Microvascular imaging: new Doppler technology for assessing focal liver lesions. Is it useful?

Microvascular imaging (MVI) is an advanced Doppler ultrasound technique, permitting detailed evaluation of microvessel architecture without the need for contrast agents. The clinical applications of the technology are broad, with a growing body of evidence suggesting a potential role for MVI in the characterisation of benign and malignant focal liver lesions (FLLs). This review discusses the current evidence regarding the use of MVI in the assessment of FLLs, with a proposed algorithmic approach to radiological work-up of FLLs based on MVI features. Ongoing research and future directions in the field are highlighted.

Clinical translation of [18F]ICMT-11 for measuring chemotherapy-induced caspase 3/7 activation in breast and lung cancer.

BACKGROUND: Effective anticancer therapy is thought to involve induction of tumour cell death through apoptosis and/or necrosis. [18F]ICMT-11, an isatin sulfonamide caspase-3/7-specific radiotracer, has been developed for PET imaging and shown to have favourable dosimetry, safety, and biodistribution. We report the translation of [18F]ICMT-11 PET to measure chemotherapy-induced caspase-3/7 activation in breast and lung cancer patients receiving first-line therapy. RESULTS: Breast tumour SUVmax of [18F]ICMT-11 was low at baseline and unchanged following therapy. Measurement of M30/M60 cytokeratin-18 cleavage products showed that therapy was predominantly not apoptosis in nature. While increases in caspase-3 staining on breast histology were seen, post-treatment caspase-3 positivity values were only approximately 1%; this low level of caspase-3 could have limited sensitive detection by [18F]ICMT-11-PET. Fourteen out of 15 breast cancer patients responded to first-line chemotherapy (complete or partial response); one patient had stable disease. Four patients showed increases in regions of high tumour [18F]ICMT-11 intensity on voxel-wise analysis of tumour data (classed as PADS); response was not exclusive to patients with this phenotype. In patients with lung cancer, multi-parametric [18F]ICMT-11 PET and MRI (diffusion-weighted- and dynamic contrast enhanced-MRI) showed that PET changes were concordant with cell death in the absence of significant perfusion changes. CONCLUSION: This study highlights the potential use of [18F]ICMT-11 PET as a promising candidate for non-invasive imaging of caspase3/7 activation, and the difficulties encountered in assessing early-treatment responses. We summarize that tumour response could occur in the absence of predominant chemotherapy-induced caspase-3/7 activation measured non-invasively across entire tumour lesions in patients with breast and lung cancer.

Microflow imaging: New Doppler technology to detect low-grade inflammation in patients with arthritis.

AIM: To assess the efficacy of microvascular imaging in detecting low-grade inflammation in arthritis compared with Power Doppler ultrasound (PDUS). METHOD AND MATERIALS: Patients presenting for ultrasound with arthralgia were assessed with grey-scale, PDUS and Superb Microvascular Imaging (SMI). Videoclips were stored for analysis at a later date. Three musculoskeletal radiologists scored grey-scale changes, signal on PDUS and/or SMI within these joints. If a signal was detected on both PDUS and SMI, the readers graded the conspicuity of vascular signal from the two Doppler techniques using a visual analogue scale. RESULTS: Eighty-three patients were recruited with 134 small joints assessed. Eighty-nine of these demonstrated vascular flow with both PD and SMI, whilst in five no flow was detected. In 40 joints, vascularity was detected with SMI but not with PDUS (p = 0.007). Out of the 89 joints with vascularity on both SMI and PDUS, 23 were rated as being equal; while SMI scored moderately or markedly better in 45 cases (p <0.001). CONCLUSION: SMI is a new Doppler technique that increases conspicuity of Doppler vascularity in symptomatic joints when compared to PDUS. This allows detection of low grade inflammation not visualised with Power Doppler in patients with arthritis. KEY POINTS: • SMI detects vascularity with improved resolution and sensitivity compared to Power Doppler. • SMI can detect low-grade inflammation not seen with Power Doppler. • Earlier detection of active inflammation could have significant impact on treatment paradigms.

Assessment of aminoglycoside dosing and estimated glomerular filtration rate in determining gentamicin and tobramycin area under the curve and clearance.

BACKGROUND: Aminoglycoside clearance depends on kidney function, but the Australian Therapeutic Guidelines for antibiotics (version 14, 2010) recommend initial dosing based on weight without consideration of kidney function. Other guidelines that modify dosing based on kidney function estimates often use the Cockroft-Gault equation, but the role of the estimated glomerular filtration rate equations for this purpose is unclear. AIM: To determine the performance of current guideline dosing in achieving target area-under-the-curve and examine the relative precision of the estimated glomerular filtration rate equations compared with traditional Cockroft-Gault creatinine clearance in predicting aminoglycoside clearance. METHODS: We analysed 496 aminoglycoside treatment episodes involving 1377 infusions in adult patients. Conformity with antibiotic guideline dosing was achieved if the discrepancy between prescribed and recommended dose was less than 15%. Aminoglycoside clearance was determined from linear regression using a one compartment model with the Aminoglycoside Levels and Daily Dose Indicator programme. We assessed the precision of the Cockroft-Gault, Modification of Diet in renal Disease Study and Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equations in predicting aminoglycoside clearance by correlation and linear regression. RESULTS: Conformity with guideline dosing was not associated with achieving target area-under-the-curve. The CKD-EPI estimated glomerular filtration rate adjusted for body surface area showed the highest correlation (gentamicin, r = 0.66; tobramycin, r = 0.82) and best predictive model for aminoglycoside clearance. CONCLUSION: Current guideline dosing may be suboptimal for achieving target area-under-the-curve. The CKD-EPI equation adjusted for patient body surface area best predicts aminoglycoside clearance, and could be evaluated as a covariate in determining initial aminoglycoside dosing.

Distal renal tubular acidosis associated with Sjogren syndrome.

Renal tubular acidosis is a common cause of normal anion gap metabolic acidosis but these disorders can be easily missed or misdiagnosed. We highlight the approach to assessing renal tubular acidosis by discussing a case study with a temporal data set collected over more than 5 weeks. We highlight the principles and the necessary information required for a diagnosis of classic distal renal tubular acidosis. We also briefly review several aspects of type 1 renal tubular acidosis related to autoimmune disease, drugs and thyroid disorders.

Uterine artery pulsatility index: a predictor of methotrexate resistance in gestational trophoblastic neoplasia.

BACKGROUND: Neo-angiogenesis is a hallmark of cancer. The aim of this study was to test the hypothesis, in a prospective patient cohort, that in low-risk gestational trophoblastic neoplasia (LR-GTN) the uterine artery pulsatility index (UAPI), a measure of tumour vascularity, can predict resistance to methotrexate chemotherapy (MTX-R). METHODS: 286 LR-GTN patients (Charing Cross Hospital (CXH) score 0-8, or FIGO score 0-6) were treated with methotrexate between January 2008 and June 2011 at CXH. During staging investigations, patients underwent a Doppler ultrasound to assess the UAPI. RESULTS: 239 patients were assessable for both UAPI and MTX-R. The median UAPI was lower (higher vascularity) in MTX-R compared with MTX-sensitive patients (0.8 vs 1.4, P<0.0001). In multivariate logistic regression, UAPI≤1 predicted MTX-R, independent of both CXH and FIGO scores. The risk of MTX-R in patients with a FIGO score of 6 and UAPI≤1 was 100% vs 20% in patients with UAPI>1 (χ(2) P<0.0001). CONCLUSION: UAPI represents an independently validated clinically useful predictor of MTX-R in LR-GTN. Further, consideration of whether to incorporate UAPI into the FIGO scoring system is now warranted so that patients with a score of 6 and a UAPI ≤1 might be upstaged and offered combination chemotherapy rather than MTX.

A comparison of 31P magnetic resonance spectroscopy and microbubble-enhanced ultrasound for characterizing hepatitis c-related liver disease.

We compared in vivo hepatic (31) P magnetic resonance spectroscopy ((31) P MRS) and hepatic vein transit times (HVTT) using contrast-enhanced ultrasound with a microbubble agent to assess the severity of hepatitis C virus (HCV)-related liver disease. Forty-six patients with biopsy-proven HCV-related liver disease and nine healthy volunteers had (31) P MRS and HVTT performed on the same day. (31) P MR spectra were obtained at 1.5 T. Peak areas were calculated for metabolites, including phosphomonoesters (PME) and phosphodiesters (PDE). Patients also had the microbubble ultrasound contrast agent, Levovist (2 g), injected into an antecubital vein, and time-intensity Doppler ultrasound signals of the right and middle hepatic veins were measured. The HVTT was calculated as the time from injection to a sustained rise in Doppler signal 10% greater than baseline. The shortest times were used for analysis. Based on Ishak histological scoring, there were 15 patients with mild hepatitis, 20 with moderate/severe hepatitis and 11 with cirrhosis. With increasing severity of disease, the PME/PDE ratio was steadily elevated, while the HVTT showed a monotonic decrease. Both imaging modalities could separate patients with cirrhosis from the mild and moderate/severe hepatitis groups. No statistical difference was observed in the accuracy of each test to denote mild, moderate/severe hepatitis and cirrhosis (Fisher's exact test P =1.00). (31) P MRS and HVTT show much promise as noninvasive imaging tests for assessing the severity of chronic liver disease. Both are equally effective and highly sensitive in detecting cirrhosis.

Quantitative contrast-enhanced ultrasound imaging: a review of sources of variability.

Ultrasound provides a valuable tool for medical diagnosis offering real-time imaging with excellent spatial resolution and low cost. The advent of microbubble contrast agents has provided the additional ability to obtain essential quantitative information relating to tissue vascularity, tissue perfusion and even endothelial wall function. This technique has shown great promise for diagnosis and monitoring in a wide range of clinical conditions such as cardiovascular diseases and cancer, with considerable potential benefits in terms of patient care. A key challenge of this technique, however, is the existence of significant variations in the imaging results, and the lack of understanding regarding their origin. The aim of this paper is to review the potential sources of variability in the quantification of tissue perfusion based on microbubble contrast-enhanced ultrasound images. These are divided into the following three categories: (i) factors relating to the scanner setting, which include transmission power, transmission focal depth, dynamic range, signal gain and transmission frequency, (ii) factors relating to the patient, which include body physical differences, physiological interaction of body with bubbles, propagation and attenuation through tissue, and tissue motion, and (iii) factors relating to the microbubbles, which include the type of bubbles and their stability, preparation and injection and dosage. It has been shown that the factors in all the three categories can significantly affect the imaging results and contribute to the variations observed. How these factors influence quantitative imaging is explained and possible methods for reducing such variations are discussed.

Recent insights into diabetic renal injury from the db/db mouse model of type 2 diabetic nephropathy.

The db/db mouse is the most widely used animal model of type 2 diabetic nephropathy. Recent studies have utilized genetic backcrossing with transgenic mouse strains to create novel db/db strains that either lack or overexpress specific genes. These novel strains [ICAM-1-/-, CCL2-/-, MKK3-/-, osteopontin-/-, plasminogen activator inhibitor-1 (PAI-1)-/-, endothelial nitric oxide synthase-/-, SOD-Tg, rCAT-Tg] have provided valuable insights into the molecular mechanisms which promote diabetic renal injury. In addition, surgical removal of one kidney has been shown to accelerate injury in the remaining kidney of diabetic db/db mice. A number of novel therapeutic agents have also been tested in db/db mice, including inhibitors of inflammation (chemokine receptor antagonists, anti-CCL2 RNA aptamer, anti-c-fms antibody); oxidative stress (oxykine, biliverdin); the renin-angiotensin-aldosterone system (aliskiren, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, eplerenone); advanced glycation end products (AGE; pyridoxamine, alagebrium, soluble AGE receptor); angiogenesis (NM-3, anti-CXCL12 RNA aptamer, soluble Flt-1); lipid accumulation (statins, farnesoid X receptor agonists, Omacor); intracellular signaling pathways (PKC-ß or JNK inhibitors); and fibrosis [transforming growth factor (TGF)-ß antibody, TGF-ßR kinase inhibitor, soluble betaglycan, SMP-534, CTGF-antisense oligonucleotide, mutant PAI-1, pirfenidone], which have identified potential therapeutic targets for clinical translation. This review summarizes the advances in knowledge gained from studies in genetically modified db/db mice and treatment of db/db mice with novel therapeutic agents.

Lymphocytes promote albuminuria, but not renal dysfunction or histological damage in a mouse model of diabetic renal injury.

AIMS/HYPOTHESIS: Diabetic nephropathy is an inflammatory disease with prominent leucocyte infiltration of the kidneys. While the importance of macrophages in diabetic renal injury has been clearly demonstrated, the role of lymphocytes is still unknown. We therefore examined the development of diabetic renal injury in lymphocyte-deficient mice. METHODS: Streptozotocin was used to induce diabetes in Rag1(-/-) mice, which lack mature T and B lymphocytes, and in wild-type (Rag1(+/+) ) controls. The development of renal injury was examined over 20 weeks of diabetes. RESULTS: Both groups developed equivalent diabetes, however only Rag1(+/+) mice had kidney infiltration with CD4, CD8, CD22 and forkhead box P3-positive cells, as well as glomerular immunoglobulin deposition. At 20 weeks, Rag1(+/+) mice exhibited renal hypertrophy, increased mesangial and interstitial matrix, kidney macrophage accumulation, tubular injury, progressive albuminuria and a decline in renal function. In comparison, diabetic Rag1(-/-) mice showed similar histological damage, matrix expansion, macrophage accrual and loss of renal function, but were protected from increasing albuminuria. This protection was associated with protection against loss of podocytes and glomerular podocin production, and with reduced glomerular macrophage activation. CONCLUSIONS/INTERPRETATION: These results show that lymphocytes contribute to the development of diabetic albuminuria, which may partly arise from increasing glomerular macrophage activation and podocyte damage. In contrast, lymphocytes do not appear to promote tubular injury, increased matrix deposition or decline in renal function in a mouse model of type 1 diabetes. Our findings suggest that innate immunity rather than adaptive immune responses are the major inflammatory contributor to the progression of diabetic renal injury.

Can contrast-enhanced sonography distinguish benign from malignant breast masses?

BACKGROUND: We investigated whether microvascular enhancement on contrast-enhanced sonographic (CEUS) imaging can aid in distinguishing between benign and malignant lesions and correlated these findings with histopathological findings. METHOD: Fifteen patients with a palpable breast mass were recruited. Following informed consent, 4.8 mL of the microbubble contrast agent SonoVue was injected intravenously. Digital video clips of lesion enhancement were obtained and reviewed by a consultant radiologist who scored each lesion on the following characteristics: homogeneous versus heterogeneous enhancement, the presence or absence of focal defects, well- versus ill-defined margins and vascular morphology score (VMS). RESULT: Histologically there were 7 malignant and 8 benign lesions. The calculated sensitivity for CEUS in the diagnosis of malignancy was 100%, with a 37.5% specificity. There was no statistically significant difference in overall mean VMS between the malignant and benign lesions. CONCLUSION: The results of our study have not shown any additional benefit in the use of CEUS over conventional triple assessment. The positive trend seen in the higher mean VMS for the malignant tumors needs further investigation with a larger cohort of patients.

Provision of a "same-day" ultrasound service in an inner-city NHS trust: report on experience and lessons learned after the first 2 years.

AIM: To assess the effect of changing from an "appointment" to a "same-day" ultrasound (US) service on referral pattern, departmental workload, and patient satisfaction. MATERIALS AND METHODS: To reduce US waiting time of 3 weeks for routine examinations, a "same-day" service was started for outpatients and general practitioner (GP) patients in September 2006. To examine the effect of this change a retrospective assessment was performed of workload during 1 week in June 2006 (appointments only) and the same week in 2008, 22 months after the implementation of the new service. Distance travelled by patients and waiting time was recorded. Patient satisfaction with the service was assessed by questionnaire in September 2008. RESULTS: Hospital referrals remained stable, but GP referrals increased from 99 to 367 (270%) and distance travelled by patients increased from a median of 3.1 km (range 0.1-12.1 km) in 2006 to 4.8 km (range 0.2-19.8 km) in 2008 (p<0.001). Non-local GP referrals increased from 20/99 in 2006 (20%) to 198/367 in 2008 (54%). The increased workload was managed by flexible working by radiologists and two additional sonographers. Departmental waiting time increased for all patients with same-day patients waiting a median of 35 min (interquartile range 19-60 min). Ninety-one percent (79/87) of same-day patients rated the service excellent or good, but many requested better information on the waiting time. CONCLUSION: There is a demand from GPs for same-day US, and it is feasible in a large hospital with flexible radiology working and increased sonographic staffing. Unless adjacent hospitals offer a similar service, continuing rise in demand could overwhelm the service.

Hepatic vein transit times of a microbubble agent in assessing response to antiviral treatment in patients with chronic hepatitis C.

Microbubble measurement of hepatic vein transit times (HVTT) may have the potential to assess severity of hepatitis C virus (HCV)-related liver disease, where there is a shorter HVTT with more severe disease. We investigated the utility of this test as a marker of response to antiviral treatment. Thirty-seven patients with biopsy-proven HCV-related disease undergoing antiviral treatment were studied. All had baseline scans and then repeat scans 6 months after the end of treatment. HVTT using Levovist were obtained from the right and middle hepatic veins, and the shorter time was used for analysis. The aspartate aminotransferase to platelet ratio index (APRI) scores were calculated retrospectively. There were seven patients with mild hepatitis, 23 with moderate/severe hepatitis and seven with cirrhosis. The mean baseline HVTT in responders ± SE increased from 27.3 ± 2.29 s to 33.5 ± 2.8 s posttreatment (P = 0.01). In the 10 nonresponders, the HVTT remained the same; 43.3 ± 9 s baseline compared to 44 ± 7.8 s posttreatment (P = 0.84). This trend was also seen with the APRI score where in responders, the mean score decreased from 1.1 ± 0.2 to 0.74 ± 1 (P = 0.03) and in nonresponders, the score remained unchanged; 0.88 ± 0.2 compared to 0.84 ± 0.2 (P = 0.31). HVTT measurement lengthened, while APRI scores decreased in patients who responded to antiviral treatment while both remained the same, shortened (HVTT) or increased (APRI), respectively, in patients who were nonresponders. These results are encouraging and indicate that these tests could be potentially used as markers of response to treatment and could obviate the need for serial biopsies in antiviral future treatment studies.

Antibody blockade of c-fms suppresses the progression of inflammation and injury in early diabetic nephropathy in obese db/db mice.

AIMS/HYPOTHESIS: Macrophage-mediated renal injury plays an important role in the development of diabetic nephropathy. Colony-stimulating factor (CSF)-1 is a cytokine that is produced in diabetic kidneys and promotes macrophage accumulation, activation and survival. CSF-1 acts exclusively through the c-fms receptor, which is only expressed on cells of the monocyte-macrophage lineage. Therefore, we used c-fms blockade as a strategy to selectively target macrophage-mediated injury during the progression of diabetic nephropathy. METHODS: Obese, type 2 diabetic db/db BL/KS mice with established albuminuria were treated with a neutralising anti-c-fms monoclonal antibody (AFS98) or isotype matched control IgG from 12 to 18 weeks of age and examined for renal injury. RESULTS: Treatment with AFS98 did not affect obesity, hyperglycaemia, circulating monocyte levels or established albuminuria in db/db mice. However, AFS98 did prevent glomerular hyperfiltration and suppressed variables of inflammation in the diabetic kidney, including kidney macrophages (accumulation, activation and proliferation), chemokine CC motif ligand 2 levels (mRNA and urine protein), kidney activation of proinflammatory pathways (c-Jun amino-terminal kinase and activating transcription factor 2) and Tnf-alpha (also known as Tnf) mRNA levels. In addition, AFS98 decreased the tissue damage caused by macrophages including tubular injury (apoptosis and hypertrophy), interstitial damage (cell proliferation and myofibroblast accrual) and renal fibrosis (Tgf-beta1 [also known as Tgfb1] and Col4a1 mRNA). CONCLUSIONS/INTERPRETATION: Blockade of c-fms can suppress the progression of established diabetic nephropathy in db/db mice by targeting macrophage-mediated injury.

Incidental findings in healthy control research subjects using whole-body MRI.

AIM: Magnetic resonance imaging (MRI) is a powerful clinical tool used increasingly in the research setting. We aimed to assess the prevalence of incidental findings in a sequential cohort of healthy volunteers undergoing whole-body MRI as part of a normal control database for imaging research studies. MATERIALS AND METHODS: 148 healthy volunteers (median age 36 years, range 21-69 years; 63.5% males, 36.5% females) were enrolled into a prospective observational study at a single hospital-based MRI research unit in London, UK. Individuals with a clinical illness, treated or under investigation were excluded from the study. RESULTS: 43 (29.1%) scans were abnormal with a total of 49 abnormalities detected. Of these, 20 abnormalities in 19 patients (12.8%) were of clinical significance. The prevalence of incidental findings increased significantly with both increasing age and body mass index (BMI). Obese subjects had a fivefold greater risk of having an incidental abnormality on MRI (OR 5.4, CI 2.1-14.0). CONCLUSIONS: This study showed that more than one quarter of healthy volunteers have MR-demonstrable abnormalities. There was an increased risk of such findings in obese patients. This has ethical and financial implications for future imaging research, particularly with respect to informed consent and follow-up of those with abnormalities detected during the course of imaging studies.

Role of MKK3-p38 MAPK signalling in the development of type 2 diabetes and renal injury in obese db/db mice.

AIMS/HYPOTHESIS: Obesity and diabetes are associated with increased intracellular p38 mitogen-activated protein kinase (MAPK) signalling, which may promote tissue inflammation and injury. Activation of p38 MAPK can be induced by either of the immediate upstream kinases, MAP kinase kinase (MKK)3 or MKK6, and recent evidence suggests that MKK3 has non-redundant roles in the pathology attributed to p38 MAPK activation. Therefore, this study examined whether MKK3 signalling influences the development of obesity, type 2 diabetes and diabetic nephropathy. METHODS: Wild-type and Mkk3 (also known as Map2k3) gene-deficient db/db mice were assessed for the development of obesity, type 2 diabetes and renal injury from 8 to 32 weeks of age. RESULTS: Mkk3 (+/+) db/db and Mkk3 (-/-) db/db mice developed comparable obesity and were similar in terms of incidence and severity of type 2 diabetes. At 32 weeks, diabetic Mkk3 (+/+) db/db mice had increased kidney levels of phospho-p38 and MKK3 protein. In comparison, kidney levels of phospho-p38 in diabetic Mkk3 ( -/- ) db/db mice remained normal, despite a fourfold compensatory increase in MKK6 protein levels. The reduced levels of p38 MAPK signalling in the diabetic kidneys of Mkk3 ( -/- ) db/db mice was associated with protection against the following: declining renal function, increasing albuminuria, renal hypertrophy, podocyte loss, mesangial cell activation and glomerular fibrosis. Diabetic Mkk3 ( -/- ) db/db mice were also significantly protected from tubular injury and interstitial fibrosis, which was associated with reduced Ccl2 mRNA expression and interstitial macrophage accumulation. CONCLUSIONS/INTERPRETATION: MKK3-p38 MAPK signalling is not required for the development of obesity or type 2 diabetes, but plays a distinct pathogenic role in the progression of diabetic nephropathy in db/db mice.

Colorectal breast metastases presenting with atypical imaging features.

Breast metastases from non-breast primaries are rare in female patients and exceedingly rare in male patients, with only a handful of cases described. Lymphoma, metastatic melanoma and bronchial carcinoma are the primary sites for the majority of breast metastases. Breast metastases from colorectal carcinoma have been described previously in only a small number of cases in the literature. Here, we report a further two patients with biopsy-proven colorectal carcinoma metastases to both breasts, who demonstrate contrasting unusual and atypical imaging features that have not been reported previously. In one case, the imaging appearances mimic a multifocal primary breast carcinoma. Metastatic disease in the breast is a marker for disseminated metastatic spread, with a correspondingly poor prognosis. Therefore, we review the imaging features that differentiate metastatic breast disease from multifocal breast primaries, which are important to recognize because the management options for these patients differ greatly.

Methylene blue related sterile endophthalmitis.

To report a case of methylene blue related endophthalmitis. Observational case report. Review of clinical record, photographs. A 60 year old man developed endophthalmitis after methylene blue was accidentally used to stain the anterior capsule during phacoemulsification of cataract. His left visual acuity deteriorated from 6/12 to 6/36 two weeks after the operation. Despite intensive treatment with topical and intravitreal antibiotics, his condition deteriorated. A vitrectomy and silicone oil injection eventually managed to control the progression of the disease and salvage the eye. However the visual outcome remained poor due to corneal decompensation and retinal ischemia. Both vitreous tap and vitreous biopsy were negative for any organism. Methylene blue is extremely toxic to ocular structures and should not be used intraocularly.