Search PubMed⌕ Search

Biomedical subjects

D R Olsen

Publications and source records attributed to D R Olsen.

At least 19 recordsLinked to original sources
PubMed2005

Comparative analyses of the dynamic properties of the bladder wall studied by repetitive pelvic CT scans of patients and cryo-sections of cadavers.

In radiotherapy planning systems, delineation of hollow normal tissue organs, such as the bladder, is time-consuming. Automated delineation may presuppose two assumptions: (1) the bladder resembles a spherical shell and (2) the volume of bladder tissue is preserved regardless of the volume of urine (luminal volume) inside. The purpose of the present study was to test these assumptions. 22 CT scans from 7 patients were studied retrospectively. Transverse cross-sectional areas enclosed by the outer contour (A(out)) and inner contour of the bladder (A(in)) were recorded from the images. Hence, the transverse cross-sectional area of the wall, A(wall)=A(out)-A(in), and the volume of bladder tissue at various luminal volumes, could be calculated. To quantify the method uncertainty, the same procedure was applied on three spherical plastic phantoms. The results were also compared with data from the Visible Human Project's photographs of cadaver cryo-sections. Assumption no. 1 stated above, implies that A(wall) is constant regardless of the level of intersection of the sphere. The data from cryo-sections revealed a positive correlation for A(wall) and A(out), in contradiction to assumption no. 1 (p<0.001). The corresponding association derived from the repetitive CT scans of patients was also statistically significant (p<0.001) although linear regression revealed a less steep slope. A relationship was found between the volume of bladder tissue and luminal volume, hence contradicting assumption no. 2 (p<0.001). In conclusion the cross-sectional wall areas of the bladder, measured from patient CT scans, increase slightly with luminal cross-sectional areas in contradiction to expected values derived from a simplistic spherical shell model. In addition, the volume of bladder tissue is related to the luminal volume. Our results may be of practical value when developing automated delineation tools in radiotherapy planning systems.

Cryopreservation↗
PubMed2003

Comparative analyses of the dynamic properties of the rectum studied by cryo-sections of human cadavers and pelvic CT scans of patients.

Optimization of radiotherapy treatment plans based on dose-volume histograms relies on accurate organ delineation. Hollow organs, such as the rectum, are difficult and time-consuming to delineate owing to unclear visualization of the border between wall tissue and filling. Automated hollow organ delineation would be a valuable tool, but its development depends upon improved understanding of the dynamics of the rectum in response to filling. Two reasonable assumptions proposed in the literature are that (1) the rectal wall tissue along a constant length of the rectal cylinder is preserved over time and (2) the rectal wall tissue is distributed homogeneously along the cylinder. Therefore, variations in wall thickness can be explained by variable rectal filling. To investigate these assumptions, transversal cross-sectional areas enclosed by the outer contour (A(out)) and inner contour (A(in)) of the rectum were recorded from digital photographs of cadaver cryo-sections from the U.S. National Library of Medicine's Visible Human Project. In addition, A(out) and A(in) were recorded from 19 CT scans of 5 of our own patients. The transversal cross-sectional area of the wall of the rectum, A(wall)=A(out)-A(in), was calculated. The data derived both from cryo-sections and repetitive CT scans of patients, revealed that there was a significant correlation between A(wall) and A(out), in contradiction to assumption (1) stated above (male cryo-sections: p<0.001, female cryo-sections: p=0.03, repetitive CT scans p<0.001). Moreover, the mean A(wall) calculated from one CT scan differed significantly from the mean A(wall) from other CT scans and was correlated with the mean A(out), i.e. rectal filling (p<0.001). This finding was confirmed by careful analysis of another study (p=0.001) and opposes assumption (2). Hence, the amount of wall tissue within a constant length of rectum is not preserved over time, but increases with increased filling. This implies that the longitudinal length of the rectum decreases in response to distension of the organ.

Cadaver↗
PubMed2002

Long-term renal function after treatment for malignant germ-cell tumours.

OBJECTIVE: To evaluate prospectively renal function in patients with malignant germ-cell tumours (MGCTs) >10 years after retroperitoneal lymph node dissection alone (RPLND), radiotherapy alone (RAD) or different schedules of cisplatin-based chemotherapy with or without surgery/radiotherapy (CHEM). PATIENTS AND METHODS: In 85 patients, three groups were identified: RPLND, 14; RAD, 18; CHEM, 53, with subdivision of the latter group according to the cumulative cisplatin dose or the additional use of radiotherapy. Renal function was determined by 131Iodine Hippuran clearance or 99m DTPA glomerular filtration rate, and was assessed before treatment and four times during 14 years of follow-up. A value of <70% of the upper limit of the normal range identified impaired renal function. RESULTS: Twenty-five patients displayed long-term impaired renal function, 23 of them from the RAD or CHEM group. In the RAD group, renal function decreased by 8%, whereas a 14% reduction of renal function was observed in the CHEM group. In the CHEM group the cumulative dose of cisplatin, and in the RAD group the age at treatment, were associated with impairment of renal function. Combining all patients, age at treatment and the type of treatment were associated with impaired renal function. CONCLUSIONS: In 20-30% of the patients with germ-cell tumour, standard radiotherapy and chemotherapy strategies are followed by long-term subclinical impaired renal function. These findings support current intentions to avoid overtreatment with these treatment modalities.

Adolescent↗
PubMed2001

[The radiotherapy satellite in Kristiansand--a model for Norwegian regional hospitals?].

BACKGROUND: During the first decade of 2000, significant increase of radiotherapy capacity in Norway will take place, as the number of linear accelerators will increase from 24 to 36. In Norway, radiotherapy departments are traditionally located only in university hospitals. However, six of the new accelerators will not be installed in existing radiotherapy centres, but in small, new radiotherapy units, set up in selected county hospitals and organized as satellites of the university hospitals, in order to secure the treatment quality. The university hospital is responsible for both medical and technical standards in the satellite, while the county hospitals have the financial responsibility. RESULTS: The satellite model combines two important aspects of hospital management; treatment is geographically decentralized, while treatment quality is centralized. The first radiotherapy satellite was established in the town of Kristiansand in January 2001. We report our experience with this new concept in radiotherapy. INTERPRETATION: The satellite model should be evaluated also for other medical specialties within the university hospitals.

Health Planning↗
PubMed2001

Production of human type I collagen in yeast reveals unexpected new insights into the molecular assembly of collagen trimers.

Substantial evidence supports the role of the procollagen C-propeptide in the initial association of procollagen polypeptides and for triple helix formation. To evaluate the role of the propeptide domains on triple helix formation, human recombinant type I procollagen, pN-collagen (procollagen without the C-propeptides), pC-collagen (procollagen without the N-propeptides), and collagen (minus both propeptide domains) heterotrimers were expressed in Saccharomyces cerevisiae. Deletion of the N- or C-propeptide, or both propeptide domains, from both proalpha-chains resulted in correctly aligned triple helical type I collagen. Protease digestion assays demonstrated folding of the triple helix in the absence of the N- and C-propeptides from both proalpha-chains. This result suggests that sequences required for folding of the triple helix are located in the helical/telopeptide domains of the collagen molecule. Using a strain that does not contain prolyl hydroxylase, the same folding mechanism was shown to be operative in the absence of prolyl hydroxylase. Normal collagen fibrils were generated showing the characteristic banding pattern using this recombinant collagen. This system offers new opportunities for the study of collagen expression and maturation.

Circular Dichroism↗
PubMed2001

Inter fraction variations in rectum and bladder volumes and dose distributions during high dose rate brachytherapy treatment of the uterine cervix investigated by repetitive CT-examinations.

PURPOSE: To evaluate variation of dose to organs at risk for patients receiving fractionated high dose rate gynaecological brachytherapy by using CT-based 3D treatment planning and dose-volume histograms (DVH). MATERIALS AND METHODS: Fourteen patients with cancer of the uterine cervix underwent three to six CT examinations (mean 4.9) during their course of high-dose-rate brachytherapy using radiographically compatible applicators. The rectal and bladder walls were delineated and DVHs were calculated. RESULTS: Inter fraction variation of the bladder volume (CV(mean)=44.1%) was significantly larger than the inter fraction variation of the mean dose (CV(mean)=19.9%, P=0.005) and the maximum dose (CV(mean)=17.5%, P=0.003) of the bladder wall. The same trend was seen for rectum, although the figures were not significantly different. Performing CT examinations at four of seven brachytherapy fractions reduced the uncertainty to 4 and 7% for the bladder and rectal doses, respectively. A linear regression analysis showed a significant, negative relationship between time after treatment start and the whole bladder volume (P=0.018), whereas no correlation was found for the rectum. For both rectum and bladder a linear regression analysis revealed a significant, negative relationship between the whole volume and median dose (P<0.05). CONCLUSION: Preferably a CT examination should be provided at every fraction. However, this is logistically unfeasible in most institutions. To obtain reliable DVHs the patients will in the future undergo 3-4 CT examinations during the course of brachytherapy at our institution. Since this study showed an association between large bladder volumes and dose reductions, the patients will be treated with a standardized bladder volume.

Adult↗
PubMed2000

Production of recombinant human type I procollagen trimers using a four-gene expression system in the yeast Saccharomyces cerevisiae.

The expression of stable recombinant human collagen requires an expression system capable of post-translational modifications and assembly of the procollagen polypeptides. Two genes were expressed in the yeast Saccharomyces cerevisiae to produce both propeptide chains that constitute human type I procollagen. Two additional genes were expressed coding for the subunits of prolyl hydroxylase, an enzyme that post-translationally modifies procollagen and that confers heat (thermal) stability to the triple helical conformation of the collagen molecule. Type I procollagen was produced as a stable heterotrimeric helix similar to type I procollagen produced in tissue culture. A key requirement for glutamate was identified as a medium supplement to obtain high expression levels of type I procollagen as heat-stable heterotrimers in Saccharomyces. Expression of these four genes was sufficient for correct assembly and processing of type I procollagen in a eucaryotic system that does not produce collagen.

Biopolymers↗
PubMed2000

Modeling normal tissue complication probability from repetitive computed tomography scans during fractionated high-dose-rate brachytherapy and external beam radiotherapy of the uterine cervix.

PURPOSE: To calculate the normal tissue complication probability (NTCP) of late radiation effects on the rectum and bladder from repetitive CT scans during fractionated high-dose-rate brachytherapy (HDRB) and external beam radiotherapy (EBRT) of the uterine cervix and compare the NTCP with the clinical frequency of late effects. METHODS AND MATERIALS: Fourteen patients with cancer of the uterine cervix (Stage IIb-IVa) underwent 3-6 (mean, 4.9) CT scans in treatment position during their course of HDRB using a ring applicator with an Iridium stepping source. The rectal and bladder walls were delineated on the treatment-planning system, such that a constant wall volume independent of organ filling was achieved. Dose-volume histograms (DVH) of the rectal and bladder walls were acquired. A method of summing multiple DVHs accounting for variable dose per fraction were applied to the DVHs of HDRB and EBRT together with the Lyman-Kutcher NTCP model fitted to clinical dose-volume tolerance data from recent studies. RESULTS: The D(mean) of the DVH from EBRT was close to the D(max) for both the rectum and bladder, confirming that the DVH from EBRT corresponded with homogeneous whole-organ irradiation. The NTCP of the rectum was 19.7% (13.5%, 25. 9%) (mean and 95% confidence interval), whereas the clinical frequency of late rectal sequelae (Grade 3-4, RTOG/EORTC) was 13% based on material from 200 patients. For the bladder the NTCP was 61. 9% (46.8%, 76.9%) as compared to the clinical frequency of Grade 3-4 late effects of 14%. If only 1 CT scan from HDRB was assumed available, the relative uncertainty (standard deviation or SD) of the NTCP value for an arbitrary patient was 20-30%, whereas 4 CT scans provided an uncertainty of 12-13%. CONCLUSION: The NTCP for the rectum was almost consistent with the clinical frequency of late effects, whereas the NTCP for bladder was too high. To obtain reliable (SD of 12-13%) NTCP values, 3-4 CT scans are needed during 5-7 fractions of HDRB treatments.

Algorithms↗
PubMed2000

[Radiotherapy of skeletal metastases].

INTRODUCTION: Patients with skeletal metastases represent a large cohort in clinical oncology, and the single most frequent indication for palliative radiotherapy. Patients with cancer of the breast, lung, prostate and those with myelomatosis, constitute approximately 80% of this group. MATERIAL AND METHODS: This paper summarizes data from relevant published clinical trials employing external irradiation for painful skeletal metastases. More recent randomised trials support the view that a single radiation dose of 8-10 Gy is equally efficient as ten treatments of 3 Gy delivered over two weeks. However, some still believe that fractioned regimes to a higher total dose provide better pain relief of a longer duration than a single fraction. RESULTS: We review the current diagnosis and treatment of patients with skeletal metastases and discuss some aspect of tumour biology. The etiology of pain and the pathogenesis of tumour cells affecting bone tissue, resulting in osteolysis and/or osteosclerosis, are discussed. Associated leukocyte-derived osteoclast-activating cytokines that stimulate pain receptors locally, can in part explain why radiotherapy gives such rapid pain relief. INTERPRETATION: The aims of radiotherapy must be assessed in relation to the life expectancy of the patient. Based on actual publications and own experiences, we suggest treatment with 8 Gy x 1 for the majority of patients, and reserve 3 Gy x 10 for patients with longer life expectancy. Both regimes allow retreatment, if and when pain eventually reoccur in previously irradiated areas.

Bone Neoplasms↗
PubMed2000

Telemedicine in radiotherapy treatment planning: requirements and applications.

BACKGROUND AND PURPOSE: Telemedicine facilitates decentralized radiotherapy services by allowing remote treatment planning and quality assurance of treatment delivery. A prerequisite is digital storage of relevant data and an efficient and reliable telecommunication system between satellite units and the main radiotherapy clinic. The requirements of a telemedicine system in radiotherapy is influenced by the level of support needed. In this paper we differentiate between three categories of telemedicine support in radiotherapy. RESULTS AND DISCUSSION: Level 1 features video conferencing and display of radiotherapy images and dose plans. Level 2 involves replication of selected data from the radiotherapy database - facilitating remote treatment planning and evaluation. Level 3 includes real-time, remote operations, e.g. target volume delineation and treatment planning performed by the team at the satellite unit under supervision and guidance from more experienced colleagues at the main clinic.

Humans↗
PubMed2000

Intra-operative irradiation (IORT) for primary advanced and recurrent rectal cancer. a need for randomised studies.

The aim of this study was to determine the impact of intra-operative irradiation (IORT) combined with pre-operative external beam irradiation (EBRT) and surgical resection in patients with locally advanced primary or recurrent rectal cancer. 64 patients with locally advanced primary cancer and 104 with recurrence had EBRT (46-50 Gy) before surgery. 80 patients received IORT (median dose 15 Gy energy 12 MeV). 80 patients had R0 resections, 47 R1 and 41 R2 resections. More R1 resections were performed in the IORT group, more R0 and R2 resections in the non-IORT group. Median follow-up was around 22 months. 146 patients were resected, 22 had exploratory laparotomy. The cumulative overall survival was similar for both the IORT and non-IORT groups. 5-year survival for primary cancers was 48% versus 28% for recurrences. No R2 resections survived 3.5 years. 5-year-survival for R0 resections was nearly 60% and around 30% for R1 resections. The survival curves of the patients given and not given IORT treatment was not statistically different when R0, R1 and R2 resections were analysed separately. IORT did not seem to influence the local recurrence rate when R0 and R1 resections were analysed separately or in a multivariate analysis. The IORT and non-IORT groups were not identical with regard to type of cancer and R-stage. Still the lack of an identifiable impact of IORT suggests that there is a need for randomised studies of the IORT effect.

Adenocarcinoma↗
PubMed2000

Exposure of human osteosarcoma and bone marrow cells to tumour-targeted alpha-particles and gamma-irradiation: analysis of cell survival and microdosimetry.

PURPOSE: This study was designed to compare the cytotoxic effects of an alpha-emitting radioimmunoconjugate, which binds to osteosarcoma but not to bone marrow cells, with those of external gamma-irradiation. MATERIALS AND METHODS: The human osteosarcoma cell line, OHS-s1, and mononuclear cells from bone marrow (BM) harvested from healthy donors, were used for these experiments. Cells in suspension were added to various activity concentrations of the anti-osteosarcoma monoclonal antibody TP-3 radiolabelled with 211At. Following incubation for 1 h, unbound radioactivity was washed off and cell survival was determined from clonogenic assays. Microdosimetry was calculated based on binding and retention kinetics of 211At to the cells, as well as cellular and nuclear diameters. For comparison, cell suspensions were irradiated with a single dose of 60Co gamma-rays. RESULTS: 211At-labelled TP-3 showed heterogeneous binding to OHS-s1 cells, with a considerable variation among experiments. About 78% of the initially bound 211At decayed while associated with the OHS-s1 cells. D0 values estimated by microdosimetry were 0.33 (0.22-0.48, range) Gy and 1.18 (0.89-1.89) Gy for OHS-s1 and BM cells, respectively, whereas D0 values after external beam irradiation were 0.86+/-0.07Gy and 1.71+/-0.22Gy. The relative biological effectiveness (RBE) of 211At-labelled TP-3 at 37% survival was 3.43 for OHS-s1 and 1.55 for BM. CONCLUSIONS: High-LET targeted alpha-particle exposure killed osteosarcoma cells more effectively than bone marrow cells, although heterogeneous antigen expression among these tumour cells limited the magnitude of this effect.

Alpha Particles↗
PubMed2000

Dose distribution measurements by MRI of a phantom containing lung tissue equivalent compartments made of ferrous sulphate gel.

Gel dosimetry based on magnetic resonance imaging (MRI) has previously been shown to provide verification of calculated dose distributions in soft tissue equivalent homogeneous phantoms. This study demonstrates how measurements of dose distribution can also be achieved in a phantom containing porous, lung-equivalent, Fricke gel. A phantom was made of Fe2+ infused low-density gel and conventional ferrous sulphate gel, filled in separate compartments in a Perspex container. Absorbed dose measurements were accomplished by MR imaging and by calibrating the proton spin-lattice relaxation rate (R1) versus absorbed dose by means of TLD measurements. This study shows that the production of lung-equivalent low-density (LD) dosimeter gel (mean CT number of -610 HU) is feasible. The MR signal detected in the LD gel dosimeter was substantially more noisy (i.e. displayed larger random fluctuations) than the signal from conventional gel, as expected. A deviation between calculated (TPS) and measured dose of about 3% (6 MV) and 4-7% (15 MV) was found in the LD region of the phantom. These results correspond well with data from other studies of dose distribution in lung-equivalent phantoms. The Fe2+ infused LD gel therefore seems suitable for measurement of absorbed dose distribution in phantoms that contain lung tissue compartments.

Ferrous Compounds↗
PubMed1999

Long-term morbidity and quality of life in patients with localized prostate cancer undergoing definitive radiotherapy or radical prostatectomy.

PURPOSE: To assess morbidity, side effects, and quality of life (QoL) in patients treated for localized prostate cancer with curative aim. METHODS AND MATERIALS: This descriptive cross-sectional study comprises 154 patients who had undergone definitive radiotherapy (RAD) and 108 patients with radical prostatectomy (PRECT) at the Norwegian Radium Hospital during 1987-1995. At least 1 year after treatment the patients completed several questionnaires assessing quality of life (European Organization for Research and Treatment of Cancer QLQ-C30 instrument [EORTC QLQ-C30]), lower urinary tract symptoms (LUTS): International Prostate Symptom Score (IPSS), or sexuality (selected questions from the Psychosocial Adjustment to Illness Scale [PAIS]). Urinary incontinence and bowel distress were evaluated by ad hoc constructed questionnaires. A control group (OBS) consisted of 38 patients following the watch-and-wait policy. RESULTS: Twenty percent of the patients from the RAD Group had moderate (14%) or severe (6%) LUTS as compared to 12% in the PRECT group. However, 35% of men from the latter group reported moderate to severe urinary incontinence. "Overall" sexuality was moderately or severely impaired in 71% of the PRECT and 50% of the RAD patients. In the former group high age was correlated with erectile impotency (p < 0.001). In the RAD comorbidity was associated with erectile impotency (p < 0.001). Between 13-38% of the patients recorded moderate or severe bowel distress (blood per rectum: 13%; bowel cramps: 26%; flatulence: 38%), without significant differences comparing patients who had received conventional small 4-field box radiotherapy and patients who had undergone strictly conformal radiotherapy. Despite malignancy and/or treatment-related morbidity, QoL was comparable in both groups with respectively 9% and 6% RAD and PRECT patients, reporting moderately or severely impaired QoL. In the multivariate analysis physical function, emotional function and fatigue were significantly correlated with QoL, whereas sexuality, lower urinary symptoms, and urinary incontinence correlated with QoL only in the univariate analysis. CONCLUSION: In spite of considerable malignancy and/or treatment-related morbidity QoL was good or only slightly impaired in the majority of patients with localized prostate cancer who presented with stable disease > 1 year after definitive radiotherapy or radical prostatectomy with no difference as compared to the age-matched normal population. Clinicians should be aware of the fact that general QoL dimensions (physical function, emotional function, fatigue) are as a rule of greater significance for QoL than sexuality and lower urinary tract symptoms.

Aged↗
PubMed1999

Normal tissue complication probabilities correlated with late effects in the rectum after prostate conformal radiotherapy.

PURPOSE: Radiation therapy of deep-sited tumours will always result in normal tissue doses to some extent. The aim of this study was to calculate different risk estimates of late effects in the rectum for a group of cancer prostate patients treated with conformal radiation therapy (CRT) and correlate these estimates with the occurrences of late effects. Since the rectum is a hollow organ, several ways of generating dose-volume distributions over the organ are possible, and we wanted to investigate two of them. METHODS AND MATERIALS: A mathematical model, known as the Lyman-Kutcher model, conventionally used to estimate normal tissue complication probabilities (NTCP) associated with radiation therapy, was applied to a material of 52 cancer prostate patients. The patients were treated with a four field box technique, with the rectum as organ at risk. Dose-volume histograms (DVH) were generated for the whole rectum (including the cavity) and of the rectum wall. One to two years after the treatment, the patients completed a questionnaire concerning bowel (rectum) related morbidity quantifying the extent of late effects. RESULTS: A correlation analysis using Spearman's rank correlation coefficient, for NTCP values calculated from the DVHs and the patients' scores, gave correlation coefficients which were not statistically significant at the p<0.01 level. The correlation coefficients based on histograms of the whole rectum were larger than those derived from histograms of the rectum wall. Also, simpler descriptive measures as Dmax, of the whole rectum, correlated better to observed late toxicity than Dmax derived from histograms of the rectum wall. Correlation coefficients from "high-dose" measures were larger than those calculated from the NTCP values. Accordingly, as the volume parameter of the Lyman-Kutcher model was reduced, raising the impact of small high-dose volumes on the NTCP values, the correlation between observed effects and NTCP values became significant at p<0.01 level. CONCLUSIONS: 1) High-dose levels corresponding to small volume fractions of the cumulative dose-volume histograms were best correlated with the occurrences of late effects in the rectum as measured with questionnaires. This is compatible with a more serial organisation of the rectal tissue architecture than previously reported. 2) Reducing the Lyman-Kutcher model's volume parameter, thus allowing small high-dose regions to determine the NTCP, improved the correlation, but not beyond that of high-dose levels corresponding to small volume fractions of the cumulative dose-volume histograms.

Diarrhea↗
PubMed1999

Monitoring of tumor reoxygenation following irradiation by 31P magnetic resonance spectroscopy: an experimental study of human melanoma xenografts.

BACKGROUND AND PURPOSE: Inadequate tumor reoxygenation during radiation therapy may cause local treatment failure. This study was aimed at investigating the potential usefulness of 31P-MRS in monitoring tumor reoxygenation following radiation treatment. MATERIALS AND METHODS: Tumors of two human melanoma xenograft lines (BEX-t and HUX-t) were exposed to 15.0 Gy, and then the fraction of radiobiologically hypoxic cells, measured by using the paired survival curve method, or tumor bioenergetic status, measured by 31P-MRS as the (PCr + NTPbeta)/Pi resonance ratio, was determined versus time after the radiation exposure. RESULTS: Untreated BEX-t and HUX-t tumors showed similar fractions of radiobiologically hypoxic cells and similar bioenergetic status, whereas both parameters differed substantially between the lines in irradiated tumors. A close association was found between radiation-induced changes in tumor bioenergetic status and radiation-induced changes in the fraction of radiobiologically hypoxic cells. CONCLUSION: 31P-MRS is a potentially useful method for monitoring tumor reoxygenation following radiation treatment.

Animals↗
PubMed1999

Effects of hyperthermia on bioenergetic status and phosphorus T1S in human melanoma xenografts monitored by 31P-MRS.

Conventional hyperthermia enhances tumor response to radiotherapy through thermal cell inactivation and vascular shut-down, whereas mild hyperthermia potentiates the effect of radiotherapy by improving tumor oxygenation. The work reported here was aimed at investigating whether 31P-magnetic resonance spectroscopy (31P-MRS) measurements of tumor bioenergetic status; i.e., the (PCr + NTPbeta)/Pi resonance ratio, and/or the spin lattice relaxation times, T1s, of the Pi and NTPbeta resonances can be used to distinguish between the effects of conventional and mild hyperthermia. BEX-t human melanoma xenografts were treated at 43.0 degrees C for 15 or 60 min, and bioenergetic status and T1s were measured as function-of-time after treatment. Hyperthermia-induced effects on tumor blood flow was measured by using the 86Rb uptake method. The morphology of the capillary network in treated and untreated tumors was studied by histologic examination. Tumors treated for 15 min showed increased blood flow and dilated capillaries, whereas tumors treated for 60 min showed decreased blood flow and capillary occlusions; i.e., 43.0 degrees C for 15 min was a treatment consistent with mild hyperthermia and 43.0 degrees C for 60 min was consistent with conventional hyperthermia treatment of BEX-t tumors. Bioenergetic status increased after treatment at 43.0 degrees C for 15 min, and decreased after treatment at 43.0 degrees C for 60 min, similar to the blood flow. Likewise, the T1 of the Pi resonance increased after treatment at 43.0 degrees C for 15 min, and decreased after treatment at 43.0 degrees C for 60 min. The T1 of the NTPbeta resonance showed a similar change as the T1 of the Pi resonance, but less pronounced. Consequently, 31P-MRS measurements of tumor bioenergetic status and the T1 of the Pi resonance may perhaps be utilized to distinguish between vascular effects of mild and conventional hyperthermia.

Animals↗