Kidney Lymphoma and the Importance of Computed Tomography (CT)

By MC Raflesia

Kidney lymphoma is most frequently observed along with multisystemic, dispersed lymphoma or as tumor reappearance. Kidney lymphoma might be observed in immunocompromised patients or, hardly ever, as primary disease as well.
With the kidneys being the most usually involved organs, extranodal spread of lymphoma frequently influences the genitourinary system.
The lymphoma can obstruct urine from leaving the kidney. This could cause kidney failure, which could lead to low urine output, weariness, loss of appetite, nausea, or swelling in the hands or feet. The lymphoma could obstruct feces as well moving by means of the bowel. This bowel stumbling block could lead to nausea, vomiting, and serious abdominal pain.
Lymphoma of the kidneys is detected at the time of autopsy in nearly one half of cases. It is seldom suspected on conventional urologic surveys like intravenous urography.
In the nonattendance of right clinical treatment, since involvement of the kidneys typically points to dispersed disease the prognosis is poor. The disease can present with progressive kidney failure. Survival is really poor in principal kidney lymphoma: in less than 1 year 75% of patients die. By early detection of the disease and by doing systemic chemotherapy the prognosis could be recovered.
Kidney lymphoma displays no racial predilection. Kidney lymphoma shows no sex predilection. Nonetheless, it is allegedly perceived more frequently in male patients. Kidney lymphoma takes place in every age group. The disease typically influences adults; but, kidney lymphoma has been reported in childhood as well.
For the detection, diagnosis, staging, and monitoring of kidney lymphoma, contrast material-enhanced computed tomography (CT) remains the modality of option. In patients in whom intravenous administration of iodinated contrast material is contraindicated, magnetic resonance (MR) imaging is principally helpful. Ultrasonography (US) is less sensitive than CT and MR imaging for identifying kidney lymphoma, though really useful for diagnosing lymphoma in the testis or epididymis.
However, in patients with suspected kidney lymphoma, the most sensitive, efficient, and complete examination for evaluation of the kidneys is computed tomography (CT). Helical CT especially recovers detection and characterization of lymphomatous kidney involvement by optimizing contrast dynamics and data acquisition. It is the present modality of option for precise staging of lymphoma.
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Computed Tomographic Angiography in the Diagnosis of Coronary Artery Stenosis and for the Evaluation of Acute Chest Pain

COMPUTED TOMOGRAPHIC ANGIOGRAPHY IN THE DIAGNOSIS OF CORONARY ARTERY
STENOSIS AND FOR THE EVALUATION OF ACUTE CHEST PAIN
A Technology Assessment
INTRODUCTION
The California Technology Assessment Forum was requested to review the scientific evidence for the use of
cardiac computed tomographic angiography in the diagnosis of coronary artery stenosis and for the
evaluation of acute chest pain. This review was prompted by reports that there may be new information
about cardiac computed tomography published since this topic was evaluated by the Blue Cross Blue Shield
Association Technology Evaluation Center (BCBSA TEC) in August, 20061.
BACKGROUND
Coronary artery disease (CAD) is the number one cause of death in men and women. CAD is caused by atherosclerotic plaques developing in the coronary arteries. Many therapies have been shown to decrease CAD mortality, therefore early detection and treatment is critical.

The gold standard for defining coronary artery anatomy is angiography. During coronary angiography, a
catheter is introduced into the femoral, brachial or radial artery and is then passed up to the aorta. Iodinated
contrast dye is then directly injected into the coronary arteries, while digital X-ray images are taken.
Although the risks are generally considered low, there are some risks to the procedure. These include
bleeding and other complications at the catheter insertion site, catheter manipulation causing embolization
of plaque leading to stroke or myocardial infarction, dye related complications, including allergic reactions
and renal toxicity, and exposure to radiation, which may be associated with an increased risk of cancer2, 3.
Coronary artery computed tomography (CT) angiography (CTA) is a non-invasive technology that can
directly image coronary artery anatomy, while decreasing some of the risks associated with an invasive
procedure. It has been proposed as an alternative to coronary angiography. CTA requires the use of
contrast material (administered intravenously) and high speed high resolution CT machinery to take detailed
volumetric pictures of blood vessels.

There are several technical challenges involved in getting good images with CTA. First, the image must be
obtained in a short period of time to avoid blurring. Sometimes beta blockers are given before the
procedure to slow the heart down; therefore pictures can then be taken during diastole when motion is
reduced. Second, rapid scanning is best so that the images can be taken while the patient is holding his/her
breath. Third, thin sections enable higher quality images. Volumetric imaging is then performed and
enables multiple images to be reconstructed to fully demonstrate the coronary arteries.
Multidetector row CT (MDCT) scanning uses helical CT (rotating a tube around the patient to get continuous spiral images). They have multiple detectors – 4, 8, 16, 32, 40 or 64. Limitations of MDCT include: 1) it is harder to obtain good images with a fast heart rate, and 2) the distal portions of the coronary arteries are more difficult to see due to more motion artifact. Many of the earlier studies were done with 16 row MDCT, but MDCT with at least 32 rows is soon likely to become standard.

Important negative consequences of CTA are radiation exposure, which is significantly higher than
conventional angiography3, and nephrotoxicity from the dye. An additional potential complication is the
identification of incidental non-coronary lesions, which then require additional evaluation to determine their
significance.
Two potential uses of CTA are addressed in this report; 1) Use of CTA to diagnose coronary artery stenosis,
and 2) use of CTA in the evaluation of acute chest pain.
Use of CTA to diagnose coronary artery stenosis has the goal of determining whether or not patients have
significant stenoses of the coronary arteries, while avoiding an invasive procedure. CTA could be used as
an alternative to invasive angiography or as an additional noninvasive cardiac test that may be
complementary to other noninvasive tests routinely used (e.g. exercise stress tests). An important issue to
consider is whether or not it replaces other diagnostic tests or becomes an additional or additive test.
For patients with acute chest pain being evaluated in the emergency room, an important goal would be to exclude clinically significant CAD, so as to avoid unnecessary hospitalization. It would thus potentially be most useful in a low risk chest pain population.

Coronary Computed Tomography Angiography: General Considerations

Coronary computed tomography (CCTA) is currently considered to be a technique for high-resolution computed tomography (CT) imaging of the heart. It has become generally accepted that patients with negative CT cardiac results will not need to undergo cardiac catheterization. The radiation dose for the CCTA with modern techniques is much lower than even a few years ago and in some cases, even lower than for cardiac catheterization.

The 64-Slice CT scanner is considered to be the high-end CT system and is preferable for CCTA. However, even earlier generation CT systems are suitable for this task.

In some research studies, there has been an attempt to determine the most beneficial use of cardiac CT scanners, and the consensus appears to be that the high negative predictive value of the multislice CT scanner, used to filter out those patients who do not require further investigatory tests for coronary disease, is where it is currently used most effectively.

CCTA is a non-invasive test, requiring only a contrast injection and for some patients, beta blockers. Therefore the CT scan can be performed as an outpatient examination. The disadvantage of CCTA is that there is a limitation with respect to the image quality for patients with irregular or high heart rates. In such cases, patients may be medicated by beta blockers.
CCTA is also limited where there is extensive calcification, as the high contrast of the calcium leads to "blooming" artifact.

The implementation of X- ray tube current modulation resulted in a dramatic decrease in radiation. In addition, the use of CT scans with ECG -triggering of the radiation resulted in average doses around 3 MSV.

The cost of premium-class, 64-slice CT scanning can be $1.2 - $1.5 million. A dual-source, 64-slice CT scan system costs $1.9 - $2.5 million.
The running costs including: a service contract, three full- time staff members and contrast media are $700 - $850k. In terms of potential revenue, the CCTA exam costs about 10% to 12% of the cost of cardiac catheterization.

Technical Considerations

CCTA requires an accurate imaging of coronary arteries, which move with the cardiac and respiratory cycles. Therefore, high spatial resolution and high temporal resolution are essential.

High contrast-to-noise ratio is of primary importance. To achieve a good enough ratio, it is possible to either increase the X-ray tube output and use thicker slices, or to increase the contrast. The spatial resolution will be impaired by increasing the slice width and filtering the signals.

To eliminate cardiac motion artifact, high-rotation speed system is necessary. Current cardiac CT scanners have 3-3.3 R.P.M speed.

For higher temporal resolution, half the gantry rotation time is used for the reconstruction. To assure the best temporal resolution, it is important to acquire the image in the most stationary phase of the cardiac cycle. Therefore, ECG signal is used to enable the reconstruction of the CCTA image in the cardiac phase of least motion.

The typical scan length of a CCTA examination is about 14 CM. It is essential that the CT scan is completed well within a patient's breathhold, so as to avoid respiratory motion artifacts.

Imaging of the coronary arteries can be achieved on a CT scanner in a variety of different ways. Where the complete heart cycle is scanned, greatest flexibility is available in selecting the optimal phase for coronary artery image reconstruction. This approach enables the best functional analysis. However, the dose to the patient is high. Where only a selected part of the cardiac cycle is CT scanned, the radiation is only during a short interval. In this situation, the radiation is low. There is also the merging of the two approaches: all phases of the heart are CT scanned with reduced radiation, and only the stationary phase window is fully illuminated. Full image quality is obtained for the coronary artery image required phase, whereas the images for functional analysis have lower quality.

In general, the CCTA systems can be classified in 4 groups:

1. Axial scan, Prospective ECG Triggered: this is the most commonly used mode, due to the resultant lower dose. Modern systems typically require 3-4 rotations. It is suitable for patients with heart rates below 70 BMP.

2. Axial scan, Retrospective ECG Gated: in this mode, the axial scan is performed over the full cardiac cycle, over a number of gantry rotations (depending on the detector coverage) so the patient is exposed to high-dose rates.

3. Helical Scan, Retrospective ECG Gated: in this mode the radiation is continuous, while the heart is covered with a low-pitch helical scan. The involved radiation dose is high. This is the mode of choice for patients with high or unstable heart rates.

4. Helical scan, Prospective ECG Triggered: in this mode, the radiation is triggered by ECG, as it is with the axial triggered systems. Systems with dual source (two x-rays tubes and detectors which are positioned at 90 degrees each to other) can be operated at high pitch. A full scan can be performed in less than 0.5 seconds.

Low-pitch prospective systems are rare nowadays.

Performance of CCTA
CT scanning results in a plain-scan resolution of approximately 0.5 mm. With a typical reconstruction field of view of 25 cm, and a reconstruction matrix of 512×512, the pixel size is approximately 0.5 mm, which is a good match for the resolution.

The longitudinal axis resolution of modern, quality CT scanner systems approaches 0.5 mm.

Magnetic Resonance Imaging (MRI) And Functional Computerized Tomography (4DCT) In Radiotherapy

Magnetic resonance imaging (MRI) is traditionally used in the diagnostic and staging parts of a patient's treatment pathway. More recently however, it has also been used to help determine the planning target volume (PTV). In many CNS patients their diagnostic MRI scan is fused with their radiotherapy planning CT scan. (REF) The oncologist is then able to outline the tumour mass on the MRI as a GTV, which can then be superimposed on the planning CT scan, to check the area for treatment and the margins to be used. This fusion of images, is advantages for two reasons. Firstly the MRI image shows far greater resolution in soft tissue, than the CT, and secondly because the CT scan is carried out post surgery following de-bulking, whilst the MRI is carried out prior to any clinical intervention. Therefore the oncologist is in effect, able to treat where the gross tumour was actually initially located.

Functional MRI (fMRI) is a relatively new technology, which is used with the aim to try to determine precisely which part of the brain is handling which critical functions. This is called brain mapping and is used primarily during surgery before the patient comes for any radiotherapy. The use of fMRI has been extended more recently, as it has now also been used as tool, in order to monitor the growth and function of any remaining brain tumour following treatment.

Functional computerised tomography (4DCT) is a normal CT scanner with software incorporated, or hardware adaptations, which allow it to look at organ motion in relation to bony anatomy. These fall into three main categories; 1 Breath Hold, 2 Gating and 3 Tracking the movements of the tumour.

Another method, which can also be used to monitor and control organ motion linked to breathing, is a type of active breathing control device. An active breathing device allows imaging in only one specific part of the patient's breathing cycle. The benefit of this is that it allows for the scan to be constructed with the tumour in one position, and therefore hopefully not as effected by organ motion. The same active breathing device is then used each day while the patient is having their radiotherapy treatment, so the tumour is localised while the treatment machine is delivering dose. This technique does require much cooperation from the patient, and would only be suitable for patients whose thoracic tumours were not too severe to have caused severely laboured, or erratic breathing patterns.

Another type of tumour tracking device uses reference points that are actually attached to the patient's skin surface. These reference points are then tracked while the patient is being CT scanned to determine at which point in their breathing cycle they were at any given point during the scan. When the data from the CT scan is then being consolidated, this additional motion information is added allowing the actual specific motion of any tumour to be linked to each patient's own specific breathing cycle.


The 3rd 4DCT method effectively builds a margin around the GTV as it continually moves within the body. This technique aims to determine the true extent of each patient's actual tumour motion, so a personalised plan can be produced which gives a treatment dose to the GTV, even though it is moving throughout the treatment. The main problem with this technique is a large volume normally needs to be treated, if the tumour motion is of significance and is therefore not generally useful when using radical radiotherapy treatment techniques.

Low-dose CT cuts lung-cancer deaths - Clinical Advisor

Posterior CT shows the lung affected by cancer (blue).

Initial results from a large study have shown there to be 20% fewer deaths from lung cancer among people screened with low-dose helical computed tomography (CT) compared with standard chest x-ray, prompting investigators to stop the trial. ?

The National Lung Screening Trial enrolled 53,500 current or former smokers (at least 30 pack-years, as calculated by multiplying the average number of packs of cigarettes smoked per day by the number of years a person has smoked). The participants had no signs, symptoms, or history of lung cancer—the current leading cause of cancer mortality in the United States. They were randomized to three annual screens with either the low-dose helical CT (often referred to as spiral CT) or the x-ray. ?

By October 2010, 354 lung-cancer deaths had occurred in the CT group, compared with 442 in the x-ray arm. This 20.3% reduction represents the first clear evidence of a significant decrease in lung-cancer mortality with a screening test in a randomized controlled trial. The difference was statistically significant enough to end the study. The findings were published online ahead of print in the journal Radiology.?

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