Ultrasound directed extrahepatic bile duct intraluminal brachytherapy

Use of ultrasound in image-guided high-dose-rate brachytherapy: enumerations and arguments

Inherently, brachytherapy is the most conformal radiotherapeutic technique. As an aid to brachytherapy, ultrasonography (USG) serves as a portable, inexpensive, and simple to use method allowing for accurate, reproducible, and adaptive treatments. Some newer brachytherapy planning systems have incorporated USG as the sole imaging modality. Ultrasonography has been successfully used to place applicator and dose planning for prostate, cervix, and anal canal cancers. It can guide placement of brachytherapy catheters for all other sites like breast, skin, and head and neck cancers. Traditional USG has a few limitations, but recent advances such as 3-dimensional (3D) USG and contrast USG have enhanced its potential as a dependable guide in high-dose-rate image-guided brachytherapy (HDR-IGBT). The authors in this review have attempted to enumerate various aspects of USG in brachytherapy, highlighting its use across various sites.

Postoperative endoscopic retrograde high dose-rate brachytherapy for cholangiocarcinoma

Cholangiocarcinoma typically presents with disease unlikely to be completely resected, and prognosis remains poor. Improvements in imaging, endoscopy, and stenting have given rise to renewed interest in brachytherapy. Several recent retrospective series suggest a benefit to intraluminal brachytherapy, most commonly delivered by the transhepatic route. We describe a case in which brachytherapy was delivered via the nasobiliary route to address positive margins at the common bile duct stump. A custom catheter was manufactured to make the procedure feasible. Pertinent literature is reviewed, which supports the view that these malignancies benefit from high doses of radiation, if this can be achieved respecting normal tissue tolerance.

Intraductal US in assessing the effects of radiation therapy and prediction of patency of metallic stents in extrahepatic bile duct carcinoma

BACKGROUND

We assessed the local effects of radiation therapy using intraductal ultrasonography (US) to predict the subsequent patency of metallic stents in bile duct carcinoma.

METHODS

Data from 16 patients with extrahepatic-suprapancreatic bile duct carcinoma were prospectively analyzed. Thin-caliber US probes (2.0 mm diameter/20 MHz frequency and 2.8 mm diameter/10 MHz frequency) were inserted into the bile duct via a percutaneous transhepatic approach pre- and postradiation therapy to evaluate the effects of treatment. When intraductal US showed a reduction in bile duct wall thickness of 30% or greater or showed a lessening of vessel (portal vein or right hepatic artery) invasion, radiation therapy was judged to be effective. Noncovered metallic stents were then inserted, and their patency was evaluated over time.

RESULTS

When radiation therapy was effective (n = 7), the metallic stent was patent for 522 +/- 571 days. When radiation was ineffective (n = 9), the metallic stent was patent for only 188 +/- 159 days. When radiation therapy was ineffective, stent obstruction occurred in 6 of 9 (66.7%) patients during this period, significantly more frequently than when radiation therapy was effective (14.3%, p < 0.05).

CONCLUSIONS

Assessment of local radiation effects by intraductal US is useful for predicting patency of metallic stents in bile duct cancer.

Endoscopic ultrasound-guided brachytherapy of head and neck tumours. A new procedure for controlled application

Brachytherapy is an established procedure in primary and in recurrent cancer. We perform afterloading brachytherapy during general anaesthesia. The target organ is punctured with hollow needles which are loaded with 192iridium via remote control. The depth and number of needles depend on tumour extension. In the interdisciplinary approach of our departments, this method has been improved and supplied by B-scan ultrasound control. Needles are positioned under continuous ultrasonographic guidance, and adjacent structures (e.g. the carotid artery) are localized ultrasonographically. Thus violation of the large vessels is avoided and the exact position of the needles within the tumour is improved. In this paper, we report results on 22 patients suffering from recurrent carcinoma of the head and neck following surgery and curative radiation, and 17 patients with first onset of cancer. We did not observe any severe complications such as haemorrhage, osteomyelitis, or dyspnoea. The only side-effect was temporary oedema, sometimes associated with a short-term increase of pain. No systemic side-effects occurred. The method is described and results from both patient groups are reported in detail. We conclude from our data that ultrasonographically-controlled endoscopic brachytherapy is a valuable procedure in locally-advanced primary, and in recurrent head and neck cancer.

Brachytherapy and pancreatic cancer

Advances in diagnostic and therapeutic technology have not appreciably changed the outlook of patients with pancreatic cancer. While those patients presenting with localized resectable disease have the best prognosis, local control and intra-abdominal metastases remain significant obstacles to survival. Localized chemoradiation has modestly improved median survival in localized and locally advanced disease. Patients presenting with locally advanced disease at diagnosis benefit from surgical palliation which includes biliary and gastric bypass. Intraoperative interstitial brachytherapy has been effective when utilized at laparotomy to improve local control in locally advanced disease. Advances in laparoscopic techniques have provided the ability to more accurately stage patients prior to laparotomy and perform palliative procedures without the need for laparotomy. The utilization of high-dose-rate brachytherapy has proven effective in palliating obstructive symptoms with minimal morbidity on an outpatient basis. Recent efforts have focused on preoperative chemoradiation to improve resectability in selected patients and prophylactic hepatic irradiation to reduce metastases for patients with locally advanced disease.

Measurement of the ultrasonic attenuation of fat at high frequency

RATIONALE AND OBJECTIVES

High-frequency ultrasound devices are often limited by a decreased depth of acoustic imaging caused by the increased attenuation of tissue at high frequencies. We investigated the role of adipose tissue in this phenomenon.

METHODS

A substitution technique was used to calculate the ultrasonic attenuation (decibels per centimeter) of fresh samples of sheep rumen, omental fat, and back fat and swine back fat and various concentrations of bovine milk fat at 22 degrees C and 37 degrees C for frequencies of 15 and 20 MHz.

RESULTS

The attenuation was significantly higher for sheep adipose tissue than for the intestinal wall, in descending order, omental fat, back fat, and rumen wall (P < 0.01). A correlation was found between bovine milk fat concentrations and attenuation at both frequencies (R2 > 0.9). The attenuation of adipose tissues decreased significantly with an increase in temperature (P < 0.01), whereas the attenuation of sheep rumen showed no significant change (P > 0.1).

CONCLUSIONS

The ultrasonic attenuation of fat may contribute to limitations on the use of high-frequency ultrasound in clinical situations in which adipose tissue is present.