11/3/200611ENGG 167 MEDICAL IMAGINGNov. 6Nuclear Medicine & SPECT imagingReferences: The Essential Physics of Medical Imaging, Bushberg et al, 2nded.Chapters 19, 21, 22, 24.Physics and Radiobiology of Nuclear Medicine, G. B. Saha, 2nded. 2001.2Schedule This Week1) No class Wednesday2) Journal club Thurs/Friday(choose a paper on MRI/PET/SPECT imaging)3) Lab 5 can be due on Friday4) No lab this week!5) Scan through Chapters 19, 21& 24 in Bushberg11/3/200623Nuclear MedicineRef: Bushberg1) Gamma Camera & SPECT imaging2) Radionuclides3) Dose AssessmentNo lab this week!Scan through Chapters 19, 21& 24 in Bushberg3rdJournal Club Review – Thursday/Friday(see last slide today for instructions)4Nuclear Imaging with a Gamma CameraRadioactive atom held within a pharmaceutical molecule, allowing specific localization and imaging Often used to search for bone metastases of cancer tumors11/3/200635Nuclear Imaging with a Gamma Camera - example 1Reference: http://www.med.harvard.edu/JPNM/TF99_00/Sept21/WriteUp.htmlPresentationA 65 year old male with a history of non-insulin dependent diabetesmellitus, alcohol abuse, and severe peripheral vascular diseasepresented with a non-healing ulcer of the left first toe. Three Phase Bone Scan25 millicuries of Tc-99m MDP were administered intravenously. Dynamic 2-5 second images were obtained for 60 seconds after injection (angiographic phase). A static tissue phase image was obtained. Delayed skeletal phase images were obtained at 2-4 hours after injection. Gallium Scan5 milliCuries of Ga- 67 citrate were administered intravenously. Delayed images of the feet were obtained at 48 hours. Imaging FindingsRadiography, three phase bone scan and gallium scan were performed. Three Phase Bone ScanThe flow phase of the three-phase bone scan demonstrates diffuse increased flow to the left foot with focal accumulation in the first digit. On the tissue phase, there is marked asymmetry with increase activity in the left foot. In addition, there is mild localization in the first digit (shown by arrow). The delayed images demonstrate focal uptake at the left first MTP joint and first interphalangeal joint (shown by arrows). The uptake in three phase bone scans is related to blood flow and osteoblastic activity. In the study by R.H. Gold et al, the mean sensitivity is 85% and the specificity is 54% (3). Gallium ScanThe gallium scan (bottom two images) demonstrates focal increased tracer uptake in the left first toe.Mechanisms of Ga-67 citrate uptake include: (1) direct leukocyte and bacterial uptake, (2) lactoferrin and transferring binding, (3) increased vascularity, and (4) increased bone turnover. 6Single photon emission computed tomography (SPECT) with gamma camerasRef: Bushberg11/3/200647Gamma camera design – scintillators with PMTsRef: Bushberg8Localizing the signal Æ X, Y, ZRef: Bushberg11/3/200659Nuclear Medicine RadionuclidesRef: Bushberg10Tc99m - most common radionuclide usedRef: Bushberg11/3/2006611SPECT images – detection of countsRef: Bushberg12Gamma camera – has limitation of resolution versus distanceRef: Bushberg11/3/2006713Gamma camera imaging system performanceRef: Bushberg14camera images – correction for sparse samplingRef: Bushberg11/3/2006815emission images – homogeneous test fieldsRef: Bushberg16Multiple sequential projections for SPECT imaging11/3/2006917Filtered Backprojection SPECT imagingRef: Bushberg18Attenuation correction in computed SPECT imagingRef: Bushberg11/3/20061019Imaging the temporal sequence of radiation can be essential for useful information about function.Ref: BushbergTime-activity curve20Sequenced imaging - heart imagingRef: Bushberg11/3/20061121Sequenced imaging - heart imagingRef: BushbergTc99m labeled red blood cells22Thyroid Scan - single element gamma cameraRef: Bushberg• Safety monitoring for those who handle I-123 or I-131.• swallow capsule of weakly activated NaI• measure uptake in thyroid, compare values to that of a phantom and subjects thigh.• this activity provides a reference, and higher values than normal indicate occupational exposure has occurred.11/3/20061223Nuclear Fission Reactor production of 99MoRef: BushbergFission products are generated from rods of 235U inserted into reactor core.Chemical separation of 99Mo, 131I, 133Xe is readily possible from rod material.24Nuclear Fission Reactors are also used to generate isotopes via neutron captureRef: BushbergLow specific activity due to problems separating target materialfrom product, but can readily produce:One exception which has high separation yield is 125I11/3/20061325Radionuclide generators: separate long decay parent from fast decay daughter nuclideRef: Bushberg99Mo from 99mTc26Radionuclide generators: separate long decay parent from fast decay daughter nuclideRef: BushbergTypically delivered with 37 to 111 GBq activity (1 to 3 Cu)Mo decay allows the generator to be “milked” every dayTc buildup occurs between milkingsGenerator last about 1 week Tc-99m radiopharmaceutical prepared by injection of 99mTcO4into a sterile vial of freeze-dried pharmaceutical.11/3/20061427Medical Radionuclide Uses - I Ref: Bushberg28Medical Radionuclide Uses - IIRef: Bushberg11/3/20061529Shielding calculations Ref: Bushberg30Ref: Bushberg11/3/20061631Exposure Rate Constants Ref: