technetium-tc-99m-medronate and Ischemia

To what extent lateral retinacular release done in total knee arthroplasty compromises patellar viability has been debated. This study is a prospective study to assess patellar viability using Technetium-99m methylene diphosphate (Tc-99m MDP) scintigraphy. Between 2005 and 2006, 59 patients (72 knees) who underwent primary total knee arthroplasty were studied, of which 36 required lateral release. All patients underwent regional bone scan using Tc-99m MDP before and 1 to 3 weeks after the surgery. Two nuclear medicine consultants using both qualitative and quantitative assessment interpreted the scans independently. Fourteen knees with lateral release showed scintigraphic signs of hypovascularity in the early postoperative period that normalized in 8-week postoperative period. This study documents the greater incidence of transient patellar hypovascularity associated with lateral release.

Topics: Aged; Aged, 80 and over; Arthritis, Rheumatoid; Arthroplasty, Replacement, Knee; Female; Fractures, Bone; Humans; Ischemia; Knee Joint; Knee Prosthesis; Male; Middle Aged; Osteoarthritis, Knee; Osteonecrosis; Patella; Prospective Studies; Radionuclide Imaging; Risk Factors; Technetium Tc 99m Medronate; Treatment Outcome

We aimed to preserve sternal vascularity better by harvesting only midsegment of the right internal thoracic artery (RITA) than using conventional bilateral internal thoracic artery (BITA) harvesting method, and we evaluated the sternal vascularity with single photon emission computed tomography (SPECT).. In this prospective clinical randomized investigation, 135 patients undergoing coronary artery bypass surgery (CABG) were divided into three groups: Full-RITA group who had a full length of both ITA as a graft for CABG (n=45); mid-RITA group - a midsegment of RITA and left internal thoracic artery (LITA) (n=45); and non-RITA group who had only LITA (n=45). Before and after surgery, all patients underwent a bone scan with single photon emission computed tomography (SPECT) to evaluate the sternal vascular activity. Comparisons of variables were performed by Chi-square, ANOVA, Tukey HSD and paired t test as appropriate. The Bonferroni correction was applied for multiple comparisons.. Postoperative early scans (6.9+/- 0.9 days) showed a reduction of blood flow in the both sides of the sternum compared with the preoperative scans (p<0.001). In full-RITA group, there was no significant difference between left and right hemi-sternum (0.56+/- 0.04 and 0.55+/- 0.02 respectively). However, in mid-RITA and non-RITA groups, right hemi-sternum showed significantly better vascularity than left hemi-sternum in the early postoperative period (p<0.001). Three patients (6.6%) with diabetes mellitus in full-RITA group had sternal infection; one of them was deep sternal infection with dehiscence. In mid-RITA group, there was only two patients who had superficial infection (4.4%) and in non-RITA group there was no infection (p=0.234).. Mid-RITA harvesting technique can be preferred to preserve sternal vascularity better than conventional technique. By improving new techniques and methods, more acceptable sternal complications could be achieved than full-RITA technique.

Topics: Coronary Artery Bypass; Female; Humans; Ischemia; Male; Mammary Arteries; Middle Aged; Radiopharmaceuticals; Regional Blood Flow; Sternum; Technetium Tc 99m Medronate; Tomography, Emission-Computed, Single-Photon; Vascular Surgical Procedures

Coronary artery bypass grafting (CABG) is one of the most frequently performed operations in the United States. The use of internal mammary artery (IMA) grafting has been identified as increasing the risk of sternal wound infections and mediastinitis. The purpose of our study was to prospectively evaluate the effect of different techniques of left internal mammary artery (LIMA) harvesting on sternal vascularity. Thirty-three patients undergoing primary coronary artery bypass grafting were studied. The patients were divided into groups that received a skeletonized IMA (group I, n=11), a pedicled IMA (group II, n=12), or a semiskeletonized IMA (group III, n=10) graft. Each patient underwent a preoperative 99mTc-methylene diphosphonate bone scan using single photon emission computed tomography (SPECT). The ratio of the mean counts/pixel for each side of the sternum was obtained. Post-operatively, all patients had a repeat bone SPECT. Ratios of unilateral sternal uptakes were compared to the preoperative study. A univariable analysis of post-operative to pre-operative ratios revealed statistically significant reduction in vascularity to the left side of the sternum post-operatively in group II compared with groups I and III (0.68 0.12 vs 0.99 0.24 and 0.93 0.09; P<0.01). There was no difference between groups I and III (P=1). Multivariable analysis revealed only the type of harvesting to be associated with post-operative reduction in left to right sternal activity ratio (P<0.02). Pairwise comparisons revealed that differences are due to pedicled type of harvesting (group II vs group I, P=0.03; II vs III, P=0.001; and I vs III, P=0.115). A pedicled IMA graft causes acute post-operative sternal ischaemia. This does not occur when the IMA is skeletonized or semiskeletonized. Hence, it may be prudent to minimize dissection during mobilization of the IMA to decrease the likelihood of post-operative sternal complications.

Topics: Aged; Bone and Bones; Coronary Artery Bypass; Female; Follow-Up Studies; Humans; Ischemia; Male; Mammary Arteries; Middle Aged; Postoperative Complications; Radiopharmaceuticals; Regional Blood Flow; Sternum; Technetium Tc 99m Medronate; Tomography, Emission-Computed, Single-Photon; Vascular Surgical Procedures

Topics: Aged; Aged, 80 and over; Female; Humans; Ischemia; Lower Extremity; Male; Middle Aged; Muscle, Skeletal; Necrosis; Peripheral Arterial Disease; Radionuclide Imaging; Radiopharmaceuticals; Retrospective Studies; Technetium Tc 99m Medronate; Whole Body Imaging

A 51-year-old woman on peritoneal dialysis for chronic renal failure secondary to diabetic and nonsteroidal anti-inflammatory drug nephropathy was referred for a Tc-99m MDP bone scan to assess firm subcutaneous plaques in the sacral and gluteal regions. This showed extensive superficial tracer localization in the subcutaneous tissues as well as visceral tracer activity in the myocardium, lungs, stomach, and kidneys. These findings were typical for calciphylaxis (calcific uremic arteriolopathy), a form of metastatic calcification encountered in patients with chronic renal failure that is characterized by subcutaneous soft tissue calcification, painful ulcerations, high morbidity, and mortality. Treatment with sodium thiosulfate resulted in dramatic scintigraphic improvement.

Topics: Bone and Bones; Calcinosis; Calciphylaxis; Female; Humans; Ischemia; Kidney Failure, Chronic; Middle Aged; Necrosis; Neoplasm Metastasis; Radionuclide Imaging; Technetium Tc 99m Medronate; Thiosulfates; Tissue Distribution

Topics: Diagnosis, Differential; Female; Foot; Humans; Ischemia; Leg; Middle Aged; Radionuclide Imaging; Radiopharmaceuticals; Reflex Sympathetic Dystrophy; Self-Injurious Behavior; Technetium Tc 99m Medronate; Tourniquets

We sought to prospectively evaluate the long-term effect of left internal thoracic artery harvesting on sternal vascularity.. Twelve consecutive patients undergoing primary coronary artery bypass grafting were studied. In all patients a pedicled left internal thoracic artery was harvested. Each patient underwent a preoperative technetium-99m methylene diphosphonate bone scan with single photon emission computed tomography. The ratio of the mean counts per pixel for each side of the sternum was obtained. All patients had early repeat bone scans 6 plus minus 2.4 days postoperatively and late repeat bone scans 18.6 plus minus 3.5 months after the operation. Ratios of unilateral sternal uptakes were compared between the different scans. One patient died during follow-up and was excluded from the study.. There was a significant decrease in flow to the left hemisternum in the early postoperative scan compared with that in the preoperative scan (P <.001). At late follow-up scans, flow to the left hemisternum had returned to normal (P =.119). Midterm clinical follow-up demonstrated 3 superficial wound infections. No musculoskeletal pain existed at the time of follow-up, but 3 patients had numbness or tingling at the skin area corresponding to the site from which the left internal thoracic artery was harvested.. Acute postoperative sternal ischemia caused by harvesting of a pedicled left internal thoracic artery is temporary and resolves with time.

Topics: Aged; Coronary Artery Bypass; Humans; Ischemia; Male; Middle Aged; Prospective Studies; Radiopharmaceuticals; Specimen Handling; Sternum; Technetium Tc 99m Medronate; Thoracic Arteries; Time Factors; Tomography, Emission-Computed, Single-Photon

Topics: Acute Disease; Aged; Atrial Fibrillation; Female; Hepatitis; Humans; Ischemia; Liver; Radionuclide Imaging; Sensitivity and Specificity; Technetium Tc 99m Medronate

Previous studies have identified focal areas of alveolar tenderness, elevated mucosal temperature, radiographic abnormality, and increased radioisotope uptake or "hot spots" within the quadrant of pain in most patients with chronic, idiopathic facial pain (phantom pain, atypical facial neuralgia, and atypical facial pain).. This retrospective investigation radiographically and microscopically evaluated intramedullary bone in a certain subset of patients with histories of endodontics, extraction, and fixed partial denture placement in an area of "idiopathic" pain.. Patients from 12 of the United States were identified through tissue samples, histories, and radiographs submitted to a national biopsy service. Imaging tests, coagulation tests, and microscopic features were reviewed. Of 38 consecutive idiopathic facial pain patients, 32 were women.. Approximately 90% of subpontic bone demonstrated either ischemic osteonecrosis (68%), chronic osteomyelitis (21%), or a combination (11%). More than 84% of the patients had abnormal radiographic changes in subpontic bone, and 5 of 9 (56%) patients who underwent radioisotope bone scan revealed hot spots in the region. Of the 14 patients who had laboratory testing for coagulation disorders, 71% were positive for thrombophilia, hypofibrinolysis, or both (normal: 2% to 7%). Ten pain-free patients with abnormal subpontic bone on radiographs were also reviewed.. Intraosseous ischemia and chronic inflammation were suggested as a pathoetiologic mechanism for at least some patients with atypical facial pain. These conditions were also offered as an explanation for poor healing of extraction sockets and positive radioisotope scans.

Topics: Adult; Aged; Biopsy; Blood Coagulation Tests; Chronic Disease; Denture, Partial, Fixed; Facial Pain; Female; Fibrinolysis; Humans; Ischemia; Male; Mandible; Mandibular Diseases; Maxilla; Maxillary Diseases; Middle Aged; Neuralgia; Osteomyelitis; Osteonecrosis; Radiography; Radiopharmaceuticals; Retrospective Studies; Root Canal Therapy; Technetium Tc 99m Medronate; Thrombophilia; Tooth Extraction; Wound Healing

We compared growth in vascularised allograft transplants, autografts and in non-operated physes in rabbits immunosuppressed with cyclosporin A and in non-immunosuppressed animals. Molecular haplotyping was undertaken before operation to ensure allogenicity. Postoperative bone scans and fluorochrome labelling were used to confirm physeal vascularity. The animals were killed at three or five weeks. Proximal tibial physeal autografts, with or without cyclosporin A, or allografts with cyclosporin A, grew at similar rates to the physes of non-operated rabbits. All the operated physes grew at rates significantly greater than their contralateral controls. 99mTc-MDP bone scans accurately predicted the viability of the epiphyseal plate. Quantitative histomorphological analysis of the heights of the physeal proliferative and hypertrophic zones showed that successful physeal transplants have a normal appearance, but when unsuccessful have thickened hypertrophic zones compatible with physeal ischaemia. We discuss the significance of these results in relation to the transplantation of physes in children.

Topics: Analysis of Variance; Anastomosis, Surgical; Animals; Cyclosporine; Follow-Up Studies; Growth Plate; Hypertrophy; Immunosuppression Therapy; Ischemia; Microsurgery; Polymorphism, Restriction Fragment Length; Rabbits; Radiography; Radionuclide Imaging; Technetium Tc 99m Medronate; Tibia; Transplantation, Autologous; Transplantation, Homologous

In patients affected by unbearable pain secondary to peripheral vascular disorders beyond surgical repair such as thromboangitis obliterans, diabetic microangiopathy, arteriosclerosis obliterans, there is a need to establish the degree of micro-circulation functionality before proceeding with invasive pain therapy, such as Spinal Cord Stimulation (SCS). From our series some cases of refractory ischaemic pain subjected to nuclear medicine techniques assessment before and after SCS implant will be presented; these data suggest that the use of radionuclides for quantifying regional perfusion, in view of the information it offers us both in the dynamic angiographic phase and in the later static phase, constitutes a very valid aid in the diagnosis and treatment of chronic pain conditions of ischaemic origin. Cutaneous, musculoskeletal and bone flow scintiscan is a non-invasive procedure which allowed us to make an objective selection of patients who are candidates for prolonged conservative treatment thus limiting the incidence of ineffective permanent SCS implants.

Topics: Adult; Aged; Bone and Bones; Electric Stimulation Therapy; Female; Humans; Infusions, Intravenous; Ischemia; Male; Middle Aged; Muscles; Pain; Pain Management; Peripheral Vascular Diseases; Radionuclide Imaging; Regional Blood Flow; Skin; Spinal Cord; Technetium Tc 99m Medronate

Topics: Hepatitis; Humans; Ischemia; Liver; Radionuclide Imaging; Technetium Tc 99m Medronate

Scintigraphy with technetium-99m methylene diphosphonate (MDP) delineates a wide spectrum of nonosseous disorders. Neoplastic, hormonal, inflammatory, ischemic, traumatic, excretory, and artifactual entities demonstrate abnormal soft-tissue uptake of Tc-99m MDP. Mechanisms leading to increased extraosseous Tc-99m MDP uptake include extracellular fluid expansion, enhanced regional vascularity and permeability, and elevated tissue calcium concentration. The composition of the calcium deposition and the presence of other metallic ions (eg, iron and magnesium) are important. Soft-tissue Tc-99m MDP uptake is seen in benign (tumoral calcinosis, myositis ossificans) and malignant (sarcomas, adenocarcinomas, metastases) neoplastic entities. Hormonal disturbances in calcium metabolism, especially in hyperparathyroidism, can lead to metastatic calcification, visualized with Tc-99m MDP scintigraphy. Tissue damage from inflammation, infection, or physical trauma results in localized hyperemia, edema, or calcium (and hemosiderin) deposition based on their pathophysiologic characteristics. Urinary tract obstruction, anomalies, or dysfunction are demonstrated by Tc-99m MDP imaging. Common artifacts are related to faulty radiopharmaceutical preparation, Tc-99m MDP administration, and imaging technique. Recognition of these modes of extraskeletal Tc-99m MDP uptake can enhance the diagnostic value of bone scintigraphy.

Topics: Adult; Aged; Artifacts; Bone and Bones; Child; Child, Preschool; Endocrine System Diseases; Female; Humans; Inflammation; Ischemia; Male; Middle Aged; Neoplasms; Radionuclide Imaging; Technetium Tc 99m Medronate; Urologic Diseases; Wounds and Injuries

Internal mammary artery (IMA) dissection may cause sternal devascularization and ischemia resulting in sternal wound complication. To evaluate the effect of median sternotomy and IMA dissection on sternal vascular supply, sternal bone tomography was performed 7 days and 1 month after cardiac operation in 67 patients. Seventeen nondiabetic patients had single IMA grafts, 18 had double IMA grafts, and 12 had only saphenous vein grafts or valve replacement. Twenty diabetic patients were studied after any one of these operations. Seven patients were restudied 1 month after the operation. Sternal technetium-99m-methylene diphosphate tomography was performed. The sternum was visualized and focal zones of hypoactivity represented sternal hypoperfusion. The ratio of hypoactivity area over total sternal area was calculated for every patient. After median sternotomy without single or double IMA grafts, the averaged hypoperfusion ratio was 4% +/- 1% compared with 13% +/- 3% after single IMA grafts and 24% +/- 6% after double IMA grafts (p less than 0.0001). Diabetic patients without IMA, with single IMA, and with double IMAs showed hypoperfusion areas of 5% +/- 3%, 15% +/- 5%, and 23% +/- 9%, respectively, a result similar to that of nondiabetic patients. One month after operation the hypoperfusion area decreased to 2% +/- 2% (p less than 0.05) in restudied patients. Our results indicate that IMA dissection causes a significant although partial and temporary sternal ischemia, which is more severe after double IMA than single IMA mobilization and which may be incriminated in the development of sternal wound infection. This vascularization defect was not greater among patients with diabetes mellitus.

Topics: Body Mass Index; Diabetes Complications; Dissection; Female; Humans; Ischemia; Male; Mammary Arteries; Middle Aged; Myocardial Revascularization; Obesity; Prospective Studies; Radionuclide Imaging; Reoperation; Saphenous Vein; Staphylococcal Infections; Sternum; Surgical Wound Infection; Technetium Tc 99m Medronate

Topics: Female; Humans; Ischemia; Liver; Middle Aged; Radionuclide Imaging; Technetium Tc 99m Medronate

We present a patient with diffuse and intense uptake in the soft tissues of both lower legs and feet seen on 99mTc-HMDP bone scintigraphy. This finding presumably resulted from compromised blood supply to the lower legs plus a cold environment. The extraosseous bone imaging agent localization was presumably related to an existing ischemic condition that was exacerbated by cold. Differential diagnosis of the scan pattern should be differentiated from the artifact of socks contaminated by radioactive urine.

Topics: Aged; Frostbite; Humans; Ischemia; Leg; Male; Radionuclide Imaging; Technetium Tc 99m Medronate

In 20 cases of fresh cervical hip fracture, treated with primary prosthetic replacement, preoperative 99mTc-MDP scintimetry was compared with histologic findings of the extracted femoral heads. The radionuclide uptake was classified into three types according to the activity distribution; overall increase, focal decrease, and overall decrease. Histologically, the location and extent of ischemic necrosis in the femoral heads were closely related to the distribution of decreased activity.

Topics: Aged; Aged, 80 and over; Female; Femur Head; Hip Fractures; Humans; Ischemia; Male; Middle Aged; Necrosis; Radionuclide Imaging; Technetium Tc 99m Medronate

During arterial flow scintigraphy, increased tracer uptake in the upper extremity has been noted secondary to induced ischemia distal to blood-pressure cuffs and simple tourniquets, employed prior to the injection. We prospectively studied 68 patients undergoing three-phase bone scintigraphy to evaluate the frequency and magnitude of this artifact. The results showed that when a blood-pressure cuff was applied virtually all patients demonstrated increased activity in the extremity of cuff application. When a simple rubber tourniquet was applied few patients demonstrated the artifact. Only one patient, a case of reflex sympathetic dystrophy syndrome, had increased uptake on blood-pool and skeletal-phase images. We recommend that in flow studies of the hands, wrists, and forearms, blood pressure cuffs not be employed and that at least 3 min should elapse between release of the occlusive device and injection. Asymmetry of flow under these conditions is unlikely to be artifact.

Topics: Blood Pressure Determination; Bone and Bones; Hand; Humans; Ischemia; Prospective Studies; Radionuclide Imaging; Regional Blood Flow; Technetium Tc 99m Medronate; Tourniquets

In eight undisplaced intracapsular fractures of the femoral neck, an intracapsular hematoma was diagnosed by computed tomography. 99mTc-MDP scintimetry revealed markedly reduced or absent blood supply to the head of femur. The intracapsular pressure was 23 (2.7-43) kPa with the hip in neutral position. Following aspiration of 12 (0.5-36) ml of blood, pressure was reduced to zero, and postaspiration scintimetry revealed restitution of blood supply to the femoral head. Hip joint tamponade in these patients has caused femoral head ischemia, reversible by aspiration.

Topics: Aged; Aged, 80 and over; Femoral Neck Fractures; Femur Head; Hemarthrosis; Hip Joint; Humans; Ischemia; Middle Aged; Pressure; Radionuclide Imaging; Suction; Technetium Tc 99m Medronate; Time Factors; Tomography, X-Ray Computed

A noninvasive radionuclide technique to visualize ischemic small intestine was evaluated. Vascular ligation of 20-30 cm ileum was done in rabbits. After induction of ischemia, technetium (99mTc) methylene diphosphonate (TMDP) was injected IV at intervals up to 24 hours. Images were recorded 1 and 3 hours after injection of radioisotope and showed preferential (9:1) uptake by ischemic bowel. Positive scans were present in all animals up to 4 hours and in 75% at 10-12 hours, but in none 24 hours after induction of ischemia. Nonocclusive intestinal ischemia was simulated in 4 dogs by infusing norepinephrine into a jejunal mesenteric arterial branch. After 1 hour, an IV bolus of TMDP was injected and images recorded at intervals up to 3 hours. Selective uptake of isotope by the ischemic segment was observed in all animals. Angiography confirmed that isotope uptake was confined to the infused segment. These studies show that occlusive intestinal ischemia can be detected, by radionuclide imaging up to 12 hours, and nonocclusive (low flow) ischemia for at least 4 hours, after onset.

Topics: Acute Disease; Animals; Arterial Occlusive Diseases; Disease Models, Animal; Dogs; Evaluation Studies as Topic; Ileum; Ischemia; Jejunum; Rabbits; Radionuclide Imaging; Technetium Tc 99m Medronate; Time Factors

99mTc-MDP-scintimetry was performed in 25 consecutive cases of radiographically silent transient synovitis of the hip in children. Fourteen cases had normal scintimetry; seven cases had an increased uptake in the epiphysis; four cases had markedly defective uptake in the epiphysis, indicating interrupted vascular supply. At repeat scintimetry 6 weeks later, the uptake was normal or increased in three of these four cases; the one case with a persistent defect was the only case in this series who later developed radiographic evidence of Legg-Calvé-Perthes' disease. In some cases presenting with clinical symptoms of synovitis of the hip, there is a transient, spontaneously recovering ischaemia of the proximal femoral epiphysis, not followed by radiographic evidence of necrosis. This should be considered in attempts to make a pre-radiographic diagnosis of Legg-Calvé-Perthes' disease by radionuclide methods.

Topics: Child; Child, Preschool; Diphosphonates; Female; Femur Head; Hip; Humans; Infant; Ischemia; Legg-Calve-Perthes Disease; Male; Pain; Radionuclide Imaging; Synovitis; Technetium; Technetium Tc 99m Medronate

Two elderly patients had pain after hip trauma with no radiographic evidence of fracture. Computed tomography demonstrated capsular haematoma. Scintimetry revealed femoral head ischaemia. Intracapsular hip joint pressure in extension was 240 and 176 mm Hg, respectively, in neutral position and 280 and 360 mm Hg in internal rotation. The hip joints were aspirated for 8 ml and 5 ml of blood, respectively, leading to pain relief and regained radiotracer uptake in the femoral head. It is concluded that traumatic hip joint tamponade may cause femoral head ischaemia which may be reversed by aspiration.

Topics: Accidents, Home; Aged; Diphosphonates; Female; Femur Head; Hip Injuries; Hip Joint; Humans; Ischemia; Male; Pressure; Radionuclide Imaging; Suction; Technetium; Technetium Tc 99m Medronate; Tomography, X-Ray Computed

In order to evaluate renal ischemic damage in transplanted kidneys, renal scintigraphy with 99mTc-methylene diphosphonate was performed in 30 kidney grafts within 36 h after transplantation. The renal uptake was monitored for 100s at 10-min intervals during 90 min following injection. Seventeen patients had an average uptake of radioactivity in the kidney on the 60-, 70-, 80-, and 90-min scintigrams expressed as a percentage of the activity present on the 10-min scintigram of 150% or less (low) and 13 patients had an average uptake of radioactivity of above 150% (high). There was no relationship between the average uptake of radioactivity and warm and cold ischemia times (or the combined value: corrected ischemia), maximal function, reversible rejection, and ureteral obstruction. A significant correlation was found between the average uptake of radioactivity in the kidney and onset of function. Seventy-six per cent of the grafts with a low average uptake of radioactivity had an onset of function on or before day 10 after operation (early) whereas only 15% of the kidneys with a high average uptake of radioactivity had an early onset of function. Twelve per cent of the patients with a low average uptake of radioactivity in the kidneys had their grafts removed for various reasons within 2 months after transplantation, whereas 54% with a high average uptake of radioactivity had their grafts removed. It is concluded that 99mTc-methylene diphosphonate scintigraphy may be useful in the prognostic assessment of graft onset of function and of graft survival.

Topics: Adolescent; Adult; Animals; Diphosphonates; Dogs; Female; Graft Rejection; Humans; Ischemia; Kidney; Kidney Transplantation; Male; Middle Aged; Prognosis; Rabbits; Technetium; Technetium Tc 99m Medronate; Time Factors; Tomography, Emission-Computed

Topics: Diaphragm; Diphosphonates; Female; Humans; Infant; Ischemia; Technetium; Technetium Tc 99m Medronate

Topics: Diphosphonates; Forearm; Glycogen Storage Disease; Glycogen Storage Disease Type V; Humans; Ischemia; Middle Aged; Muscles; Muscular Diseases; Myoglobinuria; Radionuclide Imaging; Technetium; Technetium Tc 99m Medronate