Investigation into the radiobiological consequences of pre-treatment verification imaging with megavoltage X-rays in radiotherapy.

OBJECTIVE: The aim of this study was to investigate the effect of pre-treatment verification imaging with megavoltage X-rays on cancer and normal cell survival in vitro and to compare the findings with theoretically modelled data. Since the dose received from pre-treatment imaging can be significant, the incorporation of this dose at the planning stage of treatment has been suggested. METHODS: The impact of imaging dose incorporation on cell survival was investigated by clonogenic assay of irradiated DU-145 prostate cancer, H460 non-small-cell lung cancer and AGO-1522b normal tissue fibroblast cells. Clinically relevant imaging-to-treatment times of 7.5 and 15 min were chosen for this study. The theoretical magnitude of the loss of radiobiological efficacy due to sublethal damage repair was investigated using the Lea-Catcheside dose protraction factor model. RESULTS: For the cell lines investigated, the experimental data showed that imaging dose incorporation had no significant impact on cell survival. These findings were in close agreement with theoretical results. CONCLUSION: For the conditions investigated, the results suggest that allowance for the imaging dose at the planning stage of treatment should not adversely affect treatment efficacy. ADVANCES IN KNOWLEDGE: There is a paucity of data in the literature on imaging effects in radiotherapy. This article presents a systematic study of imaging dose effects on cancer and normal cell survival, providing both theoretical and experimental evidence for clinically relevant imaging doses and imaging-to-treatment times. The data provide a firm foundation for further study into this highly relevant area of research.

Radiosensitising nanoparticles as novel cancer therapeutics--pipe dream or realistic prospect?

The field of high atomic number nanoparticle radiosensitising agents is reviewed. After a brief discussion of the new mode of physicochemical action implied by irradiation of high atomic number nanoparticles embedded in biological systems, a series of exemplars are discussed. Silver-, gadolinium- and gold-based nanoparticles are discussed in order of increasing atomic number with functionalisation strategies being outlined. In vitro and in vivo evidence for radio-enhancement and the mechanisms attributed to the increased biological effect are discussed.

An in vitro study of the radiobiological effects of flattening filter free radiotherapy treatments.

Flattening filter free (FFF) linear accelerators allow for an increase in instantaneous dose-rate of the x-ray pulses by a factor of 2-6 over the conventional flattened output. As a result, radiobiological investigations are being carried out to determine the effect of these higher dose-rates on cell response. The studies reported thus far have presented conflicting results, highlighting the need for further investigation. To determine the radiobiological impact of the increased dose-rates from FFF exposures a Varian Truebeam medical linear accelerator was used to irradiate two human cancer cell lines in vitro, DU-145 prostate and H460 non-small cell lung, with both flattened and FFF 6 MV beams. The fluence profile of the FFF beam was modified using a custom-designed Nylon compensator to produce a similar dose profile to the flattened beam (6X) at the cell surface but at a higher instantaneous dose-rate. For both cell lines there appeared to be no significant change in cell survival. Curve fitting coefficients for DU145 cells irradiated with constant average dose-rates were 6X: α = 0.09 ± 0.03, ß = 0.03 ± 0.01 and 6FFF: α = 0.14 ± 0.13, ß = 0.03 ± 0.02 with a significance of p = 0.75. For H460 cells irradiated with the same instantaneous dose-rate but different average dose-rate the fit coefficients were 6FFF (low dose-rate): α = 0.21 ± 0.11, 0.07 ± 0.02 and 6FFF (high dose-rate): α = 0.21 ± 0.16, 0.07 ± 0.03, with p = 0.79. The results indicate that collective damage behaviour does not occur at the instantaneous dose-rates investigated here and that the use of either modality should result in the same clinical outcome, however this will require further validation in vivo.

Immediate reconstruction of the perineal wound with gracilis muscle flaps following abdominoperineal resection and intraoperative radiation therapy for recurrent carcinoma of the rectum.

BACKGROUND: Morbidity associated with a nonhealing perineal wound is the most common complication following proctectomy, particularly in the setting of recurrent carcinoma of the rectum and radiation therapy. Immediate reconstruction using the gracilis myocutaneous and muscle flaps significantly reduces the incidence of major infection associated with perineal wound closure. The purpose of this study was to assess the value of immediate reconstruction of the perineal wound using a gracilis flap in patients undergoing abdominoperineal resection and intraoperative radiation therapy. METHODS: This study retrospectively reviewed our experience with immediate pelvic reconstruction using gracilis muscle flaps for patients undergoing rectal extirpation and irradiation for recurrent carcinoma of the rectum. From 1990 to 1995, 16 patients underwent abdominoperineal resection (APR) or pelvic exenteration accompanied by immediate wound closure with unilateral or bilateral gracilis muscle flaps. Morbidity and mortality outcomes were compared to those of 24 patients from our institution who, between 1988 and 1992, underwent proctectomy and irradiation for recurrent rectal carcinoma with primary closure of the perineal wound. RESULTS: Major complications (i.e., major infection requiring hospitalization and/or operation) occurred in 2 (12%) of the patients with gracilis flaps versus 11 (46%) of the patients with primary closure (P = .028 by chi2 analysis for flap vs. primary closure). Minor complications (i.e., persistent sinus and subcutaneous abscess) occurred in 4 (25%) of the patients with gracilis flaps versus 5 (21%) of those with primary closure. CONCLUSION: Immediate perineal reconstruction using the gracilis myocutaneous flap following proctectomy and irradiation for recurrent rectal carcinoma significantly reduces the incidence of major infection associated with perineal wound closure.

Immediate breast reconstruction using the skin expander: a modification in technique.

A modification in the technique of immediate postmastectomy reconstruction of the small to moderate-size breast using the skin expander is presented. The advantage of the technique is that it simplifies the replacement of the expander with the permanent prosthesis while establishing a symmetrical inframammary crease and a laterally supported breast mound. Representative cases are shown.

Subcutaneous mastectomy. Promises and pitfalls.

The subcutaneous mastectomy is constantly being reevaluated and its place in the treatment of breast dysplasias debated. Our indications for the procedure and the techniques, which we believe provide a thorough, safe, and cosmetically satisfactory result, are presented.

Soft-tissue expander for delayed and immediate breast reconstruction.

The soft-tissue expander is a new and clinically useful method for delayed and immediate reconstruction of the breast. Our experience and reported experience to date using submuscular implantation have resulted in an aesthetically satisfactory reconstructed breast without concomitant donor site morbidity.

A re-appraisal and modification of the Lauritzen technique of microvascular anastomoses.

Twenty arterial anastomoses were performed in ten Sprague-Dawley rats, utilising a modification of the Lauritzen technique which was being re-evaluated because of its apparent simplicity and high patency rate. In 90% of the anastomoses performed patency was confirmed one week after operation. Histological examination at this time revealed neo-endothelialisation across the anastomotic site. It is clear that this technique is a very efficient method of anastomosing vessels of similar size in the experimental animal where tension is not a problem and should be considered for use in suitable cases in man.

Plastic surgery in Tunisia--an experience with CARE/MEDICO.

From October, 1978, to October, 1979, the author worked for CARE/MEDICO in Tunisia. The purpose of this stay was to initiate the formation of a plastic surgery program at the Aziza Othmana, a university-affiliated hospital in Tunis. The roles of the Visiting Volunteer Specialist and contract surgeon are described. The major difficulty in establishing a long-term project was the failure of the host country to provide a counterpart to codirect the service and ensure continuity of the training program. Though overseas work has many rewards, the author suggests that several short tours of duty precede a longer commitment.

The needle holder.

A technique to facilitate the retrieval of a microneedle following knot tying is described. A small foam block is mounted on the non-dominant-hand forceps, where the needle can be easily stored and relocated during microsurgical procedures.

Microvascular free groin flap for soft-tissue coverage of the extremities.

Six cases of microvascular free flap, composite tissue transfer are presented. The advantages of utilizing this modality of tissue coverage are that it is a direct one-stage procedure which, in experienced hands and using a two-team approach, can solve complex reconstructive problems with a minimal hospital stay and minimal morbidity.

Free groin flap to the hand with end-to-side vessel anastomosis.

A single case of successful free groin flap transfer to the hand is presented. Its use demonstrates a distinct advantage of free flap transfer, preventing dependent edema and enforced immobilization of the hand necessitated by conventional technics. It also demonstrates a successful end-to-side microarterial anastomosis, thus allowing a continued normal blood supply to the hand.

Surgical management of chronic hidradenitis suppurativa of the perineum.

Two cases of chronic hidradenitis suppurativa of the perineum are presented. Both patients suffered through many years of discomfort and social isolation, undergoing multiple temporizing procedures. The treatment course pursued is described in detail. It is hoped that a greater appreciation of the disabling nature of this disease will lead to earlier, definitive therapy.