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Nuclear Medicine

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  • Nuclear medicine techniques Nuclear medicine images arise from injected radioactive tracers which subsequently emit radiation from within body organs. The radioactive compounds tend to be designed to accumulate selectively in specific tissues. For example, lung scans used in the diagnosis of pulmonary embolus arise from technetium-labeled macroaggregated albumin, which when injected into a vein, spreads and is deposited relatively evenly throughout normally perfused lung micro-vasculature. This creates an image solely of the lungs. Pulmonary vessels blocked by emboli will appear as defects (photon-poor) regions of the image. The thyroid can be imaged with radioactive iodine which is trapped by normal glandular tissue. Nuclear cardiology Several forms of nuclear imaging of the heart exist including techniques for directly imaging the myocardium such as shown here, or imaging of the blood pool cavities by technetium labeling of red blood cells. Nuclear-tagged compounds can provide a mechanism for selectively directing a radioactive material to specific tissues for creation of a nuclear image. In the case of myocardial imaging, compounds such as thallium 201 which is an analog of potassium, preferentially accumulate in perfused myocardium. Therefore, scarred (infarcted) or even ischemic areas of myocardial wall may lack brightness (radiation) in comparison to the brighter signature of normally perfused myocardium. Besides thallium, other radionuclides such as technetium can be attached to tissue seeking molecules (such as sestamibi) which provide a mechanism for creating a radioactive image of the perfused portions of the myocardium as shown in this image. Single photon emission computed tomography is a nuclear technique which uses multiple digital nuclear imaging views of the myocardium, permitting a tomographic reconstruction of individual slices. Alternatively, technetium radioactive labeling of red blood cells which are stable enough to permit equilibrium imaging of the major vessels and cardiac blood pool primarily of the cardiac chambers, when gated with the electrocardium into 15 to 20 time segments between systole and diastole, create a radionuclide angiogram from which calculation of ventricular ejection fraction, regional wall motion, and general chamber sizes can be assessed. These blood pool images are known variously as MUGA (multi-gated acquisition) or more conventionally, ERNA (equilibrium radionuclide angiogram). This technique is considered one of the most accurate for estimating left ventricular systolic function.
  • Planar perfusion imaging Planar nuclear projection images of myocardial perfusion using technetium-99m sestamibi as the perfusion agent demonstrates the anterior, left anterior oblique, and left lateral nuclear images compared to comparable anatomic illustrations. The majority of the nuclear myocardial image is provided by the full thickness of the left ventricular myocardium. The right ventricular free wall and atrial walls are much thinner structures but define the outline of their cavities. Planar imaging cameras The planar nuclear imaging camera is a large scintillation crystal with attached photomultiplier tubes that collects and locates individual nuclear decay events arising from a body organ. Each view is a projection which accumulates all counts through the full thickness of the radioactivity tagged organ. In this illustration, technetium 99M radioactive labelled material (tagging myocardium which has blood flow) appears as bright areas on the display and the blood-containing chambers of the heart show lower activity and therefore appear darker.
  • Planar perfusion imaging Planar nuclear projection images of myocardial perfusion using technetium-99m sestamibi as the perfusion agent demonstrates the anterior, left anterior oblique, and left lateral nuclear images compared to comparable anatomic illustrations. The majority of the nuclear myocardial image is provided by the full thickness of the left ventricular myocardium. The right ventricular free wall and atrial walls are much thinner structures but define the outline of their cavities. Planar imaging cameras The planar nuclear imaging camera is a large scintillation crystal with attached photomultiplier tubes that collects and locates individual nuclear decay events arising from a body organ. Each view is a projection which accumulates all counts through the full thickness of the radioactivity tagged organ. In this illustration, technetium 99M radioactive labelled material (tagging myocardium which has blood flow) appears as bright areas on the display and the blood-containing chambers of the heart show lower activity and therefore appear darker. Planar perfusion imaging Planar nuclear projection images of myocardial perfusion using technetium-99m sestamibi as the perfusion agent demonstrates the anterior, left anterior oblique, and left lateral nuclear images compared to comparable anatomic illustrations. The majority of the nuclear myocardial image is provided by the full thickness of the left ventricular myocardium. The right ventricular free wall and atrial walls are much thinner structures but define the outline of their cavities. Planar imaging cameras The planar nuclear imaging camera is a large scintillation crystal with attached photomultiplier tubes that collects and locates individual nuclear decay events arising from a body organ. Each view is a projection which accumulates all counts through the full thickness of the radioactivity tagged organ. In this illustration, technetium 99M radioactive labelled material (tagging myocardium which has blood flow) appears as bright areas on the display and the blood-containing chambers of the heart show lower activity and therefore appear darker.
  • SPECT imaging camera The SPECT camera is a large scintillation crystal connected to multiple photo-multiplier tubes which detect radiation emanating from the body. The technology of single photon emission tomography arises from positioning the camera head at multiple angles around the body accumulating as many as 180° of views at specific angular intervals. A certain number of counts are obtained from each view. In some cases multi-headed cameras are used to increase the speed of acquisition. Software then allows integration of all individual projection views into a composite data set which can be re-displayed as tomographic slices. Obviously, patient or organ motion, as well as variations in attenuation from different viewpoints can have a profound effect on the quality of the tomographic view.
  • SPECT perfusion imaging Nuclear myocardial perfusion tomograms using the radioactive compound technetium-99m sestamibi are shown compared to illustrations of the heart from similar views. Note that most of the myocardial wall activity arises from the left ventricular myocardium since it is considerably thicker (11 mm) than the right ventricular free wall (3 mm). The short axis tomogram shows the left ventricular myocardium as a donut shape while the vertical long axis and horizontal long axis tomograms display the myocardial wall as U-shaped structures. SPECT perfusion imaging Nuclear myocardial perfusion tomograms using the radioactive compound technetium-99m sestamibi are shown compared to illustrations of the heart from similar views. Note that most of the myocardial wall activity arises from the left ventricular myocardium since it is considerably thicker (11 mm) than the right ventricular free wall (3 mm). The short axis tomogram shows the left ventricular myocardium as a donut shape while the vertical long axis and horizontal long axis tomograms display the myocardial wall as U-shaped structures.
  • Nuclear blood-pool imaging of the heart Technetium radioactive labeling of red blood cells which are stable enough to permit equilibrium imaging of the major vessels and cardiac blood pool primarily of the cardiac chambers, when gated with the electrocardium into 15 to 20 time segments between systole and diastole, create a radionuclide angiogram from which calculation of ventricular ejection fraction, regional wall motion, and general chamber sizes can be assessed. These blood pool images are known variously as MUGA (multi-gated acquisition) or more conventionally, ERNA (equilibrium radionuclide angiogram). This technique is considered one of the most accurate for estimating left ventricular systolic function. With nuclear-tagged red-cells using Technetium 99m (Tc-99m sestamibi), ECG-gated nuclear emission images of the cardiac chambers can be obtained by accumulating radiation counts emanating from the body over several minutes, and then partitioning those counts to specific segments of the ECG cycle. Since these are projection images it is useful to create several different angular views to separate out the different chambers. Note that the left anterior oblique (LAO) view separates the blood-filled left and right ventricular chambers, with the interventricular septum appearing as a photon deficient space (occupied by the interventricular septum)between them.
  • Normal Aging These images are from an 81 year old woman, in excellent health, who participated in research on normal aging.
  • These images show typical findings in AIDS dementia: patchy hypoperfusion with a multifocal distribution which tends to be seen prominently in the frontal lobes. Compare with normal . Defects in cerebral perfusion have been previously reported in HIV positive individuals by single photon emission computed tomography (SPECT)[Masdeu, 1989 ][Pascal, 1991 ][Pohl, 1988 ][Holman, 1992 ][Schielke, 1990]. The anatomic and clinical significance of these findings, however, has remained uncertain. Because previous studies have shown that AIDS dementia complex (ADC) is associated with both functional defects and structural evidence of brain volume loss, we spatially matched (registered) the functional and structural data to assess the extent to which observed perfusion defects were "real", that is, represented low tracer uptake from structurally normal brain. The image datasets shown here are sampled along the same plane of view, to permit the direct comparison of SPECT and MR images in ADC. This type of analysis shows that there are functional defects (ie perfusion defects) in areas that appear non-atrophic. These are perhaps sites of early damage in which the structural images are still relatively normal.
  • Lyme Encephalopathy The patient was a 35 year old right- handed construction worker who was well until July 1979. At that time, he developed erythema migrans in association with flu-like symptoms. Four days later right facial palsy and fatigue developed, but resolved within one month. Five months later, in December, he developed oligoarticular arthritis affecting the knees which resolved spontaneously by 1983. In 1985, 6 years after onset of infection, the patient's wife noted that he had become very forgetful and was tending to fall asleep in the afternoons while on the job. There were no symptoms of another disease process, new medicines, or drug abuse to explain his symptoms. On examination at the bedside he appeared normal. However, on neuropsychological tests he had a markedly abnormal verbal memory despite a normal IQ. His spinal fluid showed no pleocytosis but had an elevated protein of 97 mg %. His serum Lyme titer was elevated, but more importantly, he had selective concentration of antibody in spinal fluid with a CSF/serum ratio of 1.3. MR of the brain and a polysomnogram were normal. He was treated with a one month course of IV ceftriaxone and gradually improved over 3-6 months with decrease in his spinal fluid protein from 97 to 70 to 52. Neuropsychologic tests improved but were still slightly abnormal at 6 months after therapy. Perfusion SPECT shows multifocal abnormalities of perfusion largely affecting the frontal lobes and hemispheric white matter. MR is normal. After antibiotic therapy, the perfusion abnormalities improved. To see this best, use the "time" button.
  • Astrocytoma This 35 year old man began having headaches eight months previouslsy. A CT scan was unremarkable. Two months prior to the current studies, he underwent brain biopsy, after progressive symptoms led to MR imaging. A low grade glioma was found, and he was treated with radiation. The MR demonstrates an area of mixed signal intensity on proton density (PD) and T2-weighted (T2) images in a left occipital region. Contrast enhancement shows the lesion to contain cystic elements. Thallium images show an anterior border of high uptake, consistent with a small region of tumor recurrence.
  • T1 MRI and FDG PET of normal brain Axial, Sagittal, and coronal
  • Astrocytoma A 53 y.o. right handed man sought medical attention because of a grand mal seizure. Brain biopsy revealed grade IV astrocytoma. The MR demonstrates an area of mixed signal intensity on proton density (PD) and T2-weighted (T2) images in a right parietal-occipital region. The central rounded core of the lesion is seen after contrast enhancement to contain cystic elements. Glucose metabolism is very low on the first PET study, but has increased three months later. This suggests tumor recurrence, and effectively rules out radiation necrosis. Like Thallium SPECT, the PET scan has been very useful in differentiating tumor recurrence and radiation necrosis. It also allows specific targeting of the area of recurrence, which may be surrounded by radiation necrosis in those patients who have received radiation. Case contributed by Drs. C. D. Sturm and R. Bucholz, St. Louis University.
  • Bone Scan Whole body bone scan and spot views of the legs show focal very avid uptake in the proximal right tibia and fibula ( shown by arrows ). There are foci of abnormal uptake throughout the right femoral diaphysis, metaphysis and head with expansion of the intertrochanteric region. Abnormal increased uptake in the L4 vertebra, left 8th rib, right 11th rib, distal right humerus and skull base (shown by arrowheads). Diagnosis Radiographic Diagnosis Fibrous dysplasia with sarcomatous degeneration in the tibia. Pathologic Diagnosis A CT guided biopsy of the lesion showed chondrosarcoma, grade 2 arising within a pre-existing lesion. Follow up A CT of the Chest showed no evidence of pulmonary metastases. The patient underwent resection of the right proximal tibia and fibula followed by placement of a knee prosthesis. Discussion Fibrous Dysplasia Fibrous dysplasia is a congenital, non-hereditary skeletal disorder that occurs with equal frequency in males and females. It is a developmental anomaly of bone formation in which the marrow is replaced by fibrous tissue. One percent of biopsied bone lesions are due to fibrous dysplasia. Monostotic disease is more common than polyostotic disease. When polyostotic, all the lesions tend to occur on one side of the body. The bones most frequently involved are the long bones: femur (most common), skull, and the ribs. Polyostotic disease can be associated with abnormal skin pigmentation (ipsilateral to the osseous lesions) and endocrinopathies. The constellation of polyostotic fibrous dysplasia, skin pigmentation and precocious puberty has the eponym McCune Albright Syndrome. Mazabraud Syndrome is fibrous dysplasia associated with soft tissue myxomas (1).

Nuclear Medicine Presentation Transcript

  • 1. Nuclear Medicine Planar Scintigraphy, SPECT, and PET
  • 2. Gamma Camera
  • 3. Myocardial Planar Scintigraphy
  • 4. Myocardial Perfusion Planar Scintigraphy
  • 5. SPECT
  • 6. SPECT Perfusion
  • 7. MUGA (ERMA)
  • 8. All Previous images taken from Yale Cardiovascular Imaging Site: http://info.med.yale.edu/intmed/cardio/imaging/
  • 9. Normal Brain
  • 10. AIDS Dementia
  • 11. Lyme Encephalopathy After treatment
  • 12. Astrocytoma – Tc SPECT (T1 MRI)
  • 13. PET
  • 14. PET-Astocytoma
  • 15. All Previous images taken from Harvard-The Whole Brain Atlas http://www.med.harvard.edu/AANLIB/
  • 16. Whole Body Bone Scan