PubMed Health⌕ Search

Biomedical subjects

J P Ritz

Publications and source records attributed to J P Ritz.

At least 19 recordsLinked to original sources
PubMed2001

Laser-induced thermotherapy: intra- and extralesionary recurrence after incomplete destruction of experimental liver metastasis.

PURPOSE: The aim of this study was to determine the energy (J/mm3 tumor volume) and temperature required for a complete laser-induced thermotherapy (LITT) of experimental liver tumors, and to find out causes and areas of local recurrence followed by incomplete treatment. METHODS: In VX-2 tumor-bearing rabbits LITT was performed using neodymium:yttrium-aluminum-garnet (Nd:YAG) laser (1064 nm) with a diffuser-tip applicator and a temperature feedback system. The animals were randomized into four groups (n = 20) that differed in the target temperature at the tumor border as follows: 45 degrees C, 50 degrees C, 55 degrees C and 60 degrees C. The target temperature was held for 10 min constant. Histologic examination (hematoxylin and eosin [H and E], nicotinamide adenine dinucleotide phosphate [NADPH]-dehydrogenase) was performed at 0 h, 24 h, 96 h, and 14 days after LITT. RESULTS: The pretreatment tumor volume of 2191 +/- 61 mm3 was the same for all groups (p > 0.05). Energy up to target temperature and total energy required, lesion size, and the rate of incomplete tumor ablation (recurrences) are listed below (ap < 0.05, Kruskal-Wallis test). Histologically, two forms of local recurrences could be differentiated intralesionary and extralesionary. CONCLUSIONS: To achieve complete in situ ablation under the given conditions, it is necessary to apply laser energy of 3 J/mm3 tumor volume. A minimum temperature of 60 degrees C on the tumor border presumed an application of 10 min. Recurrence was found outside the coagulation zone (extralesionary) and in high vascularized areas within the coagulation zone (intralesionary).

Animals↗
PubMed2001

MR-guided interstitial laser-induced thermotherapy of hepatic metastasis combined with arterial blood flow reduction: technique and first clinical results in an open MR system.

The feasibility and safety of percutaneous laser-induced thermotherapy (LITT) of liver metastases in an open low-field magnetic resonance imaging (MRI) system combined with microsphere-modulated blood flow reduction were tested. Nd:YAG laser therapy with an internally cooled laser applicator was performed under local anesthesia on 20 patients with 34 liver metastases. To increase the effectiveness of LITT, degradable starch microspheres were injected into the proper hepatic artery through an MR-visible catheter initially inserted under fluoroscopy. Near real-time imaging was used for positioning the laser applicator. A T1-weighted gradient-echo breath-hold sequence was used for catheter localization and temperature monitoring. The volumes of the liver metastases and the thermonecroses were determined. MRI-guided LITT could be performed in all patients with no clinically relevant complications. Intraprocedural imaging underestimated the extent of thermonecrosis. In conclusion, percutaneous LITT of liver metastases after injection of starch microspheres is both technically feasible and safe in an open MRI system. J. Magn. Reson. Imaging 2001;13:31-36.

Aged↗
PubMed2001

Continuous changes in the optical properties of liver tissue during laser-induced interstitial thermotherapy.

BACKGROUND AND OBJECTIVE: Laser-induced thermotherapy (LITT) is a promising treatment for irresectable liver tumors. To predict the effects of laser applications and to optimize treatment planning in LITT, it is essential to gain knowledge about light distribution in tissue, tissue optical properties (absorption, scattering, anisotropy, penetration depth), and their continuous changes during therapy. STUDY DESIGN/MATERIALS AND METHODS: Measurements of optical properties were performed with a double integrating-sphere system and a laser diode (830 nm). Porcine liver tissue samples were examined in a native state (35 degrees C) and after exposure to different temperatures (45 degrees C to 80 degrees C). RESULTS: Rising temperature was accompanied by a decrease in the absorption coefficient and anisotropy factor and an increase in the scattering coefficient. These changes were only significant in the temperature range of 50 degrees to 65 degrees C (P < 0.01). The optical penetration depth decreased from 3.1mm in the native state to 1.7mm at 65 degrees C (P < 0.01). Above 65 degrees, there was no significant change in the tissue optical properties. CONCLUSIONS: The optical properties of liver tissue change significantly under the influence of tissue heating, resulting in a decreased optical penetration depth. These changes occur mainly in the temperature range of 50 degrees C to 65 degrees C, corresponding to protein denaturation. To ensure a safe and effective procedure, an adjustment of the laser power to the actual penetration depth is recommended during therapy.

Animals↗
PubMed2001

Optical properties of native and coagulated porcine liver tissue between 400 and 2400 nm.

BACKGROUND AND OBJECTIVE: Laser induced thermotherapy (LITT) is a promising treatment for irresectable liver tumors. For predicting the effects of laser applications and optimizing irradiation planning in LITT, knowledge about light distribution in tissue, optical tissue properties (absorption, scattering, anisotropy, penetration depth) and their changes due to thermal denaturation is indispensable. STUDY DESIGN/MATERIALS AND METHODS: The optical parameters in healthy porcine liver were determined in the native state and after thermal coagulation using a double integrating sphere system in the wavelength range of 400-2400 nm. RESULTS: Optical parameters showed significant fluctuations in the examined wavelength range mainly due to the water and hemoglobin content in the tissue. The greatest optical penetration depth of 7.46 mm was achieved at 1070 nm. After thermal coagulation, a clear increase in scattering and a slight decrease in absorption was found, which results in a decreased optical penetration depth. CONCLUSIONS: In order to ensure a safe and effective procedure, an adjustment of the laser power to the decreasing penetration depth is recommended during therapy. These results provide a better understanding of laser-tissue interaction and may be helpful to investigators in the field of light dosimetry in liver tissue.

Animals↗
PubMed2000

Esophageal hypermotility associated with intramural pseudodiverticulosis. Primary esophageal disease or epiphenomena?

Esophageal intramural pseudodiverticulosis is a very rare disease of unclear etiology. The clinical picture is characterized by progressive dysphagia. Because of its frequent association with alcohol abuse and subsequent weight loss, it must be differentiated reliably from esophageal carcinoma. The diagnosis is established by the characteristic detection of multiple intramural contrast accumulations in the barium esophagogram. Additional endoscopic and endosonographic confirmation and histological examination are required to exclude a malignant tumor. Moreover, associated diseases are almost always present and should also be diagnosed by pH-metry, cytology, and esophageal manometry. Good and long-lasting therapeutic success can be achieved by bouginage of the stenosis with concomitant treatment of the associated esophageal diseases. Based on two case reports of patients with this disease, we discuss the unusual association with esophageal hypermotility as well as the symptoms, clinical course, therapy, and pathogenesis of the disease.

Aged↗
PubMed2000

[Topics and focuses of clinical studies in gastroenterological surgery].

High-quality clinical research offers the opportunity to exert a direct influence on medical decision-making. To take stock of the current situation in clinical gastroenterological surgery, a questionnaire was sent to 171 surgical departments focussing on visceral surgery. Of the 93 that responded, 45.2% conducted a total of 91 clinical studies. Only 8.8% of these were described as prospective randomized clinical studies; 60% were single-center studies. The studies were financed from the department budget in 60 cases, supported by industry in 27 cases and funded by independent institutions such as German Research Foundation or the Federal Ministry for Education and Research in 4 cases. Of the researchers performing the studies, 7.7% had been exempted from other duties and 92.8% were additionally involved in the clinical routine. The majority of the clinical studies in Germany deal with diseases of the esophagus and pancreas or with chronic inflammatory bowel diseases. The old and new states of the Federal Republic of Germany show no appreciable differences in the development and performance of clinical studies.

Clinical Trials as Topic↗
PubMed2000

[Laser-induced thermotherapy (LITT) for liver metastasis in an open 0.2T MRI].

OBJECTIVE: To test the feasibility and safety of the laser-induced thermotherapy (LITT) for liver metastases in open MR imaging system operating at 0.2 Tesla. METHOD: Laser therapy using the Nd:YAG laser was performed on 25 patients with a total of 41 liver metastases. An open low-field MRI scanner was used for puncture, positioning of the laser applicator, and monitoring the therapy. A true FISP sequence was used to track the puncture in close to real-time. Localization diagnostics and temperature monitoring were aided by T1-weighted gradient echo sequences in the breath-holding technique. In the first follow up after 24-48 hours, a contrast-enhanced T1-weighted gradient-echo sequence was performed in an MRI scanner at 1.5T. The pre-, intra- and postinterventional volumes of the liver metastases as well as the thermolesions and the thermonecroses were determined. RESULTS: LITT in an open MRI system was technically feasible in all patients with no clinically relevant complications. The mean volumes of the thermolesions measured during intervention in low-field MRI were lower than the volumes of the thermonecroses measured after intervention in high-field MRI. CONCLUSION: The technique presented here of laser-induced thermotherapy for liver metastases in an open MRI system is technically feasible and safe.

Aged↗
PubMed1999

Laser-induced thermotherapy combined with hepatic arterial embolization in the treatment of liver tumors in a rat tumor model.

OBJECTIVE: To assess the effect of combined laser-induced thermotherapy (LITT) and hepatic arterial embolization with degradable starch microspheres (DSM) on tumor response and intrahepatic temperature distribution in rats with liver tumors. SUMMARY BACKGROUND DATA: Laser-induced thermotherapy is a promising in situ ablation technique for malignant liver tumors. However, clinical use is still limited, mainly because of the small size of the inducible coagulation necroses. This results in insufficient tumor destruction. METHODS: Colon carcinoma CC531 was implanted in 60 WAG rat livers. Fourteen days later, a silicon catheter was implanted in the hepatic artery for DSM administration. Tumors were exposed to 1064 nm Nd:YAG laser light at 2 watts for 10 minutes from a diffuser tip applicator placed in the tumor. The animals were randomized into a sham-operated control (group I) and three test groups. Group II received DSM alone, group III received LITT alone, and group IV received DSM + LITT. Tumor control was examined 1, 7, and 14 days after treatment. RESULTS: A complete tumor remission was achieved in all rats treated with LITT + DSM (group IV). In contrast, tumor progression was seen in animals treated with LITT alone (group III) or DSM alone (group II), as well as in the sham-operated controls (group I). CONCLUSIONS: The authors' results suggest that the combination of LITT and DSM considerably increases the efficacy of LITT in the treatment of liver metastases in the rat.

Animals↗
PubMed1998

Interstitial laser coagulation: evaluation of the effect of normal liver blood perfusion and the application mode on lesion size.

BACKGROUND AND OBJECTIVE: The effect of temporarily interrupted hepatic blood flow and multiple-fiber application on necrosis volume in interstitial laser coagulation (ILC) was investigated. STUDY DESIGN/MATERIALS AND METHODS: Single- and multiple-fiber ILC were performed in porcine livers with normal as well as interrupted perfusion. Temperatures were determined. Lesions were measured and studied by light microscopy 4 hours post-treatment. RESULTS: ILC with multiple-fiber application led to significantly greater individual lesion volumes (3.7 +/- 0.5 cm3) than single-fiber application (2.5 +/- 0.5 cm3) (P < .01). The interruption of hepatic perfusion led to a significant increase in lesion volume with single- (7.5 +/- 1.0 cm3) as well as multiple-fiber application (12.6 +/- 2.2 cm3) (P < .01). Superposition of the lesions in the multiple-fiber application mode was only determined with interrupted perfusion (total volume: 50.3 +/- 6.6 cm3). CONCLUSION: Interruption of hepatic perfusion increases lesion volumes significantly. ILC for treating liver tumors should preferably be performed by application routes that permit temporary interruption of hepatic perfusion.

Animals↗
PubMed1998

Optical properties of native and coagulated human liver tissue and liver metastases in the near infrared range.

BACKGROUND AND OBJECTIVE: Knowledge about optical parameters and the resultant light distribution in laser-treated tissue is important for predicting the effects of laser-induced thermotherapy of liver metastases (LITT). MATERIALS AND METHODS: The absorption and scattering coefficients as well as the anisotropy factors and the optical penetration depths of human liver tissue and colorectal liver metastases were determined at 850, 980, and 1,064 nm under native and thermocoagulated conditions. RESULTS: Liver metastases had a lower anisotropy factor, absorption, and scattering coefficient than healthy liver (P < 0.01), resulting in a significantly higher optical penetration depth in metastatic tissue. Coagulation significantly changes the optical parameters by reducing the optical penetration depth in both tissue types (P < 0.01). CONCLUSIONS: A greater optical penetration depth in metastatic tissue is advantageous for LITT, since larger tumor volumes can be coagulated. At the same time, an adjustment of the application parameters during LITT is necessary to achieve optimal therapeutic success.

Adenocarcinoma↗
PubMed1998

[Laser-induced thermotherapy. Technical prerequisites for treatment of malignant liver tumors].

Laser-induced thermotherapy is an in situ ablation method for the local treatment of liver tumors. The basic prerequisite for induction of adequate treatment volumes for clinical use was the development of a thermostable application system. In an ex vivo test series, the specially developed application system (diffuser tip) with 5760 J had a higher thermic loading capacity than the Ringmode applicator with 4200 J, thus enabling the induction of significantly larger lesions with a volume of 7.6 cm3. The results of a further in vivo test series demonstrated that the lesions were subject to a four-phase connective-tissue organization within a 6-month period. Furthermore, the same laser energy (4200 J) was associated with a significantly lower lesion volume of 2.5 cm3 in the in vivo than in the ex vivo test series. The influence of liver perfusion on the inducible lesion volume was examined in a further animal experimental study. By temporarily interrupting hepatic blood perfusion (Pringle's maneuver) during laser application, the effective volume could be increased to 50.3 cm3 (P < 0.01) using an optical beam splitter. These results show that the technical prerequisites for reliable clinical application of laser-induced thermotherapy have been fulfilled.

Animals↗
PubMed1998

Extent of surgery and recurrence rate of hidradenitis suppurativa.

Hidradenitis suppurativa (HS) is a chronic fistula- and abscess-forming disease of the cutis and subcutis of unknown etiology. Disease recurrence is frequent and may cause severe complications. We analyzed patients with HS who underwent surgery between 1976 and 1997. The operative procedures were divided into drainage procedures (n = 6), limited regional (n = 14), and radical wide excisions (n = 11). The extent of surgery was examined in terms of the clinical course and late postoperative sequelae of HS. At a mean follow-up of 72 months, we found developed locoregional recurrent HS in 45% of patients. There was 100% recurrence after drainage, 42.8% after limited, and 27% after radical excision (P < 0.05). HS recurred after a median interval of 3 months for drainage, 11 months for limited excision, and 20 months for radical excision (P < 0.05). The disease-free interval continued up to 35 months. Long-term sequelae included penile amputation and a case of fatal squamous cell carcinoma. Although radical wide excision of the HS-affected cutis is associated with the lowest recurrence rate, it is still considerable and warrants long-term follow-up.

Adult↗
PubMed1998

Laparoscopic gastrostomy according to Janeway.

Percutaneous endoscopic gastrostomy is not suitable for all patients requiring gastrostomies. Patients with endoscopically impassable tumors require a safe and effective alternative procedure for paraesophageal alimentation. We present the surgical technique and results of the laparoscopic gastrostomy according to Janeway. Using an endoscopic stapling device a gastric tube is created from a stomach fold, led out through the trocar site, and fixed to the skin in the left upper quadrant. Via an inserted catheter enteral alimentation can be performed intermittently since the gastrostoma is continent. Between July 1995 and November 1996 laparoscopic gastrostomy was performed in 15 patients (10 male, five female) with tumors in the pharynx or esophagus. Mean operation time was 35 min. One stoma necrosis developed; the other postoperative courses were complication-free. All gastrostomies were continent. Laparoscopic gastrostomy is easy to perform and involves minimal discomfort and complications for the patient.

Deglutition Disorders↗
PubMed1998

Laser-induced thermotherapy for the treatment of liver metastasis. Correlation of gadolinium-DTPA-enhanced MRI with histomorphologic findings to determine criteria for follow-up monitoring.

PURPOSE: To evaluate gadolinium (Gd)-diethylenetriamine-pentaacetic-acid (DTPA)-enhanced magnetic resonance imaging (MRI) for follow-up monitoring of laser-induced thermotherapy (LITT) and to determine a useful examination schedule. METHODS: LITT of the liver was performed in 55 rabbits using a neodymium: yttrium-aluminum-garnet (Nd:YAG) laser (4-W power output, 840-s exposure time). Gd-DTPA MRI and histologic examinations were performed at different times (0-168 days). RESULTS: Laser-induced lesions underwent regeneration and volume size reduction (69% after 168 days). The correlation coefficient (MR vs. macroscopic analysis) for the mean lesion diameter was r = 0.96. Histology of lesions comprised the four zones that correlated best with MRI findings. Coagulation necroses immediately after LITT was seen as an area of no enhancement on Gd-DTPA MRI. Circular enhancement was first seen 72-96 h after LITT, which was due to early mesenchymal proliferation. CONCLUSIONS: Gd-DTPA MRI is a good monitoring procedure for LITT. MRI should be performed 24 and 96 h after LITT.

Animals↗
PubMed1998

[Significant modification of the hyperthermic effect by starch microspheres (Spherex) of laser-induced hypertheria in the rat liver metastasis model].

This experimental study in an animal liver metastasis model (adenocarcinoma) investigated whether the "cooling effect" can be eliminated by temporary embolization with starch microspheres (Spherex) and the hyperthermic efficiency was improved. In this connection, groups of 15 test animals were treated with LITTmono, Embolizationmono or LITTembolization. In the LITTembolization group, 1/15 animals had vital tumor tissue after 24 h, 7 and 28 days, but tumor growth was found in the other 2 groups in 13/15 (LITTmono) and 14/15 (Embolization(mono)). These results demonstrate that the application of starch microspheres led to a significant increase in the hyperthermic effect of LITT under the selected testing conditions.

Adenocarcinoma↗
PubMed1998

[Optimized laser-induced thermotherapy in treatment of liver metastases of colorectal carcinomas, an interdisciplinary responsibility--a clinical study].

In a clinical study, it was investigated whether local tumor control is attainable with laser-induced thermotherapy (LITT) in the treatment of colorectal liver metastasis tumors. Local control of tumor growth was obtainable in completely hyperthermic tumors. Due to the small and inhomogeneous patient population (n = 32), an assessment of the method regarding prognostic gain for the patient is not possible in such a short follow-up period.

Adult↗