Intrauterine Tandem Research Articles

PO41 Presentation Time: 4:45 PM: Initial Experience with the New Commercial Aarhus MR Compatible Hybrid Interstitial Brachytherapy Applicator in Indian Setting

<h3>Purpose -</h3> We have been using CT based intracavitary applicator in our clinic for cervical cancer. The advent of new hybrid applicator and short sequence cube MRI sequence opened up opportunity to do advanced MRI based brachytherapy in our clinic. We present the initial clinical experience of Aarhus ring and tandem MR compatible hybrid interstitial applicator with both straight and oblique needles and no ring channel (Varian may need to add TM) which was recently approved for use in a patient with bulky cervical cancer. <h3>Material and methods -</h3> A 45 years old lady, with initial diagnosis of carcinoma cervix, stage 1B3, completed External beam radiotherapy to a total dose of 45Gy in 25 Fractions, with a good clinical response, was taken up for further treatment with brachytherapy to a total dose of 28 Gy in 4 fractions. Brachytherapy was split into two applications one week apart and two treatment fractions delivered with each application, with 8 hours gap between each fraction.We used 60 degree Aarhus applicator set with Intrauterine tandem of 40 mm length and outer ring diameter of 32 mm. The Ring includes 19 guide holes for plastic interstitial needles arranged in 2 circles, 9 in inner circle for oblique needles and 10 in outer circle for straight needles.After external radiation patient underwent MRI pelvis with only T2 weighted axial and Cube sequences, which showed residual disease limited to cervix on the right side. The depth of needle insertion into the cervix was measured on MRI to be 3cms. Procedure performed under short general anaesthesia and 4 straight plastic needles through the ring were inserted with two on either side along with 4 cm central Tandem. CT and MR performed for both applications and fused. GTV-primary and HR CTV delineated on MRI, while OARs were delineated on CT. A dose of 7 Gy per fraction prescribed to HR CTV. An optimised plan was generated on eclipse treatment planning system with repeat CT planning for remaining fractions. <h3>Results -</h3> Treatment delivery went uneventful with very minimal blood loss. Average Dose per fraction received by 90 % of volume (D90) of HR CTV was 7.617 Gy and D98 of GTV primary was 10.35 Gy, delivering a total EQD2 of 89 Gy to HR CTV and at the same time delivering 115 Gy to the GTVp. OAR doses were well constrained with Bladder 2cc receiving 79.25 Gy, Rectum 2cc constrained to 53.48 Gy, sigmoid 2cc to 58.99 Gy and small bowel to 51.98 Gy. <h3>Conclusions -</h3> We successfully implemented MRI based planning with new Aarhus applicator in our clinic. Procedure was uneventful with excellent dosimetry. We will continue to use it in our clinic for patients with locally advanced cancer.

3D Printing in Combination With Kelowna GYN Template-Based High-Dose Rate Interstitial Brachytherapy: Design and Dosimetric Results

The Kelowna GYN template is a perineal template for interstitial GYN brachytherapy designed for compatibility with a single channel vaginal cylinder. We present the first reported series of patients treated with this system and an additional 3D printed modification for utilization of this template with an intrauterine tandem. Indications generally included large tumors not amenable to intracavitary +/- free hand needles approach, and/or vaginal involvement (tumor thickness greater than 0.5 cm), and/or bladder invasion, and primary vaginal carcinomas and recurrent endometrial carcinomas with depth of invasion >0.5cm per GEC-ESTRO and ABS guidelines. The Kelowna template allows placement of interstitial needles with straight angled holes to provide coverage of the craniocaudal and lateral extension up to 3 cm from the vaginal cylinder. A modified applicator system using a custom 3D printed adaptor piece allows secure attachment of the tandem to the template for patients with an intact uterus. Transabdominal ultrasound was utilized to guide needle placement. CT treatment planning was performed with stepwise dwell weight adaptation and needle loading to achieve optimal dose coverage. Dosimetric data was evaluated including the D90 of high risk-clinical target volume (HR-CTV) with total EQD2 including whole pelvis radiotherapy. D2cc of OARs were recorded. Between October 2018 and January 2020, 17 patients (6 cervical; 7 recurrent endometrial; 2 vaginal; 2 recurrent cervical) with GYN malignancies were treated using the Kelowna template. All of the patients got external beam initially while all brachytherapy was done at a single NCI designated comprehensive cancer center. Patients with cervical cancer had bulky tumors at the time of implant (median HR-CTV volumes of 48 cm3). Indications for treatment were tumor >4cm (n = 5), vaginal involvement (n = 8), >0.5cm depth of invasion (n = 10). Median number of needles utilized was 12 (range 5 to 17). Treatments consisted of 3 or 4 fractions on consecutive days (BID). Dosing was 21 Gy in 3 fractions (n = 10), 24 Gy in 4 fx (n = 1), 28 Gy in 4 fx (n = 5), and 35 Gy in 5 fx (n = 1). For cervical and recurrent tumors, the median D90 was 81.6 Gy (range 86.3 - 92.6). For vaginal and recurrent endometrial, the median D90 was 86.9Gy (range 74.8 - 103.2). The median dose to OARs was within standard limits for intracavitary brachytherapy alone (EQD2cc for bladder of 72.4 Gy (IQR 67.2 - 77.5 Gy) and rectum of 61.2 Gy (IQR 58.7 - 62.7)). No patients needed adjustment in needle position between treatments. No patients had grade 3 acute toxicities. No patients had recurrence on follow-up. The Kelowna template allows for customized safe, robust, and reproducible implants with interstitial only or combined interstitial-intracavitary applicator for selected cases of bulky, asymmetric cervical, vaginal, and recurrent endometrial cancer and works well with customized 3D printed components.

A novel minimally invasive dynamic-shield, intensity-modulated brachytherapy system for the treatment of cervical cancer.

To present a novel, MRI-compatible dynamicshield intensity modulated brachytherapy (IMBT) applicator and delivery system using 192 Ir, 75 Se, and 169 Yb radioisotopes for the treatment of locally advanced cervical cancer. Needle-free IMBT is a promising technique for improving target coverage and organs at risk (OAR) sparing. The IMBT delivery system dynamically controls the rotation of a novel tungsten shield placed inside an MRI-compatible, 6-mm wide intrauterine tandem. Using 36 cervical cancer cases, conventional intracavitary brachytherapy (IC-BT) and intracavitary/interstitial brachytherapy (IC/IS-BT) (10Ci 192 Ir) plans were compared to IMBT (10Ci 192 Ir; 11.5Ci 75 Se; 44Ci 169 Yb). All plans were generated using the Geant4-based Monte Carlo dose calculation engine, RapidBrachyMC. Treatment plans were optimized then normalized to the same high-risk clinical target volume (HR-CTV) D90 and the D2cc for bladder, rectum, and sigmoid in the research brachytherapy planning system, RapidBrachyMCTPS. Plans were renormalized until either of the three OAR reached dose limits to calculate the maximum achievable HR-CTV D90 and D98 . Compared to IC-BT, IMBT with either of the three radionuclides significantly improves the HR-CTV D90 and D98 by up to 5.2%±0.3% (P<0.001) and 6.7%±0.5% (P<0.001), respectively, with the largest dosimetric enhancement when using 169 Yb followed by 75 Se and then 192 Ir. Similarly, D2cc for all OAR improved with IMBT by up to 7.7%±0.6% (P<0.001). For IC/IS-BT cases, needle-free IMBT achieved clinically acceptable plans with 169 Yb-based IMBT further improving HR-CTV D98 by 1.5%±0.2% (P=0.034) and decreasing sigmoid D2cc by 1.9%±0.4% (P=0.048). Delivery times for IMBT are increased by a factor of 1.7, 3.3, and 2.3 for 192 Ir, 75 Se, and 169 Yb, respectively, relative to conventional 192 Ir BT. Dynamic shield IMBT provides a promising alternative to conventional IC- and IC/IS-BT techniques with significant dosimetric enhancements and even greater improvements with intermediate energy radionuclides. The ability to deliver a highly conformal, OAR-sparing dose without IS needles provides a simplified method for improving the therapeutic ratio less invasively and in a less resource intensive manner.

SU‐F‐T‐47: MRI T2 Exclusive Based Planning Using the Endocavitary/interstitial Gynecological Benidorm Applicator: A Proposed TPS Library and Preplan Efficient Methodology

Purpose:ABS and GEC‐ESTRO have recommended MRI T2 for image guided brachytherapy. Recently, a new applicator (Benidorm Template, TB) has been developed in our Department (Rodriguez et al 2015). TB is fully MRI compatible because the Titanium needles and it allows the use of intrauterine tandem. Currently, TPS applicators library are not currently available for non‐rigid applicators in case of interstitial component as the TB.The purpose of this work is to present the development of a library for the TB, together with its use on a pre‐planning technique. Both new goals allow a very efficient and exclusive T2 MRI based planning clinical TB implementation.Methods:The developed library has been implemented in Oncentra Brachytherapy TPS, version 4.3.0 (Elekta) and now is being implemented on Sagiplan v 2.0 TPS (Eckert&amp;Ziegler BEBIG). To model the TB, free and open software named FreeCAD and MeshLab have been used. The reconstruction process is based on three inserted A‐vitamin pellets together with the data provided by the free length. The implemented preplanning procedure is as follow: 1) A MRI T2 acquisition is performed with the template in place just with the vaginal cylinder (no uterine tube nor needles). 2) The CTV is drawn and the required needles are selected using a developed Java based application and 3) A post‐implant MRI T2 is performed.Results:This library procedure has been successfully applied by now in 25 patients. In this work the use of the developed library will be illustrated with clinical examples. The preplanning procedure has been applied by now in 6 patients, having significant advantages: needle depth estimation, needle positions and number are optimized a priori, time saving, etcConclusion:TB library and pre‐plan techniques are feasible and very efficient and their use will be illustrated in this work.

Uterine perforation and its dosimetric implications in cervical cancer high-dose-rate brachytherapy

PurposeTo retrospectively assess the incidence of sub-serosal and uterine perforation of intra-uterine tandem in intracavitary high-dose-rate (HDR) brachytherapy for cervical cancer, and to evaluate its dosimetric implications on computed tomography (CT)-based treatment planning.Material and methodsComputed tomography images and brachytherapy plans of cervical cancer patients treated from February 2006 to December 2012 were reviewed for sub-optimal implants (sub-serosal and uterine perforation), and their correlation with cancer FIGO stage and patients’ age. For each patient, the plans showing sub-optimal insertion of intra-uterine tandem were analyzed and compared to plans with adequate insertion. The difference in dose coverage of clinical-target-volume (CTV) and variation of the dose delivered to organs-at-risk (OARs) rectum and bladder were evaluated.ResultsA total of 231 brachytherapy plans for 82 patients were reviewed. We identified 12 (14.6%) patients and 14 (6%) applications with uterine perforation, and 12 (14.6%) patients and 20 (8.6%) applications with sub-serosal insertion of tandem. Data analysis showed that advanced stage correlates with higher incidence of sub-optimal implants (p = 0.005) but not the age (p = 0.18). Dose-volume-histograms (DVHs) analysis showed large variations for CTV dose coverage: D90 significantly decreased with average of –115.7% ± 134.9% for uterine perforation and –65.2% ± 82.8% for sub-serosal insertion (p = 0.025). The rectum and bladder dose assessed by D2cc increased up to 70.3% and 43.8%, respectively, when sub-optimal insertion of uterine tandem occurred.ConclusionsWe report a low incidence of uterine perforation and sub-serosal insertion of uterine tandem in intracavitary HDR brachytherapy for cervical cancer. However, the effects on treatment plan dosimetry can be considerably detrimental. Therefore, we recommend image-guided insertion, at least for the challenging cases.

TU-D-BRB-06: Localizing Intracavitary Brachytherapy Applicators from Conebeam CT X-Ray Projections Via a Novel Iterative Forward Projection Matching (IFPM) Algorithm

Purpose: To present a novel method for reconstructing the 3D pose (positions & orientations) of radio‐opaque objects of known but arbitrary shape from a small set of 2D x‐ray projections, in support of intraoperative brachytherapy planning. Methods and materials: IFPM finds the object pose by minimizing the sum‐of‐squared‐intensity‐differences (SSD) between the computed and experimentally‐acquired auto‐segmented object projections. Starting with an initial estimate of the applicator pose, IFPM iteratively refines the pose parameters (positions and 3 Euler angles) until the SSD converges. The applicator model is a mesh of discrete points derived from a complex combinatorial geometric model of the actual applicator. Three pairs of computed and measured projection images, with known imaging geometry, are used. Projection images of an intrauterine tandem were acquired from Acuity digital‐simulator. Image pre‐processing step was performed to create blurred binary applicator‐only images. To quantify IFPM accuracy, the reconstructed 3D pose of the applicator model was forward projected and overlaid with the measured images and the dice similarity coefficient (DSC) was computed for each image‐pair.Results: In the numerical simulations, the tandem and colpostats positions (x, y, z) and orientations (α, β, γ) were estimated with (0.28, 0.3, 0.37) mm and (0.9, 0.8, 1.0)° accuracies, respectively. For the measured tandem images, the DSC was better than 0.88 for each image‐pair.Discussion: We have developed a new, accurate, and completely automatic method to localize radio‐opaque applicators of arbitrary shape from x‐ray projections. Also, no lateral film is required. By localizing the applicator internal structure and the sources, the effect of intra/inter‐applicator attenuation can be included in the resultant dose distribution. Further development and validation tests with tandem and colpostats will be performed for the accurate and robust applicator/sources localization in ICB patients. Supported by Varian Medical Systems

Retrospective Dosimetric Comparison of Low-Dose-Rate and Pulsed-Dose-Rate Intracavitary Brachytherapy Using a Tandem and Mini-Ovoids

The purpose of this study was to compare the dose distribution of Iridium-192 ( 192Ir) pulsed-dose-rate (PDR) brachytherapy to that of Cesium-137 ( 137Cs) low-dose-rate (LDR) brachytherapy around mini-ovoids and an intrauterine tandem. Ten patient treatment plans were selected from our clinical database, all of which used mini-ovoids and an intrauterine tandem. A commercial treatment planning system using AAPM TG43 formalism was used to calculate the dose in water for both the 137Cs and 192Ir sources. For equivalent system loadings, we compared the dose distributions in relevant clinical planes, points A and B, and to the ICRU bladder and rectal reference points. The mean PDR doses to points A and B were 3% ± 1% and 6% ± 1% higher than the LDR doses, respectively. For the rectum point, the PDR dose was 4% ± 3% lower than the LDR dose, mainly because of the 192Ir PDR source anisotropy. For the bladder point, the PDR dose was 1% ± 4% higher than the LDR dose. We conclude that the PDR and LDR dose distributions are equivalent for intracavitary brachytherapy with a tandem and mini-ovoids. These findings will aid in the transfer from the current practice of LDR intracavitary brachytherapy to PDR for the treatment of gynecologic cancers.

The Vienna applicator for combined intracavitary and interstitial brachytherapy of cervical cancer: Design, application, treatment planning, and dosimetric results

To present a combined intracavitary and interstitial dedicated applicator and magnetic resonance imaging (MRI) treatment planning for cervical cancer brachytherapy. A modified ring applicator allows interstitial needles to be implanted in parallel to the intrauterine tandem. MRI treatment planning based on a standard loading pattern with stepwise dwell weight adaptation and needle loading is performed to achieve optimal dose coverage and sparing of organs at risk. Dose constraints are applied for dose-volume histogram parameters. The use of additional interstitial needles provides prescription dose up to 15 mm lateral to point A. Twenty-two patients with high-risk clinical target volumes of mean 44 cm3 were treated with a mean prescribed total dose of 85 Gy (biologically equivalent to 2 Gy fractionation, alpha/beta = 10 Gy) and 93% coverage (V100). The dose to organs at risk was within standard limits for intracavitary brachytherapy alone. A combined interstitial-intracavitary applicator results in reproducible implants for cervical cancer brachytherapy. MRI-based treatment planning based on a target concept, dose-volume constraints, and limitations for the relative dwell weight allows for an increase in target coverage, treated volume, and total dose without increasing the dose to critical structures.

Variations of intracavitary applicator geometry during multiple HDR brachytherapy insertions in carcinoma cervix and its influence on reporting as per ICRU report 38

Purpose: This paper examines the extent of variation in the applicator geometry during multiple high dose rate (HDR) intracavitary brachytherapy (ICBT) applications and its impact on reporting as per ICRU report 38. Materials and methods: Eighty orthogonal radiographs from 20 consecutive patients of carcinoma cervix (FIGO stages, IIA–IIIB) having four HDR ICBT applications of 6 Gy each at weekly intervals following teletherapy were evaluated. The applicator consisted of a flexible intrauterine tandem (IUT) independent of the ovoid assembly. The applicator geometry was evaluated in terms of: α angle, β angle, intrauterine length (IUTL), interovoid (IOV), os to right ovoid (ORT) and os to left ovoid (OLT) distances along with vertical (VDL) and anteroposterior displacements (ADL) of the os with respect to the ovoids. The Cartesian co-ordinates ( X, Y, and Z) of the IUT tip, centre of both ovoids and os were also measured. Doses to right point A (ARD), left point A (ALD), along with a reference volume of 6 Gy for ICRU height (IRH), width (IRW), thickness (IRT) and volume (IRV) were estimated for each application. Results: Highly significant differences ( P<0.001) between four insertions in any given patient across 20 patients for α angle, β angle, IUTL, IOV, ORT, VDL, co-ordinates of the IUT, ovoids and os were observed, except for ADL ( P=0.041) and OLT ( P=0.247). As a consequence, variations were observed in ARD ( P=0.027), ALD ( P=0.017); IRH, IRW, IRT and IRV (all P<0.001). Applicator factors which influenced the various dose specification parameters were: β angle and ORT for both ARD and ALD; UTLN, VDL and ORT for IRH; UTLN and IOV for IRW; UTLN for IRT and VDL for the 6 Gy IRV. Conclusions: A significant variation of the applicator geometry and its movement was observed in patients undergoing multiple HDR ICBT. This could have implications for reporting dose and volume specifications as required by ICRU report 38.

On the validity of the superposition principle in dose calculations for intracavitary implants with shielded vaginal colpostats.

Intracavitary vaginal applicators typically incorporate internal shielding to reduce dose to the bladder and rectum. While dose distributions about a single colpostat have been extensively measured and calculated, these studies neglect dosimetric perturbations arising from the contralateral colpostat or the intrauterine tandem. Dosimetric effects of inhomogeneities in brachytherapy is essential for both dose-based implant optimization as well as for a comparison with alternate modalities, such as intensity modulated radiation therapy. We have used Monte Carlo calculations to model dose distributions about both a Fletcher-Suit-Delclos (FSD) low dose-rate system and the microSelectron high dose-rate remote afterloading system. We have evaluated errors, relative to a Monte Carlo simulation based upon a complete applicator system, in superposition calculations based upon both precalculated single shielded applicator dose distributions as well as single unshielded source dose distributions. Errors were largely dominated by the primary photon attenuation, and were largest behind the shields and tandem. For the FSD applicators, applicator superposition showed differences ranging from a mean of 2.6% at high doses (>Manchester Point A dose) to 4.3% at low doses (<Manchester Point A dose) compared to the full geometry simulation. Source-only superposition yielded errors higher than 10% throughout the dose range. For the HDR applicator system, applicator superposition-induced errors ranging from 3.6%-6.3% at high and low doses, respectively. Source superposition caused errors of 5%-11%. These results indicate that precalculated applicator-based dose distributions can provide an excellent approximation of a full geometry Monte Carlo dose calculation for gynecological implants.

Optimization in high dose rate brachytherapy for utero-vaginal applications

Background and purpose: High dose rate (HDR) remote afterloading intracavitary brachytherapy is an effective treatment modality which has some advantages over low dose rate (LDR) techniques for gynaecological cancer. Optimization is one of the possibilities of modern brachytherapy techniques, especially the stepping source technology. The use of the term ‘optimization’ implies achieving the desired optimum dose distribution by changing some parameters of the treatment. The aim of this study was to theoretically evaluate the optimization possibilities by modifying dwell times and dwell positions of the uterine and vaginal sources. Materials and methods: Working on a virtual utero-vaginal model, the dose distribution variations in the rectum, bladder, mean point B reference points and volume parameters were investigated whilst giving a standard dose to point A in the Manchester system. In this model, the intrauterine tandem consisted of 27 dwell positions for 2.5 mm steps and 14 dwell positions for 5 mm steps. Vaginal colpostats consisted of five dwell positions each for 2.5 mm steps. Using a Nucletron Plato treatment planning system and a Microselectron Ir-192 HDR stepping source unit, the dwell times of the intrauterine ( T u) and vaginal sources ( T v) were modified at the ratios of ( T u/ T v) 1:1; 1:2; 1:3; 1:4; 1:0.50; 1:0.33; and 1:0.25 for the two different dwell positions, 2.5 and 5 mm steps, of the intrauterine tandem. Results: All evaluated parameters decreased with increasing dwell time ratios of uterine tandem to vaginal colpostats, with the greatest fall in the percentage of rectum reference dose ( D R %), 23 and 28% for 2.5 and 5 mm dwell positions respectively; in addition, the reference isodose volume decreased by 14 and 17% for 2.5 and 5 mm dwell positions, respectively. All evaluated parameters increased with decreasing dwell time ratios of uterine tandem to vaginal colpostats for both dwell positions. The DR% of 1:1–1:4 ( T u/ T v) weightings showed an increase from 40.6 to 58.3 (44%) for 2.5 mm and from 49.2 to 67.5 (37%) for 5 mm dwell positions. The volume was increased by 27 and 37% for 2.5 and 5 mm dwell positions respectively. Conclusions: Modern brachytherapy techniques enable the individualization of treatments by optimization procedures in gynaecological brachytherapy applications. By altering the dwell time and position, some important changes in reference points, volume and treatment time can be achieved, whilst maintaining a standard dose to point A.

Dosimetry and Dose Specification for a New Gynecological Brachytherapy Applicator: International Journal of Radiation Oncology, Biology, and Physics, Vol. 22, No. 5, 1992, pp. 1117–1124

Abstract A new afterloadable gynecological intracavitary applicator has been designed and is now in use for the treatment of a wide range of vaginal, cervical, and endometrial cancers in a single application, with a dose distribution that more closely matches the prescribed treatment than previous methods. The plexiglass applicator consists of a bulbous section that is inserted up to the vaginal apex and loaded with right and left ovoid sources. The distal portion is cylindrical with a central channel for tandem sources. A straight tandem is used when the target volume extends to the vaginal apex, but an intrauterine tandem can also be used. Extensive dosimetric and radiographic evaluations were performed to guide design refinements and to validate the surface dose predictions of the brachytherapy treatment planning system. The final applicator design delivers 110–120 cGy/hr to the vaginal apex'surface and 95–100 cGy/hr to the distal vaginal surfaces when loaded with a 144.6 U (20 mgRaEq) cesium tube'in each ovoid channel and 72.3, 72.3, and 144.6 U (10, 10, and 20 mgRaEq) cesium tubes in the vaginal cylinder channel. A system for treatment dose specification has been established that includes dose tables for manually calculating surface doses to reference points. A dose distribution comparison with a sequential colpostat-vaginal cylinder treatment demonstrates that dose delivery is more precise and uniform with this new applicator.

Dosimetry and dose specification for a new gynecological brachytherapy applicator

A new afterloadable gynecological intracavitary applicator has been designed and is now in use for the treatment of a wide range of vaginal, cervical, and endometrial cancers in a single application, with a dose distribution that more closely matches the prescribed treatment than previous methods. The plexiglass applicator consists of a bulbous section that is inserted up to the vaginal apex and loaded with right and left ovoid sources. The distal portion is cylindrical with a central channel for tandem sources. A straight tandem is used when the target volume extends to the vaginal apex, but an intrauterine tandem can also be used. Extensive dosimetric and radiographic evaluations were performed to guide design refinements and to validate the surface dose predictions of the brachytherapy treatment planning system. The final applicator design delivers 110–120 cGy/hr to the vaginal apex'surface and 95–100 cGy/hr to the distal vaginal surfaces when loaded with a 144.6 U (20 mgRaEq) cesium tube'in each ovoid channel and 72.3, 72.3, and 144.6 U (10, 10, and 20 mgRaEq) cesium tubes in the vaginal cylinder channel. A system for treatment dose specification has been established that includes dose tables for manually calculating surface doses to reference points. A dose distribution comparison with a sequential colpostat-vaginal cylinder treatment demonstrates that dose delivery is more precise and uniform with this new applicator.

Ultrasound used for assessing the in situ position of intrauterine tandems

Intracavitary radiation is an integral part of the treatment in many gynecologic cancers. The intrauterine tandem has a well-established role in treating both cervical and endometrial malignancies. The effectiveness of this therapy and its complications are directly related to the proper intracavitary position of the tandem. To date, there has been no objective technique appropriate for routine use in assessing the precise in situ location of these devices, apart from plain abdominal films. As such, little is known about the incidence or types of procedural complications and the sequelae associated with improper tandem placement. Here it is reported that ultrasound is an effective tool for evaluating the in situ position of the intrauterine tandem. Two cases are presented demonstrating important applications of this method.

Radium implant to the parametrium in the treatment of stage IIIB carcinoma of the cervix: Analysis of dosimetry

Radium needle implant to the parametrium in order to supplement the dose rates to the cervix, parametrium and pelvic wall from a protruding intrauterine tandem was simulated using the skeleton of an adult pelvis in a water phantom. The results of direct dosimetry are presented. The parametrial implant approach was instituted in our clinic in 1975 to minimize local failures, especially parametrial, in Stage IIIB carcinoma of the cervix. The technique is used with patients who cannot accomodate two vaginal ovoids with the intrauterine tandem for conventional intracavitary radium therapy because of the extent of the neoplastic disease. Our dosimetric results showed an increase in the parametrial and pelvic wall dose rates of better than 60% with a typical implant of six half-intensity (0.33 mg/cm.) needles to the affected parametrium; the bladder and rectum dose rates increased by less than 17%. There was a relatively minimal (8–13%) increase in the dose rates to other pelvic node-bearing sites. Results for a minimal implant to both proximal parametria and a clinical example of the parametrial implant application are also presented.

Indications and Limitations of Transvaginal Roentgen Therapy for Cancer of the Cervix

If the rays we use to destroy cancer cells, or to inhibit their growth, were harmless to all other cells, the solution of the problem of how to cure cancer of the cervix would be easy. We could deliver to every part of the pelvis a lethal cancer dose of roentgen rays, which is now considered to be about 6,000 r. But x-rays are not innocuous, and if we tried to administer, in a short time, such an enormous dose to such a large area, few of our patients would recover. We must compromise between the ideal and the practical. In this country, it is now pretty generally agreed that the best plan of attack on cervical cancer is to administer to the primary tumor, in and around the cervix, a destructive dose, or as nearly a destructive dose as we dare to give. This is supplemented by a smaller dose to the entire pelvis, which we believe, or at least hope, is large enough to inhibit the growth of cancer cells. The most commonly employed method of destroying the primary tumor is to use tubes of heavily filtered radium in colpostats in the lateral vaginal fornices, in combination with an intra-uterine tandem. Although gamma rays have great penetrative power, radium must be placed so close to the tissues to be treated that its action is uneven. With the best possible technic, not more than 30 per cent of the surface dose reaches a depth of 3 cm. (1). This means that, if we deliver a destructive dose to the third centimeter of tissue, the first centimeter receives more than three such doses. The Chaoul technic is also used to deliver a destructive dose of roentgen rays to the cervix. The tube itself is inserted into the vagina and, with good technic (100 kv. and 5 cm. A.S.D.), the distribution of the radiation is about the same as with good radium technic, but no better. About 28 per cent of the surface dose reaches a depth of 3 cm. (2). The transvaginal method of direct roentgenization of the cervix, introduced by Merritt (3, 4), in what I believe to be the most valuable contribution to radiotherapy since the adoption of the international unit, is by far the most efficient method of destroying the primary tumor. The principal objection to it is the difficulty of exposing a field large enough to include the entire lesion and the lateral fornices. Incidentally, this is a good place to say that the treatment of cervical cancer through radio-opaque cylindrical specula, exposing a single field smaller than the lesion, is hopelessly inadequate and should be abandoned. Merritt exposes a large field by using a speculum transparent to the rays, allowing the expanding beam to pass through a part of the vagina. Wasson and Bouslog (5) do it by using multiple overlapping fields, and we do it by retracting the vaginal walls (6, 7, 8). In our modification of the transvaginal method of irradiation, the following physical factors are employed: kv. 200; ma. 20; A.S.D. 25 cm.; effective filter, Cu 0.75 mm.; hardness expressed as half-value layer in copper, 0.9 mm.

The Use of Interstitial Radiation in the Treatment of Primary and Recurrent Carcinoma of the Uterine Cervix

IN many clinics there is a tendency to standardize the treatment of cervical cancer so that a routine method of radiation is used for all patients. No single method is suitable for all individuals, but in most instances there are certain advantages to be gained if treatment is begun with external radiation (8). By that means the amount of infection in the lesion can be reduced, which, in turn, will lessen the local reaction from radium applied at a later date. A preliminary course of x-rays also facilitates radium treatment by producing some regression in the size of the primary lesion. However, if the percentage of cures is to be increased materially, it is essential to individualize both the roentgen and radium treatment of each patient to meet the requirements of the lesion in question, rather than to apply a single method to all patients with cervical cancer. In a previous publication (2) diagrams illustrating the distribution of roentgen radiation within the average female pelvis were given for different physical factors of radiation. In the treatment of carcinoma of the cervix it is essential that a large dose be given to the parametrium without over-radiating normal structures in other regions. A six-field technic (two on the anterior surface, two on the posterior, and one on each lateral aspect of the pelvis) was found to deliver the greatest amount of radiation to the parametrium without too great a percentage of the total dose falling upon the bladder and rectum. That arrangement of skin portals is suited to most patients with cervical cancer, but in every instance the attempt should be made to individualize the treatment. A different technic might be more practical for patients presenting a marked degree of involvement anterior or posterior to the cervix. There is general agreement that an intrauterine tandem containing radium will not control disease located at distances greater than 3 or 4 cm. from the cervical canal. In the attempt to increase the radius of effect from radium applied to the primary lesion, Healy (6) and others have devised various intra-vaginal applicators for use in conjunction with an intra-uterine tandem. In most patients, however, radium alone is inadequate for delivering a lethal dose to the entire tumor-bearing region. External radiation is essential in the attempt to treat adequately the disease located in outlying tumor-bearing areas, and in the deep lymphatics. The distribution of radiation for different methods of applying radium to the cervix has been shown diagrammatically by Lucas (10) and the author (1). While these diagrams show that radium alone is inadequate for most patients, they also illustrate the fact that a greater number of sources of radium distributed more widely throughout the uterus and vagina will, for specified doses, increase the minimum amount of radiation reaching the tumor, and decrease the risk of over-radiating some regions.