Skull base tumors: gadodiamide injection--enhanced MR imaging--drop-out effect in the early enhancement pattern of paragangliomas versus different tumors

Diffuse subarachnoid hemorrhage following ventriculo-peritoneal shunt insertion for acute obstructive hydrocephalus from large glomus jugulare tumor: case report

Background

Glomus jugulare tumors (GJTs) are rare intra-cranial tumors. Commonly, these lesions present with cranial nerve palsies, headaches, and hydrocephalus. Rarely, GJTs present with spontaneous subarachnoid hemorrhage. However, there has never been a report of diffuse subarachnoid hemorrhage following ventriculoperitoneal shunt insertion in a patient who developed hydrocephalus secondary to any brain tumor in general or glomus jugulare tumors in particular.

Observation

The authors presented an extremely rare complication of diffuse subarachnoid hemorrhage following the insertion of a ventriculoperitoneal shunt (VPS) in a 61-year-old female patient who was diagnosed to have both clinical and radiologic features of acute obstructive hydrocephalus secondary to a highly vascular huge glomus jugulare tumor.

Conclusion

Subarachnoid hemorrhage following ventriculoperitoneal shunt insertion for hydrocephalus caused by a mass lesion is an extremely rare complication. Preoperative CT angiography should be strongly considered to look for the associated vascular malformations in extremely vascularized mass lesions. Given the not ubiquitous availability of all therapeutic options for GJTs, especially in low and middle income settings contributes for the poor outcome of GJTs and it fosters a global neurosurgery agenda.

Vertigo as the sole complaint of tympanomastoid paraganglioma

Background

Tympanomastoid paragangliomas are usually benign, slowly growing, painless tumors. The common presenting symptoms of this tumor are pulsatile tinnitus and conductive hearing loss. Vertigo as the cardinal or initial symptom is extremely are, especially in the early stages of the disease.

Case presentation

A 53-year-old female patient presented only with intermittent recurrent vertigo and was later found to have a tympanomastoid paraganglioma. Her symptoms disappeared completely after resection of the tumor. This is the first report in literature of a case of tympanomastoid paraganglioma with vertigo as the single symptom.

Conclusion

The tympanomastoid paraganglioma is rare and its clinical symptoms are nonspecific, so it is easy to be misdiagnosed or missed. It is worth noting that although clinically uncommon, vertigo can also be the first or sole symptom of tympanomastoid paraganglioma. Detailed physical examination and imaging examination of the ear are necessary and should be carried out meticulously.

Stereotactic radiosurgery for jugular foramen schwannomas: an international multicenter study

OBJECTIVE

For some jugular foramen schwannomas (JFSs), complete resection is possible but may be associated with significant morbidity. Stereotactic radiosurgery (SRS) is a minimally invasive alternative or adjunct to microsurgery for JFSs. The authors reviewed clinical and imaging outcomes of SRS for patients with these tumors.

METHODS

Nine participating centers of the International Gamma Knife Research Foundation identified 92 patients who underwent SRS between 1990 and 2013. Forty-one patients had prior subtotal microsurgical resection. The median interval between previous surgery and SRS was 15 months (range 0.5–144 months). Eighty-four patients had preexisting cranial nerve (CN) symptoms and signs. The median tumor volume was 4.1 cm3 (range 0.8–22.6 cm3), and the median margin dose was 12.5 Gy (range 10–18 Gy). Patients with neurofibromatosis were excluded from this study.

RESULTS

The median follow-up was 51 months (range 6–266 months). Tumors regressed in 47 patients, remained stable in 33, and progressed in 12. The progression-free survival (PFS) was 93% at 3 years, 87% at 5 years, and 82% at 10 years. In the entire series, only a dumbbell shape (extension extracranially via the jugular foramen) was significantly associated with worse PFS. In the group of patients without prior microsurgery (n = 51), factors associated with better PFS included tumor volume < 6 cm3 (p = 0.037) and non–dumbbell-shaped tumors (p = 0.015). Preexisting cranial neuropathies improved in 27 patients, remained stable in 51, and worsened in 14. The CN function improved after SRS in 12% of patients at 1 year, 24% at 2 years, 27% at 3 years, and 32% at 5 years. Symptomatic adverse radiation effects occurred in 7 patients at a median of 7 months after SRS (range 5–38 months). Six patients underwent repeat SRS at a median of 64 months (range 44–134 months). Four patients underwent resection at a median of 14 months after SRS (range 8–30 months).

CONCLUSIONS

Stereotactic radiosurgery proved to be a safe and effective primary or adjuvant management approach for JFSs. Long-term tumor control rates and stability or improvement in CN function were confirmed.

A new type of gadodiamide-conjugated amphiphilic chitosan nanoparticle and its use for MR imaging with significantly enhanced contrastability

Magnetic resonance imaging (MRI) has been one of the most frequently-used diagnostic tools with high dimensional precision and positioning accuracy in clinical practices. To achieve contrast enhancement, utilization of high-efficient MR imaging contrast agents becomes a prime consideration and is indispensably reinforced the diagnosis precision, especially for the emerging precision medicine. Gadolinium (Gd)-based complexes has been widely used in current clinical MRI operations, however, numerous side effects were reported and highlighted in clinic. Those drawbacks render specific unmet needs to be clinically and technically improved with a new version of Gd-based compound. Here we report a newly-synthesized amphiphilic Gadodiamide-conjugated carboxymethyl-hexanoyl chitosan (termed as CHC-Gd) hybrid. The gadodiamide was selected is due to its smallest molecular size among other Gd-based complexes reported in literature, which assumed to give least influence on the resulting physicochemical properties such as colloidal stability, nanostructural evolution, and cytocompability, particularly self-assembly capability, of the resulting hybrid upon practical uses. Experimental outcomes showed a successful synthesis of the CHC-Gd hybrid using a one-pot synthesis protocol, where the gadodiamide complexes were covalently attached to the carboxyl groups along the CHC backbone. Self-assembly behavior can be observed to form a sphere-like nanoparticle of 100-200 nm in size as of amphiphilic native CHC macromolecule. Experimental outcomes indicated a largely improved cytocompatibility of the hybrid, compared with free Gd, suggesting the Gd⁺³ ions were well stabilized in the CHC nanostructure. Excellent contrastability in-vitro and in particular in vivo were measured, where for in-vivo test, a 10-40-folded reduction in dosage, compared with clinical Gd dose, was used and demonstrated a comparative-to-better imaging resolution and brightness. Therefore, from this preliminary investigation, a potential translation to clinical practice through the use of newly-synthesized amphiphilic CHC-Gd hybrid appears to be relatively promising.

Imaging of Parapharyngeal Space and Infratemporal Fossa

Cross-sectional imaging is an indispensable tool in the investigation of parapharyngeal space and infratemporal fossa pathologies. Computed tomography and magnetic resonance imaging exquisitely display the complex anatomy of this region and provides accurate spatial localization of pathology, differential diagnosis and vital information for treatment planning.

How to cite this article

Jain S, Kumar A, Dhongade H, Varma R. Imaging of Parapharyngeal Space and Infratemporal Fossa. Int J Otorhinolaryngol Clin 2012;4(3):113-121.

Differential diagnosis of jugular foramen lesions

The anatomy of the jugular foramen is complex. It contains the lower cranial nerves and major vascular structures. Tumors that develop within it, or extend into it, provide significant diagnostic and surgical challenges. In this article, we describe the anatomy of the jugular foramen and outline an imaging protocol that can differentiate between lesions, thereby aiding diagnosis and facilitating management.

Consensus statement and guidelines on the management of paragangliomas of the head and neck

Paragangliomas (PGLs) of the head and neck (H&N) are uncommon tumors that either arise spontaneously or as part of an inherited syndrome. Hereditary PGL is an autosomal-dominant tumor predisposition syndrome in which an affected individual has greatly increased risk of developing PGL at any or several sites in the autonomic nervous system. The mode of inheritance for some is affected by maternal imprinting. These tumors are generally very slow growing, often taking a decade to double in size. A few are or can become malignant and can metastasize widely. Because of their site of origin, patients with these tumors may develop cranial nerve deficits that have a significant impact on their quality of life. Patients may present to specialists from widely differing disciplines, and some of these may not appreciate the full implications of their patient's disease. As a result, management can become fragmented or inappropriate, and some aspects of care may even be overlooked. This article is the distillation of consensus opinion derived from current published and unpublished data in this field, with particular reference to the management of temporal bone PGLs. We propose guidelines for the management of both sporadic and hereditary PGLs. A multidisciplinary team approach to the management of this complex disorder is advocated. Progress could be made by adopting these guidelines and by widespread dissemination of standardized information. Collaborative research should be promoted with the aim of harnessing advances in molecular genetics to develop targeted therapies for patients, particularly those with hereditary PGL.

Usefulness of ultrafast dynamic 3D-T1w data acquisition in detection of hypervascular lesions of the middle ear: first experience

OBJECTIVE

To evaluate ultrafast dynamic 3D-T1w acquisition for improved detection of tympanic hypervascularized lesions.

METHODS

Retrospective evaluation of a total of 50 patients referred from ENT-Department for suspected tympanic lesion. All underwent magnetic resonance imaging including ultrafast dynamic 3D-T1w acquisition imaging. Quantitative and qualitative evaluation was performed as well as statistical analysis. Comparison with intra-operative results.

RESULTS

12/50 patients showed a hypervascularized lesion proved intraoperative as 8 paragangliomas, 2 adenoms, 1 hemangioma and 1 neurinoma. 8/50 do not show hypervascularization though an enhancement was detected. Intra-operative granulation tissue was found. 30 patients did not show any lesions or enhancement. Sensitivity and specificity was 100%/100% for ultrafast dynamic imaging.

CONCLUSION

Additional ultrafast dynamic 3D-T1w imaging is superior to conventional imaging in detection of hypervascularized lesions.

Diffusion-weighted imaging and ADC mapping of head-and-neck paragangliomas: initial experience

BACKGROUND

Paragangliomas are rare, hypervascularized benign tumors. In some cases a clear differentiation of paragangliomas and other entities is impossible.

PATIENTS AND METHODS

The authors evaluated ten patients with skull base lesions (paraganglioma n = 7, meningioma n = 1, giant cell tumor n = 1, and neurinoma n = 1) in addition to conventional magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI), and calculation of apparent diffusion coefficient (ADC).

RESULTS

Mean ADC values +/- standard deviation of the paragangliomas were 1.304 +/- 0.257 x 10(-3) mm(2)/s and differed from ADC values of the other jugular fossa tumors with 0.743 +/- 0.108 x 10(-3) mm(2)/s and measurement derived from the cerebellum with 0.802 +/- 0.075 x 10(-3) mm(2)/s.

CONCLUSION

Due to the difference of ADC values, the authors propose that DWI and ADC mapping could be a promising tool in the diagnostic work-up of paragangliomas.

Head and neck paragangliomas: value of contrast-enhanced 3D MR angiography

BACKGROUND AND PURPOSE

A rapid and accurate MR imaging technique would be beneficial to assess paragangliomas in the head and neck and to distinguish them from other lesions. The purpose of this study was to determine whether the combination of elliptic centric contrast-enhanced MR angiography (CE-MRA) and unenhanced and enhanced spin-echo imaging (conventional MR imaging) is more accurate than conventional MR imaging alone to assess paragangliomas in the head and neck.

MATERIALS AND METHODS

Three radiologists retrospectively and independently reviewed CE-MRA and conventional MR imaging in 27 patients with suspected paragangliomas. The overall image quality and the probability of paraganglioma were recorded. The results of each technique and their combination were analyzed for sensitivity and specificity. Receiver operating characteristic (ROC) analyses were performed by using histologic analysis, imaging, and/or clinical findings as the reference standard.

RESULTS

Forty-six lesions were found in 27 patients. In the assessment of paragangliomas, the combination of conventional MR imaging and CE-MRA was significantly superior to conventional MR imaging alone. Sensitivity and specificity respectively were the following: for CE-MRA, 100% and 94%; and for conventional MR imaging, 94% and 41%. The specificity of CE-MRA was significantly higher than that of conventional MR imaging (P = .004). There was good-to-excellent interobserver agreement for the paraganglioma probability with CE-MRA (nonweighted kappa, 0.67-0.77), whereas there was fair-to-good interobserver agreement with conventional MR imaging (nonweighted kappa, 0.50-0.65).

CONCLUSION

In combination with conventional MR imaging, CE-MRA yields an excellent diagnostic value for the assessment of head and neck paragangliomas; hence, the 2 techniques should be regarded as complementary.

Quantitative and qualitative characterization of vascularization and hemodynamics in head and neck tumors with a 3D magnetic resonance time-resolved echo-shared angiographic technique (TREAT)--initial results

The purpose of this paper is to characterize and quantify the vascularization and hemodynamic characteristics of head and neck tumors (HNT) with a dynamic 3D time-resolved echo-shared angiographic technique (TREAT) using the regular contrast agent (CA) bolus. Sixteen patients with HNT underwent 3D-TREAT during the CA administration on a 1.5-T magnetic resonance (MR) scanner. Using a parallel imaging acceleration factor of 2, 20 3D data sets at a temporal resolution of 2.3 s/frame were acquired. The quality of tumor delineation, vascularization type, and enhancement pattern were evaluated. Quantitative assessment included measurement of the contrast-to-noise ratio (CNR), determination of signal-intensity-over-time (SIT) curves, time-to-peak enhancement within the carotid arteries and the tumor, and the delay between both. TREAT was compared to conventional digital subtraction angiography (DSA) in six patients. Tumor delineation with TREAT was very good or good in 11/16 patients, and better with TREAT than with DSA in 3/6 cases. The CNR was significantly different for glomus tumors versus hypovascularized malignant tumors with TREAT (p=0.0001), but not on T1-weighted gradient echo (T1w GE) images. Qualitative assessment of tumor vascularization on dynamic TREAT shows good correlation (r=0.75) to quantitative SIT curves. We conclude that TREAT imaging permits the characterization of tumor vascularity and holds promise as a supplementary diagnostic tool in the differential diagnosis of HNT.

Differentiating imaging findings in primary and secondary tumors of the jugular foramen

The preoperative diagnosis of a jugular foramen tumor may be challenging, since a large variety of unusual lesions may be located in this region. These tumors may be classified as primary lesions (which are located in the jugular foramen or extend from the jugular foramen into the surrounding structures) and as secondary lesions (that extend from the surrounding structures into the jugular foramen). Primary tumors include glomus jugulare tumors, schwannomas, meningiomas and peripheral primitive neuroectodermal tumors, while secondary tumors comprise chordomas, chondrosarcomas, chondroblastomas, giant-cell tumors, cholesterol granulomas, giant cholesterol cyst, endolymphatic sac tumors, reactive myofibroblastic tumors, temporal bone carcinomas and metastases. Accurate preoperative radiological suspicion is of great value for preoperative patient counseling and has a direct impact on the surgical planning in these cases. The present study describes and discusses the main differentiating imaging features of lesions involving the jugular foramen, whose accurate preoperative radiological evaluation is essential for proper surgical planning.

Dynamic contrast enhancement of paragangliomas of the head and neck: evaluation with time-resolved 2D MR projection angiography

Our objective was to evaluate tumor hemodynamics of paragangliomas of the head and neck. A 2D magnetic resonance projection angiography (MRPA) protocol was developed. Six patients with histologically proven paragangliomas were included in the study. The sequence protocol and data post-processing procedure were optimized in view of a high temporal resolution and maximum contrast-to-noise ratio. Image-time series of two freely orientated slabs could be obtained. Correlation analysis was performed to generate selective arterial and venous weighted angiographic images. Glomus tumors showed a rapid and intense homogeneous enhancement following the intravenous administration of contrast material. The smallest tumors investigated measured 10 mm and could be visualized clearly. Time-resolved analysis of the tumor enhancement revealed an early bolus arrival within the vascular bed of the tumor and prolonged incomplete washout indicating blood pooling. The dynamic contrast enhancement of glomus tumors can be evaluated non-invasively with MRPA providing a high temporal resolution and high image quality. The characteristic contrast enhancement of glomus tumors can be helpful in the diagnostic workup of lesions that may mimic glomus tumors.

Radiographic evaluation and assessment of paragangliomas

Radiographic imaging plays an important role in the diagnosis and treatment of paragangliomas. Diagnosis and treatment should be performed as a team effort, with all the involved disciplines working together to provide the best possible individualized work-up and treatment plan for the patient.

From the archives of the AFIP. Paragangliomas of the head and neck: radiologic-pathologic correlation. Armed Forces Institute of Pathology

Paragangliomas of the head and neck are ubiquitous in their distribution, originating from the paraganglia or glomus cells within the carotid body, vagal nerve, middle ear, jugular foramen, and numerous other locations. The typical patient is middle-aged and presents late in the course of the disease, with a painless slow-growing mass. Clinical manifestations include hoarseness of voice, lower cranial nerve palsies, pulsatile tinnitus, and other neuro-otologic symptoms. The overall prognosis of patients with a cervical paraganglioma is favorable, whereas its temporal bone counterpart often results in recurrence, residual tumor, and neurovascular compromise when in the advanced stage. Pathologic examination reveals a characteristic biphenotypic cell line, composed of chief cells and sustentacular cells with a peripheral fibrovascular stromal layer that are organized into a whorled pattern ("zellballen"). Imaging hallmarks of paragangliomas of the head and neck include an enhancing soft-tissue mass in the carotid space, jugular foramen, or tympanic cavity at computed tomography; a salt-and-pepper appearance at standard spin-echo magnetic resonance imaging; and an intense blush at angiography. Imaging studies depict the location and extent of tumor involvement, help determine the surgical approach, and help predict operative morbidity and mortality. Surgical treatment is definitive. Radiation treatment is included as a palliative adjunct for the exceptional paraganglioma not amenable to surgery.

Delineation of maxillofacial cutaneous lesions by means of high-resolution magnetic resonance imaging

To evaluate the use of high-resolution magnetic resonance imaging (MRI) for the differentiation of skin tumors in the maxillofacial region, 60 patients (25 female) were examined in a 1.5-T whole-body MR imager with a 2.5-cm surface coil. Plain transverse T1-(TR 500 ms, TE 25 ms), T2-(2200 ms, TE 80 ms), fat-(TR 500 ms, TE 28 ms), and water-suppressed (TR 500 ms, TE 38 ms) SE sequences were used. Following the application of the paramagnetic contrast agent Gd-DTPA, transverse T-weighted and fat suppression sequences were repeated. Before and after contrast administration, tumor signal intensities and percent contrast enhancement were determined by a ROI technique. All tumors were classified by standard histologic technique and evaluated with regard to their response to contrast medium. Quantitative evaluation was performed by three independent radiologists. Additionally, signal- and contrast-to-noise ratios were calculated for each tumor type. All MRI findings were compared with histology. Significant contrast enhancement occurred in most tumors; malignant tumors displayed inhomogeneous enhancement. The optimal pulse sequences for tumor delineation are plain T1-weighted, water-suppressed, and contrast-enhanced fat-suppressed sequences. Tumors could not be specified by signal intensities or percent contrast enhancement, and CNR did not allow for malignant lesions to be differentiated from benign tumors. High-resolution MRI proved to be an adequate method for imaging skin tumors and their inner structure. Tumor typing was not possible by either contrast-administration or modification of sequence parameters. In this regard, further innovations in contrast agent design seem to be necessary.

Head and neck lesions. Radiologic-pathologic correlations

Correlating findings on imaging studies with those on histopathologic examination can define the limitations and strengths of the radiologist's imaging armamentarium. Although CT is particularly strong in identifying the character of the matrix of a head and neck lesion, MR imaging has proved superior in the mapping of most malignant neoplasms. Sometimes the combination of CT and MR imaging characteristics of a lesion may yield a specific diagnosis; however, in most instances, the radiologic appearance is sufficiently nonspecific that aspiration cytology or biopsy is required. This article reviews the effectiveness of imaging for characterizing and outlining lesions.

Infrahyoid neck

Imaging is an indispensable tool in patients with clinical suspicion of infrahyoid neck disease. CT and MR imaging can establish a positive diagnosis by showing a true mass (versus a pseudomass). In addition, by defining the exact space of origin of the lesion and its characteristics (CT density, MR signal, homo- or heterogeneity, contour, contrast enhancement), imaging can predict the correct diagnosis. Because it offers multiplanar, multiparameter information, MR imaging, performed with a dedicated coil and appropriate artifact-reduction techniques, usually is the modality of choice.

Failure of gadopentetate dimeglumine-enhanced, high-resolution magnetic resonance imaging to differentiate among melanin-containing skin tumors

RATIONALE AND OBJECTIVES

We evaluated the diagnostic potential of gadopentetate dimeglumine-enhanced, high-resolution magnetic resonance (MR) imaging to differentiate benign from malignant melanin-containing skin tumors.

METHODS

Forty-five patients were prospectively examined using high-resolution MR imaging at 1.5 T using a 2.5-cm surface coil. For tumor assessment, T1-weighted and T2-weighted transverse spin-echo sequences were acquired. After intravenous administration of gadopentetate dimeglumine (0.1 mmol/kg), the T1-weighted transverse sequence was repeated. Contrast enhancement was quantitatively determined as the percentage increase of signal intensity. Histologic findings were correlated using the Wilcoxon signed-ranks test. The quality of contrast enhancement was assessed by three independent investigators who were unaware of the patients' history and histologic data. The signal-to-noise ratio (SNR) was calculated in the T2-weighted sequence. Significance was tested using the Wilcoxon signed-ranks test.

RESULTS

In all tumors, contrast enhancement was visually discernible. Half of the cases were enhanced inhomogeneously. The percentage of contrast enhancement did not correlate with histologic findings. Malignant melanomas could not be differentiated from benign melanocytic nevi with the use of gadopentetate dimeglumine. Determination of the SNR in T2-weighted sequences revealed no significant difference for histologic subgroups or tumor type.

CONCLUSION

Gadopentetate dimeglumine-enhanced MR imaging does not differentiate malignant melanomas from benign melanocytic nevi. Determination of the SNR in the T2-weighted sequences revealed no significant difference for histologic subgroups.

Dynamic snapshot gradient-echo imaging of head and neck malignancies: time dependency and quality of contrast-to-noise ratio

The purpose of this study was to evaluate the time dependency of the contrast-to-noise ratio (CNR) of head and neck malignancies during contrast-enhanced MR imaging. Then we would compare the CNR of dynamic snapshot gradient-echo (SGE) images with conventional spin-echo (SE) and fast spin-echo (FSE) sequences. Fifteen patients with squamous cell carcinomas were examined with T1W-SE, T2W-FSE, contrast-enhanced Gd-T1W-SE, and T1W-SGE sequences, the latter statically and contrast-enhanced dynamically. The CNR for all sequences and adjacent tissues was computed and the time to reach maximal CNR (Tmax) was determined for dynamic studies. The CNR was time dependent with two distinct Tmax at 6-18 and 60-160 s which corresponded to two different tumor enhancement patterns. Neither enhancement pattern correlated with distinct histologic findings or tumor grading. The CNR improved for the Gd-T1W-SE images. The improvement was statistically significant in relation to T1W-SE and Gd-T1W-SE images at the floor of the mouth and at the tongue base. The good CNR of the dynamic Gd-T1W-SGE measurements justifies further investigations of this method in order to improve tumor delineation.

Neutron capture therapy with gadopentetate dimeglumine: experiments on tumor-bearing rats

RATIONALE AND OBJECTIVES

The therapeutic effect of neutron capture therapy with the gadolinium (Gd) complex gadopentetate dimeglumine was studied in vivo in rats using a beam of thermal neutrons.

METHODS

Rats with Jensen sarcomas 10-15 mm in diameter in their right thigh were irradiated with a thermal neutron beam that had fluences of 3.6 x 10(11) (20 min) or 5.4 x 10(11) n/cm2 (30 min) in the absence and presence of 5,500 or 13,750 ppm gadopentetate dimeglumine. Gadopentetate dimeglumine was administered directly into the tumor prior to neutron irradiation. Four groups of rats were studied: two groups of nonirradiated controls (Gd-n- and Gd+n-) and two irradiated groups (Gd-n+ and Gd+n+). In the follow-up period, we measured the subjects' clinical status and tumor size as a function of time postirradiation.

RESULTS

In both control groups (Gd-n- and Gd+n-), the tumor progressively grew. Pure irradiation by thermal neutrons in the Gd-n+ group resulted in a transient inhibition of tumor growth with total regressions of 15%. Intratumoral administration of 13,750 ppm gadolinium per gram of tumor and subsequent neutron irradiation (the Gd+n+ group; fluence = 3.6.10(11) n/cm2) significantly increased the tumoricidal effects (i.e., decrease of tumor growth up to a complete regression of the tumors in about 80%). Treatment-specific differences between the groups were confirmed by histologic observations.

CONCLUSION

The intratumoral administration of the hydrophilic magnetic resonance imaging contrast medium gadopentetate dimeglumine prior to irradiation with thermal neutrons leads to a therapeutic gain (i.e., reduction) on experimental Jensen sarcomas.