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Effectiveness of high-frequency holmium:YAG laser stone fragmentation: the "popcorn effect".
J Endourol. 2008 Apr; 22(4):645-50.JE

Abstract

PURPOSE

To demonstrate the validity of non-contact holmium:yttrium-aluminum-garnet laser stone fragmentation in an in-vitro model and to characterize the optimal laser settings to perform this technique.

MATERIALS AND METHODS

A caliceal model consisting of a glass test tube filled with 0.9% normal saline was created. Into this system, a 365-mum laser fiber was inserted after stabilization 2 mm above the surface of the stones. Laser experiments were conducted using tubes that contained four soda limestone phantoms with a total stone burden of approximately 0.2 g per tube. The laser energy was varied between 1.0 and 1.5 J, with a firing frequency of 20, 30, or 40 Hz. Ten tubes were tested at each setting combination for a duration of 2 minutes. Thus, 60 tubes were tested. The contents of each tube were filtered through a 2-mm sieve after treatment, and all remaining fragments were dried for 5 days. The fragments were weighed, and the difference from pretreatment was calculated. Differences in weights and laser settings were compared using one-tailed and two-sample t testing.

RESULTS

Each experiment resulted in a significant decrease in stone burden from prelaser weight (all P values = 0.00). Laser settings were manipulated between combinations of 1.0 J at a frequency of 20, 30, and 40 Hz, and an energy of 1.5 J and 20, 30, and 40 Hz. This resulted in a respective mean weight loss of -42%, -58%, and -47% at 1.0 J, and -24%, -56%, and -63% at 1.5 J. The t tests were performed to detect differences between weight loss and to determine the optimal settings. Laser settings of 1.5 J and 40 Hz for 2 minutes produced the greatest mean decrease in stone burden (63%). This loss was significantly different from that of all settings at 1.0 J and the setting of 1.5 and 20 Hz (P < 0.05). The mean percentage weight loss for each setting was then normalized to the total energy used. Settings of 1.0 J and 20 Hz were the most efficient, with a change in weight of -18% per kJ.

CONCLUSIONS

We duplicated the "popcorn effect" of non-contact laser use in vitro. In this model, the technique results in a significant decrease in stone burden (up to 63%) in just 2 minutes. Adequate energy and high frequency seemed to optimize the effectiveness of the method, but excessive energy and frequency produced diminishing returns.

Authors+Show Affiliations

Department of Urology, Thomas Jefferson University, Jefferson Medical College, Philadelphia, Pennsylvania, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Validation Study

Language

eng

PubMed ID

18307379

Citation

Chawla, Sam N., et al. "Effectiveness of High-frequency holmium:YAG Laser Stone Fragmentation: the "popcorn Effect"." Journal of Endourology, vol. 22, no. 4, 2008, pp. 645-50.
Chawla SN, Chang MF, Chang A, et al. Effectiveness of high-frequency holmium:YAG laser stone fragmentation: the "popcorn effect". J Endourol. 2008;22(4):645-50.
Chawla, S. N., Chang, M. F., Chang, A., Lenoir, J., & Bagley, D. H. (2008). Effectiveness of high-frequency holmium:YAG laser stone fragmentation: the "popcorn effect". Journal of Endourology, 22(4), 645-50. https://doi.org/10.1089/end.2007.9843
Chawla SN, et al. Effectiveness of High-frequency holmium:YAG Laser Stone Fragmentation: the "popcorn Effect". J Endourol. 2008;22(4):645-50. PubMed PMID: 18307379.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effectiveness of high-frequency holmium:YAG laser stone fragmentation: the "popcorn effect". AU - Chawla,Sam N, AU - Chang,Mark F, AU - Chang,Andrew, AU - Lenoir,James, AU - Bagley,Demetrius H, PY - 2008/3/1/pubmed PY - 2008/7/2/medline PY - 2008/3/1/entrez SP - 645 EP - 50 JF - Journal of endourology JO - J Endourol VL - 22 IS - 4 N2 - PURPOSE: To demonstrate the validity of non-contact holmium:yttrium-aluminum-garnet laser stone fragmentation in an in-vitro model and to characterize the optimal laser settings to perform this technique. MATERIALS AND METHODS: A caliceal model consisting of a glass test tube filled with 0.9% normal saline was created. Into this system, a 365-mum laser fiber was inserted after stabilization 2 mm above the surface of the stones. Laser experiments were conducted using tubes that contained four soda limestone phantoms with a total stone burden of approximately 0.2 g per tube. The laser energy was varied between 1.0 and 1.5 J, with a firing frequency of 20, 30, or 40 Hz. Ten tubes were tested at each setting combination for a duration of 2 minutes. Thus, 60 tubes were tested. The contents of each tube were filtered through a 2-mm sieve after treatment, and all remaining fragments were dried for 5 days. The fragments were weighed, and the difference from pretreatment was calculated. Differences in weights and laser settings were compared using one-tailed and two-sample t testing. RESULTS: Each experiment resulted in a significant decrease in stone burden from prelaser weight (all P values = 0.00). Laser settings were manipulated between combinations of 1.0 J at a frequency of 20, 30, and 40 Hz, and an energy of 1.5 J and 20, 30, and 40 Hz. This resulted in a respective mean weight loss of -42%, -58%, and -47% at 1.0 J, and -24%, -56%, and -63% at 1.5 J. The t tests were performed to detect differences between weight loss and to determine the optimal settings. Laser settings of 1.5 J and 40 Hz for 2 minutes produced the greatest mean decrease in stone burden (63%). This loss was significantly different from that of all settings at 1.0 J and the setting of 1.5 and 20 Hz (P < 0.05). The mean percentage weight loss for each setting was then normalized to the total energy used. Settings of 1.0 J and 20 Hz were the most efficient, with a change in weight of -18% per kJ. CONCLUSIONS: We duplicated the "popcorn effect" of non-contact laser use in vitro. In this model, the technique results in a significant decrease in stone burden (up to 63%) in just 2 minutes. Adequate energy and high frequency seemed to optimize the effectiveness of the method, but excessive energy and frequency produced diminishing returns. SN - 0892-7790 UR - https://www.unboundmedicine.com/medline/citation/18307379/Effectiveness_of_high_frequency_holmium:YAG_laser_stone_fragmentation:_the_"popcorn_effect"_ L2 - https://www.liebertpub.com/doi/10.1089/end.2007.9843?url_ver=Z39.88-2003&amp;rfr_id=ori:rid:crossref.org&amp;rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -