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James C Williams

Publications and source records attributed to James C Williams.

At least 19 recordsLinked to original sources
PubMed2007

Analysis of urinary calculi using an infrared microspectroscopic surface reflectance imaging technique.

This investigation highlights the use of infrared microspectroscopy for the morphological analysis of urinary stones. The research presented here has utilized the reflectance mode of an infrared microscope for use in creating chemically specific maps of cross-sectioned renal calculi surfaces, precisely showing the placement of renal stone components in a calculus sample. The method has been applied to renal stones of both single and multiple components consisting primarily of hydroxyapatite, calcium oxalate monohydrate and calcium oxalate dihydrate. Factors discussed include the photometric accuracy of the spectra obtained, a comparison of the surface reflectance method with existing methods such as diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and attenuated total internal reflection (ATR) analysis, and the influence of specular reflectance between polished and unpolished sample spectra. Full spectral maps of cross-sectioned renal stones provided positive localization of components using qualitatively accurate spectra similar in appearance to DRIFTS spectra. Unlike ATR and DRIFTS spectra, surface reflectance spectra lack photometric accuracy and are therefore not quantifiable; at present, however, spectra are suitable for qualitative analysis. It was found that specular reflectance increases minimally with a highly polished stone cross-section surface, though qualitative data is not affected. Surface reflectance imaging of sections of renal stones is useful for determining the identity of stone components while simultaneously providing precise locations of mineral components within the stone using presently available instruments.

Animals↗
PubMed2006

Detection of significant variation in acoustic output of an electromagnetic lithotriptor.

PURPOSE: We describe the observation of significant instability in the output of an electromagnetic lithotriptor. This instability had a form that was not detected by routine assessment, but rather was observed only by collecting many consecutive shock waves in nonstop regimen. MATERIALS AND METHODS: A Dornier DoLi-50 lithotriptor used exclusively for basic research was tested and approved by the regional technician. This assessment included hydrophone measures at select power levels with the collection of about 25 shock waves per setting. Subsequent laboratory characterization used a fiberoptic hydrophone and storage oscilloscope for data acquisition. Waveforms were collected nonstop for hundreds of pulses. RESULTS: Output was typically stable for greater than 1,000 shock waves but substantial fluctuations in acoustic pressures were also observed. For example, output at power level 3 (mean peak positive acoustic pressure +/- SD normally 44 +/- 2 MPa) increased dramatically to greater than 50 MPa or decreased significantly to approximately 30 MPa for hundreds of shock waves. The cause of instability was eventually traced to a faulty lithotriptor power supply. CONCLUSIONS: Instability in lithotriptor acoustic output can occur and it may not be detected by routine assessment. Collecting waveforms in a nonstop regimen dramatically increases sampling size, improving the detection of instability. Had the instability that we observed occurred during patient treatment, the energy delivered may well have exceeded the planned dose. Since the potential for adverse effects in lithotripsy increases as the dose is increased, it would be valuable to develop ways to better monitor the acoustic output of lithotriptors.

Acoustics↗
PubMed2006

Air pockets trapped during routine coupling in dry head lithotripsy can significantly decrease the delivery of shock wave energy.

PURPOSE: Current lithotriptors use a dry treatment head that must be coupled to the patient with gel or oil. We determined how the quality of coupling affects stone breakage under conditions that simulated patient treatment. MATERIALS AND METHODS: Experiments were performed with a Dornier (DoLi-50 electromagnetic lithotriptor. The test tank had a clear Mylar membrane for coupling with the treatment head water cushion. Thus, air pockets trapped at the coupling interface could be photographed for quantitation. Coupling efficiency was assessed using a fiberoptic hydrophone and different coupling regimes were tested for the effect on gypsum stone breakage. RESULTS: The quality of coupling was variable with air pockets covering 1.5% to 19% of the coupling area, resulting in a mean decrease in shock wave amplitude of approximately 20%. Breaking and reestablishing contact, as when a patient is repositioned during treatment, decreased acoustic pressure almost 32%, representing a 57% decrease in acoustic energy transmission. Stone breakage was also decreased when air was trapped in coupling and only 2% coverage by air pockets decreased stone breakage by 20% to 40%. CONCLUSIONS: These in vitro results suggest that coupling in lithotripsy can pose a significant barrier to the transmission of shock wave energy to the patient. Stone breakage was sensitive to air pockets at the coupling interface. Recoupling was particularly disruptive, suggesting that repositioning the patient could substantially degrade coupling quality. It seems reasonable that variability in the quality of coupling could contribute to variability in clinical outcomes.

Air↗
PubMed2006

Endoscopic evidence of calculus attachment to Randall's plaque.

PURPOSE: It has been proposed that calcium oxalate calculi begin as small stones attached to the renal papillae at sites of Randall's plaque. However, no study has investigated the prevalence of attached stones in calcium oxalate stone formers or the relationship between stone attachment site and Randall's plaque. In this study we used endoscopic examination of renal papillae in stone formers undergoing percutaneous nephrolithotomy to investigate both issues. MATERIALS AND METHODS: Idiopathic calcium oxalate stone formers undergoing PNL for stone removal were enrolled in this study. Multiple papillae were examined and images were recorded by digital video. The presence or absence of papillary plaque and attached stones was noted, as was the site of stone attachment. RESULTS: In 23 patients, 24 kidneys and 172 renal papillae were examined. All kidneys were found to have papillary plaque and 11 of the patients had attached stones. Most papillae (91%) contained plaque. CONCLUSIONS: The prevalence of attached stones in calcium oxalate stone formers (48%) is greater than that previously reported for the general population. Attachment appears to be on Randall's plaque. The high prevalence of attached stones and the appearance of the attachment site are consistent with a mechanism of calcium oxalate stone formation in which stones begin as plaque overgrowth.

Calcium Oxalate↗
PubMed2006

Why stones break better at slow shockwave rates than at fast rates: in vitro study with a research electrohydraulic lithotripter.

BACKGROUND AND PURPOSE: Stones break better when the rate of shockwave (SW) delivery is slowed. It has been hypothesized that the greater cavitation accompanying a fast rate shields pulse propagation, thus interfering with the delivery of SW energy to the stone. We tested this idea by correlating waveforms measured at the SW focus with cavitation viewed using high-speed imaging. MATERIALS AND METHODS: A series of U30 gypsum stones held in a 2-mm mesh basket were exposed to 200 SWs at 30 or 120 SW/min from a research electrohydraulic lithotripter (HM3 clone). Waveforms were collected using a fiberoptic probe hydrophone. High-speed imaging was used to observe cavitation bubbles in the water and at the stone surface. RESULTS: Stone breakage was significantly better at 30 SW/min than at 120 SW/min. The rate had little effect on SW parameters in the water free field. In the presence of particulates released from stones, the positive pressure of the SW remained unaffected, but the trailing tensile phase of the pulse was significantly reduced at 120 SW/min. CONCLUSIONS: Cavitation bubbles do not persist between SWs. Thus, mature bubbles from one pulse do not interfere with the next pulse, even at 120 SW/min. However, cavitation nuclei carried by fine particles released from stones can persist between pulses. These nuclei have little effect on the compressive wave but seed cavitation under the influence of the tensile wave. Bubble growth draws energy from the negative-pressure phase of the SW, reducing its amplitude. This likely affects the dynamics of cavitation bubble clusters at the stone surface, reducing the effectiveness of bubble action in stone comminution.

Humans↗
PubMed2006

Variability of protein content in calcium oxalate monohydrate stones.

BACKGROUND AND PURPOSE: Urinary stones are heterogeneous in their fragility to lithotripter shockwaves. As a first step in gaining a better understanding of the role of matrix in stone fragility, we measured extractible protein in calcium oxalate monohydrate (COM) stones that were extensively characterized by micro-computed tomography (micro CT). MATERIALS AND METHODS: Stones were scanned using micro CT (Scanco mCT20, 34 microm). They were ground, and the protein extracted using four methods: 0.25M EDTA, 2% SDS reducing buffer, 9M urea buffer, and 10% acetic acid. Protein was measured using NanoOrange. The SDS extracts were also examined using polyacrylamide electrophoresis (PAGE). RESULTS: Extracted protein was highest with the SDS or urea methods (0.28% +/- 0.13% and 0.24% +/- 0.11%, respectively) and lower using the EDTA method (0.17% +/- 0.05%; P < 0.02). Acetic acid extracted little protein (0.006 +/- 0.002%; P < 0.001). Individual stones were significantly different in extractability of protein by the different methods, and SDS-PAGE revealed different protein patterns for individual stones. Extracted protein did not correlate with X-ray-lucent void percentage, which ranged from 0.06% to 2.8% of stone volume, or with apatite content. CONCLUSIONS: Extractible stone-matrix protein differs for individual COM stones, and yield is dependent on the extraction method. The presence of X-ray-lucent voids or minor amounts of apatite in stones did not correlate with protein content. The amounts of protein recovered were much lower than reported by Boyce, showing that these methods extracted only a fraction of the protein bound up in the stones. The results suggest that none of the methods tested will be useful for helping to answer the question of whether matrix content differs among stones of differing fragility to lithotripter shockwaves.

Calcium Oxalate↗
PubMed2006

Calcium oxalate calculi found attached to the renal papilla: Preliminary evidence for early mechanisms in stone formation.

BACKGROUND: Calculi are commonly found attached to the renal papilla in calcium oxalate (CaOx) stone formers, but the mechanisms by which stones form in this manner are not well established. MATERIALS AND METHODS: Data are presented from three attached stones collected from different patients. Stone morphology and composition were determined using micro computed tomography (CT) and infrared microspectrometry. RESULTS: One of the stones was composed of CaOx with a peripheral region of apatite, such as might have come from a Randall's plaque. Another stone was covered with large CaOx crystals but contained at least two layers of apatite, with no apatite regions exposed at the surface. The third stone contained CaOx with inclusions of apatite and more apatite on its surface, along with a substantial volume of poorly mineralized material that could not be identified. CONCLUSIONS: The complexity of these stones and their differing morphologies do not by themselves allow inference of the mechanism of stone formation. Future work will require the careful documentation of attached stones on the papilla, as well as study of the papilla after the stone has been removed, before it can be determined whether such diverse CaOx stones originate from the same or different underlying etiologies.

Apatites↗
PubMed2005

Ultracal-30 gypsum artificial stones for research on the mechanisms of stone breakage in shock wave lithotripsy.

Artificial stones are used in research on the mechanisms of stone breakage in shock wave lithotripsy (SWL) and in assessing lithotripter performance. We have adopted Ultracal-30 gypsum as a model, finding it suitable for SWL studies in vitro, acute animal experiments in which stones are implanted in the kidney, and as a target to compare the in vitro performance of intracorporeal lithotripters. Here we describe the preparation of U-30 stones, their material properties, shock wave (SW) breakage characteristics, and methods used for quantitation of stone fragmentation with this model. Ultracal-30 gypsum cement was mixed 1:1 with water, cast in plastic multi-well plates, then, the stones were liberated by dissolving the plastic with chloroform and stored under water. Stone breakage in SWL was assessed by several methods including measures of the increase in projected surface area of SW-treated stones. Breakage of hydrated stones showed a linear increase in fragment area with increased SW-number and SW-voltage. Stones stored in water for an extended time showed reduced fragility. Dried stones could be rehydrated so that breakage was not different from stones that had never been dry, but stones rehydrated for less than 96 h showed increased fragility to SWs. The physical properties of U-30 stones place them in the range reported for natural stones. U-30 stones in vitro and in vivo showed equivalent response to SW-rate, with approximately 200% greater fragmentation at 30 SW/min compared to 120 SW/min, suggesting that the mechanisms of SW action are similar under both conditions. U-30 stones provide a convenient, reproducible model for SWL research.

Calcium Sulfate↗
PubMed2005

Shock wave lithotripsy of stones implanted in the proximal ureter of the pig.

PURPOSE: Ureteral stones can be difficult to treat with shock wave (SW) lithotripsy. A strategy for lithotripsy of proximal ureteral stones is to push them back into the renal pelvis prior to administering SWs. However, push-back is invasive and not always possible. Since there are few clues to suggest how best to treat ureteral stones with SWs in situ, we developed an animal model for research on lithotripsy for ureteral stones. MATERIALS AND METHODS: Gypsum model stones were implanted bilaterally in the proximal ureter and renal calix of the pig via percutaneous access. Lithotripsy was performed using a HM3 lithotripter (Dornier Medical Systems, Marietta, Georgia) and stones at each location were treated with the same dose (400 SWs, 20 kV and 30 SWs per minute). Fragments were collected and the percent increase in projected surface area of the particles was determined. RESULTS: The breakage (mean percent area increase) of stones implanted in the proximal ureter was significantly less than that of stones located in the renal calix treated with the same dose of shock waves (134% vs 327%, p <0.001). Also, stones that were fully confined by the ureter did not break as well as stones located at the ureteropelvic junction. This indicates that the physical environment surrounding a stone can have a significant effect on the efficiency of SW action. CONCLUSIONS: The observation that stones implanted in the ureter showed decreased breakage compared with stones in the kidney is consistent with clinical experience. This finding is a valuable and even essential prerequisite for any experimental animal model system intended for the study of SW action in the breakage of ureteral stones.

Animals↗
PubMed2005

Cystine: helical computerized tomography characterization of rough and smooth calculi in vitro.

PURPOSE: The classification of cystine stones into rough and smooth varieties has been suggested as an aid to choosing treatment for these difficult stones. Since the surface of stones is difficult to visualize preoperatively, we tested the hypothesis that the surface morphology of cystine stones correlates with their internal structure, as viewed by helical computerized tomography (CT). MATERIALS AND METHODS: Cystine stones were examined visually and categorized into rough (15 stones) and smooth (16 stones) subpopulations of similar size. Each stone was scanned in a helical CT scanner (GE Quad Scanner) to assess radiological characteristics and to measure attenuation values. Scans were also performed using a microCT 20 high resolution laboratory scanner (Scanco Medical AG, Bassersdorf, Switzerland) at 34 microm voxel size and the percent of internal voids was determined. RESULTS: Mean helical CT attenuation values +/- SD for rough stones were lower than for smooth stones (702 +/- 206 vs 921 +/- 51 HU, p <0.002) and the radiological appearance of rough stones suggested radiolucent voids. Internal voids in rough stones were confirmed using micro CT. Rough cystine stones contained a higher percent of internal voids (0.30% vs 0.06%, p <0.0001). CONCLUSIONS: Rough cystine stones can be distinguished from smooth stones using helical CT in vitro, suggesting that it may be possible to distinguish these stones preoperatively. Since rough cystine stones have been reported to be susceptible to shock wave lithotripsy, the identification of this morphology of cystine stones in the patient using attenuation values and appearance on helical CT could be valuable for planning treatment.

Cysteine↗
PubMed2005

In vitro evaluation of canine and feline calcium oxalate urolith fragility via shock wave lithotripsy.

OBJECTIVE: To test the hypothesis that feline calcium oxalate uroliths are intrinsically more resistant to comminution via shock wave lithotripsy (SWL) than canine calcium oxalate uroliths through comparison of the fragility of canine and feline uroliths in a quantitative in vitro test system. SAMPLE POPULATION: Calcium oxalate uroliths (previously obtained from dogs and cats) were matched by size and mineral composition to create 7 pairs of uroliths (1 canine and 1 feline urolith/pair). PROCEDURE: Uroliths were treated in vitro with 100 shock waves (20 kV; 1 Hz) by use of an electrohydraulic lithotripter. Urolith fragmentation was quantitatively assessed via determination of the percentage increase in projected area (calculated from the digital image area of each urolith before and after SWL). RESULTS: After SWL, canine uroliths (n = 7) fragmented to produce a mean +/- SD increase in image area of 238 +/- 104%, whereas feline uroliths (7) underwent significantly less fragmentation (mean image area increase of 78 +/- 97%). The post-SWL increase in fragment image area in 4 of 7 feline uroliths was < 50%, whereas it was > 150% in 6 of 7 canine uroliths. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that feline calcium oxalate uroliths are less susceptible to fragmentation via SWL than canine calcium oxalate uroliths. In some cats, SWL may not be efficacious for fragmentation of calcium oxalate nephroliths or ureteroliths because the high numbers of shock waves required to adequately fragment the uroliths may cause renal injury.

Animals↗
PubMed2004

Nondestructive analysis of urinary calculi using micro computed tomography.

BACKGROUND: Micro computed tomography (micro CT) has been shown to provide exceptionally high quality imaging of the fine structural detail within urinary calculi. We tested the idea that micro CT might also be used to identify the mineral composition of urinary stones non-destructively. METHODS: Micro CT x-ray attenuation values were measured for mineral that was positively identified by infrared microspectroscopy (FT-IR). To do this, human urinary stones were sectioned with a diamond wire saw. The cut surface was explored by FT-IR and regions of pure mineral were evaluated by micro CT to correlate x-ray attenuation values with mineral content. Additionally, intact stones were imaged with micro CT to visualize internal morphology and map the distribution of specific mineral components in 3-D. RESULTS: Micro CT images taken just beneath the cut surface of urinary stones showed excellent resolution of structural detail that could be correlated with structure visible in the optical image mode of FT-IR. Regions of pure mineral were not difficult to find by FT-IR for most stones and such regions could be localized on micro CT images of the cut surface. This was not true, however, for two brushite stones tested; in these, brushite was closely intermixed with calcium oxalate. Micro CT x-ray attenuation values were collected for six minerals that could be found in regions that appeared to be pure, including uric acid (3515 - 4995 micro CT attenuation units, AU), struvite (7242 - 7969 AU), cystine (8619 - 9921 AU), calcium oxalate dihydrate (13815 - 15797 AU), calcium oxalate monohydrate (16297 - 18449 AU), and hydroxyapatite (21144 - 23121 AU). These AU values did not overlap. Analysis of intact stones showed excellent resolution of structural detail and could discriminate multiple mineral types within heterogeneous stones. CONCLUSIONS: Micro CT gives excellent structural detail of urinary stones, and these results demonstrate the feasibility of identifying and localizing most of the common mineral types found in urinary calculi using laboratory CT.

Calcium Phosphates↗
PubMed2004

Helical computed tomography accurately reports urinary stone composition using attenuation values: in vitro verification using high-resolution micro-computed tomography calibrated to fourier transform infrared microspectroscopy.

OBJECTIVES: To assess the ability of helical computed tomography (CT) to differentiate regions of known mineral composition in typical, heterogeneous urinary stones. Interest is substantial in the urologic community in using radiologic imaging to determine accurately the composition of urinary calculi. Recent advances in CT make this a viable prospect, but the heterogeneity of most stones is a complicating factor. METHODS: The ability of micro-CT (a high-resolution laboratory instrument) to identify the mineral composition of stones was confirmed by calibrating micro-CT attenuation values to pure mineral regions of sliced stones using infrared microspectroscopy. Intact human urinary stones were then analyzed by micro-CT, and regions-of-interest of pure mineral were correlated with identical regions-of-interest from quad slice multi-detector row helical CT images. With helical CT, narrow slice widths were used to decrease volume-averaging errors, and bone windows were used so that internal stone structure was visible. RESULTS: When stones were imaged using helical CT at narrow slice widths, mineral-specific regions-of-interest yielded nonoverlapping attenuation values for uric acid (566 to 632 Hounsfield units [HU]), struvite (862 to 944 HU), calcium oxalate (1416 to 1938 HU), and hydroxyapatite (2150 to 2461 HU). CONCLUSIONS: High resolution helical CT yields unique attenuation values for common types of stone mineral, but proper windowing is required to localize regions of homogeneity. The results of this in vitro study suggest that high-resolution helical CT may be able to identify stone composition at patient diagnosis.

Calcium Oxalate↗
PubMed2004

In vitro assessment of lithoclast ultra intracorporeal lithotripter.

PURPOSE: The Lithoclast Ultra (Boston Scientific Corporation, Natick, MA) enables the simultaneous application of ultrasonic and pneumatic modalities for the fragmentation and removal of stones during percutaneous nephrolithotomy (PCNL). We evaluated the effectiveness of this unit using a hands-free in vitro testing system. MATERIALS AND METHODS: An in vitro test system was used to assess the efficiency of stone penetration when the Lithoclast Ultra was operated at different settings of ultrasonic power and pneumatic frequency. The pneumatic and ultrasonic handpieces were assembled, the probes were inserted into an irrigation sheath (Cook Urological, Spencer, IN), and the complete unit was mounted upright (probe tip up). A gypsum artificial stone (mean length 12.8 +/- 0.6 mm; mean diameter 7.6 +/- 0.1 mm) was centered on the probe tip. A weight (63.4 g) was placed atop the stone to provide a constant force. Pneumatic frequency settings of 12, 8, 4, and 1 Hz were tested in conjunction with ultrasonic power settings of 100%, 70%, and 40%. The times required for complete stone penetration were assessed for each combination of settings. Differences in mean stone penetration times were compared using ANOVA. RESULTS: The combination of 12 Hz and 100% produced the fastest mean stone penetration time (8.9 +/- 1.1 seconds). Stone penetration times decreased significantly with increases in pneumatic frequency (P< 0.001) as well as with increases in ultrasonic power (P= 0.001). When analyzing the effect of each modality on the total improvement in penetration time, increasing the pneumatic frequency accounted for approximately 80% of the performance improvement. The stone penetration times were better than those of the most efficient ultrasonic device previously evaluated using this test system. CONCLUSIONS: The Lithoclast Ultra exhibited excellent stone penetration efficiency when evaluated with a hands-free in vitro test system. Increases in either pneumatic frequency or ultrasonic power significantly improve penetration times, with the pneumatic modality contributing the majority of the effect.

Humans↗
PubMed2004

Progress in the use of helical CT for imaging urinary calculi.

Helical CT has become the preferred method to diagnose urinary calculi in patients presenting with abdominal or flank pain. Recent in vitro studies have shown that CT also can display the internal structure in stones with remarkable detail. Because some stones respond better to SWL than others, knowing stone structure at diagnosis could be helpful in choosing among treatment options. This paper examines the potential for CT to be used in this way. Older CT technology proved to be problematic, in that all studies using low-resolution CT will suffer from an artifact in which stone size affects apparent CT attenuation values. Thus, the observation that stones with low measured CT attenuation break more easily than stones with high attenuation could be attributable entirely to an artifact of stone size. Most stones are composed of more than one mineral, and heterogeneity of composition may contribute to variability in stone response to SWL. Older technology is not useful in evaluating stone composition, but current and emerging CT machines have sufficient resolution to determine the composition and structure of stones inside the patient, provided proper viewing windows are used. Continuing improvement in image resolution in helical CT promises to provide information about stone composition and structure that will ultimately lead to better care for patients with stone disease.

Artifacts↗
PubMed2003

Variability of renal stone fragility in shock wave lithotripsy.

OBJECTIVES: To measure, in an in vitro study, the number of shock waves to complete comminution for 195 human stones, representing six major stone types. Not all renal calculi are easily broken with shock wave lithotripsy. Different types of stones are thought to have characteristic fragilities, and suggestions have been made in published reports of variation in the fragility within some types of stones, but few quantitative data are available. METHODS: Kidney stones classified by their dominant mineral content were broken in an unmodified Dornier HM3 lithotripter or in a research lithotripter modeled after the HM3, and the number of shock waves was counted for each stone until all fragments passed through a sieve (3-mm-round or 2-mm-square holes). RESULTS: The mean +/- SD number of shock waves to complete comminution was 400 +/- 333 per gram (n = 39) for uric acid; 965 +/- 900 per gram (n = 75) for calcium oxalate monohydrate; 1134 +/- 770 per gram (n = 21) for hydroxyapatite; 1138 +/- 746 per gram (n = 13) for struvite; 1681 +/- 1363 per gram (n = 23) for brushite; and 5937 +/- 6190 per gram (n = 24) for cystine. The variation for these natural stones (83% +/- 15% coefficient of variation) was greater than that for artificial (eg, gypsum-based) stones (17% +/- 8%). CONCLUSIONS: The variability in stone fragility to shock waves is large, even within groups defined by mineral composition. Thus, knowing the major composition of a stone may not allow adequate prediction of its fragility in lithotripsy treatment. The variation in stone structure could underlie the variation in stone fragility within type, but testing of this hypothesis remains to be done.

Humans↗
PubMed2003

Cavitation bubble cluster activity in the breakage of kidney stones by lithotripter shockwaves.

BACKGROUND AND PURPOSE: There is strong evidence that cavitation bubble activity contributes to stone breakage and that shockwave-bubble interactions are involved in the tissue trauma associated with shockwave lithotripsy. Cavitation control may thus be a way to improve lithotripsy. MATERIALS AND METHODS: High-speed photography was used to analyze cavitation bubble activity at the surface of artificial and natural kidney stones during exposure to lithotripter shockwaves in vitro. RESULTS: Numerous individual bubbles formed on the surfaces of stones, but these bubbles did not remain independent but rather combined to form clusters. Bubble clusters formed at the proximal and distal ends and at the sides of stones. Each cluster collapsed to a narrow point of impact. Collapse of the proximal cluster eroded the leading face of the stone, and the collapse of clusters at the sides of stones appeared to contribute to the growth of cracks. Collapse of the distal cluster caused minimal damage. CONCLUSION: Cavitation-mediated damage to stones is attributable, not to the action of solitary bubbles, but to the growth and collapse of bubble clusters.

Calcium Sulfate↗