High dose rate brachytherapy: its clinical applications and treatment guidelines

Feasibility study of patient-specific four-dimensional in vivo tracking system for high-dose-rate brachytherapy: Experimental evaluation

BACKGROUND

High-dose-rate (HDR) brachytherapy using Iridium-192 as a radiation source is widely employed in cancer treatment to deliver concentrated radiation doses while minimizing normal tissue exposure. In this treatment, the precision with which the sealed radioisotope source is delivered significantly impacts clinical outcomes.

PURPOSE

This study aims to evaluate the feasibility of a new four-dimensional (4D) in vivo source tracking and treatment verification system for HDR brachytherapy using a patient-specific approach.

METHODS

A hardware system was developed for the experiments, featuring a high-resolution compact gamma camera with a redesigned diverging collimator, enhanced detector, and precision control system. The collimator was redesigned to improve spatial resolution by reducing the hole size and increasing the hole array, while reducing the pixel size of the detector and increasing the number of pixels. The performance was evaluated using Monte Carlo simulations, which demonstrated significant improvements in spatial resolution. Experiments were conducted in a controlled setup using a phantom to simulate clinical conditions. The phantom was positioned at various distances from the gamma camera (327.30, 377.30, and 427.30 mm) and imaged at multiple angles. The accuracy of the system was tested in four different cases: three with fixed distances and one employing a multi-focusing method. The multi-focusing method allows the gamma camera to adjust its focus based on the anatomical characteristics of individual patients, thereby enhancing source-tracking accuracy. The performance of the system was evaluated under these four different scenarios. The Euclidean distance and three-dimensional gamma analysis were used to evaluate tracking accuracy and dose distribution.

RESULTS

The redesigned collimator demonstrated significant improvements (compared to the previous design) in the spatial resolution of the gamma camera, showing 34.21% and 23.46% enhancements in the horizontal and vertical profiles, respectively. These improvements in gamma camera resolution are crucial for enhancing the tracking system's accuracy. The experimental results demonstrated varying degrees of accuracy across different cases, reflecting the performance of the system under different conditions. The average Euclidean distance errors were Case 1 (327.30 mm): 1.358 mm; Case 2 (377.30 mm): 1.731 mm; Case 3 (427.30 mm): 1.973 mm; and Case 4 (multi-focusing): 1.527 mm. The gamma pass rates for the four cases were:- Case 1: 86.39%; Case 2: 75.28%; Case 3: 72.22%; and Case 4: 81.67% (1 mm/1%). For the 2 mm/2% criterion, the gamma pass rates were 97.11, 94.72, 92.38, and 96.78% for Cases 1, 2, 3, and 4, respectively. Case 4 (multi-focusing) showed an improvement over Case 3, with a 22.6% reduction in the average Euclidean distance error and a 13.1% increase in the gamma pass rate (1 mm/1%).

CONCLUSION

These results demonstrate that the new 4D in vivo source tracking and treatment verification system for HDR brachytherapy is feasible and has potential clinical benefits.

High-Dose-Rate Brachytherapy in Cervical and Endometrial Cancer Patients: A Retrospective Study From a Tertiary Cancer Center in the UAE

Purpose This study evaluates the therapeutic outcomes and practical application of high-dose-rate (HDR) brachytherapy in managing cervical and endometrial cancers at a tertiary hospital in the UAE, focusing on treatment efficacy, safety, and patient-reported outcomes. Methods A retrospective analysis was conducted on 368 female patients treated between January 2008 and January 2022. Data included demographic information, cancer type, histopathology, treatment details, and survival outcomes. Statistical analyses were performed using descriptive and inferential statistics. Results The cohort comprised 275 cervical cancer patients (74.73%) and 93 endometrial cancer patients (25.27%). The majority were non-nationals (79.62%). The mean age was 57 years. Squamous cell carcinoma was the most common histopathological type (63.59%). HDR brachytherapy was administered to 290 patients (79.89%). The 12-month survival probability was significantly higher in the HDR-Brachy group (75%, 95% CI: 60% to 85%) compared to the noHDR-Brachy group (50%, 95% CI: 35% to 65%), with a hazard ratio of 0.953 (p=0.0035). At the last review, 86.68% of patients were alive, and disease progression was observed in 37.88% of patients. Conclusion HDR brachytherapy significantly improves survival outcomes in cervical and endometrial cancer patients. Continued efforts to enhance access and standardize brachytherapy protocols are essential to optimize treatment efficacy and patient outcomes in similar healthcare settings.

Integration of Ultrasound in Image-Guided Adaptive Brachytherapy in Cancer of the Uterine Cervix

Cervical cancer continues to be a public health concern, as it remains the second most common cancer despite screening programs. It is the third most common cause of cancer-related death for women, and the majority of cases happen in developing nations. The standard treatment for locally advanced cervical cancer involves the use of external beam radiation therapy, along with concurrent chemotherapy, followed by an image-guided adaptive brachytherapy (IGABT) boost. The five-year relative survival rate for European women diagnosed with cervical cancer was 62% between 2000 and 2007. Updated cervical cancer treatment guidelines based on IGABT have been developed by the Gynecological working group, which is composed of the Group Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology. The therapeutic strategy makes use of three-dimensional imaging, which can be tailored to the target volume and at-risk organs through the use of computed tomography or magnetic resonance imaging. Under anaesthesia, the brachytherapy implantation is carried out. Ultrasonography is utilised to assess the depth of the uterine cavity and to facilitate the dilation of the uterine canal during the application insertion. In this study, we examine data from the international literature regarding the application of ultrasound in cervical cancer brachytherapy.

Feasibility of 4D HDR brachytherapy source tracking using x-ray tomosynthesis: Monte Carlo investigation

PURPOSE

High dose rate (HDR) brachytherapy rapidly delivers dose to targets with steep dose gradients. This treatment method must adhere to prescribed treatment plans with high spatiotemporal accuracy and precision, as failure to do so may degrade clinical outcomes. One approach to achieving this goal is to develop imaging techniques to track HDR sources in vivo in reference to surrounding anatomy. This work investigates the feasibility of using an isocentric C-arm x-ray imager and tomosynthesis methods to track Ir-192 HDR brachytherapy sources in vivo over time (4D).

METHODS

A tomosynthesis imaging workflow was proposed and its achievable source detectability, localization accuracy, and spatiotemporal resolution were investigated in silico. An anthropomorphic female XCAT phantom was modified to include a vaginal cylinder applicator and Ir-192 HDR source (0.5 × 0.5 × 5.0 mm3 ), and the workflow was carried out using the MC-GPU Monte Carlo image simulation platform. Source detectability was characterized using the reconstructed source signal-difference-to-noise-ratio (SDNR), localization accuracy by the absolute 3D error in its measured centroid location, and spatiotemporal resolution by the full-width-at-half-maximum (FWHM) of line profiles through the source in each spatial dimension considering a maximum C-arm angular velocity of 30° per second. The dependence of these parameters on acquisition angular range (θtot = 0°-90°), number of views, angular increment between views (Δθ = 0°-15°), and volumetric constraints imposed in reconstruction was evaluated. Organ voxel doses were tallied to derive the workflow's attributable effective dose.

RESULTS

The HDR source was readily detected and its centroid was accurately localized with the proposed workflow and method (SDNR: 10-40, 3D error: 0-0.144 mm). Tradeoffs were demonstrated for various combinations of image acquisition parameters; namely, increasing the tomosynthesis acquisition angular range improved resolution in the depth-encoded direction, for example from 2.5 mm to 1.2 mm between θtot = 30o and θtot = 90o , at the cost of increasing acquisition time from 1 to 3 s. The best-performing acquisition parameters (θtot = 90o , Δθ = 1°) yielded no centroid localization error, and achieved submillimeter source resolution (0.57 × 1.21 × 5.04 mm3 apparent source dimensions, FWHM). The total effective dose for the workflow was 263 µSv for its required pre-treatment imaging component and 7.59 µSv per mid-treatment acquisition thereafter, which is comparable to common diagnostic radiology exams.

CONCLUSIONS

A system and method for tracking HDR brachytherapy sources in vivo using C-arm tomosynthesis was proposed and its performance investigated in silico. Tradeoffs in source conspicuity, localization accuracy, spatiotemporal resolution, and dose were determined. The results suggest this approach is feasible for localizing an Ir-192 HDR source in vivo with submillimeter spatial resolution, 1-3 second temporal resolution and minimal additional dose burden.

Efficacy of Nanoparticles in dose enhancement with high dose rate of Iridium-192 and Cobalt-60 radionuclide sources in the Treatment of Cancer: A systematic review

ABSTRACTS

A key challenge in radiation therapy is to maximize the radiation dose to cancer cells while minimizing damage to healthy tissues. In recent years, the introduction of remote after-loading technology such as high-dose-rate (HDR) brachytherapy becomes the safest and more precise way of radiation delivery compared to classical low-dose-rate (LDR) brachytherapy. However, the axially symmetric dose distribution of HDR with single channel cylindrical applicator, the physical "dead-space" with multichannel applicators, and shielding material heterogeneities are the main challenges of HDR brachytherapy. Thus, this review aimed to quantitatively evaluate the dose enhancement factor (DEF) produced by high atomic number nanoparticles (NPs) which increases the interaction probability of photons mainly through the photoelectric effect induced in the great number of atoms contained in each nanoparticle. The NPs loaded to the target volume create a local intensification effect on the target tissue that allows imparting the prescribed therapeutic dose using lower fluxes of irradiation and spare the surrounding healthy tissues. An electronic database such as PubMed/Medline, Embase, Scopus, and Google Scholar was searched to retrieve the required articles. Unpublished articles were also reached by hand from available sources. The dose is increased using the high atomic number of nanoparticle elements under the high dose iridium radionuclide whereas the cobalt-60 radionuclide source did not. However, much work is required to determine the dose distribution outside the target organ or tumor to spare the surrounding healthy tissues for the iridium source and make compressive work to have more data for the cobalt source.

American Brachytherapy Society (ABS) consensus statement for soft-tissue sarcoma brachytherapy

PURPOSE

Growing data supports the role of radiation therapy in the treatment of soft tissue sarcoma (STS). Brachytherapy has been used for decades in the management of STS and can be utilized as monotherapy or as a boost to external beam radiation. We present updated guidelines from the American Brachytherapy Society regarding the utilization of brachytherapy in the management of STS.

METHODS AND MATERIALS

Members of the American Brachytherapy Society with expertise in STS and STS brachytherapy created an updated clinical practice guideline including step-by-step details for performing STS brachytherapy based on a literature review and clinical experience.

RESULTS

Brachytherapy monotherapy should be considered for lower-recurrence risk patients or after a local recurrence following previous external beam radiation; a brachytherapy boost can be considered in higher-risk patents meeting implant criteria. Multiple dose/fractionation regimens are available, with determination based on tumor location and treatment intent. Techniques to limit wound complications are based on the type of wound closure; wound complication can be mitigated with a delay in the start of brachytherapy with immediate wound closure or by utilizing a staged reconstruction technique, which allows an earlier treatment start with a delayed wound closure.

CONCLUSIONS

These updated guidelines provide clinicians with data on indications for STS brachytherapy as well as guidelines on how to perform and deliver high quality STS brachytherapy safely with minimal toxicity.

EQD2 Analyses of Vaginal Complications in Exclusive Brachytherapy for Postoperative Endometrial Carcinoma

Background: To evaluate whether EQD2(α/β = 3Gy) at 2 cm3 of the most exposed area of the vagina is related to late vaginal toxicity in postoperative endometrial cancer (PEC) patients (p) treated with exclusive brachytherapy (BT). Methods: From 2014 to 2017, 43p were included in this study. BT was administered: 3-fractions of 6Gy in 37p and 2-fractions of 7.5Gy in 6p. The dose was prescribed at a depth of 5 mm from the applicator surface with dose-point optimization based on distance. The active treatment length was 2.5 cm. CTV-D90 and the dose to the most exposed 2 cm3 of the vagina was calculated for each patient. Late toxicity of the bladder and rectum was assessed using Radiation Therapy Oncology Group (RTOG) criteria, and vaginal toxicity by objective Late Effects Normal Tissue Task Force (LENT)-Subjective, Objective, Management, Analytic (SOMA) (LENT-SOMA) criteria. Statistics: frequency tables, mean, median, range, standard deviation, and box plot. Results: The median follow-up was 51 months (12-68). 20 p (46.5%) and 2 p (4.7%) developed G1 and G2 vaginal complications, respectively. Only 1/2 p-G2 receiving EQD2(α/β = 3Gy) at 2 cm3 >68Gy presented vaginal shortening and 18/20 p-G1 received doses < 68Gy. Conclusions: PECp receiving exclusive brachytherapy with doses < 68Gy EQD2(α/β = 3Gy) at 2 cm2 of the vagina presented only G0-G1 vaginal toxicity, except for one with bleeding telangiectasias. Larger prospective studies are necessary to confirm the present results.

Independent assessment of source transit time for the BEBIG SagiNova® cobalt-60 high dose rate brachytherapy afterloader

Independent verification of transit time and the methodology employed in commercial high dose rate (HDR) afterloaders to compensate its effect is an important part of their commissioning and quality assurance. This study aimed to independently evaluate the Co-60 source transit time of the new BEBIG SagiNova® HDR afterloader unit by employing a dosimetric approach using a well-type ionization chamber. The source was placed at three dwell positions (DPs) to mimic a variety of clinical situations with different distances from the afterloader unit. The distances of the DPs to the afterloader were 129.37 cm, 124.50 cm and 118.57 cm. Plans were generated using the SagiPlan® treatment planning system to produce 3, 5, 10, 15, 20, 30, 40, 60 and 120 s dwell times (DTs). The residual transit times (following any possible system compensation) were assessed using the ESTRO-recommended approach of obtaining transit time compensation factors and another strategy established for teletherapy sources. The mean residual transit time depended on the distance between the afterloader and the DP, ranging from 0.43 to 1.10 s. The transit dose contribution was case-specific, ranging from 0.4% for a 60 s DT at the nearest DP to the afterloader up to 15.6% for a 3 s DT at the furthest DP from the unit. The results show that currently SagiNova® afterloader does not apply transit time compensation and suggest a 0.2-0.5 s compensation for each arrival and departure DP from/to the afterloader, depending on position in an 11 cm active length.

A dosimetric comparison of Volumetric Modulated Arc Therapy (VMAT) and High Dose Rate (HDR) brachytherapy in localized cervical cancer radiotherapy

BACKGROUND

Cervical cancer radiotherapy is usually administrated through 3-Dimensional Conformal Radiation Therapy (3DCRT) followed by a brachytherapy (BT) boost.

PURPOSE

To investigate whether Volumetric Modulated Arc Therapy (VMAT) can replace High Dose Rate (HDR) intracavitary BT boost for patients undergoing cervical cancer radiotherapy.

MATERIALS AND METHODS

Computed Tomography (CT) images for ten patients with tandem and ovoids were included in this study. Target volumes, rectum, bladder, sigmoid, small bowel and both femoral heads were delineated. Two plans were carried out including (a) a BT plan optimized manually by modifying dwell time and Ir-192 source positions, (b) a VMAT plan generated using two partial arcs with 10 MV photon beam. The prescribed dose was 7 Gy. The relevant dose volume parameters (DVPs) of target volumes and OARs for the two plans were analyzed statistically using SPSS Wilcoxon Signed Rank test.

RESULTS

VMAT plan showed a significant reduction of 9.1%, 9.3%, 15.4%, 14.4% and 13.1% in rectum maximum dose, rectum D2cc, bladder maximum dose, bladder D2cc and sigmoid maximum dose (P < 0.05). VMAT and BT plans showed comparable D2cc of sigmoid and small bowel maximum doses (P = 0.333 and P = 0.646). On the other hand, VMAT showed significantly higher small bowel D2cc and maximum point dose for both femoral heads comparing to BT plan (P < 0.05). Also, VMAT plan yielded greater homogeneous target coverage compared to BT plan (P < 0.05).

CONCLUSION

The study demonstrated that VMAT plan achieves significant dose reduction of rectum, bladder and sigmoid, as well as superior homogeneous target coverage compared to BT plan. On the other hand, VMAT delivers more radiation exposures to small bowel and femoral heads.

High-dose-rate brachytherapy in severe trismus: Making it happen!

Brachytherapy has been widely employed as a salvage or adjuvant modality in localized early and/or recurrent lesions. In recent years, advances in brachytherapy techniques have helped to achieve better loco-regional disease control and higher survival rates at the cost of limited morbidity. This is mainly owing to the development of technologically advanced three-dimensional computer planning systems and treatment delivery techniques. Low-dose-rate brachytherapy has been substituted by high-dose-rate and pulsed-dose-rate techniques, which allow better dose optimization. Inter-disciplinary approach results in fabrication of customized intra-oral surface mould, which allows accurate dose delivery, excellent dose distribution, and is less time-consuming. However, fabrication of surface mould becomes extremely challenging when intra-oral anatomic factors are unfavorable. We present a report on the management of a previously-irradiated completely edentulous patient with severe trismus for whom high-dose-rate surface mould brachytherapy had been prescribed. A unique, reliable, and practical solution has been presented based firmly on the scientific knowledge of contemporary implant dentistry.

Dosimetric characterization of the M-15 high-dose-rate Iridium-192 brachytherapy source using the AAPM and ESTRO formalism

The Source Production & Equipment Co. (SPEC) model M−15 is a new Iridium−192 brachytherapy source model intended for use as a temporary high‐dose‐rate (HDR) brachytherapy source for the Nucletron microSelectron Classic afterloading system. The purpose of this study is to characterize this HDR source for clinical application by obtaining a complete set of Monte Carlo calculated dosimetric parameters for the M‐15, as recommended by AAPM and ESTRO, for isotopes with average energies greater than 50 keV. This was accomplished by using the MCNP6 Monte Carlo code to simulate the resulting source dosimetry at various points within a pseudoinfinite water phantom. These dosimetric values next were converted into the AAPM and ESTRO dosimetry parameters and the respective statistical uncertainty in each parameter also calculated and presented. The M−15 source was modeled in an MCNP6 Monte Carlo environment using the physical source specifications provided by the manufacturer. Iridium−192 photons were uniformly generated inside the iridium core of the model M−15 with photon and secondary electron transport replicated using photoatomic cross‐sectional tables supplied with MCNP6. Simulations were performed for both water and air/vacuum computer models with a total of 4×109 sources photon history for each simulation and the in‐air photon spectrum filtered to remove low‐energy photons below δ=10%keV. Dosimetric data, including D(r,θ),gL(r),F(r,θ),Φan(r), and φ¯an, and their statistical uncertainty were calculated from the output of an MCNP model consisting of an M−15 source placed at the center of a spherical water phantom of 100 cm diameter. The air kerma strength in free space, SK, and dose rate constant, Λ, also was computed from a MCNP model with M−15Iridium−192 source, was centered at the origin of an evacuated phantom in which a critical volume containing air at STP was added 100 cm from the source center. The reference dose rate, D˙(r0,θ0)≡D˙(1cm,π/2), is found to be 4.038±0.064 cGy mCi−1 h−1. The air kerma strength, SK, is reported to be 3.632±0.086 cGy cm2 mCi−1 g−1, and the dose rate constant, Λ, is calculated to be 1.112±0.029 cGy h−1 U−1. The normalized dose rate, radial dose function, and anisotropy function with their uncertainties were computed and are represented in both tabular and graphical format in the report. A dosimetric study was performed of the new M−15Iridium−192 HDR brachytherapy source using the MCNP6 radiation transport code. Dosimetric parameters, including the dose‐rate constant, radial dose function, and anisotropy function, were calculated in accordance with the updated AAPM and ESTRO dosimetric parameters for brachytherapy sources of average energy greater than 50 keV. These data therefore may be applied toward the development of a treatment planning program and for clinical use of the source.

PACS numbers: 87.56.bg, 87.53.Jw

A case report of ultrasound-guided interstitial brachytherapy for abdominal wall metastases of ovarian cancer

Purpose

To report the treatment effect of interstitial brachytherapy for abdominal wall metastases of ovarian cancer.

Material and methods

The patient is a 44-year-old female with a diagnosis of stage IA ovarian cancer. After surgery and two cycles of chemotherapy with paclitaxel and carboplatin, the patient noticed dull pain in the lower abdomen and found a mass located in the subcutaneous tissue, below the operative incision. A diagnostic biopsy showed abdominal wall metastases. After external radiotherapy with a dose of 39.6 Gy in 22 fractions, the residual tumor was treated with interstitial brachytherapy under ultrasound guidance. The brachytherapy dose was 18 Gy in 6 fractions of 3 Gy each.

Results

After 3 weeks of brachytherapy, the tumor had disappeared completely. Interstitial brachytherapy was feasible.

Conclusions

Interstitial brachytherapy may be a proposed treatment strategy for inoperable superficial metastases, especially for low radiosensitivity cancer.

Dosimetric analysis and clinical outcomes in CT-based mould brachytherapy in early oral cancers in patients unfit for surgery

Purpose

Brachytherapy in the oral cavity is an important alternative to conventional treatment, and provides a high localized dose and short overall treatment time. A rapid fall of dose beyond radioactive source makes it possible for increased tumour control and sparing surrounding tissue, while short overall treatment duration reduces risk of tumour repopulation. Moulds are fabricated to hold the catheters in position as closely as possible to tumour surface to provide adequate dose coverage of tumour volume and increase distance to other normal surrounding structures. Image based planning and dose optimisation help in better defining target volume and dose coverage.

Material and methods

A retrospective analysis of patients of early squamous cell carcinomas of lip and buccal mucosa from September 2011 to June 2014 to study response to mould brachytherapy. Double plane moulds were prepared for all lip cancer cases and single plane for buccal mucosa cases. Patients are being followed up till disease recurrence. In this study evaluation was done of the technique used, planning details, response to therapy, and reactions encountered.

Results

Nine patients treated by mould therapy were reviewed; seven cases were of lip and two of buccal mucosal cancers. Dose delivered ranged from 12.5-48 Gy in fraction sizes of 2.5-3.5 Gy. Equivalent dose in 2 Gy fractions (EQD2) ranged from 18-64 Gy. Maximum dose to organs at risk (OAR) was 91% of prescribed dose. Local mucositis was only reaction in all cases, which resolved in 3-6 weeks. Median follow-up was 19 months. Eight out of nine patients are in remission at a minimum of 7 months (1 case, rest over 14 months) post therapy and only patient had nodal recurrence at 18 months.

Conclusions

Mould therapy is an effective treatment method for selected early and superficial squamous cell carcinomas of the oral cavity, although indications are limited.

High dose rate versus low dose rate brachytherapy for oral cancer--a meta-analysis of clinical trials

OBJECTIVE

To compare the efficacy and safety of high dose rate (HDR) and low dose rate (LDR) brachytherapy in treating early-stage oral cancer.

DATA SOURCES

A systematic search of MEDLINE, EMBASE and Cochrane Library databases, restricted to English language up to June 1, 2012, was performed to identify potentially relevant studies.

STUDY SELECTION

Only randomized controlled trials (RCT) and controlled trials that compared HDR to LDR brachytherapy in treatment of early-stage oral cancer (stages I, II and III) were of interest.

DATA EXTRACTION AND SYNTHESIS

Two investigators independently extracted data from retrieved studies and controversies were solved by discussion. Meta-analysis was performed using RevMan 5.1. One RCT and five controlled trials (607 patients: 447 for LDR and 160 for HDR) met the inclusion criteria. The odds ratio showed no statistically significant difference between LDR group and HDR group in terms of local recurrence (OR = 1.12, CI 95% 0.62-2.01), overall mortality (OR = 1.01, CI 95% 0.61-1.66) and Grade 3/4 complications (OR = 0.86, CI 95% 0.52-1.42).

CONCLUSIONS

This meta-analysis indicated that HDR brachytherapy was a comparable alternative to LDR brachytherapy in treatment of oral cancer. HDR brachytherapy might become a routine choice for early-stage oral cancer in the future.

Non isocentric film-based intracavitary brachytherapy planning in cervical cancer: a retrospective dosimetric analysis with CT planning

Purpose

To compare intracavitary brachytherapy dose estimation for organs at risk (bladder and rectum) based on semi-orthogonal reconstruction of radiographs on non-isocentric X-ray unit and Computed Tomography (CT) – based volumetric planning in cervical cancer.

Material and methods

Bladder and rectal points as per International Commission on Radiation Units and Measurements (ICRU) report 38, were retrospectively evaluated on 15 high dose rate intracavitary brachytherapy applications for cervical cancer cases. With the same source configuration as obtained during planning on radiographs performed on a non-isocentric X-ray unit, the mean doses to 2cc of most irradiated part of bladder and rectum were computed by CT planning and these estimates were compared with the doses at ICRU bladder and rectal points.

Results

The mean ICRU point dose for bladder was 3.08 Gy (1.9-5.9 Gy) and mean dose to 2 cc (D2cc) bladder was 6.91 Gy (2.9-12.2 Gy). ICRU rectal dose was 3.8 Gy (2.4-4.45 Gy) and was comparable with D2cc rectum dose 4.2 Gy (2.8-5.9 Gy). Comparison of mean total dose (ICRU point vs. D2cc) for each patient was found to be significantly different for bladder (p = 0.000), but not for rectum (p = 0.08).

Conclusions

On comparison of ICRU point based planning with volumetric planning on CT, it was found that bladder doses were underestimated by the film based method. However, the rectal doses were found to be similar to the D2cc doses. The results with non isocentric film based treatment planning were similar to the existing literature on orthogonal film based simulator planning.

High dose rate brachytherapy for oral cancer

Brachytherapy results in better dose distribution compared with other treatments because of steep dose reduction in the surrounding normal tissues. Excellent local control rates and acceptable side effects have been demonstrated with brachytherapy as a sole treatment modality, a postoperative method, and a method of reirradiation. Low-dose-rate (LDR) brachytherapy has been employed worldwide for its superior outcome. With the advent of technology, high-dose-rate (HDR) brachytherapy has enabled health care providers to avoid radiation exposure. This therapy has been used for treating many types of cancer such as gynecological cancer, breast cancer, and prostate cancer. However, LDR and pulsed-dose-rate interstitial brachytherapies have been mainstays for head and neck cancer. HDR brachytherapy has not become widely used in the radiotherapy community for treating head and neck cancer because of lack of experience and biological concerns. On the other hand, because HDR brachytherapy is less time-consuming, treatment can occasionally be administered on an outpatient basis. For the convenience and safety of patients and medical staff, HDR brachytherapy should be explored. To enhance the role of this therapy in treatment of head and neck lesions, we have reviewed its outcomes with oral cancer, including Phase I/II to Phase III studies, evaluating this technique in terms of safety and efficacy. In particular, our studies have shown that superficial tumors can be treated using a non-invasive mold technique on an outpatient basis without adverse reactions. The next generation of image-guided brachytherapy using HDR has been discussed. In conclusion, although concrete evidence is yet to be produced with a sophisticated study in a reproducible manner, HDR brachytherapy remains an important option for treatment of oral cancer.

Comparison of conventional and CT-based planning for intracavitary brachytherapy for cervical cancer: target volume coverage and organs at risk doses

BACKGROUND

To compare intracavitary brachytherapy (ICBT) planning methods for cervical cancer, based on either orthogonal radiographs (conventional plan) or CT sections (CT plan); the comparison focused on target volume coverage and dose volume analysis of organs at risk (OARs), by representing point doses defined by the International Commission on Radiation Units and Measurement (ICRU) and dose volume histograms (DVHs) from 3D planning.

METHODS

We analyzed the dosimetric data for 62 conventional and CT-based ICBT plans. The gross tumor volume (GTV), clinical target volume (CTV) and organs at risk (OAR)s were contoured on the CT-plan. Point A and ICRU 38 rectal and bladder points were defined on reconstructed CT images.

RESULTS

Patients were categorized on the basis of whether the >95% isodose line of the point-A prescription dose encompassed the CTV (group 1, n = 24) or not (group 2, n = 38). The mean GTV and CTV (8.1 cc and 20.6 cc) were smaller in group 1 than in group 2 (24.7 cc and 48.4 cc) (P <0.001). The mean percentage of GTV and CTV coverage with the 7 Gy isodose was 93.1% and 88.2% for all patients, and decreased with increasing tumor size and stage. The mean D2 and D5 rectum doses were 1.66 and 1.42 times higher than the corresponding ICRU point doses and the mean D2 and D5 bladder doses were 1.51 and 1.28 times higher. The differences between the ICRU dose and the D2 and D5 doses were significantly higher in group 2 than in group 1 for the bladder, but not for the rectum.

CONCLUSION

The CT-plan is superior to the conventional plan in target volume coverage and appropriate evaluation of OARs, as the conventional plan overestimates tumor doses and underestimates OAR doses.

The use of oral transmucosal fentanyl citrate during high-dose-rate gynecologic brachytherapy

Gynecologic brachytherapy is a form of cancer treatment in which radioactive sources are placed into the pelvic organs via specialized applicators. Traditional low-dose-rate (LDR) brachytherapy has been performed over several days in a hospital setting. Since the 1990s, high-dose-rate (HDR) brachytherapy has been used increasingly because of its decreased treatment time, outpatient administration, and equal or superior efficacy compared with LDR treatment. However, the management of procedural pain in the radiation oncology setting has not been studied extensively. The purpose of this article is to discuss the use of oral transmucosal fentanyl citrate (OTFC) for the management of pain during gynecologic HDR brachytherapy. OTFC provides noninvasive, rapid analgesia with a low incidence of side effects and may be appropriate for other forms of procedure-related cancer pain.

Monte Carlo characterization of the M-19 high dose rate Iridium-192 brachytherapy source

The MCNP5 Monte Carlo code was used to simulate the dosimetry of an M-19 iridium-192 high dose rate brachytherapy source in both air/vacuum and water environments with the in-air photon spectrum filtered to remove low-energy photons below delta=10 keV. Dosimetric data was organized into an away-along table and was used to derive the updated AAPM Task Group Report No. 43 (TG-43U1) parameters including S(K), D(r, theta), lamda, gL(r), F(r, theta), phi an(r), and phi an, and their respective statistical uncertainties.

The emergence of advanced brachytherapy techniques for common malignancies

The recent advent and integration of sophisticated radiation planning and imaging modalities has improved the quality of brachytherapy treatments, allowing for more conformal radiation delivery. Further investigation and follow-up are necessary to demonstrate improvements in outcome and morbidity with these refined approaches.