Biomedical subjects

W Cecchetti

Publications and source records attributed to W Cecchetti.

6 recordsLinked to original sources

PubMed2004

Plasma bubble formation induced by holmium laser: an in vitro study.

OBJECTIVES: To use the elementary physical measurements of temperature and size to prove that the thermal effects produced by the holmium laser's pulses are due to the formation of a plasma bubble. The physical phenomenon related to high temperatures generated during procedures with the holmium laser (holmium:yttrium-aluminum-garnet) was the object of our interest. METHODS: Using a double micrometric slide attached to a 550-microm optic fiber and two thermocouples submerged in water, a series of pulses of 0.8 J at 10 to 30 Hz was delivered from a holmium:yttrium-aluminum-garnet laser, and we recorded temperatures on both frontal and lateral planes. Subsequently, samples of prostatic tissue and small stones were treated with 1.5 J at 20 Hz on both frontal and lateral planes. RESULTS: Treatment with 1.5 J at 30 Hz (frontal plane) and with 1.5 J at 20 Hz (lateral plane) produced the ablation of the structure of the thermocouple at 2 mm and 1 mm, respectively, indicating plasma formation. The dimensions of the bubble after the delivery of 1.5 J at 20 Hz was 2 x 1.5 mm. Coagulation of the prostatic tissue took place at 1 mm from the plasma bubble, on both frontal and lateral planes. CONCLUSIONS: The plasma bubble that forms at the tip of the fiber connected to the holmium:yttrium-aluminum-garnet laser makes it possible to work on stones and soft tissues. The coagulation of the prostatic tissue is caused by the hot water-vapor bubble that forms on the edge of the plasma bubble. During lithotripsy, guidewires and baskets within the expansion area of the plasma bubble risk damage.

Aluminum↗

PubMed2001

980-nm diode laser treatment for recurrent urethral strictures.

OBJECTIVES: Our experience with laser treatment of urethral strictures with a 980-nm diode laser is reported. METHODS: 45 consecutive patients with relapsing urethral strictures (mean age 65, range 25-85 years) were treated between February 1995 and February 1998. The fibrous and scar tissue was cut and vaporized at the 6 o'clock position with the laser beam. RESULTS: 44/45 patients were available for follow-up at 1 year and 32/43 at 2 years. At 12 months the average peak flow rates of the patients was 18 ml/s, and at the second year assessment it was 15.5 ml/s. Of the patients 21/44 (47.7%) were extremely satisfied (0-1 of the quality-of-life, QoL, assessment index) with the procedure, 14/44 (31.8%) were satisfied (2 of the QoL assessment index), and 9/44 (20.4%) were not satisfied (> or = 3 of the QoL assessment index) due to the low flow rate or the recurrence of the stricture. (The sum of the first two categories is 79.5%.) At the second year assessment the percentage of satisfied patients reached 78%, with 71% of the patients stable without any dilatation. CONCLUSIONS: Usually in recurrent strictures of the urethra open surgery is suggested, but we believe that there is still a place for endoscopy. With the laser we can make an incision at the 6 o'clock position without significant bleeding, very easily opening the urethra. We had 79.5 and 71% good results at the 1- and 2-year assessments (mean peak flow rate of 18 and 15.5 ml/min), respectively. To date, no definitive conclusions can be drawn, but we believe that laser treatment is indicated for recurrent strictures in high risk or elderly patients and in those who demand a minimally invasive procedure.

Adult↗

PubMed1995

Transurethral laser surgery with a conventional modified resectoscope.

A new 1,800-microns side fiber made of pure silica with laser beam deviation of 82 degrees and divergence of 18 degrees was inserted into a modified transurethral resectoscope and used to treat in vitro some prostates removed during radical prostatectomy. Sterilization of prostatic tissue with a depth of penetration of 12 mm was observed after treatment with 20 W for 2 min. Irradiation with 60 W for 1 min produced vaporization and explosion of the tissue and a depth of penetration of 15 mm. The laser resectoscope was then successfully employed for the treatment of 6 cases of benign prostatic hyperplasia (BPH) as well as in high risk patients with bulky bleeding bladder tumors (4 cases) and with transitional carcinoma of the prostate invading the parenchyma (2 cases). 3 patients with small size BPH underwent only laser irradiation. All others were submitted to traditional transurethral resection followed by laser treatment with Nd: YAG using the same instrument. Our laser resectoscope lowers costs since the side fiber is reusable for 4-5 treatments and brings laser treatment nearer to traditional endoscopic treatment, thereby making its application more comfortable for the urologist.

Cystoscopy↗

PubMed1993

Photosensitization of cystine stones to induce laser lithotripsy.

We report the preliminary results of laser lithotripsy of cystine stones accomplished in 2 patients with the use of a new method of photosensitization. Transurethral rigid ureterorenoscopy was performed with an 8.5F instrument to reach 0.8 and 1.8 cm. stones located in the right and left lumbar ureters, respectively. A 320 mu. fiber was then inserted and pushed into contact with the stone. Then, 400 preliminary impulses were released from a pulsed dye laser (504 nm) with energy output at 140 mJ. and at a rate of 5 Hz. without any visible modification of the stone structure. The saline solution used as irrigation fluid was then substituted with a 2% solution of rifamycin. Totals of 95 and 152 impulses released at the same energy output previously used were then sufficient to produce a satisfactory fragmentation of the stone in both cases. Sonography and excretory urography showed no alterations of the treated urinary tract in either case. The use of rifamycin in the irrigation fluid is suggested for laser treatment of hard or nonabsorbent stones, since this substance favors optical coupling and lowers the threshold of plasma formation on the surface of the stone.

Adolescent↗

PubMed1993

Five years experience in experimental laser lithotripsy.

In the first part of our experience approximately 300 stones of different composition have been treated in vitro with three different laser sources: Nd-YAG laser (1,064 nm), dye laser (504 nm) and alexandrite laser (755 nm). Calcium oxalate monohydrate and brushite stones appeared to be the most resistant to lithotripsy. Highest fragmentation rates were obtained for calcium oxalate dihydrate stones followed by struvite, uric acid and hydroxyapatite stones. The Nd-YAG laser did not appear to be ideal for lithotripsy since early damage to the fiber tip was observed when this source was used. Both the dye and the alexandrite lasers were almost always effective in fragmenting the various types of stones. We subsequently treated some cystine stones while immersed in water or in solutions of carmine indigo (2%), methylene blue (5%), rifamycin (0.6 and 6%) and rifampicin (0.8 and 0.3%) with the dye or the alexandrite laser. The spectra of these solutions, previously analyzed with the spectrophotometer, showed that rifamycin and rifampicin absorbed large amounts of light radiation at the wave length of the dye laser (504 nm). Successful fragmentation occurred only when the dye laser was used to treat stones immersed in the more concentrated solutions of these two substances. The quantity of fragmented material after treating a 10-cm3 cystine stone previously immersed in the more concentrated solutions of rifamycin and rifampicin (30 and 10 mm3, respectively) confirmed previous results.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗

PubMed1989

Laser-induced vaporization mass spectrometry of rifamycins.

The mass spectra of many rifamycins cannot be obtained by electron ionization (EI) owing to their thermal decomposition. When a laser beam is used to vaporize the sample through an optic fibre inserted in a hollow probe which reaches the sample cup, decomposition is minimized and the EI spectra show abundant molecular ions and fragments of structurally high diagnostic value. These ionic species are easily observed owing to the lack of chemical noise often present in soft ionization methods, such as direct liquid chemical ionization and fast atom bombardment.

Chemical Phenomena↗