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An Introduction to PET-CT Imaging¹

¹ From the Department of Radiology, University of Pittsburgh Medical Center, 200 Lothrop St, Pittsburgh, PA 15213. Received December 12, 2002; revision requested March 24, 2003; final revision received and accepted June 16. Address correspondence to V.K. (e-mail: kapoorv@msx.upmc.edu).

View larger version (24K): [in a new window]   Figure 1. Annihilation reaction. Positrons (ß+) released from the nucleus of FDG annihilate with electrons (ß-), releasing two coincidence 511-keV photons (), which are detected by scintillation crystals (blue rectangles). N = neutron, P = proton.

View larger version (60K): [in a new window]   Figure 2. Production of F-18. After acceleration in a cyclotron, negatively charged hydrogen ions (red and blue spheres) pass through a carbon foil in a carousel, which removes the electrons (blue spheres) from the hydrogen ion, leaving behind high-energy protons (red spheres). The protons are directed toward a target chamber that contains stable O-18-enriched water, thus producing hydrogen (F-18) fluoride. (Adapted and reprinted, with permission, from reference 21.)

View larger version (37K): [in a new window]   Figure 3. Uptake of FDG. FDG is a glucose analog that is taken up by metabolically active cells by means of facilitated transport via glucose transporters (Glut) in the cell membrane. In the cell cytoplasm, FDG undergoes phosphorylation to form FDG-6-phosphate (6P), which, unlike glucose, cannot undergo further metabolism and becomes trapped within the cell. N = nucleus.

View larger version (107K): [in a new window]   Figure 4a. Differential uptake of FDG. Axial fused FDG PET-CT images of patients with supraglottic squamous cell carcinoma (a) and colon cancer (b) show metastases to a left supraclavicular lymph node (a) and to the liver (b). The metastases demonstrate differential FDG uptake in proportion to their metabolic activity. The necrotic centers of the metastases (straight solid arrow) show negligible uptake compared with their hypermetabolic peripheries (open arrows). Arrowheads in b = physiologic FDG activity in the left kidney, wavy arrow in b = simple hepatic cyst without metabolic activity.

View larger version (120K): [in a new window]   Figure 4b. Differential uptake of FDG. Axial fused FDG PET-CT images of patients with supraglottic squamous cell carcinoma (a) and colon cancer (b) show metastases to a left supraclavicular lymph node (a) and to the liver (b). The metastases demonstrate differential FDG uptake in proportion to their metabolic activity. The necrotic centers of the metastases (straight solid arrow) show negligible uptake compared with their hypermetabolic peripheries (open arrows). Arrowheads in b = physiologic FDG activity in the left kidney, wavy arrow in b = simple hepatic cyst without metabolic activity.

View larger version (60K): [in a new window]   Figure 5. Photograph (frontal view) of a hybrid PET-CT scanner shows the PET ring detector system (red ring). There are up to 250 block detectors in the ring. Drawing shows a detector block with 8 x 8 smaller scintillation crystals (green and orange rectangles) linked to four photomultiplier tubes (blue circles).

View larger version (42K): [in a new window]   Figure 6. Radial blurring. The ring geometry of block detectors results in radial blurring due to nonuniform penetration of the detector elements by the coincidence photons. In more peripheral regions of the gantry (a, c), the annihilation photons may penetrate more than a single detector due to their oblique paths, thereby resulting in blurring of the final image. The degree of blurring is variable and depends on the obliquity of the paths of the photons through the detectors. Radial blurring is typically worse at the periphery of an image.

View larger version (25K): [in a new window]   Figure 7. Mean positron range and annihilation angle blurring. Positrons (ß+) travel a small distance called the mean positron range (a) before annihilating with electrons (ß-). This change in position between the origin of the positron and its site of annihilation results in positron range blurring, thus limiting the spatial localization that can be achieved with PET. In addition, positrons and electrons are in motion when they annihilate; therefore, the annihilation photons () are not at exactly 180° to each other. The unpredictable 0.5° variation (b) between the annihilation photons results in additional spatial degradation, which is called annihilation angle blurring. N = neutron, P = proton.

View larger version (73K): [in a new window]   Figure 8. Coincidence imaging. Although the photons emitted by annihilation points A and C are in coincidence, the distances that the coincident photons a and a1 and c and c1 will travel before they reach the scintillation crystals are different. There is a predetermined time window within which detected photons are considered to be in coincidence. Therefore, even though photons a and a1 and c and c1 are coincident, they will be electronically rejected as noncoincident. However, the coincident photons from point B are likely to reach the scintillation crystals within the time window and will be accepted as coincident.

View larger version (115K): [in a new window]   Figure 9. Photograph (side view) of a hybrid PET-CT scanner shows the PET (P) and CT (C) components. The distance between the PET and CT scanners is 80 cm, and the maximum coverage that can be achieved during a combined study is 145 cm. The PET and CT scanners are mechanically independent and can be used in isolation for PET or CT only.

View larger version (151K): [in a new window]   Figure 10. Recurrent colorectal carcinoma in a 65-year-old man after surgical resection. FDG PET-CT was performed to evaluate for recurrence. Axial fused FDG PET-CT image of the pelvis shows a Foley catheter in the urinary bladder (straight solid arrow). Recurrent disease in the pelvis (curved arrow) may be obscured by an FDG-distended bladder if catheterization is not used. Open arrows = metastatic left inguinal lymph node.

View larger version (126K): [in a new window]   Figure 11. Typical scout image obtained during an FDG PET-CT study. The blue-purple rectangle represents CT coverage during the study, and each overlapping green rectangle represents PET coverage. Six to seven bed positions are required for PET coverage of the neck, chest, abdomen, and pelvis.

View larger version (125K): [in a new window]   Figure 12. Display screen of the syngo software platform shows fused PET-CT images in the sagittal, coronal, and axial planes of a patient with recurrent esophageal carcinoma. Placing the crosshairs on the tumor automatically coregisters it in all three orthogonal planes. By dragging the vertical bar (arrow) along the horizontal line in the lower right quadrant of the screen, the PET and CT weighting of the image can be altered. In this image, the CT to PET ratio is 75% to 25%.

View larger version (150K): [in a new window]   Figure 13a. Metastatic squamous cell carcinoma in a 45-year-old woman. After biopsy of a right cervical lymph node revealed the carcinoma, FDG PET-CT was performed to search for the primary tumor. (a) Axial CT image obtained at the level of the oropharynx shows mild tonsillar asymmetry without a definite mass. (b) Corresponding fused FDG PET-CT image shows intense hypermetabolism in the left tonsil (arrow), which was the site of the primary tumor.

View larger version (125K): [in a new window]   Figure 13b. Metastatic squamous cell carcinoma in a 45-year-old woman. After biopsy of a right cervical lymph node revealed the carcinoma, FDG PET-CT was performed to search for the primary tumor. (a) Axial CT image obtained at the level of the oropharynx shows mild tonsillar asymmetry without a definite mass. (b) Corresponding fused FDG PET-CT image shows intense hypermetabolism in the left tonsil (arrow), which was the site of the primary tumor.

View larger version (124K): [in a new window]   Figure 14. Adenocarcinoma in a 50-year-old man with a mass in the apex of the left lung. Results of multiple biopsies were negative for malignancy. FDG PET-CT was performed for further characterization of the mass. Axial fused FDG PET-CT image shows marked hypermetabolism in the lesion (arrow), which proved to be a poorly differentiated adenocarcinoma at subsequent left upper lobectomy.

View larger version (63K): [in a new window]   Figure 15a. Laryngeal carcinoma in an 80-year-old man who underwent FDG PET-CT to characterize a new pulmonary nodule in the left upper lobe. (a) Axial fused FDG PET-CT image of the pulmonary nodule shows intense hypermetabolism (arrow), which was due to metastatic squamous cell carcinoma at wedge resection. (b) Axial CT image of the neck shows nonspecific bilateral thyroid nodules (solid arrows) with foci of calcification (open arrows), which were incidentally noted and are suggestive of multinodular goiter. (c) Corresponding fused FDG PET-CT image shows intense hypermetabolism in the left-sided thyroid nodule (curved arrow). Total thyroidectomy revealed left-sided papillary thyroid carcinoma and right-sided multinodular goiter. Open arrows = foci of calcification.

View larger version (119K): [in a new window]   Figure 15b. Laryngeal carcinoma in an 80-year-old man who underwent FDG PET-CT to characterize a new pulmonary nodule in the left upper lobe. (a) Axial fused FDG PET-CT image of the pulmonary nodule shows intense hypermetabolism (arrow), which was due to metastatic squamous cell carcinoma at wedge resection. (b) Axial CT image of the neck shows nonspecific bilateral thyroid nodules (solid arrows) with foci of calcification (open arrows), which were incidentally noted and are suggestive of multinodular goiter. (c) Corresponding fused FDG PET-CT image shows intense hypermetabolism in the left-sided thyroid nodule (curved arrow). Total thyroidectomy revealed left-sided papillary thyroid carcinoma and right-sided multinodular goiter. Open arrows = foci of calcification.

View larger version (124K): [in a new window]   Figure 15c. Laryngeal carcinoma in an 80-year-old man who underwent FDG PET-CT to characterize a new pulmonary nodule in the left upper lobe. (a) Axial fused FDG PET-CT image of the pulmonary nodule shows intense hypermetabolism (arrow), which was due to metastatic squamous cell carcinoma at wedge resection. (b) Axial CT image of the neck shows nonspecific bilateral thyroid nodules (solid arrows) with foci of calcification (open arrows), which were incidentally noted and are suggestive of multinodular goiter. (c) Corresponding fused FDG PET-CT image shows intense hypermetabolism in the left-sided thyroid nodule (curved arrow). Total thyroidectomy revealed left-sided papillary thyroid carcinoma and right-sided multinodular goiter. Open arrows = foci of calcification.

View larger version (116K): [in a new window]   Figure 16a. Biopsy-proved poorly differentiated non-small cell carcinoma in the native left lung in a 56-year-old man with idiopathic pulmonary fibrosis and a right lung transplant. (a) Axial CT image shows a large, conglomerate pulmonary mass in the left lower lobe (straight arrow) with enlargement of a subcarinal lymph node (curved arrow). (b) Corresponding fused FDG PET-CT image shows intense hypermetabolism in the mass (straight arrow) and the metastatic node (curved arrow).

View larger version (111K): [in a new window]   Figure 16b. Biopsy-proved poorly differentiated non-small cell carcinoma in the native left lung in a 56-year-old man with idiopathic pulmonary fibrosis and a right lung transplant. (a) Axial CT image shows a large, conglomerate pulmonary mass in the left lower lobe (straight arrow) with enlargement of a subcarinal lymph node (curved arrow). (b) Corresponding fused FDG PET-CT image shows intense hypermetabolism in the mass (straight arrow) and the metastatic node (curved arrow).

View larger version (44K): [in a new window]   Figure 17a. Melanoma in a 33-year-old man. The extent of disease was evaluated with FDG PET-CT. Axial (a) and sagittal (b) fused FDG PET-CT images show focal hypermetabolism in the left paraspinal soft tissue (arrow in a) and in T8 (arrow in b), findings consistent with metastases. CT showed only subtle areas of decreased attenuation. Arrowheads in a = misregistration artifact due to cardiac motion.

View larger version (133K): [in a new window]   Figure 17b. Melanoma in a 33-year-old man. The extent of disease was evaluated with FDG PET-CT. Axial (a) and sagittal (b) fused FDG PET-CT images show focal hypermetabolism in the left paraspinal soft tissue (arrow in a) and in T8 (arrow in b), findings consistent with metastases. CT showed only subtle areas of decreased attenuation. Arrowheads in a = misregistration artifact due to cardiac motion.

View larger version (127K): [in a new window]   Figure 18. Non-small cell lung carcinoma in a 78-year-old man with enlarged hilar and mediastinal lymph nodes. FDG PET-CT was performed for staging. Axial fused FDG PET-CT image shows an enlarged subcarinal node without abnormal metabolism (straight arrow), which was reactive. The metastatic left hilar node is FDG avid (wavy arrow), as was the primary tumor.

View larger version (119K): [in a new window]   Figure 19. Large B-cell lymphoma in a 74-year-old man. FDG PET-CT was performed for staging. Sagittal fused FDG PET-CT image shows wedge compression deformity of L4 with moderate hypermetabolism (arrow), which was confirmed at biopsy to be metastasis.

View larger version (57K): [in a new window]   Figure 20. Large cell lung cancer in a 54-year-old woman. Axial fused FDG PET-CT image shows hypermetabolism within a lung mass (arrow) and distal drowned lung (arrowheads). Precise localization of a tumor within a larger mass helps direct intervention such as biopsy.

View larger version (144K): [in a new window]   Figure 21a. Recurrent colorectal carcinoma in a 55-year-old woman after surgical resection. FDG PET- CT was performed to evaluate for recurrence because of a rising level of carcinoembryonic antigen. (a) Axial contrast-enhanced CT image of the pelvis shows minimal presacral soft tissue at the surgical site (arrows). (b) Corresponding fused FDG PET-CT image shows intense hypermetabolism at the surgical site (arrow), which was due to local recurrence. Arrowhead = suture from surgery.

View larger version (72K): [in a new window]   Figure 21b. Recurrent colorectal carcinoma in a 55-year-old woman after surgical resection. FDG PET- CT was performed to evaluate for recurrence because of a rising level of carcinoembryonic antigen. (a) Axial contrast-enhanced CT image of the pelvis shows minimal presacral soft tissue at the surgical site (arrows). (b) Corresponding fused FDG PET-CT image shows intense hypermetabolism at the surgical site (arrow), which was due to local recurrence. Arrowhead = suture from surgery.

View larger version (68K): [in a new window]   Figure 22. Recurrent esophageal carcinoma in a 63-year-old man after surgical resection. Follow-up CT showed an enlarging soft-tissue mass at the surgical site. FDG PET-CT was performed to evaluate for recurrence. Sagittal fused FDG PET-CT image shows intense hypermetabolism at the surgical site (black arrows), thus confirming the presence of recurrent disease. White arrow = suture from surgery.

View larger version (117K): [in a new window]   Figure 23a. Recurrent metastatic disease in a 33-year-old woman with invasive ductal carcinoma of the right breast, which was treated with surgical resection and dissection of the left axillary nodes. FDG PET-CT was performed to evaluate for recurrence. (a) Axial CT image shows a small lymph node in the right axilla (arrow). (b) Corresponding fused FDG PET-CT image shows mild hypermetabolism in the node (arrow), which represents recurrent metastatic disease. (c) Coronal fused FDG PET-CT image shows intense hypermetabolism in the left humeral head (arrow), which represents recurrent metastatic disease.

View larger version (121K): [in a new window]   Figure 23b. Recurrent metastatic disease in a 33-year-old woman with invasive ductal carcinoma of the right breast, which was treated with surgical resection and dissection of the left axillary nodes. FDG PET-CT was performed to evaluate for recurrence. (a) Axial CT image shows a small lymph node in the right axilla (arrow). (b) Corresponding fused FDG PET-CT image shows mild hypermetabolism in the node (arrow), which represents recurrent metastatic disease. (c) Coronal fused FDG PET-CT image shows intense hypermetabolism in the left humeral head (arrow), which represents recurrent metastatic disease.

View larger version (41K): [in a new window]   Figure 23c. Recurrent metastatic disease in a 33-year-old woman with invasive ductal carcinoma of the right breast, which was treated with surgical resection and dissection of the left axillary nodes. FDG PET-CT was performed to evaluate for recurrence. (a) Axial CT image shows a small lymph node in the right axilla (arrow). (b) Corresponding fused FDG PET-CT image shows mild hypermetabolism in the node (arrow), which represents recurrent metastatic disease. (c) Coronal fused FDG PET-CT image shows intense hypermetabolism in the left humeral head (arrow), which represents recurrent metastatic disease.

View larger version (52K): [in a new window]   Figure 24. Residual fibrosis in a 40-year-old man with non-Hodgkin lymphoma, which was treated with chemotherapy. Axial fused FDG PET-CT image shows extensive thickening of periaortic and retroperitoneal soft tissue without metabolic activity (arrows), findings indicative of residual fibrosis. Follow-up FDG PET-CT images were unchanged.

View larger version (58K): [in a new window]   Figure 25. Residual fibrosis in a 39-year-old man with large B-cell lymphoma. FDG PET-CT was performed for restaging after chemotherapy and radiation therapy. Axial fused FDG PET-CT image obtained at the level of the main pulmonary artery shows numerous prevascular lymph nodes—which are considered enlarged according to size criteria—with surrounding abnormal soft tissue without metabolic activity (arrow), findings indicative of residual fibrosis.

View larger version (103K): [in a new window]   Figure 26. Misregistration artifact. FDG PET-CT was performed for staging in a patient with carcinoma of the left breast. Axial fused FDG PET-CT image shows a lymph node in the left axilla (straight arrow). Focal hypermetabolism in the node (curved arrow) appears lateral to its expected location in the axilla and overlies axillary fat instead of the node. Misregistration between the CT and PET images is due to patient motion between the CT and PET portions of the examination.

View larger version (76K): [in a new window]   Figure 27a. Attenuation correction artifact. (a) Attenuation-corrected axial fused FDG PET-CT image shows a focus of hypermetabolism in the left axilla (arrow). (b) Attenuation-uncorrected fused FDG PET-CT image obtained at the same level shows lack of activity in the intensely enhancing (high-attenuation) left axillary vein (arrow), which is on the side of contrast material injection. This artifact is due to overcorrection by the attenuation correction software, which uses CT data for attenuation correction.

View larger version (57K): [in a new window]   Figure 27b. Attenuation correction artifact. (a) Attenuation-corrected axial fused FDG PET-CT image shows a focus of hypermetabolism in the left axilla (arrow). (b) Attenuation-uncorrected fused FDG PET-CT image obtained at the same level shows lack of activity in the intensely enhancing (high-attenuation) left axillary vein (arrow), which is on the side of contrast material injection. This artifact is due to overcorrection by the attenuation correction software, which uses CT data for attenuation correction.

View larger version (147K): [in a new window]   Figure 28a. Attenuation correction artifact. (a) Attenuation-corrected coronal fused FDG PET-CT image shows a focus of intense hypermetabolism in the right supraclavicular region (arrow). (b) Attenuation-uncorrected fused FDG PET-CT image obtained at the same level shows that the apparent focus of hypermetabolism is an attenuation correction artifact from a pacemaker (arrow).

View larger version (155K): [in a new window]   Figure 28b. Attenuation correction artifact. (a) Attenuation-corrected coronal fused FDG PET-CT image shows a focus of intense hypermetabolism in the right supraclavicular region (arrow). (b) Attenuation-uncorrected fused FDG PET-CT image obtained at the same level shows that the apparent focus of hypermetabolism is an attenuation correction artifact from a pacemaker (arrow).

View larger version (139K): [in a new window]   Figure 29. Physiologic muscle activity. Coronal fused FDG PET-CT image of the back shows bilateral, diffuse, symmetric moderate hypermetabolism in the paraspinal muscles (arrows). Muscular activity due to activity by the patient before or after FDG administration may result in this pattern of radiopharmaceutical uptake.

View larger version (120K): [in a new window]   Figure 30a. Large cell lung carcinoma in a 64-year-old man. (a) Pretherapy coronal fused FDG PET-CT image of the neck shows moderate hypermetabolism in the right vocal cord (arrow) with no activity in the left vocal cord (arrowhead). (b, c) Axial (b) and coronal (c) fused FDG PET-CT images of the chest show extension of the lung mass (white arrow) into the aortopulmonary window; this extension caused paralysis of the left vocal cord due to involvement of the left recurrent laryngeal nerve, thus explaining the asymmetric metabolism of the vocal cords. Also seen are encasement and marked narrowing of the left pulmonary artery (black arrows) by the mass, thus illustrating the detail seen with PET-CT. Arrowheads in c = aortic arch.

View larger version (58K): [in a new window]   Figure 30b. Large cell lung carcinoma in a 64-year-old man. (a) Pretherapy coronal fused FDG PET-CT image of the neck shows moderate hypermetabolism in the right vocal cord (arrow) with no activity in the left vocal cord (arrowhead). (b, c) Axial (b) and coronal (c) fused FDG PET-CT images of the chest show extension of the lung mass (white arrow) into the aortopulmonary window; this extension caused paralysis of the left vocal cord due to involvement of the left recurrent laryngeal nerve, thus explaining the asymmetric metabolism of the vocal cords. Also seen are encasement and marked narrowing of the left pulmonary artery (black arrows) by the mass, thus illustrating the detail seen with PET-CT. Arrowheads in c = aortic arch.

View larger version (56K): [in a new window]   Figure 30c. Large cell lung carcinoma in a 64-year-old man. (a) Pretherapy coronal fused FDG PET-CT image of the neck shows moderate hypermetabolism in the right vocal cord (arrow) with no activity in the left vocal cord (arrowhead). (b, c) Axial (b) and coronal (c) fused FDG PET-CT images of the chest show extension of the lung mass (white arrow) into the aortopulmonary window; this extension caused paralysis of the left vocal cord due to involvement of the left recurrent laryngeal nerve, thus explaining the asymmetric metabolism of the vocal cords. Also seen are encasement and marked narrowing of the left pulmonary artery (black arrows) by the mass, thus illustrating the detail seen with PET-CT. Arrowheads in c = aortic arch.

View larger version (122K): [in a new window]   Figure 31a. Metastatic disease in a 69-year-old woman with a rising level of CA-125 antigen after resection and chemotherapy of an ovarian carcinoma. FDG PET-CT was performed to evaluate for recurrence. Arrowheads = urinary bladder. (a) Coronal FDG PET image shows focal hypermetabolism in the liver (arrow), a finding suggestive of metastatic disease. Scattered foci of hypermetabolism in the abdomen and pelvis have the distribution of bowel loops. (b) Corresponding fused FDG PET-CT image shows hepatic metastatic disease (long arrow). The abdominal and pelvic hypermetabolic foci are due to diffuse peritoneal metastases (short arrows).

View larger version (107K): [in a new window]   Figure 31b. Metastatic disease in a 69-year-old woman with a rising level of CA-125 antigen after resection and chemotherapy of an ovarian carcinoma. FDG PET-CT was performed to evaluate for recurrence. Arrowheads = urinary bladder. (a) Coronal FDG PET image shows focal hypermetabolism in the liver (arrow), a finding suggestive of metastatic disease. Scattered foci of hypermetabolism in the abdomen and pelvis have the distribution of bowel loops. (b) Corresponding fused FDG PET-CT image shows hepatic metastatic disease (long arrow). The abdominal and pelvic hypermetabolic foci are due to diffuse peritoneal metastases (short arrows).

View larger version (133K): [in a new window]   Figure 32a. Diffuse large B-cell lymphoma evaluated with FDG PET-CT before therapy. Arrowheads = urinary bladder. (a) Coronal FDG PET image shows focal intense hypermetabolism in the right side of the pelvis (arrow). (b) Corresponding fused FDG PET-CT image shows that the focus of hypermetabolism is in the cecum (arrow), a common site of physiologic activity. PET-CT helps in accurate localization of normal and abnormal FDG activity.

View larger version (65K): [in a new window]   Figure 32b. Diffuse large B-cell lymphoma evaluated with FDG PET-CT before therapy. Arrowheads = urinary bladder. (a) Coronal FDG PET image shows focal intense hypermetabolism in the right side of the pelvis (arrow). (b) Corresponding fused FDG PET-CT image shows that the focus of hypermetabolism is in the cecum (arrow), a common site of physiologic activity. PET-CT helps in accurate localization of normal and abnormal FDG activity.

View larger version (132K): [in a new window]   Figure 33a. Non-Hodgkin lymphoma in a 67-year-old woman. Pretherapy FDG PET-CT was performed for staging. (a) Axial FDG PET image of the abdomen shows multiple areas of intense hypermetabolism that are difficult to localize except for a hypermetabolic focus in the posterior midline (arrow), which is in a lumbar vertebra. However, it is difficult to accurately localize the site of uptake within the vertebra—information that may be useful for biopsy guidance. (b) Corresponding fused FDG PET-CT image shows that the hypermetabolic foci are localized to a right perirenal mass (large arrowhead); pericaval and left retroperitoneal lymph nodes (short arrows); the left pedicle, adjacent body, and pars interarticularis of L4 (long arrow); and physiologic uptake in the lower pole of the left kidney (small arrowheads). Despite chemotherapy, the lesions were larger at subsequent imaging.

View larger version (60K): [in a new window]   Figure 33b. Non-Hodgkin lymphoma in a 67-year-old woman. Pretherapy FDG PET-CT was performed for staging. (a) Axial FDG PET image of the abdomen shows multiple areas of intense hypermetabolism that are difficult to localize except for a hypermetabolic focus in the posterior midline (arrow), which is in a lumbar vertebra. However, it is difficult to accurately localize the site of uptake within the vertebra—information that may be useful for biopsy guidance. (b) Corresponding fused FDG PET-CT image shows that the hypermetabolic foci are localized to a right perirenal mass (large arrowhead); pericaval and left retroperitoneal lymph nodes (short arrows); the left pedicle, adjacent body, and pars interarticularis of L4 (long arrow); and physiologic uptake in the lower pole of the left kidney (small arrowheads). Despite chemotherapy, the lesions were larger at subsequent imaging.

View larger version (146K): [in a new window]   Figure 34a. The CT portion of a PET-CT study can demonstrate diseases besides the primary malignancy that may be important in patient care. (a) FDG PET-CT was performed after surgical resection of the primary tumor in a patient with colorectal carcinoma to evaluate for recurrence. Axial fused FDG PET-CT image shows extensive segmental occlusive and subocclusive pulmonary emboli (arrows), findings that would be missed with PET. (b) FDG PET-CT was performed for staging in a patient with Hodgkin lymphoma. Axial fused FDG PET-CT image of the brain shows an aneurysm of the right middle cerebral artery (long arrow). Intense physiologic metabolism of the brain would mask this lesion on PET images. Short arrows = misregistration due to patient motion. (c) FDG PET-CT was performed for restaging in a 71-year-old man with melanoma who experienced new-onset hematuria. Axial fused FDG PET-CT image of the pelvis shows a polypoid bladder mass (arrow), which was the cause of the hematuria.

View larger version (131K): [in a new window]   Figure 34b. The CT portion of a PET-CT study can demonstrate diseases besides the primary malignancy that may be important in patient care. (a) FDG PET-CT was performed after surgical resection of the primary tumor in a patient with colorectal carcinoma to evaluate for recurrence. Axial fused FDG PET-CT image shows extensive segmental occlusive and subocclusive pulmonary emboli (arrows), findings that would be missed with PET. (b) FDG PET-CT was performed for staging in a patient with Hodgkin lymphoma. Axial fused FDG PET-CT image of the brain shows an aneurysm of the right middle cerebral artery (long arrow). Intense physiologic metabolism of the brain would mask this lesion on PET images. Short arrows = misregistration due to patient motion. (c) FDG PET-CT was performed for restaging in a 71-year-old man with melanoma who experienced new-onset hematuria. Axial fused FDG PET-CT image of the pelvis shows a polypoid bladder mass (arrow), which was the cause of the hematuria.

View larger version (63K): [in a new window]   Figure 34c. The CT portion of a PET-CT study can demonstrate diseases besides the primary malignancy that may be important in patient care. (a) FDG PET-CT was performed after surgical resection of the primary tumor in a patient with colorectal carcinoma to evaluate for recurrence. Axial fused FDG PET-CT image shows extensive segmental occlusive and subocclusive pulmonary emboli (arrows), findings that would be missed with PET. (b) FDG PET-CT was performed for staging in a patient with Hodgkin lymphoma. Axial fused FDG PET-CT image of the brain shows an aneurysm of the right middle cerebral artery (long arrow). Intense physiologic metabolism of the brain would mask this lesion on PET images. Short arrows = misregistration due to patient motion. (c) FDG PET-CT was performed for restaging in a 71-year-old man with melanoma who experienced new-onset hematuria. Axial fused FDG PET-CT image of the pelvis shows a polypoid bladder mass (arrow), which was the cause of the hematuria.