Lung Cancer Research Paper

Introduction:

Lung cancer is one of the wide spread cancers related death in the world (1). The most widely recognized destinations of metastatic spread in lung cancer are the adrenal organs, cerebrum, bones and liver.

Bone metastasis is a type of cancer where cancer cells starts from an organ and then break, enter the bloodstream, and move to the bone. Studies showed that bone metastasis is already found in 20-30% of patient when the initial diagnosis of lung cancer is occurred. This percent becomes 30-60% when a morbid anatomy is made. In fact, about 40% of these patients have no symptoms showed the involvement of bone metastasis. Thus, several diagnosis techniques are needed to detect these bone metastasis.

Bone scintigraphy (BS) is one

of the most common detection tools used in bone metastasis determination since it has high sensitivity and wide availability. However, its sensitivity and specificity is not enough for the detection of lytic lesions which are related to osteoblastic reaction. A sensitivity and specificity is increased to be 93% when a SPECT technique is added.
Recently, Positron emission tomography (PET) has gained priority in diagnosis bone metastasis and many other diseases.

PET is a remarkable technique that changed the role of nuclear medicine not only because it works better and gives more precise and efficient diagnosis than other techniques but also because it is the fastest diagnostic specialty. It can detect the early stage of disease before any other imaging tool does.

PET is a type of nuclear medicine imaging that utilized to observe metabolic processes in the body using small amounts of radioactive materials called radiotracers (1).  PET with [F-18] fluorodeoxyglucose  (FDG), which is an analogue of glucose, tracer is the most common type of PET scan that explore the possibility of cancer metastasis (spreading to other sites). It gives significant practical data taking into account the expanded glucose uptake and glycolysis of cancer cells and depicts metabolic abnormalities before morphological changes happen.

Computed tomography (CT) is another type of imaging technique that that gives multiple x-rays images of the internal body organs, bones, soft tissue and structure. It is based on the absorption of X-rays radiations that pass through exit the body

(2).
A combination of PET and computed tomography (CT) has synergistic benefits and can accomplish more than what PET or CT do alone. It gives a very unique imaging for the whole body at one time without having a patient to change position. It also provides a great information with high accuracy since it combines the high sensitivity of PET to the magnificent anatomical localization by CT. In fact, multiple studies had showed the superior value of combining PET/CT compared to many other imaging technique. They have the ability to scan invisible metastatic lesions in early stages (3).
Principles of PET Imaging:
PET imaging utilize radiopharmaceuticals labeled with radioisotopes that emit positron.

These radioisotopes are produced either in cyclotron such as N13, C11, and F18 or by in radioisotope generator such as Ga68 and Rb82. When a positron is emitted, it collides a nearby electron in the tissue and gives 2 photons which then will move in opposite directions (4). The PET device is equipped with coincidence detectors that detect these photons as they radiate simultaneously. Not all coincidence events are favorable. A single unaired photons happen when either one of these two photons is not detected by the detector or absorbed by the body. These unpaired photons are excluded by the coincidence detector. However, various processes happen in PET scanning that decrease the image quality are needed to be considered in quantitative PET scanning. As a result, additional techniques are needed for attenuation correction which is an important correction since photons emitted from the body, are attenuated to a greater range than those emitted from the periphery. Thus, the use of PET/CT isn’t only useful for anatomic localization but also for attenuation

correction.
A study has done to compare and evaluate the finding gained from Both BS and FDG PET/CT in the dete1rmination of bone metastases in patients with lung cancer.
BS mechanism:
BS is a nuclear medicine procedure which is used to search for malignant abnormalities of skeleton. It works like this:
A small amount of radioactive tracer is injected. The treacer is accumulates on the surface of the bone. A camera can take a picture of the distribution of the radiation in the body. The camera gets its name from its ability to measure the gamma radiation during the radioactive decay of the tracer. Usually, the first images taken after five minutes on it. One can see the distribution of the radioactive substance in the soft tissue. More substance accumulate in areas of increased blood circulation indicating possible inflammatory changes in those areas. After two to three hours the second picture is taken and the physicians can see how the tracer accumulated at the bone, giving a picture of the bone metabolism. With bone scintigraphy, physicians gets a live picture of the bone metabolism. Often, 3D images is taken using a technique called SPECT. SPECT is more exact dimensional images that help the physician to evaluate the pictures. The more intense the color, the larger the accumulation of the tracer.
Material and Methods:
Patients:
In this study, 32 patients diagnosed with lung cancer (30 with non-small cell lung cancer and 2 with other histological subtype) with mean age of 65 were involved (table 1). All patients undergo a BS imaging and after a mean time of 18 days they underwent a FDG PET/CT scintigraphy. Within these 18 days, none of them received a chemotherapy or radiotherapy treatment. The purpose behind the diagnosis was to determine the stage of lung cancer in 18 patients, recurrence in 7 patients, treatment response in 4 patients and follow-up in 3 patients.
BS with 99mTc-DPD:
The researchers use a device with Siemens E.CAM gamma Camera that has two detectors. The detector was equipped with low-energy high-resolution collimators. An IV injection of 99mTc-DPD was given to patients. After 3 hours, a whole body scan was done. After the physician obtained the data they need, a SPECT was made to each patient.