Reduction In Signal Intensity Research Articles

Signal intensities of radiolabeled cRNA probes used alone or in combination with non-isotopic in situ hybridization histochemistry

This study addressed the question of whether radioactive hybridization signal intensities are reduced in combined isotopic and non-isotopic double in situ hybridization (DISH) compared with those in single in situ hybridization (ISH). Non-isotopic digoxigenin (Dig)-labeled hybrids were detected using an alkaline phosphatase (AP) enzymatic reaction which results in nitroblue tetrazolium chloride (NBT)/5-bromo-4-chloro-3-indolyl phosphate (BCIP)-salt precipitation that could shield S 35-radiation from penetrating to the surface. Sections were plastic coated of with 2% parlodion to prevent a chemical reaction between AP and developer during processing of the photosensitive emulsion, which could further reduce radioactive hybridization signal detection by autoradiography. We used DISH with a hybridization cocktail of radioactive S 35- and Dig-labeled GAD67 cRNA probes. In order to avoid competition for the same complementary sequence, the probes were directed towards different sequences of the glutamic acid decarboxylase (GAD67) mRNA, resulting in co-detection of isotopic and non-isotopic hybrids in close to 100% of GAD67 positive cells. Quantitation of autoradiograms showed that there was no reduction of autoradiographic signal intensity from S 35-labeled hybrids in the presence of Dig-labeled hybrids. Plastic coating of single or dual hybridized sections did not reduce the radioactive signal intensity. When mRNAs for nicotinic acetylcholine receptor (nAChR) subunits were detected with subunit specific S 35-labeled cRNA probes in GAD67 hippocampal interneurons the total numbers of nAChR subunit expressing cells remained the same in single or double hybridized sections even for low abundant mRNAs. Together, these results indicate that combined radioactive and non-radioactive DISH does not interfere with the detection of the radiation signal from the S 35-labeled hybrids, and neither specificity nor sensitivity is compromised.

Solvent suppression without crosspeak attenuation in iZQC experiments

The observation of solvent–solute iZQC peaks is often hampered by strong nearby solvent peaks. Previous researchers have overcome this problem by adding conventional solvent suppression modules during the dipolar evolution time. Here we show that these solvent suppression modules refocus the dipolar field and lead to a substantial signal intensity reduction, which is particularly damaging for the detection of low concentration species. We analyze, in detail, the effect of such modules on the signal formation, and demonstrate a method for solvent suppression that does not interfere with dipolar field evolution, leading to cleaner spectra.

Lung morphology assessment using MRI: A robust ultra‐short TR/TE 2D steady state free precession sequence used in cystic fibrosis patients

To evaluate feasibility and diagnostic quality of ultra-short TR/TE two-dimensional (2D) steady state free precession (SSFP) MRI for cystic fibrosis (CF) patients. We performed lung MRI at 1.5 Tesla in 20 CF-patients (6-17 years, 12 males). Axial, coronal, and sagittal sections were acquired in inspiration and expiration with maximum breath-hold time 10 s. MR and CT images were scored using a modified Brody scoring system to assess bronchiectasis, mucous plugging, atelectasis/consolidations, and air trapping. All images were scored by two experienced observers. A complete MR investigation took maximally 15 min. Maximal breath-holds were only 10 s and well tolerated. MRI identified major bronchiectasis, mucous plugging and atelectasis. End-expiratory scans showed patches of parenchyma with reduced signal intensity that may corresponded to areas of trapped air on expiratory CT scans. This MRI protocol based on ultra-short TR/TE 2D SSFP is quick and well tolerated and provides highly relevant imaging features as seen on CT in CF patients. Most importantly, the SNR of the expiratory scans enables to visualize air trapping. The preliminary results of this study suggest MRI as a noteworthy additional imaging tool for routine monitoring of CF patients.

Contrast-Enhanced MR Angiography Is Not More Accurate Than Unenhanced 2D Time-of-Flight MR Angiography for Determining ≥70% Internal Carotid Artery Stenosis

Internal carotid artery (ICA) atheromatous disease is an important cause of ischemic stroke, and endarterectomy or stent placement is typically indicated for symptomatic patients with > or = 70% stenosis. Our purpose was to compare contrast-enhanced MR angiography (CE-MRA) with unenhanced 2D time-of-flight MR angiography (2D TOF MRA) in detecting hemodynamically significant ICA stenosis, by using CT angiography (CTA) as the reference standard. This was an institutional review board-approved retrospective study. We identified 177 consecutive patients (354 ICAs) who received correlative CE-MRA, 2D TOF MRA, and CTA. Two neuroradiologists blinded to the CTA data graded the degree of ICA stenosis according to a 5-point scale. Additionally, luminal signal-intensity characteristics including 1) signal intensity drop-out, 2) distal-vessel narrowing, and 3) distal-vessel signal-intensity reduction were recorded. MRA results were correlated with those of CTA, and receiver-operating-characteristic (ROC) curves were constructed. On CTA, there were 55 ICAs with and 299 without > or = 70% stenosis. CE-MRA was 84% sensitive and 96% specific for detecting > or = 70% stenosis; 2D TOF MRA was 80% sensitive and 95% specific. The area under the ROC curve was 0.97 for CE-MRA and 0.95 for 2D TOF MRA (P = .51, not significant). For both MRA studies, each of the luminal signal-intensity characteristics had high specificity (> 98%) but poor-to-mild sensitivity (35%-66%) in detecting > or = 70% stenosis. Although it is established that CE-MRA more accurately delineates neurovascular anatomy than does unenhanced 2D TOF MRA, the administration of gadolinium did not offer a significant advantage in distinguishing surgically treatable ICA stenosis. This conclusion may be important in patients with contraindications to gadolinium.

Simple Assessment of Cerebral Hemodynamics Using Single-Slab 3D Time-of-Flight MR Angiography in Patients with Cervical Internal Carotid Artery Steno-Occlusive Diseases: Comparison with Quantitative Perfusion Single-Photon Emission CT

Visualization of the peripheral arteries on single-slab 3D time-of-flight (TOF) MR angiography (MRA) can reflect blood flow velocity. The velocity in the middle cerebral artery (MCA) may correlate with cerebrovascular reactivity (CVR) to acetazolamide, which can be used to assess hemodynamic impairment. The goal of this study was to compare the signal intensity of the MCA on MRA versus CVR quantified by perfusion single-photon emission CT (SPECT). The signal intensity of the MCA on single-slab 3D time-of-flight MRA was graded according to the ability to visualize the MCA in 108 cerebral hemispheres of 87 patients with unilateral or bilateral cervical internal carotid artery (ICA) steno-occlusive diseases. SPECT-CVR was also calculated by measuring cerebral blood flow before and after acetazolamide challenge. Ten healthy subjects were studied to obtain control SPECT-CVR values. All subjects provided written informed consent before the study. CVR was significantly lower in cerebral hemispheres with reduced MCA signal intensity than in those with normal intensity (P < .05). When the reduced signal intensity of the MCA on MRA was defined as abnormal, and when a CVR less than the mean--2 SD of healthy subjects was defined as reduced, MRA grading resulted in a 86.2% sensitivity and 69.6% specificity, with 51.0% positive-predictive and 93.2% negative-predictive values to detect reduced CVR. This simple MRA method can assess hemodynamic impairment with a high negative-predictive value.

Efficacy assessment of sustained intraperitoneal paclitaxel therapy in a murine model of ovarian cancer using bioluminescent imaging.

We evaluated the pre-clinical efficacy of a novel intraperitoneal (i.p.) sustained-release paclitaxel formulation (PTXePC) using bioluminescent imaging (BLI) in the treatment of ovarian cancer. Human ovarian carcinoma cells stably expressing the firefly luciferase gene (SKOV3Luc) were injected i.p. into SCID mice. Tumour growth was evaluated during sustained or intermittent courses of i.p. treatment with paclitaxel (PTX). In vitro bioluminescence strongly correlated with cell survival and cytotoxicity. Bioluminescent imaging detected tumours before their macroscopic appearance and strongly correlated with tumour weight and survival. As compared with intermittent therapy with Taxol®, sustained PTXePC therapy resulted in significant reduction of tumour proliferation, weight and BLI signal intensity, enhanced apoptosis and increased survival times. Our results demonstrate that BLI is a useful tool in the pre-clinical evaluation of therapeutic interventions for ovarian cancer. Moreover, these results provide evidence of enhanced therapeutic efficacy with the sustained PTXePC implant system, which could potentially translate into successful clinical outcomes.

Carbohydrate Binding Mechanism of the Macrophage Galactose-type C-type Lectin 1 Revealed by Saturation Transfer Experiments

Macrophage galactose-type C-type lectins 1 and 2 (MGL1/2) are expressed on the surfaces of macrophages and immature dendritic cells. Despite the high similarity between the primary sequences of MGL1 and MGL2, they display different ligand specificities. MGL1 shows high affinity for the LewisX trisaccharide, whereas MGL2 shows affinity for N-acetylgalactosamine. To elucidate the structural basis for the ligand specificities of the MGLs, we performed NMR analyses of the MGL1-LewisX complex. To identify the LewisX binding site on MGL1, a saturation transfer experiment for the MGL1-LewisX complex where sugar-CH/CH2-selective saturation was applied was carried out. To obtain sugar moiety-specific information on the interface between MGL1 and the LewisX trisaccharide, saturation transfer experiments where each of galactose-H5-, fucose-CH3-, and N-acetylglucosamine-CH3-selective saturations was applied to the MGL1-LewisX complex were performed. Based on these results, we present a LewisX binding mode on MGL1 where the galactose moiety is bound to the primary sugar binding site, including Asp-94, Trp-96, and Asp-118, and the fucose moiety interacts with the secondary sugar binding site, including Ala-89 and Thr-111. Ala-89 and Thr-111 in MGL1 are replaced with arginine and serine in MGL2, respectively. The hydrophobic environment formed by a small side chain of Ala-89 and a methyl group of Thr-111 is a requisite for the accommodation of the fucose moiety of the LewisX trisaccharide within the sugar binding site of MGL1.

Hapten-derivatized nanoparticle targeting and imaging of gene expression by multimodality imaging systems

Non-invasive gene monitoring is important for most gene therapy applications to ensure selective gene transfer to specific cells or tissues. We developed a non-invasive imaging system to assess the location and persistence of gene expression by anchoring an anti-dansyl (DNS) single-chain antibody (DNS receptor) on the cell surface to trap DNS-derivatized imaging probes. DNS hapten was covalently attached to cross-linked iron oxide (CLIO) to form a 39+/-0.5 nm DNS-CLIO nanoparticle imaging probe. DNS-CLIO specifically bound to DNS receptors but not to a control single-chain antibody receptor. DNS-CLIO (100 microM Fe) was non-toxic to both B16/DNS (DNS receptor positive) and B16/phOx (control receptor positive) cells. Magnetic resonance (MR) imaging could detect as few as 10% B16/DNS cells in a mixture in vitro. Importantly, DNS-CLIO specifically bound to a B16/DNS tumor, which markedly reduced signal intensity. Similar results were also shown with DNS quantum dots, which specifically targeted CT26/DNS cells but not control CT26/phOx cells both in vitro and in vivo. These results demonstrate that DNS nanoparticles can systemically monitor the expression of DNS receptor in vivo by feasible imaging systems. This targeting strategy may provide a valuable tool to estimate the efficacy and specificity of different gene delivery systems and optimize gene therapy protocols in the clinic.

MRI of the basement membrane using charged nanoparticles as contrast agents

The integrity of the basement membrane is essential for tissue cellular growth and is often altered in disease. In this work a method for noninvasively detecting the structural integrity of the basement membrane, based on the delivery of cationic iron-oxide nanoparticles, was developed. Cationic particles accumulate due to the highly negative charge of proteoglycans in the basement membrane. The kidney was used to test this technique because of its highly fenestrated endothelia and well-established disease models to manipulate the basement membrane charge barrier. After systemic injection of cationic or native ferritin (CF or NF) in rats, ex vivo and in vivo MRI showed selective accumulation of CF, but not NF, causing a 60% reduction in signal intensity in cortex at the location of individual glomeruli. Immunofluorescence and electron microscopy demonstrated that this CF accumulation was localized to the glomerular basement membrane (GBM). In a model of GBM breakdown during focal and segmental glomerulosclerosis, MRI showed reduced single glomerular accumulation of CF, but a diffuse accumulation of CF in the kidney tubules caused by leakage of CF through the glomerulus. Cationic contrast agents can be used to target the basement membrane and detect the breakdown of the basement membrane in disease.

Differentiation of osteoporotic and neoplastic vertebral fractures by chemical shift {in-phase and out-of phase} MR imaging

Objective The objective of this study was to establish the cut-off value of the signal intensity drop on chemical shift magnetic resonance imaging (MRI) with appropriate sensitivity and specificity to differentiate osteoporotic from neoplastic wedging of the spine. Patients and methods All patients with wedging of vertebral bodies were included consecutively between February 2006 and January 2007. A chemical shift MRI was performed and signal intensity after (in-phase and out-phase) images were obtained. A DXA was performed in all. Results A total of 40 patients were included, 20 with osteoporotic wedging (group 1) and 20 neoplastic (group 2). They were 21 males and 19 females. Acute vertebral collapse was observed in 15 patients in group 1 and subacute collapse in another 5 patients, while in group 2, 11 patients showed acute collapse and 9 patients (45%) showed subacute vertebral collapse. On the chemical shift MRI a substantial reduction in signal intensity was found in all lesions in both groups. The proportional changes observed in signal intensity of bone marrow lesions on in-phase compared with out-of-phase images showed significant differences in both groups ( P < 0.05). At a cut-off value of 35%, the observed sensitivity of out-of-phase images was 95%, specificity was 100%, positive predictive value was 100% and negative predictive value was 95.2%. Conclusion A chemical shift MRI is useful in order to differentiate patients with vertebral collapse due to underlying osteoporosis or neoplastic process.

Effect of polymorphisms within probe–target sequences on olignonucleotide microarray experiments

Hybridization-based technologies, such as microarrays, rely on precise probe-target interactions to ensure specific and accurate measurement of RNA expression. Polymorphisms present in the probe–target sequences have been shown to alter probe- hybridization affinities, leading to reduced signal intensity measurements and resulting in false-positive results. Here, we characterize this effect on exon and gene expression estimates derived from the Affymetrix Exon Array. We conducted an association analysis between expression levels of probes, exons and transcripts and the genotypes of neighboring SNPs in 57 CEU HapMap individuals. We quantified the dependence of the effect of genotype on signal intensity with respect to the number of polymorphisms within target sequences, number of affected probes and position of the polymorphism within each probe. The effect of SNPs is quite severe and leads to considerable false-positive rates, particularly when the analysis is performed at the exon level and aimed at detecting alternative splicing events. Finally, we propose simple solutions, based on ‘masking’ probes, which are putatively affected by polymorphisms and show that such strategy results in a large decrease in false-positive rates, with a very modest reduction in coverage of the transcriptome.

Characterization and optimization of membrane inlets for a miniature ion trap mass spectrometer operating at a high background pressure of humid air

A 10-kg handheld ion trap mass spectrometer, the Mini10, operating at a high background pressure (10 −4 Torr range) of humid air was characterized and optimized with respect to the use of membrane inlets. Both flat sheet and tubular membrane inlet configurations in different dimensions were tested using aqueous solutions and inlet temperatures ranging from 25 to 90 °C. The results show that both the absolute ion abundances and the relative abundance of ions in the recorded spectra of volatile organic compounds were highly influenced by the pressure in the vacuum chamber. At elevated pressures the signal intensities dropped, and a shift from primarily electron ionization to primarily chemical ionization was observed. For some chemicals unexpected high-intensity water adduct ions were observed, as confirmed by MS/MS experiments. The pressure effects were found to be correlated with the ionization potential of the analytes, the higher the ionization potential the stronger the effects. Since the pressure in the vacuum chamber is determined by both the membrane dimensions and the temperature of the inlet, the optimization of the membrane inlet is a matter of balancing membrane dimensions and inlet temperature such that both a maximal intensity and an acceptable short response time are achieved simultaneously. In contrast to what is observed for benchtop instruments, elevated inlet temperatures may lead to reduced signal intensity, and the use of a thicker membrane may increase signal intensity. Under all circumstances we found that a linear relationship between signal intensity and sample concentration was observed over at least two orders of magnitude as long as the operational conditions of the system was kept constant. The pressure effects described here are likely to be general for all miniature ion trap mass spectrometers using low performance vacuum pumps.

In vitro investigation of poor cerebrospinal fluid suppression on fluid‐attenuated inversion recovery images in the presence of a gadolinium‐based contrast agent

Cerebrospinal fluid (CSF) enhancement on fluid-attenuated inversion recovery (FLAIR) images obtained post-gadolinium (Gd)-based agent injection is described in stroke and multiple sclerosis. Blood brain barrier (BBB) disruption with contrast agent extravasation into CSF shortens T(1) relaxation times, reducing fluid suppression. Reduced fluid suppression on FLAIR images was investigated in vitro in the presence of escalating gadopentetate dimeglumine (Gd-DTPA) concentrations mixed with artificial CSF. Low Gd-DTPA concentrations impair fluid suppression of FLAIR imaging in association with progressively reduced T(1) values. At higher concentrations, the prevalent T(2) shortening effect can explain signal intensity (SI) reduction. Post-Gd FLAIR may be useful in detecting subtle BBB leakage.

Prolonging Islet Allograft Survival Using In Vivo Bioluminescence Imaging to Guide Timing of Antilymphocyte Serum Treatment of Rejection

Bioluminescence imaging (BLI) is a sensitive and noninvasive method for tracking the fate of transplanted islets. The aim of this study was to investigate whether early detection of rejection by BLI can aid in the timing of antilymphocyte serum (ALS) treatment for prolonging islet graft survival. Transgenic islets (200 per recipient) expressing the firefly luciferase from FVB/NJ strain (H-2q) mice were transplanted under the kidney capsule of streptozotocin-induced diabetic allogeneic Balb/c strain (H-2q) mice. BLI signals and serum glucose levels were measured daily after transplant. Four groups of mice were transplanted: group 1 recipients were untreated controls (n=12), group 2 (n=8) received ALS before transplant, group 3 (n=10) received ALS at a time after transplant when normoglycemic but prompted by a reduction (approximately 30%) in BLI signal intensity for 2 consecutive days, and group 4 (n=5) received ALS after transplant when prompted by blood glucose levels increasing approximately 20% from the normoglycemic baseline (BLI reduction approximately 70%). The incidence of graft loss from rejection in groups 1, 2, 3, and 4 was 92.3%, 88%, 40%, and 100%, respectively. The mean (+/-SE) time to graft loss in groups 1, 2, 3 and 4 was 22.5+/-4.8, 29.2+/-9.9, 53.5+/-17.9, and 22.1+/-2.4 days, respectively. Noninvasive imaging modalities of functional islet mass, such as BLI (but not blood glucose levels), can prompt the appropriate timing of ALS treatment of islet allograft rejection and significantly prolong graft survival or protect the grafts from permanent loss.

Light delivery over extended time periods enhances the effectiveness of photodynamic therapy.

The rate of energy delivery is a principal factor determining the biological consequences of photodynamic therapy (PDT). In contrast to conventional high-irradiance treatments, recent preclinical and clinical studies have focused on low-irradiance schemes. The objective of this study was to investigate the relationship between irradiance, photosensitizer dose, and PDT dose with regard to treatment outcome and tumor oxygenation in a rat tumor model. Using the photosensitizer HPPH (2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide), a wide range of PDT doses that included clinically relevant photosensitizer concentrations was evaluated. Magnetic resonance imaging and oxygen tension measurements were done along with the Evans blue exclusion assay to assess vascular response, oxygenation status, and tumor necrosis. In contrast to high-incident laser power (150 mW), low-power regimens (7 mW) yielded effective tumor destruction. This was largely independent of PDT dose (drug-light product), with up to 30-fold differences in photosensitizer dose and 15-fold differences in drug-light product. For all drug-light products, the duration of light treatment positively influenced tumor response. Regimens using treatment times of 120 to 240 min showed marked reduction in signal intensity in T2-weighted magnetic resonance images at both low (0.1 mg/kg) and high (3 mg/kg) drug doses compared with short-duration (6-11 min) regimens. Significantly greater reductions in pO(2) were observed with extended exposures, which persisted after completion of treatment. These results confirm the benefit of prolonged light exposure, identify vascular response as a major contributor, and suggest that duration of light treatment (time) may be an important new treatment variable.

Antiprion Prophylaxis by Gene Transfer of a Soluble Prion Antagonist

Prion diseases are untreatable neurodegenerative disorders characterized by accumulation of PrP(Sc), an aggregated isoform of the normal prion protein PrP(C). Here, we delivered the soluble prion antagonist PrP-Fc(2) to the brains of mice by lentiviral gene transfer. Although naïve mice developed scrapie at 175 +/- 5 days postintracerebral prion inoculation (dpi), gene transfer before inoculation delayed disease onset by 72 +/- 4 days. At 170 days postintracerebral prion inoculation, PrP(Sc) accumulation and prion infectivity in PrPFc-treated brains were reduced by 3.6 and 4.2 logs, respectively. When PrP-Fc(2) was delivered 30 days after prion inoculation, survival of the treated animals was extended by 25 days. We then used tissue-specific recombination to express PrP-Fc(2) in the entire central nervous system, in only astrocytes, or in only oligodendrocytes. Oligodendrocyte-restricted PrP-Fc(2) expression impaired PrP(Sc) deposition and delayed disease even though oligodendrocytes are completely resistant to prion infection, suggesting that PrP-Fc(2) affords protection via noncell autonomous mechanisms. These results suggest that somatic gene transfer of prion antagonists may be effective for postexposure prophylaxis of prion diseases.

Expression of Long Anti-HIV-1 Hairpin RNAs for the Generation of Multiple siRNAs: Advantages and Limitations

Promoter expressed long-hairpin RNAs (lhRNAs) that can be processed into multiple small interfering RNA (siRNAs) are being considered as effective agents for treating rapidly mutating viruses such as human immunodeficiency virus (HIV). In the present study, we have generated human U6 promoter-driven lhRNAs of 50, 53, and 80 base pairs (bp) targeting contiguous sequences within the tat and rev genes of HIV-1 and evaluated the efficacy of these lhRNAs as well as their processing in cells. By using multiple G:U mismatches in the stems, we have been able to readily incorporate the long-hairpin structures into a lentiviral vector transduction system. Here we show that such long hairpins can be stably and functionally expressed for a long term in HIV-1 susceptible T cells, where they provide potent inhibition of HIV replication against both non-mutant and mutant variants of HIV-1. Our studies provide strong support for the use of the G:U wobble pair containing lhRNAs to generate multiple siRNAs from a single transcript, but we also show that lhRNAs of 80 bp may be the upper size limit for effectively producing multiple, functional siRNAs.

膀胱癌リンパ節転移に対するMRI拡散強調画像の使用経験

Diffusion-weighted MRI (DW-MRI) is a functional imaging to assess molecular diffusion. We report a case in which treatment response to lymph node metastatic bladder cancer was monitored by DW-MRI. A 67-year-old man had paraaortic lymph node metastasis from bladder cancer; the paraaortic lymph node showed high signal intensity on DW-MRI. After four course treatment of gemcitabine and cisplatin, the lesion showed reduction of signal intensity on DW-MRI and increase of the apparent diffusion coefficient value. These signal changes were consistent with the change of morphological images (CT, MRI (T1-W, T2-W)), 18F-FDG PET and tumor markers. This case suggests that DW-MRI is useful in monitoring treatment response of metastatic bladder cancer.

Thermoluminescence, ESR and x-ray diffraction studies of CaSO4 : Dy phosphor subjected to post preparation high temperature thermal treatment

Thermoluminescence (TL), electron spin resonance (ESR) and x ray diffraction studies of CaSO4 : Dy phosphor subjected to post preparation high temperature treatment were carried out. Analysis of the TL glow curve indicated that the dosimetric glow peak at 240 °C reduces, whereas the low temperature satellite peak increases with the increase in the annealing temperature in the range 650–1000 °C. The influence of the annealing atmosphere on the TL glow curve structure was also observed. Reduction of the photoluminescence intensity of the annealed phosphor indicated that the environment of Dy3+ ions might have undergone some change due to high temperature treatment. Reduction in the ESR signal intensity corresponding to and radicals was observed initially with the increase in the annealing temperaure; subsequently their intensity increased with temperature. Signals due to the radical vanished, when the phosphor was annealed beyond 800 °C. A signal corresponding to SH2− radicals was also observed in the ESR spectra for samples subjected to annealing in the temperature regime 800–1000 °C. XRD of the in situ annealed phosphor showed a change in the unit cell parameters. An endothermic peak at 860 °C in the DTA spectrum was observed.

Specimen‐induced distortions in light microscopy

Specimen-induced aberrations affect the imaging properties in optical 3D microscopy, especially when high numerical aperture lenses are used. Studies on aberrations are often properly concerned with the degradation of image quality such as compromised resolution or reduced signal intensity. Apart from these, aberration effects can also introduce geometric image distortions. The effects, discussed here are particularly strong when thick biological specimens are investigated. Using a high numerical aperture interferometer, we measured wavefront aberrations in transmission mode and quantified geometric distortions associated with specimen-induced aberrations. This assessment for a range of biological specimens allows estimation of the accuracy of spatial measurements. The results show that high-resolution spatial measurements can be significantly compromised by specimen-induced aberrations.