Non-invasive (medical)
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The term non-invasive in medicine has two meanings:

• A medical procedure which does not penetrate mechanically, nor break the skin or a body cavity, i.e., it doesn't require an (invasive) incision into the body or the removal of biological tissue.
• An abnormal tissue growth, such as a neoplasm or tumor, that doesn't spread (invade) to the surrounding healthy tissue.

For centuries, physicians have employed many simple non-invasive methods based on physical parameters in order to assess body function in health and disease (physical examination and inspection), such as pulse-taking, the auscultation of heart sounds and lung sounds (using the stethoscope), temperature examination (using thermometers), respiratory examination, peripheral vascular examination, oral examination, abdominal examination, external percussion and palpation, blood pressure measurement (using the sphygmomanometer), change in body volumes (using plethysmograph), audiometry, eye examination and many others.

The discovery of the first modern non-invasive techniques based on physical methods, electrocardiography and X-rays, dates back to the end of the 19th century. Since then, non-invasive methods – which penetrate the body nonetheless, but by electromagnetic or particle radiation rather than a scalpel – have continuously enlarged the scope of medical technology. Non-invasive techniques commonly used for diagnosis and therapy include the following:

Diagnostic images

• Bioluminescence imaging
• Dermatoscopy
• Diffuse optical tomography
• Gamma camera and other scintillographical methods, such as Positron Emission Tomography (PET) and Single-Photon Emission Tomography (SPECT), using radioactive tracers in the body
• Gene expression imaging
• Infrared imaging of the body
• Magnetic resonance elastography
• Magnetic resonance imaging, using external magnetic fields
• Magnetic resonance spectroscopy
• Optical coherence tomography
• Posturography
• Radiography, fluoroscopy and computed tomography, using X-rays
• Ultrasonography and echocardiography using ultrasound waves for imaging

A recent advance is the substitution of invasive medical tests, such as colonoscopy by computer-based 3D reconstructions, such as virtual colonoscopy.

Diagnostic signals

Electrocardiographic tracing

• Electrocardiography (EKG)
• Electroencephalography (EEG)
• Electromyography (EMG)
• Photoplethysmograph(PPG)
• Electrical impedance tomography (EIT)
• Electroneuronography (ENoG)
• Electroretinography (ERG)
• Electronystagmography (ENG)
• Magnetoencephalography (MEG)
• Evoked potentials, such as the visual evoked potentials (VEP) and the brain evoked response audiometry (BERA) tests
• Body impedanciometry
• Impedance phlebography
• Nuclear magnetic resonance spectroscopy
• Percutaneous light spectroscopy (such as in pulse oximetry and capnography)
• Actigraphy
• Breath tests, such as the urea breath test
• Intelligent biomedical clothing
• Non-invasive biomedical sensors
• Endoluminal capsule monitoring

Therapy

• Radiation therapy and radiosurgery, procedures that uses external atomic particles (protons, neutrons, photons, alpha particles, etc.) or gamma rays to destroy pathological tissue within the body
• Lithotripsy, a procedure that uses ultrasound shock waves to break urinary calculus
• Defibrillation, a procedure to block heart fibrillation and start normal rhythm
• Mechanical ventilation, such as the iron lung.
• Transdermal patches, used to deliver drugs applied to the skin.
• Biofeedback
• CPAP (Continuous Positive Airway Pressure) used to treat sleep apnea
• VPAP
• BIPAP
• Biphasic Cuirass Ventilation (BCV, eg. Hayek RTX)
• Photodynamic therapy
• Therapeutic ultrasound
• Extracorporeal thermal ablation
• Extracorporeal magnetic innervation [1]
• Photo-infrared pulsed bio-modulation [2]
• Transcranial magnetic stimulation

In some cases, non-invasive methods will not work for the intended purpose, so medical technology has developed minimally-invasive methods, such as hypodermic injection (using the syringe), endoscopy, percutaneous surgery, laparoscopic surgery, coronary catheterization, angioplasty, stereotactic surgery and many others.

The benefits for the patient are self-evident.

See also

• Medical imaging
• Biomedical engineering
• Minimally invasive
• Molecular Imaging
• Medical tests

References

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