Consideration of the effects of intense tissue heating on the RF electromagnetic fields during MRI: simulations for MRgFUS in the hip.

Due to the strong dependence of tissue electrical properties on temperature, it is important to consider the potential effects of intense tissue heating on the RF electromagnetic fields during MRI, as can occur in MR-guided focused ultrasound surgery. In principle, changes of the RF electromagnetic fields could affect both efficacy of RF pulses, and the MRI-induced RF heating (SAR) pattern. In this study, the equilibrium temperature distribution in a whole-body model with 2 mm resolution before and during intense tissue heating up to 60 °C at the target region was calculated. Temperature-dependent electric properties of tissues were assigned to the model to establish a temperature-dependent electromagnetic whole-body model in a 3T MRI system. The results showed maximum changes in conductivity, permittivity, [absolute value]B(1)(+)[absolute value] and SAR of about 25%, 6%, 2%, and 20%, respectively. Though the B1 field and SAR distributions are both temperature-dependent, the potential harm to patients due to higher SARs is expected to be minimal and the effects on the B1 field distribution should have minimal effect on images from basic MRI sequences.

Preoperative irradiation for the prevention of heterotopic ossification induces local inflammation in humans.

Radiation of the hip is an established method to prevent heterotopic ossification (HO) following total hip arthroplasty (THA) but the precise mechanism is unclear. As inflammatory processes are suggested to be involved in the pathogenesis of HO, we hypothesized that the preoperative irradiation impacts local immune components. Therefore, we quantified immune cell populations and cytokines in hematomas resulting from the transection of the femur in two groups of patients receiving THA: patients irradiated preoperatively (THA-X-hematoma: THA-X-H group) in the hip region (7 Gy) in order to prevent HO and patients who were not irradiated (THA-H group) but were postoperatively treated with non-steroidal anti-inflammatory drugs (NSAIDs). Radiation resulted in significantly increased frequencies of T cells, cytotoxic T cells, NKT cells and CD25+CD127- Treg cells, whereas the number of naive CD45RA-expressing cytotoxic T cells was reduced. These results indicate differential immune cell activation, corroborated by our findings of significantly higher concentrations of pro-inflammatory cytokines (e.g., IL-6, IFNγ) and chemokines (e.g., MCP-1, RANTES) in the THA-X-H group as compared to THA-H group. In contrast, the concentration of the angiogenic VEGF was significantly suppressed in the THA-X-H group. We conclude that preoperative irradiation results in significant changes in immune cell composition and cytokine secretion in THA-hematomas, establishing a specific - rather proinflammatory - milieu. This increase of inflammatory activity together with the observed suppression in VEGF secretion may contribute to the prevention of HO.

Relative importance of hip and sacral pain among long-term gynecological cancer survivors treated with pelvic radiotherapy and their relationships to mean absorbed doses.

PURPOSE: To investigate the relative importance of patient-reported hip and sacral pain after pelvic radiotherapy (RT) for gynecological cancer and its relationship to the absorbed doses in these organs. METHODS AND MATERIALS: We used data from a population-based study that included 650 long-term gynecological cancer survivors treated with pelvic RT in the Gothenburg and Stockholm areas in Sweden with a median follow-up of 6 years (range, 2-15) and 344 population controls. Symptoms were assessed through a study-specific postal questionnaire. We also analyzed the hip and sacral dose-volume histogram data for 358 of the survivors. RESULTS: Of the survivors, one in three reported having or having had hip pain after completing RT. Daily pain when walking was four times as common among the survivors compared to controls. Symptoms increased in frequency with a mean absorbed dose >37.5 Gy. Also, two in five survivors reported pain in the sacrum. Sacral pain also affected their walking ability and tended to increase with a mean absorbed dose >42.5 Gy. CONCLUSIONS: Long-term survivors of gynecological cancer treated with pelvic RT experience hip and sacral pain when walking. The mean absorbed dose was significantly related to hip pain and was borderline significantly related to sacral pain. Keeping the total mean absorbed hip dose below 37.5 Gy during treatment might lower the occurrence of long-lasting pain. In relation to the controls, the survivors had a lower occurrence of pain and pain-related symptoms from the hips and sacrum compared with what has previously been reported for the pubic bone.

Long-term effects on bone mineral density of different therapeutic schemes for acute lymphoblastic leukemia or non-Hodgkin lymphoma during childhood.

BACKGROUND: Little is known regarding long-term bone deficit in relationship with the modalities of cancer therapy among survivors of childhood malignancy. METHODS: Bone mineral density (BMD) was evaluated at lumbar spine (LS), total hip and femoral neck in 89 patients (44 men) more than 5 years after remission of childhood acute lymphoblastic leukemia (ALL) or non-Hodgkin lymphoma (NHL). The patients had received chemotherapy (group I; n = 41), chemotherapy and cranial irradiation (group II; n = 32), or bone marrow transplantation (BMT) with total body irradiation (TBI) (group III; n = 16). All patients had received methylprednisolone and 47 additional dexamethasone treatment. RESULTS: A reduced BMD at any site was observed in 44 of the 89 patients, more frequently in men (66%) than women (33%) (p < 0.001). In comparison with group I, mean BMD was significantly lower at all sites in group II and at the total hip and femoral neck in group III. A multivariate analysis showed independent significant influences of male gender at LS (p < 0.001) and of type of treatment and dexamethasone at the hip (p < 0.05). CONCLUSIONS: A low bone mass is frequently observed in adult survivors of childhood ALL and NHL, and is associated with male gender at the LS and with dexamethasone treatment, cranial irradiation and BMT/TBI at the hip.

Radiation dose and image information in computed radiography. A phantom study of angle measurements in the weight-bearing knee.

PURPOSE: To establish a correlation between radiation dose and diagnostic accuracy when employing a new digital method for angle determinations. The specific intention was to determine how far the radiation dose can be reduced without losing measuring accuracy and to compare this radiation dose with that employed with our conventional method. MATERIAL AND METHODS: An image succession of an anthropomorphic phantom was generated with a computed radiography (CR) system, by reducing the exposure stepwise. The images were archived and transferred to a workstation for evaluation. The intraobserver variation of two angle determinations was used as an indicator of the evaluation accuracy. Patient radiation doses were measured with thermoluminescent dosimeters. The energy imparted, indicating the relative risk associated with exposure to ionising radiation, and the effective dose, which determines the absolute risk, were calculated. RESULTS AND CONCLUSION: No significant correlation was found between patient dose and measuring accuracy within the evaluated exposure interval. At the lowest exposure of the CR system, the energy imparted to the patient was 30 microJ. Compared with our conventional analogue method this is a reduction by 98%. The effective dose was as low as 1.5 microSv. The CR technique creates possibilities to adapt exposure parameters, and thus the radiation dose to the patient, according to the purpose of the investigation.

Organ doses, detriment and genetic risk from simple X-ray examinations in Málaga (Spain).

This work has been carried out with the aim of evaluating, as a reference, some radiological magnitudes which affect patients receiving radiation from X-ray sources. The sample was the population tended by the Radiological Service of the 'Na, Sra, de la Victoria' University Hospital and who have been treated with some of the five simple explorations: chest, abdomen, lumbar spine, hip and pelvis. The primary beam of radiation delivered by the different generators have been measured by means of non-invasive methods, which allows us to estimate the effective dose. Likewise, we have evaluated the dose in gonads and the contribution that each technique provides to the genetically significant dose (GSD = 158.59 microGy) and to the somatic significant dose (SSD = 3.19 mSv-year). Moreover, we have calculated the annual dose per capita (0.15 mSv) and the contribution that performs to the detriment (G) of these tests of conventional radiology. The results obtained are analogous to the reference values proposed in the area of E.C.M. Furthermore, we also include the values of child expectancy and the number of exploration performed in the Health Sanitary Area Malaga-West classified according to type, age and sex of the patient.

Musculoskeletal complications of neutron therapy for prostate cancer.

The purpose of this study was to investigate the cause of hip complaints following conformal neutron therapy delivered by opposed lateral and oblique anterior ports to treat prostate cancer. Twenty-seven patients with hip complaints following neutron or mixed neutron and photon therapy for prostate cancer had 34 magnetic resonance imaging (MRI) studies 3-39 (mean 15.3) months following treatment; for comparison, 13 similarly treated patients without hip complaints were imaged 1-32 (mean 13.8) months post-treatment; 25/40 imaged patients received concurrent nonsteroidal hormone therapy. Coronal and axial images of the hips/pelvis were obtained utilizing T1 weighted spin echo and fat suppressed inversion recovery (STIR) sequences. Signal amplitude (SA) of involved muscles was measured on the STIR images and normalized to that of the psoas outside the treatment field. Hip complaints ranged from mild soreness or motion limitation to severe pain and limitation of ambulation; presence and severity of symptoms (sx) were significantly related to neutron dose (P = 0.020 and 0.0001) but not to hormone therapy (each P > 0.17). Normalized SA of the obturator muscles differed significantly with neutron dose (P = 0.013), the presence, and the severity, of sx (P = 0.0002 and 0.0007); estimated extent of abnormal muscle also differed significantly with neutron dose (P = 0.039), presence, and severity, of sx (P = 0.00004 and 0.0007); [hormone treatment had a profound effect on SA (P = 0.0001) and extent (P = 0.005) which was independent of sx (P = 0.10 and 0.14, respectively) and neutron dose (P = 0.33 and 0.32, respectively)]. Subcutaneous changes localized lateral to the greater trochanter were seen in all, and edema of the subjacent gluteus muscles in many, symptomatic hips; only 4/13 asymptomatic hips showed subcutaneous changes, 6 had mild gluteus edema. Avascular necrosis of the femoral head was seen in 5 symptomatic hips, with marked acetabular necrosis in 3 of these; small joint effusions were seen in 8 symptomatic hips; asymptomatic hips had no significant bone or joint abnormalities. Neutron therapy for prostate cancer designed to spare the rectum results in significant dose-dependent, musculoskeletal complications which are well demonstrated by MRI. SA abnormalities of irradiated muscle correlate significantly with neutron dose and both presence and severity of hip sx. Protocol modifications have been implemented to reduce these complications. MRI provides an objective means to assess both complications and the success of new protocols in ameliorating them. Concurrent hormone therapy has a profound effect on muscle changes on MRI which is independent of neutron dose and sx.

[Surgical treatment of radiation-induced lesions of the hip in adults]. / Traitement chirurgical des radiolésions de la hanche chez l'adulte.

The authors report their experience in the surgical management of lesions of the adult hip following radiotherapy. The diagnosis of a hip problem occurring after pelvic radiotherapy for malignant tumors is made by clinical and radiological examination. The problems include femoral head necrosis, necrosis and/or fracture of the acetabulum, or involvement of the entire hip joint (radiation coxopathy). Fractures of the femoral neck have been described in the literature, but are now very rare following the routine use of external shields as protection during irradiation. Post-irradiation lesions are often bilateral 21%. They appear after a variable latency period of two to twenty years and they progress remorselessly. A diagnosis of simple radio necrosis can only be made after using radio isotope bone scanning, MRI or CT to exclude malignant disease as acetabular metastasis, and radio-induced sarcomas. Hemiarthroplasty is often followed by collapse of the acetabulum and should no longer be used. The treatment generally practised nowadays is a Total Hip Replacement (THR). We report a retrospective study of 71 hips in 56 patients treated, between 1970 and 1982, by the use of conventional cemented components. In 49 hips this was followed by a 52% incidence of acetabular loosening resulting from the poor quality of the irradiated bone which had become necrotic and porotic. Between 1983 and 1990, we modified the technique by regularly using reinforcing the acetabulum with a metallic ring fixed by long screws, (as used in revision surgery for THR). Bone grafts were also used in 9 cases. We had a 12% incidence of loosening in 22 hips with a mean follow-up of 40 months. There were also two post-operative infection which need removal of the prostheses. This emphasizes the risk of infection in this type of surgery and is probably increased by the associated lesions of the soft tissues (lymphoedema, radiodermitis). The authors wish to stress the poor prognosis of radiation lesions of the hip which often occur in patients who have otherwise recovered from their pelvic tumour. These radiation lesions have to be recognised and treated in a specific way. Our experience and the reports in the literature suggest that the generally used conventional THR gives uncertain results, and therefore we propose a THR employing metallic reinforcement of the acetabulum with or without any necessary bone grafts. It is vital to warn the patients that the results may not be as excellent as with THR for other types of hip disorders. When there is severe destruction of the acetabulum the choice between a THR combined with massive bone allograft, and a Girdlestone hip resection must be very carefully discussed with the patient. This latter "salvage" procedure may in any case become necessary if there are local and otherwise unmanageable problems.

Hip stiffness following mixed conformal neutron and photon radiotherapy: a dose-volume relationship.

PURPOSE: To determine the relationship between dose, volume, and the incidence of hip stiffness in patients who received conformal neutron irradiation for prostate cancer. METHODS AND MATERIALS: A series of dose-searching studies using neutron irradiation for prostate cancer were performed to determine the optimal dose, fraction size, field size, technique, and proportions of photon and neutron dose. Neutron doses ranged from 9 to 20 Gy and photon doses ranged from 0 to 38 Gy. Data were analyzed by using a hip stiffness grading scale. RESULTS: Hip stiffness was recorded on follow-up examination in 30% of patients (40 out of 132) treated with fast neutrons or mixtures of fast neutron and photon radiation for prostate cancer. Hip stiffness was categorized as none (Grade 0, 92 patients), mild (Grade 1, 24 patients), moderate (Grade 2, 10 patients), or severe (Grade 3, 6 patients). The incidence of hip stiffness differed significantly by dose and volume in the five dose levels studied (p < 0.001). CONCLUSIONS: By using a mixture of conformal neutron and photon irradiation and limiting the total neutron dose to less than 13 Gy, hip stiffness toxicity could be reduced to acceptable levels.

Prevention of heterotopic ossification (HO) after total hip replacement: randomized high versus low dose radiotherapy.

In a prospectively randomized study 60 hips at high risk for heterotopic ossification (HO) received prophylactic radiotherapy (RT). Randomization was performed between a low dose (LD-RT) of 5 x 2 Gy (arm A: 32 patients) and a high dose (HD-RT) of either 10 x 2 Gy (arm B1; 8 patients) or 5 x 3.5 Gy (arm B2; 20 patients). Relevant patient and risk factors were equally distributed in both treatment arms. 4 (7%) patients developed treatment failures. A short delay of RT after postoperative day (POD) 4 was significantly correlated with failure (p < 0.001). The results suggest no difference in prophylactic efficacy between LD-RT and HD-RT treatment. 2/19 (11%) patients receiving additional diphosphonates and 2/18 (11%) on no medication failed RT treatment, but none on indomethacin did so. In conclusion, immediate postoperative RT has been shown to be an effective prophylactic treatment.

Postoperative irradiation for the prevention of heterotopic bone: analysis of different dose schedules and shielding considerations.

Ninety-seven high risk hips were irradiated postoperatively for prevention of heterotopic bone (HTB) in the UCLA Department of Radiation Oncology from 1980 to 1988. Ninety-two hips in 82 patients were eligible for analysis with a minimum follow-up of 2 months and a median follow-up of 10 months. Forty-nine of the hips had porous coated ingrowth prostheses. From 1980 to 1986, 2 Gy fractions were used to deliver 20 Gy (8 hips), 12 Gy (1 hip), and 10 Gy (27 hips). Since December of 1986, 38 hips received 8 Gy in two increments and 18 hips received a single 7 Gy fraction. All porous ingrowth components were shielded with custom blocks. Six out of 92 hips developed clinically significant (Brooker grade 3 or 4 heterotopic bone). There was one clinically significant failure in 78 hips (1.3%) when irradiation was initiated before post-operative day (POD) #6 and shielding was properly placed. One clinical failure occurred in 38 hips which received 8 Gy in two increments. One clinical failure occurred out of the 18 hips treated with 7 Gy in one fraction. This failure could be related to block malposition. There were four clinical failures in the 36 hips treated with 2 Gy fractions to total doses of 10 Gy, 12 Gy, or 20 Gy. Three of these failures were associated with initiation of treatment after POD #5, and the fourth was related to block malposition. Unshielded trochanteric osteotomies resulted in five migrations and seven fibrous unions for a total non-osseous union rate of 12/36 (33%). Shielding of the remaining 28 trochanteric osteotomies resulted in a non-osseous union rate of 7% (0 migrations and 2 fibrous unions). There were no failures of union of components, and the only side effects noted in the series were the five trochanteric migrations. In conclusion, the use of 8 Gy in two increments or 7 Gy in one fraction was found to be as efficacious as conventional 2 Gy fractionation schemes with no increase in side effects. For optimal results, treatment should be implemented prior to POD #5 with shielding of the trochanteric osteotomy. Postoperative irradiation to prevent HTB can be used in hips with porous components using properly placed blocks to shield the porous region.

A parametric study of space radiation exposures to critical body organs for low earth orbit missions.

The geomagnetically-trapped and galactic cosmic radiation environments are two of the major sources of naturally-occurring space radiation exposure to astronauts in low earth orbit. The exposure is dependent primarily on altitude, spacecraft shielding, crew stay-times, and solar cycle effects for a 28.5 deg orbital inclination. Based on Space Shuttle experience, the calculated results of a parametric study are presented for several mission scenarios using a computerized anatomical man model and are compared with the NASA crew exposure limits for several critical body organs.

Prevention of heterotopic bone formation with early post operative irradiation in high risk patients undergoing total hip arthroplasty: comparison of 10.00 Gy vs 20.00 Gy schedules.

Prior studies have demonstrated the effectiveness of postoperative radiation therapy (RT) to the hip area following total hip replacement (THR) surgery in preventing the development of heterotopic bone formation in patients considered to be at high risk for development of this complication. Previously, patients received 20.00 Gy in 10 fractions (fx) over 2 weeks, beginning as soon postop as medically feasible (usually post-op day 2). In an effort to reduce hospital stay and risk of secondary malignancy, a prospective treatment program was initiated April 1982 using a reduced dose of 10.00 Gy in 5 fx over 5-7 days. As of February 1984, 46 consecutive hips determined to be at high risk were treated with this reduced dose. Prior studies have demonstrated that heterotopic bone is always radiographically evident by 8 weeks. Of the 46 hips, 41 had been evaluated with the minimum required 8 week follow-up X ray. Twenty-five of these hips, 61%, had a mean long term follow-up of 12 months. Our historical control group, consisting of 54 consecutive high risk post-THR's, was shown to have a 68.5% incidence of heterotopic bone. The 20.00 Gy group, when RT was started by post-op day 5, demonstrated a 3.2% incidence, compared to 4.9% in the 10.00 Gy group. Complication rates were also comparable in the two RT groups, 19.4% and 7.3% respectively; 10.00 Gy is apparently as effective as 20.00 Gy in preventing heterotopic bone formation in high risk post-THR patients.

[Somatic sequelae induced by radiotherapy in bone segments in adults]. / Sequele somatiche da radioterapia in corrispondenza dei segmenti scheletrici dell'adulto.

The authors, on the basis of reports found in literature and of a personal series, discuss the radiological aspects, the differential diagnosis, the main factors that lead to bone sequelae, and the possible contributory causes and complications. The radiological aspects is characterized by the association of sclerotic and atrophic changes, with a prevalence of the latter in the involvement of the mandible and the cranial bones. Among the main factors there are the radiation dose and its chronological distribution. In fact, the higher the values of the nominal standard dose (NSD), the higher the incidence of such alterations and the more difficult to carry out the efficacy of their treatment. These alterations are found almost exclusively after treatment with administration, in terms of NSD, of more than 1352 rets. Among the contributory causes there are all the factors that may change the physiological condition of the bony tissue. The most common complications are fractures and septic osteitis, the last particularly frequent in the mandible. These alterations and mainly fractures may be solved even spontaneously, even if rather late, so that conservative treatments are indicated. After osteitis it is usually possible to avoid pseudoarthrosis. In cases irradiated with higher doses, osteotomy is often necessary sometime followed by poor results.

[Radiation lesions of the hip]. / Les radio-lésions de la hanche

Irradiation lesions of the hip are much better known than they used to be, and problems diagnosis no longer arise. Study of these 49 cases of irradiation lesions of the hip shows that they occur in 1 to 36 per cent of patients irradiated for pelvic cancer. The rate of occurrence may be reduced by selection and improvement in the techniques of radiotherapy. The extent of the lesions is determined from the time that irradiation is stopped. The lesions appear after a delay of several months and develop progressively throughout their extent. This confer on them a false appearance of a progressive lesion. There are severe lesions, which seriously threaten ambulation. Trans-cervical fractures should be considered separately; these are usually isolated lesions, simple to treat and of good prognosis. Fractures of the acetabulum and necroses of the acetabular roof or of the femoral head, developing usually as paired lesions or in the context of an irradiation coxopathy, constitute another group, in which treatment by total prosthesis raises numerous technical problems. Total prosthesis has however given to these hips; in almost 2 cases out of 3, a function which is at present satisfactory but whose future is unknown. The abnormality high levels of infection and in particular loosening are related to the extent to which the lesions have progressed. Resection of these prosthesis in cases of failure is similar to resection of the head and neck, and has its place as a salvage operation since its allows mobility and pain relief to be obtained at the price of stability.