarsal tunnel. Familiarity with the normal anatomic appearance and pathologic features of the ankle extensor compartment at US and MR imaging as well as potential imaging pitfalls is critical for accurate injury evaluation.

A Pediatric Patient with Severe Obstructive Sleep Apnea and Comorbid Depression and Substance Abuse.

Obstructive sleep apnea (OSA), depression, and substance abuse problems share similar symptomatology and have significant interplay. An underlying diagnosis of OSA can often be overlooked in patients with significant psychiatric illness and polysubstance use. Pediatric OSA is often associated with adenotonsillar hypertrophy and frequently requires surgical intervention for resolution of symptoms. Untreated OSA can worsen mental status and encourage polysubstance abuse as a form of self-medication. Proper identification and management of OSA plays an important role in treating psychiatric conditions. We report a 16-year-old with major depressive disorder (MDD), suicide attempts, polysubstance use disorder, and severe OSA admitted to an inpatient psychiatric facility. History included sleep and mood disturbances started at age 12. Patient presented with apnea-hypopnea index greater than 50 and started on bilevel-positive airway pressure (BiPAP) prior to admission. Management of OSA led to significant improvement of MDD, insomnia, and polysubstance abuse. OSA can often be overlooked in patients with MDD or substance abuse. Among adolescent patients with poorly managed psychiatric conditions, significant sleep disturbances, and polysubstance abuse, providers should maintain a high degree of suspicion for OSA, as its proper management will aid in the management of the other conditions.

NONSYNDROMIC RETINITIS PIGMENTOSA WITH BILATERAL RETINAL NEOVASCULARIZATION DUE TO HGSNAT MUTATION.

PURPOSE: To describe a case of nonsyndromic retinitis pigmentosa caused by presumed compound heterozygous A615T and T522M mutations in HGSNAT, characterized by bilateral cystoid macular edema and retinal neovascularization. METHODS: Case report. The patient underwent clinical evaluation, multimodal imaging, and next-generation panel sequencing. In silico analysis was performed with PolyPhen-2, SIFT, and MutationTaster. Segregation analysis was not available. RESULTS: A 35-year-old hypertensive man presented with nyctalopia, photopsia, and difficulty reading for six months. He had no family history of visual deficits. The best-corrected visual acuity was 20/25 in the right eye and 20/20 in the left eye. Examination revealed midperipheral bone spicules and macular neovascularization in both eyes. Multimodal imaging demonstrated cystoid macular edema, ellipsoid band loss outside the central macula, and leakage from the neovascularization in both eyes. Sequencing detected four mutations in three genes, including two heterozygous mutations in HGSNAT (c.1843G>A, p.A615T and c.1565C>T, p.T522M). A615T is a pathogenic, hypomorphic mutation. T522M has not been previously phenotypically described. It is predicted damaging by in silico analysis and occurs at a conserved position near the eighth transmembrane domain, adjacent to residues in which missense mutations result in protein misfolding. CONCLUSION: This is, to the best of our knowledge, the first reported case of retinal neovascularization in a case of nonsyndromic retinitis pigmentosa due to HGSNAT mutation. The T522M variant likely functions as a severe mutation alongside the hypomorphic A615T mutation. These findings expand the genotypic and phenotypic spectrum of nonsyndromic retinitis pigmentosa.

NIVOLUMAB-INDUCED HARADA-LIKE UVEITIS WITH BACILLARY DETACHMENT MIMICKING CHOROIDAL METASTASIS.

PURPOSE: To describe a patient with metastatic clear cell renal cell carcinoma in remission on maintenance nivolumab therapy who developed late-onset ocular toxicity manifesting as creamy chorioretinal lesions with exudative retinal detachment concerning for choroidal metastasis. METHOD: Case report. Main outcome measures include ophthalmoscopic examination, fundus photography, fundus autofluorescence, fluorescein angiography, indocyanine green angiography, spectral domain optical coherence tomography, and B-scan ultrasonography. RESULTS: A 49-year-old woman with a medical history of metastatic clear cell renal cell carcinoma in remission for two years after immunotherapy with four cycles of ipilimumab and nivolumab followed by maintenance nivolumab infusions developed lesions concerning for choroidal metastases in her right eye. Optical coherence tomography of the lesions revealed a bacillary layer detachment containing possible fibrinous exudate organized into layers and underlying choroidal thickening with chorioretinal folds. Later, choroidal thickening and chorioretinal folds also occurred in the left eye. Given that pan imaging detected no metastasis and the posterior segment abnormalities resolved after cessation of nivolumab and treatment with systemic corticosteroids, the patient was diagnosed with nivolumab-induced Vogt-Koyanagi-Harada-like uveitis. CONCLUSION: This case expands on the clinical spectrum of nivolumab-induced Vogt-Koyanagi-Harada-like uveitis, a condition that can also present with bacillary layer detachment mimicking an early choroidal metastasis, manifest asymmetrically in each eye, and develop after long-standing treatment.

Superselective embolization in management of remnant renal moiety and vessels after radical nephrectomy in horseshoe kidney.

Horseshoe kidney is a congenital disorder in which two kidneys are fused together in the isthmus. The anatomy could lead to increased risk of urinary tract infections and renal cancers. When performing a hemi-nephrectomy, it is important to identify all blood supply and ensure total excision of parenchyma and collecting system of the moiety operated upon. We present a case of left heminephrectomy complicated by urinoma secondary to residual tissue in the left moiety. We discuss the role of superselective embolization and other technologies in management of this complication and challenges faced due to aberrant vascularity and abnormal anatomy.

Bartonella henselae-associated recurrent, bilateral segmental periphlebitis.

Purpose: To describe a patient with atypical Bartonella henselae (B. henselae)-associated ocular inflammation that manifested with recurrent, bilateral segmental periphlebitis. Observations: A 32-year-old White man presented with multiple paracentral scotomata in each eye. Examination revealed mild vitreous cell, segmental sheathing of the retinal veins, and inflammation of the paravenous retina in each eye. Multimodal imaging, including optical coherence tomography as well as widefield fundus autofluorescence, fluorescein angiography, and indocyanine green angiography, was consistent with bilateral, segmental retinal periphlebitis with paravenous inflammation and retinochoroidal scarring. Serology showed elevated B. henselae antibody titers, but was otherwise unrevealing, and the patient was diagnosed with presumed B. henselae-associated ocular inflammation. Treatment with systemic doxycycline (100 mg PO BID) for four weeks improved the patient's symptoms and posterior uveitis. However, after an asymptomatic period of nearly one year, his bilateral pericentral scotomata recurred and posterior segment examination confirmed new foci of retinal periphlebitis in each eye. Re-treatment with doxycycline (100 mg PO BID) for four weeks again yielded improvement, but one month after completing his antibiotic course, his visual symptoms recurred, and we observed additional areas of periphlebitis and paravenous retinitis with associated branch retinal vein occlusions in each eye. This time a dual antibiotic regimen of doxycycline (100 mg PO BID) and rifampin (300 mg PO BID) was administered for three months, with improvement. Over the next eight years, the patient experienced no further disease relapse, and the previous sites of retinal periphlebitis eventually developed perivenous fibrosis with paravenous retinochoroidal scarring. Conclusion: Rarely, patients with B. henselae-associated ocular inflammation develop segmental retinal periphlebitis with or without retinal vein occlusion. This form of ocular bartonellosis can recur, requiring multiple courses of antimicrobial therapy.

Phonological but not semantic influences on the speech-to-song illusion.

In the speech to song illusion, a spoken phrase begins to sound as if it is being sung after several repetitions. Castro et al. (2018) used Node Structure Theory (NST; MacKay, 1987), a model of speech perception and production, to explain how the illusion occurs. Two experiments further test the mechanisms found in NST-priming, activation, and satiation-as an account of the speech to song illusion. In Experiment 1, words varying in the phonological clustering coefficient influenced how quickly a lexical node could recover from satiation, thereby influencing the song-like ratings to lists of words that were high versus low in phonological clustering coefficient. In Experiment 2, we used equivalence testing (i.e., the TOST procedure) to demonstrate that once lexical nodes are satiated the higher level semantic information associated with the word cannot differentially influence song-like ratings to lists of words varying in emotional arousal. The results of these two experiments further support the NST account of the speech to song illusion.

Giant abdominal aortic aneurysms.

Giant abdominal aortic aneurysms (AAAs) are defined as AAAs >10 to 13 cm in the maximum transverse diameter. We have described a case of a patient who had presented for open repair of an 18-cm AAA and a review of reported cases of giant AAAs >10 cm in the maximum transverse diameter. Forty cases were compiled. The average maximum AAA diameter was 14.5 ± 4.1 cm. The AAA was ruptured on presentation in 12 patients (30%). Of the 40 cases, 34 (85%) were repaired with open surgery. The reported mortality was 15%. Despite the case complexity, five endovascular repairs were attempted.

Microstructural correlations of white matter tracts in the human brain.

The purpose of this study is to investigate whether specific patterns of correlation exist in diffusion tensor imaging (DTI) parameters across different white matter tracts in the normal human brain, and whether the relative strengths of these putative microstructural correlations might reflect phylogenetic and functional similarities between tracts. We performed quantitative DTI fiber tracking on 44 healthy adult volunteers to obtain tract-based measures of mean diffusivity (MD), fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD) from four homologous pairs of neocortical association pathways (arcuate fasciculi, inferior fronto-occipital fasciculi, inferior longitudinal fasciculi, and uncinate fasciculi bilaterally), a homologous pair of limbic association pathways (left and right dorsal cingulum bundles), and a homologous pair of cortical-subcortical projection pathways (left and right corticospinal tracts). From the resulting inter-tract correlation matrices, we show that there are statistically significant correlations of DTI parameters between tracts, and that there are statistically significant variations among these inter-tract correlations. Furthermore, we observe that many, but by no means all, of the strongest correlations are between homologous tracts in the left and right hemispheres. Even among homologous pairs of tracts, there are wide variations in the degree of coupling. Finally, we generate a data-driven hierarchical clustering of the fiber pathways based on pairwise FA correlations to demonstrate that the neocortical association pathways tend to group separately from the limbic pathways at trend-level statistical significance, and that the projection pathways of the left and right corticospinal tracts comprise the most distant outgroup with high confidence (p<0.01). Hence, specific patterns of microstructural correlation exist between tracts and may reflect phylogenetic and functional similarities between tracts. The study of these microstructural relationships between white matter pathways might aid research on the genetic basis and on the behavioral effects of axonal connectivity, as well as provide a revealing new perspective with which to investigate neurological and psychiatric disorders.

Three-Dimensional-Printed Uterine Model for Surgical Planning of a Cesarean Delivery Complicated by Multiple Myomas.

BACKGROUND: Uterine myomas encountered at cesarean delivery increase the complexity and risk of the procedure. Preoperative planning of such deliveries may help optimize patient outcomes. The application of three-dimensional printing technology is rapidly expanding in many surgical specialties. We created a three-dimensional-printed model from the magnetic resonance images (MRIs) of a gravid uterus with multiple myomas for surgical planning of cesarean delivery. INSTRUMENT: A three-dimensional-printed uterine model from MRIs of a pregnant patient with multiple uterine myomas as a tool for planning cesarean delivery. EXPERIENCE: A 33-year-old woman with a myomectomy history presented to our institution for prenatal care. Initial ultrasound imaging revealed multiple uterine myomas. A three-dimensional-printed uterine model, based on subsequent MRI, was created for presentation at an obstetric multidisciplinary meeting. The model accurately represented the number, size, and locations of uterine myomas, aiding surgical planning, including skin and uterine incisions. At the time of cesarean delivery, the model was directly correlated with patient anatomy to further determine the optimal placement of uterine incision. Maternal and fetal outcomes were excellent. CONCLUSION: Three-dimensional-printed models, through improved surgical planning, could optimize outcomes for patients with uterine myomas undergoing cesarean delivery.

Public attitudes towards mobile health in Singapore: a cross-sectional study.

BACKGROUND: Smartphone-mediated mobile health (mHealth) may assist patients with medication adherence, and disease monitoring. This study aimed to describe awareness and usage of, and attitudes towards, mHealth among the public in Singapore who own a smartphone. It also aimed to identify factors that influenced the above in the study population. METHODS: An online cross-sectional survey was administered via convenience sampling in November 2017. Participants were included if they were at least 18 years old and owned a smartphone. No identifiable data was collected. Responses were summarized using descriptive statistics. Multiple logistic regression analysis was used to identify factors associated with awareness and usage of, and attitudes towards, mHealth. RESULTS: Participants (n=199) were mostly of Chinese ethnicity (84.4%), female (64.8%), young (mean age 33.7 years), and generally healthy (86.9% reported no chronic medical conditions). On average, participants were aware of 4.4 out of 7 mHealth functions and used 2.2 functions. Managing appointments, and fitness/diet tracking were the most well-known (93.5% and 82.4% respectively), and widely used (80.6% and 59.8% respectively) functions. A simple interface, data security, and being free to use, were rated as the most important factors influencing participants' willingness to use mHealth. Most (64.3%) participants were keen to learn to use mHealth in future, 49.7% believed mHealth could help improve their health, but only 13.1% were willing to pay for it. Being employed (OR 3.71) was associated with higher mHealth usage, adjusted for baseline smartphone usage. Participants living in non-subsidized housing were more keen to try (OR 3.18), and willing to pay (OR 3.36) for mHealth. CONCLUSIONS: Participants generally held positive attitudes towards mHealth, although usage was low. Lack of willingness to pay, and socioeconomic factors, are potential barriers to the widespread adoption of mHealth. Future research specifically involving patients is needed.

Image quality comparison between single energy and dual energy CT protocols for hepatic imaging.

PURPOSE: Multi-detector computed tomography (MDCT) enables volumetric scans in a single breath hold and is clinically useful for hepatic imaging. For simple tasks, conventional single energy (SE) computed tomography (CT) images acquired at the optimal tube potential are known to have better quality than dual energy (DE) blended images. However, liver imaging is complex and often requires imaging of both structures containing iodinated contrast media, where atomic number differences are the primary contrast mechanism, and other structures, where density differences are the primary contrast mechanism. Hence it is conceivable that the broad spectrum used in a dual energy acquisition may be an advantage. In this work we are interested in comparing these two imaging strategies at equal-dose and more complex settings. METHODS: We developed numerical anthropomorphic phantoms to mimic realistic clinical CT scans for medium size and large size patients. MDCT images based on the defined phantoms were simulated using various SE and DE protocols at pre- and post-contrast stages. For SE CT, images from 60 kVp through 140 with 10 kVp steps were considered; for DE CT, both 80/140 and 100/140 kVp scans were simulated and linearly blended at the optimal weights. To make a fair comparison, the mAs of each scan was adjusted to match the reference radiation dose (120 kVp, 200 mAs for medium size patients and 140 kVp, 400 mAs for large size patients). Contrast-to-noise ratio (CNR) of liver against other soft tissues was used to evaluate and compare the SE and DE protocols, and multiple pre- and post-contrasted liver-tissue pairs were used to define a composite CNR. To help validate the simulation results, we conducted a small clinical study. Eighty-five 120 kVp images and 81 blended 80/140 kVp images were collected and compared through both quantitative image quality analysis and an observer study. RESULTS: In the simulation study, we found that the CNR of pre-contrast SE image mostly increased with increasing kVp while for post-contrast imaging 90 kVp or lower yielded higher CNR images, depending on the differential iodine concentration of each tissue. Similar trends were seen in DE blended CNR and those from SE protocols. In the presence of differential iodine concentration (i.e., post-contrast), the CNR curves maximize at lower kVps (80-120), with the peak shifted rightward for larger patients. The combined pre- and post-contrast composite CNR study demonstrated that an optimal SE protocol has better performance than blended DE images, and the optimal tube potential for SE scan is around 90 kVp for a medium size patients and between 90 and 120 kVp for large size patients (although low kVp imaging requires high x-ray tube power to avoid photon starvation). Also, a tin filter added to the high kVp beam is not only beneficial for material decomposition but it improves the CNR of the DE blended images as well. The dose adjusted CNR of the clinical images also showed the same trend and radiologists favored the SE scans over blended DE images. CONCLUSIONS: Our simulation showed that an optimized SE protocol produces up to 5% higher CNR for a range of clinical tasks. The clinical study also suggested 120 kVp SE scans have better image quality than blended DE images. Hence, blended DE images do not have a fundamental CNR advantage over optimized SE images.