This work focuses on the structural similarity (SSIM) index as a tool for optimization of the perceived visual image quality obtainable by continuous scanning 2D LAICPMS bioimaging, but also other mass spec imaging techniques may benefit from this approach. This index quantifies the differences between a distorted image and a reference image based on parameters associated with luminance, contrast, and noise. Since reference images are not normally available, a protocol was developed to virtually apply distortion-related information introduced by the LAICPMS imaging system to a reference image of one’s choice. Distortion-related information in the form of blur and noise was experimentally retrieved from line scans across a laser milled knife edge on custom-prepared gelatin standards (mimicking proteinaceous biomatrixes). Distorted images were generated via computational procedures developed earlier, warranting objective image quality assessment via the SSIM indices. We illustrate the potential of this approach for image quality optimization for a suite of LA-ICPMS imaging conditions.
COBISS.SI-ID: 6351642
Pulsed laser ablation (LA) devices in laser ablation inductively coupled plasma mass spectrometry (LAICPMS) imaging have become very advanced, delivering laser pulses with high temporal accuracy and stable energy density. However, unintentional imaging artifacts may be generated in 2D element maps when the LA repetition rate and the data acquisition parameters of ICPMS instruments with a sequential mass spectrometer (i.e., quadrupole filter or sector-field mass spectrometer) are desynchronized. This may potentially lead to interference patterns, visible as ripples in elemental images, and thus, compromised image quality. This paper describes the background of aliasing in continuous scanning mode through simulation experiments and ways to modulate the effect. The existence of this image degradation source is demonstrated experimentally via real-life imaging of a homogeneous glass standard.
COBISS.SI-ID: 6321178
In the past decade, the development of single particle-inductively coupled plasma mass spectrometry (SPICPMS) has revolutionized the field of nanometallomics. Besides differentiation between dissolved and particulate metal signals, SP-ICPMS can quantify the nanoparticle (NP) number concentration and size. Because SP-ICPMS is limited to characterization of NPs in solution, we show how solid sampling by laser ablation (LA) adds spatial-resolution characteristics for localized NP analysis in biomaterials. Using custom-made gelatin standards doped with dissolved gold and commercial or synthesized gold nanoparticles, LA-SP-ICPMS conditions such as laser fluence, beam size, and dwell time were optimized for NP analysis to minimize NP degradation, peak overlap, and interferences from dissolved gold. A data-processing algorithm to retrieve the NP number concentration and size was developed for this purpose. As a proof-of-concept, a sunflower-root-sample cross-section, originating from a sunflower plant exposed to gold NPs, was successfully imaged using the optimized LA-SP-ICPMS conditions for localized NP characterization.
COBISS.SI-ID: 5054543
There are several avenues and schools of thought on how to generate good 2D LA-ICP-MS (multi)elemental maps. Especially with the recent advent of “fast” LA cells and the use of simultaneous ICP-TOFMS detectors, instead of the commonly used sequential ICP-QMS detectors, the playing field has changed radically. Generally, data are generated in line scanning mode by pulsed laser ablation of the surface and ICP-MS sampling (signal integration) of one or more pulses. In the imaging process we may encounter all kinds of imaging artifacts such as blur, smear, aliasing and noise that may deteriorate the image quality. In this paper deeper insights into the selection of optimal conditions for fast and high-quality 2D LA-ICP-MS (multi)elemental mapping are given to circumvent or minimize these artifacts based on a modeling approach.
COBISS.SI-ID: 6702874
Highly homogeneous multi-element gelatin calibration standards were fabricated for quantitative LA-ICP-MS bioimaging. Heterogeneity issues caused by the so-called “coffee-stain” and/or “Marangoni” effects were found to be element-dependent but could be circumvented by careful selection of drying/setting conditions. A micro-homogeneity test was developed for certification of the standards.
COBISS.SI-ID: 6223130