All images are displayed in the same order. The reader can look at three images: PET, CT and fused all at the same time, or choose to look at one at a time. The images are also sliced into coronal, sagittal, and transaxial planes, which are available for CT, P.E.T., and the fused images; these will need when reading the P.E.T./CT scan.

Instructor's Comment:
Q: Is this a function of a specific software application, or is this preferential for best practice for reader image evaluation?

In this case the coronal images best display the focus of tracer uptake in the left axilla. The CT is useful in showing that the “hot” areas are tissue rather than bone because of the location of the focus; if not for the CT it may be difficult to tell whether the uptake was located in the lymph nodes or the ribs. These images are usually viewed via monitor, but the images can be printed if needed.

Radiopharmaceutical

The radiopharmaceutical used for this study was F-18, FDG.

Instructor's Comment:
Q: What is F-18, and what are its radionuclidic characteristics?
Q: What is the chemical name of FDG?

It is the appropriate imaging agent because it localizes through regional glucose metabolism. FDG is a radioactive pharmaceutical that is used to detect cancer cells. This is achieved by introducing FDG into the blood stream and simulating cellular glucose metabolism. Glucose is taken into the cell by the process of hexokinase. Once the glucose in inside the cell, it is phosphorylated into and turned into water and carbon dioxide and used as energy. The same principle applies to FDG, with the exception that after the FDG in transported into the cell it is not further metabolized. So, the radioactive form of glucose remains within the cells and can then be used for imaging.

Biodistribution

Most cells take in FDG and treat it as glucose with the exception of the tubular cells of the kidney. The kidneys and bladder excrete FDG.

Instructor's Comment:
Q: Why?
A: These cells of the kidneys are able to differentiate between useable glucose and the “false glucose” in FDG.

Excessive uptake in any other area is an indication of increased glucose utilization. In this case the tracer activity there are multiple large nodes in the left axilla with a maximum SUV of 11.1, which is consistent with malignancy.

Instructor's Comment:
Q: What is an SUV, and how is “11.1” consistent with malignancy?

Anatomy & Physiology of FDG

It is important to note that the CT and P.E.T. scans are a fusion of hardware as well as in imaging. The CT portion is used to demonstrate the anatomical location of the increased tracer accumulations; this is a non-contrast, non-breath hold, low mA CT. The P.E.T. scan is acquired to show the physiological function of the cells. After FDG is taken into the cells the “hot spots” seen in the left axillary region indicate areas of increased activity. This means that there is more cellular metabolism in this area of the body more so than anywhere else, and is indicative of cancer cells.

Instructor's Comment:
Q: What is the significance of cardiac tracer uptake? Is it the same for all patients?

Hodgkin’s Disease Information

Diagnosis of Hodgkin’s disease is defined according classification. There are two, nodular lymphocyte predominant Hodgkin’s lymphoma and Classical Hodgkin’s lymphoma. Of all HD cases nodular lymphocyte predominant ( LP) HD accounts for only 3-8%. This type of HD may or may not have diffuse areas. Due to the histology and number of cells, they are sometimes called “popcorn cells”. Lymphocyte predominant HD is more common in adults than children, and found more often in male than females in their early thirty’s. It has been recorded that more than 70% of stages I and II cases have a very favorable outcome, relapses are also more common than in other histologies. LPHD can progress to a large B-cell NHL in 3% of patients.

This case is unique because the patient does not have the common characteristics that are usually associated with this type of HD. The fact that this type of HD is so rare is well worth noting, but the fact that the patient is a 42-year-old, female with this type of HD is very unusual.

Staging of HD is arranged according to the extent of node region involvement. The stages range from I toIV. Stage I is said to have only one region involved, stage II incorporates two or more node regions on the same side of the diaphragm, stage III has involvement on both sides of the diaphragm, and finally stage IV having diffuse extralymphatic involvement. There are also substages to stages I and II. It is suggested that a number of diagnostic tests be administered to accurately stage the disease. Among the tests that can be done( CT, CXR, and SPECT) a PET scan is recommendable for staging for treatment.

Instructor's Comment:
Q: Is PET reimbursable for all types of Hodgkins Disease?

This patient received two PET/CT scans for her LPHD. The first of which was performed after a CT showed a suspicious area in her left axilla. The first PET/CT scan did show that the area of interest was in fact consistent for malignancy. The second PET/CT scan, after chemotherapy, showed no abnormal tracer uptake and a decrease in tumor size.

Treatment for HD is mostly successful even with advanced stage disease. While radiation therapy is recommended for early stage disease, chemotherapy is necessary for those with advanced cases of HD. ABVD is considered to be the standard regimen of chemotherapy for advanced HD because it has been reported to have much success in curing the disease with little recurrence or secondary malignancy.

This patient’s chemotherapy was successful.

Instructor's Comment:
Q: What treatment options are available for non-refractory Lymphoma?

Impression/Summary

On the first P.E.T./CT scan the radiologist noted multiple enlarged nodes in the left axilla with a maximum SUV of 11.1, which is consistent with malignancy. This finding was consistent with the previous mammogram and chest CT of the left axilla. There was no other abnormal uptake noted at that time.

After chemotherapy another P.E.T./CT scan was performed which showed no abnormal uptake of FDG in the area of interest and no metastisis to any other area. A full diagnostic CT is recommended as a follow up to this last finding.